Musculoskeletal Disorders in Health-Related Occupations (Biomedical and Health Research, 49)

MUSCULOSKELETAL DISORDERS IN HEALTH-RELATED OCCUPATIONS

Biomedical and Health Research Volume 49 Earlier published in this series Vol. 14. G. ter Heege (Ed.), EURO-QUAL Vol. 15. N. Katunuma, H. Kido, H. Fritz and J. Travis (Eds.), Medical Aspects of Proteases and Protease Inhibitors Vol. 16. P.I. Haris and D. Chapman (Eds.), New Biomedical Materials Vol. 17. J.J.F. Schroots, R. Fernandez-Ballesteros and G. Rudinger (Eds.), Aging in Europe Vol. 18. R. Leidl (Ed.), Health Care and its Financing in the Single European Market Vol. 19. P. Jenner and R. Demirdamar (Eds.), Dopamine Receptor Subtypes Vol. 20. P.I. Haris and D. Chapman (Eds.), Biomembrane Structures Vol. 21. N. Yoganandan, F.A. Pintar, S.J. Larson and A. Sances Jr. (Eds.), Frontiers in Head and Neck Trauma Vol. 22. J. Matsoukas and T. Mavromoustakos (Eds.), Bioactive Peptides in Drug Discovery and Design: Medical Aspects Vol. 23. M. Hallen (Ed.), Human Genome Analysis Vol. 24. S.S. Baig (Ed.), Cancer Research Supported under BIOMED 1 Vol. 25. N.J. Gooderham (Ed.), Drug Metabolism: Towards the Next Millennium Vol. 26. P. Jenner (Ed.), A Molecular Biology Approach to Parkinson's Disease Vol. 27. P.A. Frey and D.B. Northrop (Eds.), Enzymatic Mechanisms Vol. 28. A.M.N. Gardner and R.H. Fox, The Venous System in Health and Disease Vol. 29. G. Pawelec (Ed.), EUCAMBIS: Immunology and Ageing in Europe Vol. 30. J.F. Stoltz, M. Singh and P. Riha, Hemorheology in Practice Vol. 31. B.J. Njio, A. Stenvik, R.S. Ireland and B. Prahl-Andersen (Eds.), EURO-QUAL Vol. 32. B.J. Njio, B. Prahl-Andersen, G. ter Heege, A. Stenvik and R.S. Ireland (Eds.), Quality of Orthodontic Care Vol. 33. H.H. Goebel, S.E. Mole and B.D. Lake (Eds.), The Neuronal Ceroid Lipofuscinoses (Batten Disease) Vol. 34. G.J. Bellingan and G.J. Laurent (Eds.), Acute Lung Injury: From Inflammation to Repair Vol. 35. M. Schlaud (Ed.), Comparison and Harmonisation of Denominator Data for Primary Health Care Research in Countries of the European Community Vol. 36. F.F. Parl, Estrogens, Estrogen Receptor and Breast Cancer Vol. 37. J.M. Ntambi (Ed.), Adipocyte Biology and Hormone Signaling Vol. 38. N. Yoganandan and F.A. Pintar (Eds.), Frontiers in Whiplash Trauma Vol. 39. J.-M. Graf von der Schulenburg (Ed.), The Influence of Economic Evaluation Studies on Health Care Decision-Making Vol. 40. H. Leino-Kilpi, M. Valimaki, M. Arndt, T. Dassen, M. Gasull, C. Lemonidou, P.A. Scott, G. Bansemir, E. Cabrera, H. Papaevangelou and J. Me Parland, Patient's Autonomy, Privacy and Informed Consent Vol. 41. T.M. Gress (Ed.), Molecular Pathogenesis of Pancreatic Cancer Vol. 42. J.-F. Stoltz (Ed.), Mechanobiology: Cartilage and Chondrocyte Vol. 43. B. Shaw, G. Semb, P. Nelson, V. Brattstrom, K. M01sted and B. Prahl-Andersen, The Eurocleft Proje 1996-2000 Vol. 44. R. Coppo and L. Peruzzi (Eds.), Moderately Proteinuric IgA Nephropathy in the Young Vol. 45. L. Turski, D.D. Schoepp and E.A. Cavalheiro (Eds.), Excitatory Amino Acids: Ten Years Later Vol. 46.1. Philp (Ed.), Family Care of Older People in Europe Vol. 47. H. Aldskogius and J. Fraher (Eds.), Glial Interfaces in the Nervous System Vol. 48. H. ten Have and R. Janssens (Eds.), Palliative Care in Europe

ISSN: 0929-6743

Musculoskeletal Disorders in Health-Related Occupations Edited by Thomas Reilly Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom

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Preface Musculoskeletal disease constitutes an enormous problem for contemporary workforces. Back problems in particular have been targeted as a major focus for research. The economic benefits of reducing musculoskeletal complaints are well recognised but the emphasis on quantitative costing has been in terms of treatment rather than prevention. Since musculoskeletal disease may be insidious in its emergence rather than linked directly with a single event, the link with working practices is not easily proven. Lifting and manual handling activities have been associated with musculoskeletal complaints, due to excessive acute loading or repetitive loading on the human. A hallmark of an ergonomics approach towards improving safety in the working environment is the design of a better fit between the demands of the job and the capabilities of the individual worker to meet these demands. This book owes its origin to the Biomed IV project, a collaborative research programme funded by the European Commission (Contract BmH4-CT96-1057) Liverpool John Moores University, Free University of Amsterdam, Vrije Universiteit Brussel. The partners were three Universities steeped in a tradition of ergonomics work. The research programme was focused on musculoskeletal disorders in healthrelated occupations. It is ironical that among health carers there is a concern that working practices themselves can be a source of damage to the health of the worker. The fifteen chapters in this book offer a glimpse into the problems of musculoskeletal disorders and the means of their investigation. Ergonomics entails multidisciplinary research and this approach permeates the contents. The background to the research programme as a whole is presented at the outset and the research is rounded off in the final chapter. In between are reviews of more fundamental work so that the methodologies used may be appreciated. Their applications are illustrated where appropriate with observations from the Biomed IV project. A comprehensive set of reviews is provided, in particular for the research techniques used by the various investigators. These include the application of precision stadiometry, electromyography, epidemiology, the Delphi method, dynamic goniometry and body composition analysis. The anthropometric studies from the Brussels project are summarised since the outcomes had implications for the anthropometric investigations of Belgian nurses that formed an element of the programme at Brussels. In other instances, for example the use of physiological indices of occupational strain, the application follows on directly from the literature review. In the main, individual studies illustrate how hospital specialisms fit into the broader ergonomics context. These are reported as self-contained entities in some instances, for example spinal shrinkage in the hospital porters or diurnal variation of spinal segment motion in nurses. In other instances the research findings have already been communicated and a list of publications from the project appears as an Appendix. These include the observation that an ergonomic approach which allows nurses the opportunity to adjust the height of their hospital patient's bed helps to enhance the quality of spinal motion.

The publication of this book should be of interest to ergonomists, health and safety engineers, occupational health workers and health-care professionals and educators. The work incorporated a number of deliverables for exploitation, especially those concerned with methodological approaches. These included: i) questionnaire tool for epidemiological investigations; ii) confirmed use of heart rate, oxygen uptake and spinal shrinkage in combination for ergonomic assessment of occupational load; iii) integrated motion analysis and profile of individual characteristics into formal risk assessments; iv) multidisciplinary preventive model for implementation in back-care education and reducing musculoskeletal loading. The book as a whole provides insights into the multivariate issues in musculoskeletal disorders and methods of investigating them. It serves a purpose also for research workers, for whom there are many projects in this area waiting to be undertaken. These are likely to remain a challenge to researchers for some years into the future.

Thomas Reilly Director, Research Institute for Sport and Exercise Sciences Liverpool John Moores University

Acknowledgements The success of the project concerned with musculoskeletal disorders in health-related occupations was attributable to the many people who contributed to it in one way or another. First, the award of research grant (BmH4 - CT96-1057) by the European Commission made the investigations possible. For their execution, the help of the administrative staff at the EC's offices in Brussels and in the three contributing universities is gratefully acknowledged. For the conduct of the studies a debt of gratitude is due to the research staff members who worked full-time on the project at various stages. These included Caryl Beynon, Joanne Burke, Diana Leighton, Mark Verlinden and Evert Zinzen. Thanks are due to the laboratory technical staff at each of the collaborating universities. The loan of equipment from Dr Kim Burton at the University of Huddersfield is also appreciated. Other individuals and institutions who supported components of the programme are acknowledged within the appropriate chapter of this text. The collation of the material and its organisation into a camera-ready manuscript were accomplished by Ms Lesley Roberts at the Research Institute for Sport and Exercise Sciences (Liverpool John Moores University). Her care and computing skills brought this book to completion.

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The participating institutions The Department of Experimental Anatomy at Vrije Universiteit Brussel is a basis for fundamental research of topographical, functional and clinical anatomy, polarised around the human body and its body composition. The department has a Director (Prof. Dr. Jan Pieter Clarys, e-mail: [email protected]), 10 members of staff and a full-time secretary (Mrs Jenny Mertens) and sits within the Faculty of Physical Education and Physiotherapy. Both dissections (a detailed study of the interior human body) and plastinated models (made of prepared parts of the human body) are elements of every student contact with anatomy. The research findings (anatomical variations and detailed within the experiment) keep being updated as a function of this type of education, with variable accents in clinical anatomy, anatomy in vivo and kinesiology. Furthermore, its application towards rehabilitation sciences, sport sciences (performance analysis and analysis of the human motor behaviour) and ergonomics (simulation conditions and task analysis) are domains that are explored on a continuous basis. The use of electromyography, the capture of muscular activity by means of surface electrodes, is a means of to approach and study applied biomechanics, which reveals the magnificent world of the muscles of the living body in its dynamic context. The Department of Experimental Anatomy is also home of the Manual Therapy, arthrokinematics, isokinetics, body composition and EMG scientific supported education. The facilities for study of cadavers are unrivalled elsewhere in Europe. The Brussels Cadaver Analysis Study has stimulated international collaboration, most notably with researchers in Canada and Sweden. Much of the pioneering work on kinesiological electromyography also was instigated within the department. The study of muscle function is pursued using isokinetic dynamometry, complemented by its academic programmes in manual therapy and physiotherapy. Its activities are aligned to those in human biometry and physical education at the University's Hilok campus. Research in ergonomics at the Free University of Amsterdam is conducted within the Faculty of Human Movement Sciences, in close conjunction with the University Medical Centre Nijmegen. Together these units constitute the Institute of Fundamental and Clinical Human Movement Science which is approved by the Royal Netherlands Academy of Arts and Sciences. This research institute (IFKB) was founded in 1995 and is the only research school in the Netherlands that focuses exclusively on human movement. The Dean of the Faculty is Professor Peter Hollander (e-mail: [email protected]) and the head of the Research School is Dr Huub Toussaint (e-mail: H M [email protected]). The research of the IFKB is organised around three themes. These themes are studied in historically evolved cohesive groups called research lines, which are ordered according to the themes. Each line is headed by a line co-ordinator who is responsible for the realisation of the scientific goals of the line and its financial management. The line co-ordinators form the advisory body to the board of the IFKB. An education programme committee assists the board in the evaluation of the graduate educational programme.

The object of the study of the IFKB is human movement. The research is focused on three themes, each theme comprising several research lines. The themes are: A. Physical load and capacity of the human action system B. Energy metabolism and fatigue C. movement co-ordination. This structure has stimulated the integration of knowledge within the three themes, lending itself suitable for ergonomics also. The academic programmes include a specialisation in ergonomics work. This aspect of work is supported by a vibrant enterprise culture and projects funded by national industries. The Research Institute for Sport and Exercise Sciences at Liverpool John Moores University was established in November 1997, being the first research unit formally endorsed by the Academic Board of the University with this title. The designation followed its top rating nationally in the Research Assessment Exercise of 1996 and acknowledged the international status of the research programmes in sport and exercise sciences. The Research Institute has a Director (Professor T. Reilly, e-mail: [email protected]), a Deputy Director (Professor Adrian Lees, e-mail: A.Lees @ livjm.ac.uk), an Advisory Board (made up of its Professors and Readers), a full-time Secretary/Administrator (Ms Lesley Roberts) and a membership exceeding 60 individuals. There are in excess of 40 research students (M.Phil, PhD) registered within the Institute, and a limited number of Research Studentships are advertised annually on a competitive basis. The research student body includes international students and the majority of students are externally funded or self-sponsored. The Research Institute also offers a one-year training programme leading to an MRes (Sports Science) award. The research programmes span the range of disciplines within the human sciences. There are three major areas for highlighting: i)

human performance: focuses on biomechanics, motor control, fitness evaluation, training, elite performance; there is a particular interest in science and football, and in sports ergonomics; ii) exercise and health; includes aspects of musculoskeletal disease and injury prevention, diet and nutrition, environmental stress; cardiovascular health and occupational ergonomics; iii) exercise and biological rhythms, circadian rhythms, sleep, travel fatigue, circamensal rhythms, women and exercise. There is a range of externally funded projects and supportive sponsors. Research programmes operate in harmony with the activities of the Human Performance Unit where work is related to national governing bodies, Olympic athletes and ergonomics projects. The activities are complemented by research consultancy contracts with sports industries. A wide range of activities is organised under the aegis of the Institute. These include one-day symposia, international conferences (e.g. The International Conferences on Sport, Leisure and Ergonomics held every 4 years in affiliation with the Ergonomics Society; conference of the World Commission on Science and Sports), and national scientific events (the BASES Conference in September, 2000 and the Football Association's Coaching Association Conference, November 2001).

The Research Institute also hosts each year a limited number of honorary Research Fellowships and welcomes post-doctoral and visiting professors from overseas. The Research Institute also houses the offices of the World Commission for Science and Sports. The website address of the Research Institute is www.livjm.ac.uk/hhs/RISES. Collectively the three institutions have common strands within the fields of ergonomics and other human sciences. Collaboration has been effected long term by mutual research training schemes, ERASMUS programmes and exchange visits supported by the British Council. There have also been short-term exchanges for cooperative doctoral work and sharing of research plans. This team-work culminated in the Biomed IV Programme which is the subject of this book.

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Contents Preface

v

Acknowledgements

vii

The participating institutions

ix

1.

Introduction to Musculoskeletal Diseases: The Biomed IV Project T. Reilly

1

2.

The Identification and Measurement of Risk D.J. Leighton and C. Beynon

7

3.

Measurement of Spinal Loading: Shrinkage T. Reilly

25

4.

Epidemiology: Musculoskeletal Problems in Belgian Nurses E. Zinzen

41

5.

Epidemiology of Musculoskeletal Disorders in a Sample of British Nurses and Physiotherapists C. Beynon and T. Reilly

63

6.

Electromyography in Occupational Activities J.P. Clarys and T. Reilly

85

I.

The Implementation of Additional Software for 3-D Analysis of Coupled Motion in the Cervical Spine by Means of an Electromagnetic Tracking Device P. Van Roy, J.P. Baeyens, R. Lanssiers, A. Vermoesen, D. Caboor, E. Zinzen, M. Verlinden and J.P. Clary s

97

8.

A Method for Job Evaluation using a Modified Delphi-Survey D. Caboor

107

9.

Physiological Assessments of Occupational Activities T. Reilly, J. Burke, S.D.M. BotandA.P. Hollander

117

10.

Spinal Shrinkage during Simulated Nursing and Porters' Tasks C. Beynon

127

II.

The Effects of the Nurse's Job on the Diurnal Variation of the Segments of the Spine - An Anthropometric Approach D. Caboor

137

12.

Body Composition: Part I. Physical and Structural Distribution of the Human Skin J.P. Clarys and M. Marfell-Jones

143

13.

Body Composition: Part II. "Whole-Body Adiposity" Prediction: Males versus Females J.P. Clarys, A. Martin and D. Drinkwater

151

14.

Body Composition: Part III. In vivo Application of a Selection of Formulae for Predicting Whole-Body Adipose Tissue in Male and Female Nurses J.P. Clarys, K. Alewaeters and E. Zinzen

163

15.

Musculoskeletal Disorders in Health-Related Occupations: Project Overview and Outcomes T. Reilly, D. Leighton, C. Beynon, J. Burke, J.P. Clarys, P. Van Roy, E. Zinzen, D. Caboor, M. Verlinden and A. P. Hollander

171

Subject Index

187

Appendix: Publications and Communications from the Biomed IV Research Project

189

Author Index

191

Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

INTRODUCTION TO MUSCULOSKELETAL DISEASES: THE BIOMED IV PROJECT Thomas Reilly Research Institute for Sport and Exercise Sciences LiverpoolJohn Moores University, Henry Cotton Campus 15-21 Webster Street, Liverpool, L3 2ET United Kingdom Abstract: incidence and prevalence of back pain are high in nursing personnel compared to other occupational groups and the problem may extend to other healthrelated professions and other musculoskeletal diseases. The current project was undertaken by three collaborative European institutions to investigate musculoskeletal diseases in nurses, physiotherapists and hospital-based porters. A multivariate approach was adopted and the work distributed according to the strengths of the participating research groups.

1. Background and rationale Lower back pain affects a large part of the adult population, over 60% of whom have a cumulative lifetime prevalence of the syndrome. Back pain is a very common cause of morbidity, disability and threat to health and well-being. The lower back is more commonly affected by occupational over-exertion than are other parts of the body, and accounts for about two-thirds of total occupationally related injuries. The major part of the remainder is attributable to other musculoskeletal disorders (MSD) associated with poor working postures or working practices. Such postures and manual handling practices are evident in occupations within healthcare professionals and the hospital environment. Data from the United Kingdom and Belgium emphasise the huge economic consequences to industry of certified sickness due to working days lost as a consequence of musculoskeletal disorders. Since their causes are multifactorial, it is important that an ergonomics appraisal should take an interdisciplinary approach towards identifying critical epidemiological factors. Identification of the interactions between factors would help form a strategy for reducing the incidence of musculoskeletal disorders. A decrease in prevalence would have huge economic benefits to the employers. Since these disorders adversely influence participation in leisure and recreational activities in those people affected, any improvement in the preventive practices would help preserve the health and well-being of workers, especially among the European communities.

2

T. Reilly /Introduction to Musculoskeletal Diseases: the Biomed IV Project

It was envisaged that the outcomes of the work from this research programme would have potential also for the education and training of personnel at risk of musculoskeletal disorders in the workplace. The ergonomics check-list incorporated into the preventive model (which represented the culmination of the current project) could form a basis for reducing occupationally related biological problems and thereby benefit the employer in healthcare professions.

2. Objectives and organisation of the research programme The project was focussed on health-related occupations to compare the prevalence of musculoskeletal disorders in different specialisms, identify causes of occupational strain, establish physiological indices of strain, evaluate the effects of altering typical work-rest cycles and develop a multidisciplinary preventive model. The specific objectives and primary approach were as follows:i)

ii) iii)

iv) v)

establish prevalence of musculoskeletal diseases among nurses and physiotherapists by means of an extensive questionnaire and information gained from hospital Occupational Health Department records ; identify possible causes of occupational strain using questionnaire and extensive ergonomic risk assessment within the hospital environment; establish the interaction between risk factors in the workplace environment and the incidence and prevalence of occupational musculoskeletal diseases, employing a multivariate approach to data collection; examine the physiological and biomechanical effects of alterations in work-rest schedules among hospital porters using physiological and physical indices of occupational strain; develop a model to be used in the prevention of back problems in nursing personnel based on synthesis of data collected from a variety of different tests.

The project was co-ordinated from Liverpool John Moores University and its partners included research groups from Vrije Universiteit Brussel and Free University of Amsterdam. Previous work at Liverpool had embraced epidemiological aspects of back pain in nurses and comparisons of its prevalence in the general population (Leighton and Reilly, 1995). Results for back pain and sickness absences in comparison with the general population data are shown in Table 1. The epidemiological approach was complemented by measurements of spinal loading associated with particular occupational tasks. A range of patient-transfer procedures were implicated as causative in precipitating back pain by nurses who had both indicated an annual prevalence of back pain and recalled a particular incident. The most common task implicated by the nurses was positioning a patient in bed, followed in importance by moving a patient from bed and moving a patient from a chair (Leighton and Reilly, 1995).

T. Reilly /Introduction to Musculoskeletul Diseuses: the Biomed IV Project

3

Table 1. Back pain and sickness absence figures for nursing personnel and members of the general population (from Leighton and Reilly, 1995). Nursing personnel (n = 1134)

General population (n = 315)

24.4 25.1 Point prevalence 58.8 57.8 Annual prevalence 61.4 58.9 Lifetime prevalence 14.7 11.5 Annual incidence 14.2 35.1 Sickness absence* * Number of days absent due to back pain expressed as a percentage of days lost for all causes.

The magnitude of the back-pain problem appears to have increased among nursing personnel since the results of a survey by Stubbs et al. (1983). Whilst nurses may have been singled out for detailed attention (Buckle, 1987; Garg and Owen, 1992; Pheasant and Stubbs, 1992), other professions within the health-care system are also vulnerable. These include physiotherapists (Scholey and Hair, 1989) and possibly also hospital porters. These professions were of interest in the current project. There are various techniques that are used in ergonomic analyses of occupational tasks. Once problems are identified within habitual activity profiles, the critical tasks may be isolated by formal risk assessment. The research group at Vrije Universiteit Brussel planned to follow up their epidemiological surveys with task analyses to establish the ‘Top 10’ most heavy nursing duties in bed-patient related tasks. Sophisticated opto-electronic devices are now available for detailed motion analysis which can be combined with electromyography. The main muscles associated with movements of the trunk are listed in Table 2. In addition spinal movement may be monitored in three dimensions using electrogoniometry. Using this combination of methods (and the associated computer software systems), the consequences of redesigning particular tasks could be evaluated. An example is the redesign of bedheight so that the task is harmonised to the individual. The efficacy of such an intervention requires profiling the anthropometric and individual characteristics. The eventual goal of such multivariate analysis is to establish a predictive model. Table 2. The muscles associated with movements of the trunk.

Movement

Muscles

Extension of the trunk

Erector spinae, multifidus, lumborum, interspinales.

Flexion of the trunk

Psoas major, psoas minor. Abdominal muscles: obliquus externus abdominis, obliquus internus abdominis, rectus abdominis.

Rotation of the trunk

Obliquus internus abdominis, multifidus, obliquus externus abdominis, rotatores, semispinalis.

Lateral flexion of the trunk

Obliquus externus abdominis, rectus abdominis, obliquus internus abdominis, erector spinae, multifidus, quadratus lumborum, intertransversarii.

semispinalis,

quadratus

T. Reilly / Introduction to Musculoskeletal Diseases: the Biomed IV Project

Whilst low-back pain may have been the main focus of research attention, other areas are implicated in musculoskeletal disease. Spinal loading and poor ergonomic working practices may have consequences in neck pain. Repetitive manual handling tasks might also be linked with problems in the upper limb. The syndrome of repetitive strain injury, chronic injury linked with repeated fast actions leading to pain in the musculotendinous complex, is another recognised entity. Overall physiological strain has traditionally been indicated by global measures such as heart rate and energy expenditure. Generally, the responses are averaged over an entire work-shift, the assumption being that the measures are representative of steady state conditions. The responses can be gauged against a classification system such as Christensen's (1953). The categories of work severity shown in Table 2 may be related to subjective exertion using Borg's (1970) scale. Table 3. Christensen's classification of occupational work.

Energy expenditure kcal (kJ).min'1

Heart rate (beats.min"1)

Body temperature (°C)

175

39.0

150

38.5

125

38.0

5.0 (20.9)

100

37.5

2.5(10.5)

75

37.0

Too heavy 12.5(52.3) Very heavy 10.0(41.9) Heavy 7.5(31.4) Medium Light Very light

Once physiological systems are strained, there is a need for rest to allow recovery to the original state. This necessity raises questions about the optimal work-rest ratio. If rest periods are too long, the individual worker is under-productive; in contrast, the worker will underperform if fatigued from previous physical activity. The research at Amsterdam focussed on the validity of physiological indices of work-stress in nonsteady state conditions, prior to investigations of the work-load of hospital porters. 3. Distribution of project-based work 3.1 The Liverpool project Separate epidemiological surveys were planned in order to investigate musculoskeletal disease in health-related professions. The first investigation consisted of a cross-sectional survey of nurses and physiotherapists. In the second phase of investigation a prospective study was conducted within an 'occupational health' department, also targeted at nursing personnel and physiotherapists. The surveys were designed as a prelude to an ergonomic evaluation of hospital based nursing and physiotherapy tasks. Techniques included a formal risk assessment and observation whilst shadowing individuals at their work-place.

T. Reilly / Introduction to Musculoskeletal Diseases: the Biomed IV Project

The final phase of the work was concentrated on hospital-based porters. Their normal activities had first to be examined in order to design alternative work-rest schedules. The modifications can be examined for any benefits using a multidisciplinary approach incorporating physiological responses, subjective reactions, and physical response (spinal shrinkage). These measures are harmonised with ratings of postural discomfort whereby the affected anatomical areas are identified by the subject and discomfort is rated on a seven-point scale (Corlett and Bishop, 1976). 3.2 Vrije Universiteit Brussels The whole programme was backed up by a large relevant literature database. An epidemiological survey was planned to establish lifetime prevalence for low-back pain and neck pain in Belgian nurses. An array of individual characteristics and lifestyle factors was used to identify likely sufferers. A preventative programme could be outlined once the relative weightings of predictive variables were calculated. A comprehensive task analysis was intended to identify discrete nursing 'jobs' and isolate those that are 'heaviest'. Those 'jobs' could be evaluated in both existing and re-designed bed-patient set-ups. Force platform, motion analysis and electromyography could be combined to investigate the strain associated with the tasks that were scheduled for investigation. 3.3 Free University Amsterdam The work at Amsterdam was designed to feed into the later stages of the investigation of work-rest ratios at Liverpool. A work-cycle incorporating periodic vigorous bouts of activity, superimposed on an intermittent work-rest cycle was designed for the study of the relation between heart rate and oxygen consumption. The preliminary investigation of activity of hospital-based porters was set up for comparison with the later research at Liverpool.

4. Overview Musculoskeletal disorders are the most commonly reported occupational diseases within work-forces of the European Union. This project was focused on healthrelated occupations to compare the prevalence of musculoskeletal disorders in different specialisms, identify causes of occupational strain, establish physiological indices of strain, evaluate effects of altering typical work-rest cycles and develop a multidisciplinary preventive model. It was intended that a broad range of methodologies was to be employed in the research utilising the technical and scientific skills of the three university-based groups in the collaboration. A range of outcomes was anticipated from the research. Firstly, a new methodology for epidemiological studies was expected which would take the form of a validated questionnaire tool. Secondly, there should be an indication of how spinal shrinkage combined with conventional measures such as heart rate and oxygen uptake in ergonomic assessment of occupational load. Third, motion analysis and individual characteristic profiling were to be integrated with formal risk assessment. A multidisciplinary preventive model would have value if implemented in back care education and training for manual handling.

T. Reilly / Introduction to Musculoskeletal Diseases: the Biomed IV Project

References Borg, G. (1970). Perceived exertion as an indication of somatic stress. Scandinavian Journal of Rehabilitation Medicine, 2, 92-98. Buckle, P. (1987). Epidemiological aspects of back pain in the nursing profession. International Journal of Nursing Studies, 24, 319-324. Christensen, E. H. (1953). Physiological valuation of work in the Nykroppa Iron Works. In: Symposium on Fatigue (edited by W. F. Floyd and A. T. Welford). London: H. K. Lewis. Corlett, E. N. and Bishop, R. P. (1976). A technique for assessing postural discomfort. Ergonomics, 19, 175-182. Garg, A. and Owen, B. (1992). Reducing back stress to nursing personnel: an ergonomic intervention in a nursing home. Ergonomics,35, 1353-1375. Leighton, D. J. and Reilly, T. (1995). Epidemiological aspects of back pain: the incidence and prevalence of back pain in nurses compared to the general population. Occupational Medicine, 45, 263-267. Pheasant, S. and Stubbs, D. (1992). Back pain in nurses: epidemiology and risk assessment Applied Ergonomics, 23, 226-232. Scholey, M. and Hair, M. (1989). Back pain in physiotherapists involved in back care education. Ergonomics, 32, 179-190. Stubbs, D. A., Buckle, P. W., Hudson, M. P., Rivers, P. M. and Worringham, C. J. (1983). Back pain in the nursing profession. 1. Epidemiology and pilot study. Ergonomics, 26, 755-765.

Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

THE IDENTIFICATION AND MEASUREMENT OF RISK D.J. Leighton and C. Beynon Public Health Sector School of Health and Human Sciences Liverpool John Moores University 70 Great Crosshall Street, Liverpool L3 2AB United Kingdom

Abstract. Epidemiological evidence supports the existence of risk factors for workrelated musculoskeletal disorders (MSDs). Recognised risk factors include manual handling, posture, task repetition, vibration and psychosocial factors. The combination and interaction of risk factors for MSDs make assessment of exposure to risk difficult. The focus of this chapter is the development and application of a comprehensive risk assessment tool for use within a health care setting. In total, 294 individual risk assessments were performed on nurses and physiotherapists undertaking their normal work activities. The work tasks associated with the highest risk were those concerned with transferring and lifting patients and those involving a static hold. Senior physiotherapists were shown to be at greater risk than lower grade staff, as were nurses and physiotherapists between the ages of 20 and 39 years. Risk was related to the speciality in which staff worked, with the spinal injuries unit being associated with higher risk tasks. The potential risk associated with performing occupational tasks decreased after 19:00 hours for all staff. The epidemiological studies described in this chapter and elsewhere in this publication provide supporting evidence for the validity of the risk assessment tool.

1.

Introduction

The potentially hazardous nature of certain work activities is recognised in European Union legislation and the associated guidance/initiatives produced/undertaken by member states. In the United Kingdom, for example, guidance on the Manual Handling Operations Regulations 1992 (Health and Safety Executive, 1998) provides advice for employers on the identification and control of risk factors within the work environment. As a result, there has been particular interest in the performance of practical risk assessments for work-related musculoskeletal disorders (MSDs). The assessment of risk for work-related musculoskeletal disorders is dependent upon the existence of recognised 'risk factors'. It is well established that causes of MSDs are multifactorial, where a number of risk factors (physical, psychosocial, environmental, personal) singularly or in combination, contribute to the development of a condition. Substantial epidemiological research has provided evidence for the effect of specific

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(mostly physical) (Li and Buckle, 1999) work activities on the development of MSDs in some body parts. This knowledge is essential, and should form the scientific basis for the development of any exposure assessment tool which aims to identify the risk associated with the performance of work activities and the incidence of MSDs. The combination and interactions of risk factors for MSDs make exposure assessment difficult. However, a risk assessment tool which incorporates physical, personal and environmental elements of the work being performed and the worker performing it, provides a comprehensive assessment from which more information concerning the potential interaction of risk factors may be gleaned. In this chapter the risk factors for which there is evidence of a causal link will be described. Similarly, the relative merits and shortcomings of a number of published exposure assessment tools will be discussed as a basis for the development of a risk assessment methodology for application in a healthcare setting. The findings from the epidemiological studies of this work programme provide supporting evidence for the validity of this risk assessment tool.

2. Epidemiological evidence for risk factors associated with MSDs 2.1 Manual handling It is widely accepted that the manual manipulation of heavy loads has the potential to cause back problems. Convincing evidence of a causal relationship between heavy physical work and back problems was acknowledged in the comprehensive review by NIOSH (1997). More specifically, repetitive lifting of heavy loads is recognised as increasing the potential for back pain by exceeding the strength of the anatomical structures involved (Videman et al., 1995). de Zwart et al. (1997) analysed repeated questionnaire data over a four-year period to evaluate a range of musculoskeletal complaints relative to work demands. For most complaints, there were significantly greater increases in prevalences for those working in heavy physical work than in the control group. 2.2 Posture Sustained abnormal postures lead to muscle imbalance, with certain muscles being overused and opposing muscles being under-used. Muscles in either a lengthened or shortened position will be at a mechanical disadvantage and gradually become weak. Certain postures render the worker more prone to this muscle imbalance (Higgs and Mackinnon, 1995). For example, symptoms in the neck and shoulder region have been linked to static muscle activity and short work-cycle time in Danish wood and furniture workers due to prolonged forward and lateral flexions of the neck in certain tasks (Christensen et al., 1995). Punnett et al. (1991) indicated that musculoskeletal problems of the back were associated with mild (21° - 45°) and severe (>45°) flexion, or lateral bend in excess of 20°. Although insufficient evidence for either the presence or absence of a causal relationship between static work posture and MSDs was noted in the NIOSH review (1997), it did acknowledge evidence of a positive relationship between posture in general and MSDs in the following anatomical areas: neck, shoulder, elbow (in combination with other risk factors such as force, repetition), hand/wrist and the back.

D.J. Leighton and C. Beynon / The Identification and Measurement of Risk

2.3 Repetition Due to ever increasing automation within the western world, work is becoming more repetitive with constrained ranges of motion and infrequent task rotation. This situation places sustained demands on the same anatomical area (Peate, 1994). Repetitive work is linked to problems of the neck, shoulder, elbow, wrist and hand (Ohlsson et al, 1995; NIOSH, 1997). As indicated above, repetition may interact with other risk factors (force, posture) to cause work-related MSDs. 2.4 Vibration The most pronounced long-term effect of whole-body vibration is damage to the spine. Kelsey and White (1980) reported that prolonged periods of driving increased the risk of disc prolapses and vibration was given as one of several associated causes (BieringSarensen and Thomsen, 1986). Vibration puts the back muscles under stress which is augmented by the need to maintain balance and whole-body vibration is a particular risk factor for the onset of low-back pain in drivers when coupled with other activities such as loading and unloading a truck. The back is not the only anatomical area affected. The vibration effects of handheld power tools have been linked to a variety of hand and wrist disorders, often described as hand-arm vibration syndrome, and more specifically includes carpal runnel syndrome and Raynaud's phenomenon (Bonney, 1995; Atterbury et al, 1996). 2.5 Psychosocial factors Traditionally, research has focused on the physical risk factors associated with musculoskeletal disorders (Vender et al., 1995). The multi-factorial aetiology of musculoskeletal disorders is now well recognised and psychological factors relating to the individual and the occupation must be considered (Lungberg, 1995). Similarly, Li and Buckle (1999) acknowledged the increasing evidence to support the contribution of psychosocial factors in the development of work-related musculoskeletal disorders. Psychosocial hazards can be defined as 'aspects of job content, work organisation and management and of environmental, social and organisational conditions which have the potential for psychological and physical harm' (Cox, 1993). Exposure can affect individuals directly, by physical mechanisms and indirectly, by mechanisms mediated by psychological stress. For example, noise, heat and humidity can be physically detrimental and also act as a psychological stressor. Work is usually perceived as stressful when it involves demands which can not be matched by the individual's real and perceived capabilities, especially when the workers have little or no control (Cox, 1993; Lungberg, 1995). While the study of general stress and its associated physical problems is useful, it is more valuable to discriminate occupational stresses into their causative factors to establish which exact stress factors relate to musculoskeletal disorders. Work pace (Bernard et al, 1994; Ekberg et al, 1994), work load (Ohlsson et al, 1994; Daniels and Guppy, 1995), little control of work (Leino and Hanninen, 1995; Ekberg and Wildhagen, 1996; Hemingway et al, 1997) and poor communication at work (Bernard et al, 1994; Ekberg et al, 1994; Faucett and

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Rempel, 1994) have all been associated with musculoskeletal disorders of various anatomical regions. 2.6 Personal/Individual factors Personal characteristics and social background have also been considered in epidemiological investigations. Age (Badley and Ibanez, 1994), sex (Ohlsson et al., 1994), stature (Arad and Ryan, 1986), smoking (Frymoyer and Gordon, 1989), alcohol consumption (Arad and Ryan, 1986) and social background (income and years of schooling) (Viikari-Juntura et al., 1991) and their association with musculoskeletal symptoms have also been considered. Personal factors, such as age and sex, may be recorded during a risk assessment so that their association with the risk of the task can be ascertained. However, according to NIOSH (1997) there is little evidence to show that personal factors interact synergistically with physical factors. 3. Measurement tools 3.1 The necessity for techniques Employers have become increasingly aware of the effects that work tasks and workspace design have on the health of employees. This awareness has led to a corresponding demand for methodologies to assess work practices, both to identify problems and evaluate the effectiveness of interventions and ensure compliance with legislation (Haslegrave and Corlett, 1995). Techniques are needed to assess the demands of the work tasks and establish whether these demands constitute a risk of causing musculoskeletal problems (Haslegrave and Corlett, 1995). Risk assessments constitute a method for prioritising work-place improvements as the same procedure can be used to establish the comparative risk of different work tasks. The same assessment should be performed before and after a work-place intervention to enable such strategies to be evaluated (Li and Buckle, 1999). Three general types of measurement strategies exist for the identification of risk factors for musculoskeletal disorders; i) self-reports by workers (subjective reporting), ii) risk assessments by an individual trained in the technique (systematic observations) and iii) measurements using some instrumentation (direct measurements). Exposure to risk factors should also be expressed by all three principal dimensions reported by Burdorf and van der Beek (1999): level, duration and frequency. Li and Buckle (1999) also explained how exposure assessment methods/tools may be described in terms of sensitivity and generality and this approach will be indicated in the following sections. Self-reports by workers, for example using a questionnaire (i.e. the Nordic Musculoskeletal Questionnaire) or check-list, are useful for collecting large amounts of information and are particularly useful for the measure of psychosocial stressors (Hagberg et al., 1995). Measurement of physical factors using some instrumentation gives more specific information regarding precise work tasks. For example, myoelectric signals (EMGs) indicate the electrical activity of contracting muscles (Hagberg et al., 1995), goniometers measure angles to the vertical of body segments to assess posture (Corlett, 1995). Such direct measurements may be costly and require specialist training

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and equipment. These methodologies are not within the scope of this chapter but are covered in part elsewhere in this book and shall not be discussed further. Numerous risk assessment procedures have been developed and validated. These can be adapted for individual purposes. Alternatively a new procedure can be developed so that the capabilities and specific working knowledge of the individual to perform the assessment can be considered (Li and Buckle, 1999). Personnel undertaking such assessments may have little training in ergonomics and so the assessments should be fairly simple with well-defined procedures (Haslegrave and Corlett, 1995). Risk assessments may be completed instantaneously or recorded on video and analysed later. If the risk assessment is to be completed instantaneously, including a large number of observations will reduce the accuracy of the observations (Kilbom, 1994). Training and pilot work must be undertaken to ensure that the risk assessments are completed reliably. For the purpose of this chapter, examples of risk assessment procedures concerned with assessing i) the physical loading of muscles as a result of manual handling, ii) assessing working postures, and iii) evaluating psychological load shall be discussed. These are the factors associated with the occurrence of musculoskeletal problems. 3.2 The assessment of physical load The NIOSH Equation (National Institute of Occupational Safety and Health) was developed in the USA and can be used to calculate the 'Recommended Weight Limit' for a given task, assuming a baseline limit of 23 kg under the best conditions; these best conditions are a sagittal plane lift, occasional lifting, good coupling (handholds), less than 25 cm vertical displacement of load, and a situation in which the lift is made at a vertical height of 75 cm from the floor and a horizontal reach distance of no more than 25 cm from the mid-point between the ankles. This is thought to represent a situation in which 90% of a healthy working population could perform lifting work over the time period without increasing the likelihood of suffering a back problem. Detailed information on specific parameters of the posture of the individual/task under study is required. This obviously gives high specificity, but no general information about the task is obtained (Li and Buckle, 1999). Whilst the NIOSH Equation is a useful guideline, it has yet to be validated and has limitations for use in a practical setting. Firstly, the equation only applies to lifting/lowering tasks and not to carrying, pulling, pushing and it only applies to tasks that are performed whilst standing. It does not take into consideration non-uniform loads or shifts in load distribution or objects with poor coupling. These two factors are important when considering nursing and physiotherapy where the 'object' is a patient; holds can be poor and the patient can be unpredictable, resulting in the load shifting position (Stobbe et al., 1988). Finally it is not designed to assess lifting single-handedly, lifting a load with more than one person, loads lifted in constrained spaces or poor conditions and unusual loads such as contaminated material (Haslegrave and Corlett, 1995). The danger of a lifting limit is that it assumes that lifting below this weight will not cause harm. 3.3 The assessment of work posture Several other direct observational procedures are available to assess the risk of different working postures, although historically such methods are time consuming and labour intensive. One of the earliest whole-body posture coding systems for industrial use was

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developed in Finland to investigate working postures in steelworks (Karhu et al, 1977). This OWAS system (Ovako Working posture Analysis System) records the position of the back, arms and legs respectively as the first three numbers. The fourth figure indicates the load or force used and the final two digits represent the stage in the cycle or task. This procedure allows for the estimation of the proportion of time tasks require the exertion of force or the maintenance of certain postures. An assessment sheet allows for the evaluation of the likely musculoskeletal load experienced when performing a specific task. Action categories are used for prioritising interventions for various postures in relation to their estimated times of use during the working day. The OWAS approach has a wide range of uses but the results can be low in detail, rendering the method 'general' as opposed to 'specific'. Other postural risk assessment procedures exist for specific applications. For example, RULA (Rapid Upper Limb Assessment) assesses the exposure of people to postures, forces and muscle activity known to contribute to upper limb disorders (Corlett, 1995). 3.4 Psychological assessment In relation to musculoskeletal disorders, psychological measurement tools are based on the assumption that comfort/discomfort in performing a task will be related to the load on the tissues, with pain or discomfort indicating the potential for damage to tissues (Hagberg et al., 1995). Corlett and Bishop (1976) demonstrated that if a force was exerted for as long as possible until the pain was unbearable and estimates of the discomfort levels made on a scale (5 or 7 points) at intervals during the holding time, growth in feelings of discomfort were linearly related to holding time regardless of the level of force being exerted. A linear scale for discomfort therefore exists. A body map was used in the methodology to divide the body into different segments. At various predetermined times of the day, workers are asked to give the site of discomfort and a rating of discomfort from 0 to either 5 or 7 (Corlett, 1995). This simple method gives an indication of which tasks cause the greatest discomfort and which anatomical areas are most affected. This method appears to have good sensitivity and allows for the detection of fatigue at a number of sites (Hagberg et al, 1995). Psychosocial job exposure may also be obtained from self-report questionnaires or diary. However, inherent problems with such methods are validity and reliability. 3.5 Exposure assessment Whichever method is chosen for exposure assessment, it is the opinion of 'experts' reported by Li and Buckle (1999) that: • • • • •

The method has to be cheap, easy to learn and use. The method should be applicable to all sections of working life, and should take the environmental and psychosocial aspects into consideration. The measurements have to be repeatable under re-described conditions, i.e. within the range of movements normally occurring in the actual work station. The recording equipment should not interfere with the movements being recorded and should not interfere with the worker's work. The method should have high validity, reliability and sensitivity.

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Assessment data should be readily coded for computer storage and analysis.

In accordance with the above recommendations, established risk factors and methods of assessment, a comprehensive risk assessment procedure was developed specifically for the Biomed work programme. The tool was designed to be specific to the population under assessment (applicable to both patient and non-patient handling tasks) but which balanced sensitivity with generality and took into consideration the potential interaction of risk factors for musculoskeletal disorders.

4. The development of a risk assessment tool for nursing and physiotherapy tasks 4.1 Requirements for risk assessment For use in a hospital (real-time) setting, a risk assessment must be performed objectively, quickly, accurately and in a non-invasive manner. It is important that the assessment incorporates occupational, environmental, organisational and personal elements to ensure that data are collected on a range of risk factors (physical, environmental, psychosocial, occupational, personal). For the purposes of this work programme, the risk assessment procedure was to be developed to quantify the more evident factors associated with work that may be associated with musculoskeletal disorders. An attempt was made to develop a tool to identify those nursing and physiotherapy tasks with the highest risk score. Assessments had to consider the task being performed but also the environment in which the staff members were working. The risk assessment developed should be quick, instantaneous and a non-intrusive method of collecting data. 4.2 Designing the risk assessment pro-forma The paper-based risk assessment was designed as a pro-forma with six sub-sections. A large number of observed factors decreases the precision of observations (Kilbom, 1994) but including small sub-sections rather than one whole reduced this problem. The six sub-sections detailed task, posture, load, environmental conditions, the psychological state of the individual and forces acting on the wrists and fingers. A cumulative scoring system was devised, the total score indicating the overall risk of performing a specific activity. Each task/posture was awarded a score in each of the six sub-sections depending on the risk. For example, trunk flexion of 45° scored 2, compared to flexion of 90° which scored 4. A short description of the task was included at the time of recording so that a composite score was associated with specific activities. Figure 1 shows the risk assessment pro-forma.

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D.J. Leighton and C. Beynon / The Identification and Measurement of Risk

AGE FEMALE NURSE GRADE SPECIALITY

TASK

WALKING STANDING SITTING PUSHING PULLING KNEEL RUNNING ST. HOLD LIFTING

DOMINANT SIDE. DATE TIME WARD NO SUBJECT NO

MALE PHYSIO,

( ( ( ( (

) ) ) ) )

( ) ( ) ( ) ( )

OBJECT ALONE

( ) ( )

PATIENT 2PEOPLE

AMBULIFT WALKING BELT PAT SLIDE

DEVICES

( ) ( ) ( )

( ) ( )

MORE

( )

EASY SLIDE

( ) ( ) ( )

DESCRIBE TASK REPEATED ( STOOPING ( TWISTING ( TRUNK FLEXION ( LATERAL POSTURE BENDING ( SHOULDERS SAGITTAL ( SHOULDERS FRONTAL (

) ) ) )

<20 ( )

)

LEFT ( )

)

+90 ( ) +135 ( )

)

+90 ( )

<45 ( ) <70 ( )

<90 ( )

BW ( )

RIGHT ( )

+135 ( )

NECK

EXTENDED (

)

WRISTS FORCE

FLEXED ( ) YES ( )

FINGERS FORCE

YES ( ) NO ( )

FLEXED ( )

EXTENDED ( ) NO ( )

HANDS

EFFORT LOAD

EASY ( ) STABLE( )

WEIGHT CENT. OF GRAVITY <20 ( ) 35 ( )

HARD ( ) UNSTABLE ( ) 50 ()

70 ()

+70

Figure 1. The risk assessment pro-forma.

()

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The risk assessment was based upon guidelines provided by the Health and Safety Executive [Guidance on Manual Handling Operations Regulations, 1992 (1998)] and pilot work was performed to ensure that all normal actions could be recorded. Two observers were used during pilot work and they recorded the instantaneous risk assessment discretely but at the same time. When inter-subject variability had been eliminated, data collection could begin. Eliminating inter-subject variability ensured minimal intra-subject variability so assessments were reliable. Within the Biomed work programme, the risk assessment pro-forma was used not for the purposes of management or control of risk within the specific hospital environment but in order that data on potential risk factors could be analysed and interpreted in relation to the additional epidemiological data collected. 4.3 Data collection The nine nursing and physiotherapy (hospital-based) specialties included in the study were as follows and the hours of observations in each are shown in the brackets: casualty (28), out-patients (50), haematology (38), care of the elderly (50), general medicine (31), intensive care (20), orthopaedics (27), surgical (7), and spinal injuries (24). The assessor 'shadowed' one member of staff for a one-hour period during the course of the individual's working day and an instantaneous assessment was carried out every 10 minutes. By remaining with the member of staff continuously for the one-hour period, the assessor was able to assess the psychological characteristics of the individual. Overall, data were collected for 46 hours and constituted 276 risk assessments. Assessments were performed on both nurses and physiotherapists, at different times of the day, on both sexes and on different occupational grades to ensure that a cross-section of information was obtained. Altogether, 197 nurse assessments and 97 physiotherapy assessments were performed. The mean age of the nurses and physiotherapists was 40.5 (± 9.99) and 31 (+ 9.92) years, respectively. By collecting large amounts of data on numerous individuals, any individual differences in the way the personnel performed the task were smoothed out. A mean score for performing each task was therefore obtained. 4.4 Analysis of data The data collected were analysed using Minitab statistical software (version 9.2). Analysis of variance was used to examine differences in tasks and subjects. When residuals were saved from the above analysis, the residuals failed to show a normal distribution using Anderson-Darling test of normality as implemented in Minitab (MINITAB, 1995). A Kruskal-Wallis non-parametric test was used to indicate which tasks were producing the highest risk scores. This process was repeated to establish which of the six sub-sectional scores were responsible for the increased overall score of the high risk tasks and to indicate whether other factors such as age, nursing/physiotherapy grade and specialty and time of day had any significant effect on the overall task score.

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Walking/standing (41) Talking to staff/relatives (29) Talking to patients (24) Walking patients (7) Other (8) Patient assistance (9) Preparing/checking equipment/treatment (23) Writing notes (39) Bed making/tidying (4) rehabilitation exercises (14) Treating patients (medical procedures) (15) Assisting patient (feeding, washing etc) (11) Chest physiotherapy (7) Transfer/push/pull equipment (16) Physiotherapy manipulations (4) Static hold/standing patients (10) Transferring/lifting patients (14)

3

4

5

6

Median risk scores

Figure 2. Median risk scores for tasks undertaken by nurses and physiotherapists (the number of observations is given in parentheses).

5. Assessment of risk of nursing and physiotherapy tasks 5.1 High risk tasks The tasks identified as having the highest risk were those concerned with transferring and lifting patients (manual handling) and those involving a static hold component or standing patients in a static position as part of the rehabilitation process (Figure 2). These differences were significant (p<0.05). 5.2 High risk components of tasks The scores in the 'task' sub-section of the pro-forma differed significantly depending on which overall task was being considered (p<0.05). The tasks with the highest median score for this sub-section were transferring/pushing/pulling equipment (median=5), static hold/standing patients (median=5) and lifting/transferring patients (median=4). The highest possible score for this section was 6.0. Scores also differed significantly for the sub-section 'posture' depending on the task being performed (p<0.05). The tasks with the highest risk in this section were transferring/lifting patients (median=3.5), assisting patients (median=3.0) and bedmaking/tidying, treating patients and chest physiotherapy (all with a median score of 2.0).

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The sub-section concerned with forces acting on the fingers and wrists had a total possible score of 3.0. Again, the median scores were significantly different depending on the task being performed (p<0.05). Physiotherapy manipulations scored highest (median=1.5), followed by chest physiotherapy and writing/reading notes (median=1.0). When considering 'load', tasks involving a static hold or assisting patients to maintain a standing position had a median score of 5 (total possible=5). Transferring/lifting patients had a median score of 1.0. All other tasks had a median score of zero, these differences being significant (p<0.05). The final two sub-sections considered the effects of the environment and the psychological state of the individual on the task score. Neither of these subsections yielded significant results (p>0.05). 5.3 Risk score differences related to other factors A Kruskal-Wallis test was performed on the total risk scores to identify the effects of other factors. The median scores were not significantly related to sex or left/right handedness (p>0.05). The median scores were also not affected by the nursing grade, but were significantly different when the grade of the physiotherapist was considered (p<0.05). This can be seen in Figure 3, with the risk being greatest for Senior 2 physiotherapists and least for physiotherapy assistants. When time of day was considered, the median scores were significantly lower for tasks performed between 19.00 hours and 22.00 hours than those tasks performed between 08.00 and 19.00 hours (p<0.05).

Superintendent (6)

Senior 1 (37)

Senior 2 (6)

Junior/basic physio (35)

Assistant (13)

3

4

Median risk score

Figure 3. Median values (number of observations in parentheses) for the different physiotherapy grades.

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The median score differed significantly when different subject age groups were considered. The younger age groups had the increased risk (p<0.05)(Table 1).

Table 1. Median task scores and the number of observations for each age group.

Age groups (years)

Median scores

Number of observations

20-29

3.00

93

30-39

3.00

65

•'40'- 49

2.00

62

50-59

2.00

55

The risk score was also significantly affected by the specialty in which the subject was working (p<0.05). The specialty with the highest risk was 'spinal injuries' followed by 'care of the elderly' and 'surgical' (Figure 4). When the two occupations were compared, the median risk scores were significantly different (p<0.05), physiotherapists being at greater risk than nursing staff.

Orthopaedics (27) Casualty (28) Out patients (50) Haematology (38) General medicine (31) Intensive therapy unit (20) Surgical (7) Care of elderly (50) Spinal injuries (24)

3

4

Median risk scores

Figure 4. Median task scores (number of observations in parentheses) for each hospital speciality.

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6. Interpretation of findings The results of the risk assessment indicated that manual handling scored highest in the sub-section 'posture' but scored lower than static holding/standing patients in the section 'load'. The load lifted/transferred by nurses and physiotherapists was reduced by assistive devices and also most manual handling tasks were performed by two or sometimes more members of staff. This is not to say that the load handled during manual handling tasks is not an important consideration for musculoskeletal disorders. It may not be a single lift/transfer that precipitates the onset of back pain, but repeatedly performing lifts over a period of time (Anderson, 1980). Manual handling had the highest risk score for the sub-section 'posture', indicating that individuals were often subjected to obstruction when performing handling tasks. 'Static holding/standing of patients' was shown to have the same overall risk as transferring/lifting patients. A static hold was characterised as the maintenance of a posture for five seconds or more where some load was being applied. An example is holding a patient in a sitting position whilst a colleague proceeds to 'bed bath' the individual. Assisting patients to maintain a standing position was a task usually performed by the physiotherapist to facilitate weight-bearing and circulation and again usually proceeded for a number of seconds. They were therefore stationary tasks. Such static actions have been shown to occur almost as commonly as dynamic actions (Harber et al., 1987; Blue, 1996). The large amount of evidence detailing lifting and manual handling to be major risk factors for musculoskeletal disorders means the importance of static holding is often neglected and its potential for initiating musculoskeletal disorders must not be ignored. Static holding/standing patients scored considerably higher than any other activity for the sub-section 'load'. The high score of this task was mainly because patients were held by one member of staff, who was often in an unstable posture. Also patients could not always be held close to the body, because of environmental constraints such as medical attachments. The impact of various external factors on the task risk score was investigated. The risk was not significantly related to gender or left/right handedness. There was only a small percentage of male subjects in the sample and all of these were physiotherapy staff, due to the lack of males in the chosen specialties. The task score was not related to the grade of nursing personnel, but was significantly different when the grade of the physiotherapists was considered (p<0.05). The risk was lowest for the assistant and basic physiotherapist and greatest for Senior 2, Senior 1 and Superintendent grades, with Senior 2 grade having the highest risk. It is suggested that the lower grades work with Senior 2 and Senior 1 physiotherapists and that their role is a more assistive one, with Senior 2 and Senior 1 taking more responsibility in the treatment. It is also conceivable that Senior 1 and Superintendent physiotherapists become more involved in the administration of operations and their 'hands on' treatment becomes reduced. This would leave Senior 2 physiotherapists as having the largest physical work load. Additional work is needed to support or reject this proposition. When time of day was considered, the potential risk of performing occupational tasks decreased significantly after 19:00 hours (p<0.05). Prior to this time, the potential risk remained at a constant level throughout the working day (08:00 hours to 19:00 hours). Buckle et al. (1980) showed that 40% of injuries occurred within the first hour of work starting and 65% between 06:00 hours and 12:00 hours. Ryden et al. (1989) suggested that a time of day effect influencing back injuries in nursing may exist, with

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the highest proportion occurring at the beginning of a shift when staff are not 'warmed up' and at the end of a shift when personnel are in a hurry to leave or fatigue has set in. It was expected that the times of day with the highest risk would be in the morning and in the early evening when patients are being assisted out of and back into bed, with these periods involving a high proportion of patient handling tasks. The data show that there are potentially detrimental tasks with a high risk score occurring throughout the day. The highest score was observed between 12:00 hours and 13:00 hours. No explanation can be given for this being considerably higher than any other time of the day, except that it was approximately the time at which patients were taken to the toilet or assisted on to the commode prior to lunch time. Scores after 19:00 hours were considerably lower and this time coincides with when most patients had eaten their evening meal and were back in bed. Once back in bed the patients required little assistance from nursing staff, especially if relatives were visiting, and this therefore represented a quieter time for staff. Physiotherapy staff finished work at approximately 17:00 hours, except for those on call who were there throughout the night. When the ages of the nursing and physiotherapy staff were considered together, those between the ages of 20 and 39 were at a significantly higher risk than those who were older (p<0.05). It is conceivable that young staff perform more 'hands-on' work than older staff, older staff having worked their way up into positions of task delegation. If this were true, it would be expected that staff at higher grades (usually older staff) would be performing activities of less potential risk. The data did not support this suggestion and shall be discussed further below. Finally, the task scores were related to the specialty in which they were performed in order to establish whether certain specialties required the performance of higher risk tasks. The differences between the specialties were significant (p<0.05), with the spinal injuries unit being associated with higher risk tasks. The specialties deemed to have the lowest risk were orthopaedics and casualty. Owen (1986) and Vasiliadou et al. (1995) reported the highest number of back injuries occurred in specialties requiring physically demanding work. The high risk score for the spinal injuries unit is not surprising if this situation is true, with spinal patients requiring a great deal of physical assistance. These results would suggest that staff working in certain specialties are at a greater risk of suffering musculoskeletal disorders than in other specialties. Harber et al. (1985) believed that there would be no such difference because all aspects of nursing had a high risk component and that nurses would 'select' themselves out of specialties they found particularly detrimental.

7. Supporting evidence from epidemiological studies Epidemiological work is useful in providing an overview of the problem of musculoskeletal disorders within the healthcare professionals involved. A risk assessment provides an objective method of assessing the risk of performing certain occupational activities. Adopting two different but complementary approaches to the same problem produced greater success in identifying some of the main underlying causes than adopting a single method of investigation alone. Patient handling is often cited as a main causal factor preceding a period of lowback pain in both nurses (Jensen, 1990) and physiotherapists (Bork et al., 1996). When nurses and physiotherapy staff were asked to state the cause of their musculoskeletal

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disorder in the epidemic logical work, patient handling was the major cause cited. The risk assessment supported the argument for the detrimental nature of lifting/handling, indicating these as high risk tasks. Static holding/standing of patients was shown to have risk equally high as the risk for lifting/handling patients. The potential for static, isometric contractions to have adverse consequences was supported by the epidemiological study of British physiotherapists (Bork et al., 1996), with physiotherapists whose work regularly required the adoption of maintained stooped positions having a 23% higher risk of suffering musculoskeletal symptoms than those who stated their work did not require the maintenance of this posture (logistic regression analysis). Manual handling scored highest in the sub-section 'posture' of the risk assessment, potentially because the ideal lifting techniques taught in the classroom are not always possible in the working environment due to obstructions. Harber et al. (1988) stated that 30% of all actions had a medical attachment present to hinder correct patient movement. Of those individuals who responded to the epidemiological questionnaire, 40% deemed the work environment to be unsuitable, with 61% of these perceiving the main problem to be poorly designed working areas or space constraints. The adoption of non-optimum handling postures could be a serious consideration in the risk of musculoskeletal disorders. The age of symptomatic and asymptomatic respondents was significantly different in the epidemiological work. Personnel aged between 30 and 59 and particularly between 50 and 59 years showed the greater percentage of musculoskeletal disorders. The initial reaction would be to conclude that the older staff had increased prevalence due to the probability of increased time in the occupation. However, the number of years in the occupation showed no predictive power when entered into the logistic regression model, so the physiological ageing process was thought to be more important in symptom onset than years in the job. Conversely, the risk assessment showed the staff aged between 20 and 39 actually performed activities with a higher risk. This was not related to the individual's grade and would appear to support the conclusion that the increased prevalence with age was due to the ageing process. Job specialty was shown by the epidemiological work to have predictive value for musculoskeletal disorders in both professions and low-back pain in physiotherapists. It was also shown to influence significantly the overall task scores in the risk assessment. The influence of specialty of musculoskeletal disorders is difficult to clarify because it relies on staff being able to recall exactly which specialty they were working in at the onset of symptoms. The effects of work in previous specialties must be considered.

8. Conclusions The risk assessment protocol described in this chapter was used to identify the tasks with the highest potential for causing musculoskeletal problems (transferring and lifting patients and static postures). It proved to be a quick and non-invasive method of quantifying the performance of work activities associated with risk. It was also used to assess how a variety of external factors such as age and the specialty in which the task was performed affected the overall risk score. The main (and positive) elements of the risk assessment protocol are highlighted below:

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D.J. Leighton and C. Beynon / The Identification and Measurement of Risk

• • • • • • • • •

May be applied at any time and during all work tasks (patient and non-patient handling tasks). Incorporates occupational, environmental, organisational, and personal elements. Ensures data are collected on a range of known risk factors (physical, environmental, psychosocial, occupational and personal). Allows rapid assessment. Is non-intrusive. Inter- and intra-person reliability demonstrated. Is a valid risk assessment tool to be used in the management or control of risk. Provides an overall risk score but high risk components of tasks may be identified with ease. Enables relationships with external work factors to be established.

The value of comparing the risk assessment data with the results of the epidemiological surveys (detailed elsewhere in this book) has been recognised and the data provide an element of validation to both methodologies. In addition, a risk assessment methodology which allows both detailed information on the activity which is being performed and the general description of the task to be obtained is beneficial. References Anderson, J.A.D. (1980). Occupational aspects of low back pain. Clinics in Rheumatic Diseases, 6, 1735. Arad, D. and Ryan, M.D. (1986). The incidence and prevalence in nurses of low back pain. A definitive survey exposes the hazards. The Australian Nurses Journal, 16,44-48. Atterbury, M.R., Limke, J.C., Lemasters, O.K., Li, Y., Forrester, C., Stinson, R. and Applegate, H. (1996). Nested case-control study of hand and wrist work-related musculoskeletal disorders in carpenters. American Journal of Industrial Medicine, 30, 695-701. Badley, E.M. and Ibanez, D. (1994). Socio-economic risk factors and musculoskeletal disability. The Journal of Rheumatology, 21, 515-522. Bernard, B., Sauter, S., Fine, L., Petersen, M. and Hales, T (1994). Job task and psychosocial risk factors for work-related musculoskeletal disorders among newspaper employees. Scandinavian Journal of Work, Environment and Health, 20,417-426. Biering-S0rensen, F. and Thomsen, C. (1986). Medical, social and occupational history as risk indicators for low-back trouble in a general population. Spine, 11, 720-725. Blue, C.L. (1996). Preventing back pain among nurses. Orthopaedic Nursing, 15, 9-21. Bonney, R.A. (1995). Human responses to vibration: principles and methods. In: Evaluation of Human Work. A Practical Ergonomics Methodology, (edited by J.R. Wilson and E.N. Corlett), p. 543. London: Taylor and Francis Ltd. Bork, B.E, Cook, T.M., Rosecrance, J.C., Engelhardt, K.A., Thomason, M.E.J., Wauford, I.J. and Worley, R.W. (1996). Work-related musculoskeletal disorders among physical therapists. Physical Therapy, 76,827-835. Buckle, P.W., Kember, P.A., Wood, A.D. and Wood, S.N. (1980). Factors influencing occupational back pain in Bedfordshire. Spine, 5, 254-258. Burdorf, A. and van der Beek, A. (1999). Exposure assessment strategies for work-related risk factors for musculoskeletal disorders. Scandinavian Journal of Work, Environment and Health, 25 (supplement 4), 25-30

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Christensen, H., Pedersen, M.B. and Sj0gaard, G. (1995). A national cross-sectional study in the Danish wood and furniture industry on working postures and manual materials handling. Ergonomics, 38, 793-805. Corlett, E.N. (1995). The evaluation of posture and its effects. In Evaluation of Human Work. A Practical Ergonomics Methodology, (edited by J.R. Wilson and E.N. Corlett), pp. 686-674. London: Taylor and Francis Ltd. Corlett, E.N. and Bishop, R.P. (1976). A technique for assessing postural discomfort. Ergonomics, 19, 175-182. Cox, T. (1993). Stress research and stress management: putting theory to work. HSE Contact Research Report No. 61. Daniels, K. and Guppy, A. (1995). Stress, social support and psychological well-being in British accountants. Work and Stress, 9,432-447. de Zwart, B.C.H., Broersen, J.P.J., Frings-Dresen, M.H.W. and van Dijk, F.J.H. (1997). Repeated survey on changes in musculoskeletal complaints relative to age and work demands. Occupational and Environmental Medicine, 54, 793-799. Ekberg, K., Bjorkqvist, B., Malm, P., Bjerre-Kiely, B., Karlsson, M. and Axelson, O. (1994). Casecontrol study of risk factors for disease in the neck and shoulder area. Occupational and Environmental Medicine, 51, 262-266. Ekberg, K. and Wildhagen, I. (1996). Long-term sickness absence due to musculoskeletal disorders: the necessary intervention of work conditions. Scandinavian Journal of Rehabilitation Medicine, 28, 3947. Faucett, J. and Rempel, D. (1994). VDT-related musculoskeletal symptoms: interactions between work posture and psychosocial work factors. American Journal of Industrial Medicine, 26, 597-612. Frymoyer, J,W. and Gordon, S.L. (1989). Research prespectives in low-back pain. Report of a 1988 workshop. Spine, 14, 1384-1390. Health and Safety Executive (1998). Guidance on Manual Handling Operations Regulations, 1992. London: HMSO Hagberg, M., Silverstein, B., Wells, R., Smith, M.J., Hendrick, H.W., Carayon, P. and Perusse, M. (1995). In: Work Related Musculoskeletal Disorders (WMSDs): A reference book for prevention (edited by I. Kuorinka and L. Forcier), pp. 177-181 London: Taylor and Francis. Harber, P., Billet, E., Gutowski, M., SooHoo, K., Lew, M. and Roman, A. (1985). Occupational lowback pain in hospital nurses. Journal of Occupational Medicine, 27, 518-524. Harber, P., Shimozaki, S., Gardner, G., Billet, E., Vojtecky, M. and Kanim, L. (1987). Importance of nonpatient transfer activities in nursing-related back pain: 2. Observational study and implications. Journal of Occupational Medicine, 29, 971-974. Harber, P., Billet, E., Shimozaki, S. and Vojtecky, M. (1988). Occupational back pain of nurses: Special problems and prevention. Applied Ergonomics, 19, 219-224. Haslegrave, C.M. and Corlett, E.N. (1995). Evaluating work conditions and risk of injury - techniques for field surveys. In: Evaluation of Human Work. A Practical Ergonomics Methodology, (edited by J.R. Wilson and E.N. Corlett), pp. 892-893. London: Taylor and Francis Ltd. Hemingway, H., Shipley, M.J., Stansfeld, S. and Marmot, M. (1997). Sickness absence from back pain, psychosocial work characteristics and employment grade among office workers. Scandinavian Journal of Work, Environment and Health, 23, 121-129. Higgs, P.E. and Mackinnon, S.E. (1995). Repetitive motion injuries. Annual Review of Medicine, 46, 116. Jensen, R.C. (1990). Back injuries among nursing personnel related to exposure. Applied Occupational and Environmental Hygiene, 5, 38-45. Karhu, O., Kansi, P. and Kuorinka, I. (1977). Correcting working postures in industry: a practical method for analysis. Applied Ergonomics, 8, 199-201. Kelsey, J.L. and White, A.A.N (1980). Epidemiology and impact of low-back pain. Spine, 5, 133-142. Kilbom, A. (1994). Assessment of physical exposure in relation to work-related musculoskeletal disorders - what information can be obtained from systematic observations? Scandinavian Journal of Work, Environment and Health, 20, 30-45. Leino, P.I. and Hanninen, V. (1995). Psychosocial factors at work in relation to back and limb disorders. Scandinavian Journal of Work Environment and Health, 21, 134-142.

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Li, G. and Buckle, P. (1999). Evaluating change in exposure to risk for musculoskeletal disorders - a practical tool. Contract Research Report 251/1999. London: HSE Books. Lungberg, U. (1995). Methods and applications of stress research. Technology and Health Care, 3, 3-9. MINITAB INC. (1995). MINITAB Reference Manual. State College, PA: Minitab Inc. NIOSH (1997). Musculoskeletal Disorders and Workplace Factors: A critical Review of Epidemiologic Evidence for Work-Related Musculoskeletal Disorders of the Neck, Upper Extremity and Low Back. (ed. B. Bernard), National Institute for Occupational Safety and Health. Ohlsson, K., Hansson, G.A., Balogh, I., Stromberg, U., Palsson, B., Norander, C., Rylander, L. and Skerfving, S. (1994). Disorders of the neck and upper limbs in women in the fish processing industry. Occupational and Environmental Medicine, 51, 826-832. Ohlsson, K., Attewell, R.G., Palsson, B., Karlsson, B., Balogh, I., Johnsson, B., Ahlm, A. and Skerfving, S. (1995). Repetitive industrial work and neck and upper limb didorders in females. American Journal of Industrial Medicine, 27, 731-747. Owen, B.D. (1986). Personal characteristics important to back injury. Rehabilitation Nursing, 11, 12-16. Peate, W.F. (1994). Occupational musculoskeletal disorders. Occupational Health, 21, 313-327. Punnett, L. Fine, L.J., Keyersling, W.M., Herrin, G.D. and Chaffm, D.B. (1991). Back disorders and nonneutral trunk postures of automobile assembly workers. Scandinavian Journal of Work, Environment and Health, 17, 337-346. Ryden, L.A., Molgaard, C.A., Bobbit, S. and Conway, J. (1989). Occupational low-back injury in a hospital employee population: An epidemiological analysis of multiple risk factors of a high-risk occupational group. Spine, 14, 315-320. Stobbe, T.J., Plummer, R.W., Jensen, R.C. and Attfield, M.O. (1988). Incidence of low back pain injuries among nursing personnel as a function of patient lifting frequency. Journal of Safety Research, 19, 2128. Vasiliadou, A., Karvountzis, G.G., Soumilas, A., Roumeliotis, D. and Theodosopoulou, E. (1995). Occupational low-back pain in nursing staff in a Greek hospital. Journal of Advanced Nursing, 21, 125-130. Vender, M.I., Kasdan, M.L. and Truppa, K.L. (1995). Upper extremity disorders: A literature review to determine work-relatedness. The Journal of Hand Surgery, 20A, 534-541. Videman, T., Sarna, S., Battie, M.C., Koskinen, S., Gill, K., Paananen, H. and Gibbons, L. (1995). The long-term effects of physical loading and exercise lifestyles on back-related symptoms, disability and spinal pathology among men. Spine, 20, 699-709. Viikari-Juntura, E., Vuori, J., Silverstein, B.A., Kalimo, R., Kusoma, E. and Videman, T. (1991). A lifelong prospective study on the role of psychosocial factors in neck-shoulder and low-back pain. Spine, 16, 1056-1061.

Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

MEASUREMENT OF SPINAL LOADING: SHRINKAGE Thomas Reilly Research Institute for Sport and Exercise Sciences Liverpool John Moores University Henry Cotton Campus 15-21 Webster Street, Liverpool, L3 2ET United Kingdom

Abstract: stature is a fundamental measure in anthropometry: changes in total body length are indicative of loss of height from intervertebral discs. This shrinkage in stature is measurable with precision stadiometry and can be used as an index of spinal loading. Precision stadiometry has been applied in industrial contexts for evaluating equipment and occupational tasks and in exercise contexts for assessing activities with induced spinal compressive loads. The methodology has potential in a range of physical work activities related to health professions and for complementing other ergonomics research tools.

1. Introduction The aetiology of back-pain syndrome is manifold and is often difficult to establish. There may be structural damage to the spinal motion segment, several factors being possible causes of degeneration in one or more of the individual segments. Among these are repetitive heavy lifting, manual handling of awkward loads, constant forward bending, twisting and asymmetric loading of the trunk. Poor ergonomic working postures can also be implicated (Marras et al., 1995). During everyday activities the intervertebral discs experience axial loading and lose height as they are compressed. Whenever the osmotic pressure of the discal tissues is exceeded by the compressive load, fluid is expelled (Tyrrell et al., 1985). The expulsion of fluid is followed by changes in the dynamic response characteristics of the intervertebral joint complex, and with time there is a reduced resistance to failure under either static, dynamic or vibratory load. In a degenerated disc, deformation under load is more rapid than normal (Kazarian, 1975). Thus the cumulative effects of static and dynamic loading are significant to the aetiology of back symptoms and back injury. Our concern has been with the use of changes in stature to monitor creep effects in the spine. The spinal column constitutes about 40% of total body length and approximately 33% of total spinal column length is occupied by intervertebral discs. The intervertebral discs respond to loading and unloading forces by altering their size. The mechanism affecting the loss of disc height with compressive loading has been

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attributed to elimination of fluid from the nucleus pulposus (Kazarian, 1975). Water is removed from the disc when the sums of the imbibition pressure of the proteinpolysaccharide complex of the nucleus pulposus and the osmotic gradient across the disc membrane are exceeded. Recovery ensues when the compressive forces are withdrawn or when the spine is distracted. Creep in the disc and subsequent recovery are not solely matters of fluid exchange since extension and contraction of the fibres of the annulus fibrosus are also implicated (Koeller et al., 1984). Measurement of changes in stature can reflect shrinkage in spinal length and consequently in aggregate disc height. Variations in stature due to compression of appendicular structures are negligible compared to changes within the spinal column. Compression of soft-tissue in the soles of the feet reaches equilibrium quickly when bearing body-weight and is unaffected by experimental spinal loading (Fitzgerald, 1972). Exact reproduction of the standing posture in successive measurements, whilst allowing for differences in postural contour between individuals, is an essential requirement for measuring fine changes in stature. Such precision has been achieved by Eklund and Corlett (1984) and Corlett et al. (1987). Prior to the description of precision stadiometry, a brief outline of the anatomy of the spine is presented. 2. Anatomy of the spine The vertebral column is formed by 33 vertebrae, 24 of which are moveable and separated by intervertebral discs. The cervical, thoracic, lumbar and sacrococcygeal curves provide a spring-like response to loading as well as offering balance to the spine as a whole. There are 7 cervical, 12 thoracic, 5 lumbar vertebrae and a fusion of the sacral bones and coccyx (see Figure 1). The adjacent vertebrae and the tissues that connect them form the vertebral motion segment. The vertebrae articulate with each other by three joints i) anteriorly, by a symphysis joint between the adjacent bodies ii) posteriorly, by a pair of synovial joints known as the apophyseal or facet joints. The posterior part of the motion segment includes the neural arch, the apophyseal joints, the transverse and spinous processes and ligaments. The vertebral body is in the front part, the vertebral bodies being separated by the intervertebral discs which provide functional mobility for the spine and act as shock absorbers. Four ligaments support the posterior part of the vertebral segment. The ligamenta flava have elastic qualities and connect the adjacent vertebral arches longitudinally, attaching to the lamina. The supraspinous and interspinous ligaments run from one spinous process to the next, and help to resist stress and forward flexion forces on the spine. The inter-transverse ligaments connect between the two transverse processes, resisting lateral flexion of the spine. The intervertebral discs lying between the vertebral endplates consist of two parts: a central part known as the nucleus pulposus and an outer ring, the annulus fibrosus. The nucleus pulposus consists of a hydrophillic gel and large proteoglycan molecules; the outer annular ring consists mainly of collagen fibres attached around the edge of the vertebral endplate. This forms an extremely long network that will expand upon vertical compression but not give way. Fluid exchange and structural deformation have both been associated with changes in disc height. The fluid exchange theory proposes that pressure gradient changes occur upon compressive loading (Kramer, 1985). Compressive loads that exceed the interstitial osmotic pressure of the nucleus pulposus cause fluid to be

T. Reilly /Measurement of Spinal Loading: Shrinkage

Figure 1. A lateral view of the vertebral column viewed from the left.

expelled into intra-discal spaces across the cartilage endplates and a decrease in disc height or "creep" occurs as a result. Dynamic response characteristics of the disc become altered as the stiffness of the disc increases. Reversal of this fluid extrusion process occurs upon unloading the spine, for example when lying supine. Experiments have also demonstrated that disc height alterations due to creep and subsequent recovery occur as the fibres of the annulus fibrosus extend and contract in response to loading and unloading conditions. It is acknowledged that the mechanisms involved are not fully understood (Koeller et al., 1984). The bony processes on the posterior of the vertebral column form suitable sites for the attachment of skeletal muscles. Some muscle fibres are long, extending from sacrum to thorax, others are short and span 1-3 joints. Vertically arranged fibres pull the spine into extension whereas those arranged obliquely rotate one vertebra on the next one; lateral fibres attached to the angles of the ribs are engaged in lateral flexion of the spine. The largest muscle group of the deep back muscles is the erector spinae which originate from a thick broad tendon. The muscles of the abdominal wall form a four-way girdle between the ribs and the pelvis. The rectus abdominis is a vertical panel running down the centre, the external and internal obliques form diagonal fibres on the side of the trunk, and the transversus abdominis forms a large horizontal waistband. The abdominal muscles are the prime flexors of the trunk, during which movement the erectal spinae act to stabilize the individual motion segments. During extension, the erector spinae become the prime movers in combination with the gluteal muscles, whilst the abdominals act as stabilizers. Flexion of the spine leads to deformation of the intervertebral disc. The nucleus pulposus then becomes wedge-shaped and the tension in the posterior part of the

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annulus fibrosus increases. If flexion of the spine is accompanied by a compressive spinal loading, the fibres of the annulus are vulnerable to tearing with a resultant bulge developing. If the tear and the bulge are accentuated over time, the nuclear material may be extruded. One outcome then is pressure on nerves exiting from the vertebral canal which causes intense pain: the condition is referred to as a prolapsed disc and constitutes a severe form of back pain. 3. Stadiometry as an index of spinal loading Stature is a fundamental variable in anthropometry and ergonomics. For conventional descriptive purposes, measurement to the nearest centimetre has been considered satisfactory. Much more precise measurement is possible in assessment of transient intra-individual changes if the subject's posture is finely controlled whilst observations are being made. Compressive loading of the spine causes a reduction in the length of the spinal column which is reflected in changes in stature and is referred to as shrinkage. The spinal column represents approximately 40% of the total body length, the intervertebral discs occupying about one-third of the spine's overall length. As the spine is subjected to compressive forces, the discs lose height due to fluid being eliminated from their nucleus pulposus. As explained earlier, this occurs once the applied load exceeds the sum of the imbibition pressure of the nucleus pulposus complex and the osmotic gradient across the disc membranes. In addition to fluid exchange, extension and contraction of the fibres of the disc's annulus fibrosus are also implicated in disc height losses. Changes within the spinal column are largely responsible for the shrinkage in stature, alteration in other anatomical structures being thought negligible. The amount of shrinkage is related to the magnitude of the compressive load on the spine: consequently shrinkage has been used as an index of spinal loading (Corlett et al., 1987). Changes in total body length have been employed to examine the effects of physical regimens that load the spine. Additionally the technique has been used to evaluate manoeuvres for unloading the spine such as traction, gravity inversion, and the so-called Fowler position - supine posture, feet supported on a chair, hip at about 45°flexion (Boocock et al, 1988). 4. Measurement of spinal shrinkage Special apparatus which allows intra-individual variation in spinal configuration to be accommodated and intra-individual postures to be reproduced accurately under relaxed conditions has been developed (Corlett et al., 1987). Relaxation is achieved by inclining the subject backwards by up to 15°. Design features control the position of and contour of the spinal curves, position of head and limbs, head angle in the sagittal plane, and weight distribution between heels and forefoot. The phase of the respiratory cycle is also controlled, after subjects have been given a brief training session to accustom them to the apparatus. The apparatus used at Nottingham, Linkoping, Helsinki and Liverpool differs in minor respects, but measurement error reported in each laboratory is small (Corlett et al., 1987; Reilly et al., 1991). The standard practice is to commence experimental work only when subjects can produce 10 consecutive measurements of alteration in

T. Reilly / Measurement of Spinal Loading: Shrinkage

stature with a standard deviation of less than 0.5 mm. Earlier versions of the stadiometer were described by Tyrrell et al. (1985) and Boocock et al. (1986). The system currently used at Liverpool (see Figure 2) employs a microcomputer for calibration purposes, for controlling the measurement protocol, and finally for recording observations.

Figure 2. The subject is positioned on the precision stadiometer. The body is tilted to facilitate relaxation and measurements are automatically recorded at the end of a respiratory cycle.

The central pillar, supported by an aluminium framework, possesses adjustable rods and plates activating on micro-switches. These are used to contact and record prominent points including buttocks, lumbar and cervical curves, mid-scapulae and head. An electronic weighing scale is set into the base to monitor equal weight distribution through both feet. Head alignment is standardised by use of an infra-red emitter on spectacles worn by the subject and an infra-red receiver set into an adjustable panel in front of the subject's face. The panel also has five light-emitting diodes (LEDs) activated by the microswitches. The LEDs give feedback of the required posture to the subject and measurement automatically proceeds when all seven (including one for weight and one linked to the head aligning device) are illuminated. A plastic disc, 150 mm in diameter, resting carefully on top of the subject's head, is connected to a vertical rod. This device can be located at various positions on the main frame to accommodate persons of various height, each time allowing up to 50 mm of travel. The rod activates upon a Mercer dial gauge having a precision of 0.01 mm. Two strain gauges on opposite faces of a spring travelling on the upper surface

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of the disc are fed with current from an electronic amplifier and convert vertical displacement into an electrical signal. The change in voltage passing through the strain gauge is linearly related to vertical displacement of the head disc. The voltage signal is passed to a microcomputer for A-D conversion. The computer displays, processes and stores the data on floppy disk. Quality control of data collection is incorporated into the computer program during subjects' first introduction to the procedure in which it is established that repeatable measurement is obtainable (standard deviation of less than 0.5 mm). Later, it is achieved by means of the procedure already explained. An alternative approach has been to correct for the normal diurnal variation that occurs during the day in cases where changes in stature are monitored over long work-shifts (Althoff et al, 1992). This research group also tried to eliminate any problem in controlling the position of the head by measuring changes in a landmark positioned in the subject's neck (1.5 cm above C7). The training programmes described above are usually sufficient to guarantee quality control of measurements with pre-set head positions.

5. Industrial applications Measurements of spinal shrinkage are non-invasive and give a good indication of the load on the spine without disturbing the subject or his/her working environment. Measures are taken before and on completion of the work task and therefore have advantages over invasive techniques. The stadiometer, used to measure shrinkage, is relatively easy to transport and assemble, and can be used in virtually any setting which may be of interest to the ergonomist. However, because of inter-individual differences such as age, spinal length and so on, each subject must be used as his/her own control. Fitzgerald (1972) realised that the creep effect characteristics of the intervertebral discs under conditions of loading, were reflected in loss of stature. He studied the effect of postural loads on healthy young male adults, having been concerned over the incidence of back pain symptoms in aircraft pilots. His findings showed that shrinkage was related to the magnitude of the load. Eklund and Corlett (1984) evaluated changes in posture under three seating conditions: a stool without a back-rest, an office chair with a back-rest and an easy chair. The subjects were seated for 1.5 h. The mean loss in stature on the stool was 4.6 mm and negligible for the two other conditions. On sitting whilst applying a horizontal pushing force of 25 N with alternate hands for 30 min, with and without a back-rest, it was shown that with a back-rest height was gained while without it height was lost. Eklund and Corlett also investigated the effect of a chair with a high backrest (38 cm) and a chair with a low lumbar support (18 cm), on a 45-min, two-handed pushing task (force 25 N). The chair with the high back-rest caused significantly less shrinkage than the lumbar support chair, 0.66 mm and 1.37 mm respectively, and was therefore deemed the better. Eklund et al. (1987) used spinal shrinkage to evaluate chair design and seated work tasks in conjunction with measures of biomechanical load, posture and discomfort evaluation, both in the field and in the laboratory. Shrinkage measurements correlated well with the other methods employed as indices of spinal loading in the workplace. The tasks observed included forward force development, assembly work with restricted knee room, vision to one side, grinding and press punch

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work. Generally, it was found that the more flexion a posture involved the greater the biomechanical load on the spine, the greater the discomfort and the greater the shrinkage. For the forward force development task a low back-rest seat caused greater shrinkage than the high back-rest (1.37 mm to 0.66 mm, respectively), as was the case for the grinding work (2.41 mm to 0.93 mm, respectively). In punch press work, however, height was gained with both the conventional and sit-stool seats (0.19 mm and -0.48 mm, respectively). These results have demonstrated that simple alterations to the workplace based on sound ergonomic evaluation using spinal shrinkage measurements, can greatly affect the load imposed on the spine. The potential health effects with respect to the low back of office chairs with a moveable seat and back rest were examined by van Dieen and co-workers (2001). In this instance a gain in stature was deemed to be a positive influence of the chair design. There was a large stature gain when using two dynamic chairs (one with a seat and back rest moveable in a fixed ratio with respect to each other, and another with a freely moveable seat and back rest) compared to responses when working on a chair with fixed seat and back rest. The observations suggest that dynamic office chairs offer a potential advantage over fixed chairs. Foreman and Troup (1987) also demonstrated the use of the stadiometer in workplace evaluation. They measured changes in stature in conjunction with a computerised activity coding system, to investigate diurnal variations in spinal loading and the effects on stature of nursing activities. The probability of experiencing back pain in nursing is related to patient handling. Young nurses in their first practical year are most at risk and ergonomic intervention may be necessary to reduce this. Precision stadiometry has also been used in comparing the effects of different work-shifts. The relation between shrinkage and activity was investigated under three conditions: a work day on 'early' shift, a work day on 'late' shift and a 12-h period during a day off. The mean loss of stature (n = 11) across the early shift was 10.2 (+SD - 2.8) mm and 9.8 (+SD = 3.8) mm across the late shift, although the difference was not significant. The mean total shrinkage during a 12-h period on the day off was 8.14 (+SD = 3.35) mm. As expected the duration for which the spine was 'offloaded' was inversely related to loss of stature. During the late shift a significant relationship was found between loss of stature and total lifting duration (r = 0.66) and loss of stature and the duration of "lean/stoop" postures (r = 0.57). In the early shift the durations of "lean/stoop" and lifting activities were related to loss of stature. These studies show that the stadiometer is a useful tool for the ergonomist involved in work-place design who wishes to reduce spinal loading. Shrinkage measures are of value in assessing and re-designing work furniture or testing working practices. Its value is most appreciated when used in conjunction with information on preceding activities, subjective psychophysiological ratings of discomfort or exertion and biomechanical loading. The studies reviewed here have implications for the assessment of workload from stature measures, and illustrate how stadiometry can be a valuable tool in designing workplaces, equipment and working practices. Similarly, sports scientists may be able to devise training schedules for athletes which decrease the load on the spine. In both the work-place and the gymnasium it may be possible to reduce the effects of spinal loading by adopting specific practices, either pre-exercise or in post-exercise recovery.

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6. Weight training Static shoulder loads using rucksack and barbells have been examined by Tyrrell et al. (1985). Observations were made at 2-min intervals during 20 min of experimental loading, measurement taking about 2 min. Shrinkage of 5.45 mm was incurred with the 10-kg rucksack and 5.14 mm with the barbell. Shrinkage increased with increased barbell loading to 7.11 mm (20 kg), 9.42 mm (30 kg) and 11.2 mm (40 kg). The data indicated a linear relationship between shrinkage and external load (see Table 1). Dynamic loading, induced by lifting a barbell (from floor using weight-lifter's crouch position to knuckle height standing) 12 times per minute for 20 min, produced a greater shrinkage than static loading. This difference was 3.3 mm for a 40-kg load. Table 1. Mean (+SD) loss in height due to experimental static loading of the spine.

Static load

Height loss (mm)

2.5-kg rucksack

3.87 + 1.98

10-kg rucksack

5.45 + 2.12

10-kg barbell

5.14+1.99

20-kg barbell

7.11+3.18

30-kg barbell

9.42 + 3.57

40-kg barbell

11.2 + 4.60

Circuit weight-training, as employed for stressing the oxygen transport system rather than muscle conditioning, has also been examined. Nine males rotating around nine exercise stations for 25 min were found to lose on average 5.49 mm in stature (Leatt et al., 1986). The weights varied from 14 to 32 kg for the different exercises. A comparison of results with those of Tyrrell et al. (1985), who found shrinkage of 7.11 mm with 20-kg dynamic loading over 20 min, would suggest that the strain on the spine may have been eased by some of the exercises in the circuit. However, the data may not be directly comparable due to the manual control of the procedures and the more primitive apparatus used in the pioneering work of Tyrrell et al. (1985). Ten female subjects repeating a sequence of eight weight-training exercises for 20 min were examined by Wilby et al (1987). The regimen was performed immediately after rising from sleep and in the evening at 22:00 hours. A greater loss of height was observed in the morning than in the evening, mean values being 5.4 and 4.33 mm, respectively. This difference was attributed to the diurnal variation in stature. The rate of change in stature varies throughout the day, being greatest in the morning, whereas disc imbibition and recovery are rapid in the early hours of sleep. A diurnal peak-to-trough variation in stature of 15.4 mm and 19.3 mm has been shown for females (Wilby et al., 1987) and males (Reilly et al., 1984), respectively. Regaining height during recovery in a relaxed standing posture after weighttraining has been found, in general, to be proportional to loading. Between 74-79% of the losses incurred in static loading were regained within 10 min in the study of

T. Reilly / Measurement of Spinal Loading: Shrinkage

Tyrrell et al. (1985). The height regained in Fowler's position in a similar period in fact exceeded the height lost during loading. McGill et al. (1996) compared the effects of holding a static load (15.3 kg) for 20 min with dynamic lifting. After 20 min on the dynamic task the mean shrinkage was 1.23 mm compared with 2.16 mm in the static load condition. There was a large variability in the subjects' responses to loading. Althoff et al. (1992) undertook a series of measurements on subjects using shoulder loads up to 30 kg. Spinal shrinkage was proportional to the load applied on the spine. Again there was a large inter-subject variability, attributed by the authors to individual differences in cross-sectional area of the disc. Subjects with small disc dimensions would incur a greater spinal shrinkage than those with larger discs. The effects of different external load conditions on spinal shrinkage were examined by Reilly and Peden (1989). On three separate days, six females performed i) 10 min stepping onto a bench 30 cm high without load; ii) the same activity with 10 kg and 15 kg carried on the back; iii) the same task but with a load of 15 kg on the back. Mean shrinkage at the end of the unloaded condition was 1.1 mm. There was a significant increase in shrinkage at 10 min in both conditions with 15 kg-load (front bag 2.79 mm; back bag 2.78 mm). It was suggested that tasks such as repeated bench stepping performed with external load above 16% body mass may increase the risk of back injury. Weightlifting belts are available commercially and marketed with the aim of preventing back injuries whilst lifting heavy weights. It is believed that they do so by helping to support and stabilise the spine. They may also have an effect on intraabdominal pressure, the mechanism widely held responsible for reducing spinal compressive forces. Bourne and Reilly (1991) examined the effect of a weightlifting belt on spinal shrinkage in subjects performing a circuit weight-training session. Wearing the belt tended to induce less spinal shrinkage and caused significantly less discomfort compared to lifting without a belt. The observations suggested there were potential benefits in wearing a weightlifting belt and supported the hypothesis that the belt helps in stabilising the trunk. The work on the protective effects of wearing a belt during weightlifting was extended by Reilly and Davies (1995). They examined the efficacy of a weighlifter's belt in attenuating spinal shrinkage during multiple repetitions of the 'dead-lift'. A further aim was to examine the relationship between shrinkage and the estimated cross-sectional area of the lumbar discs. The subjects performed 8 sets of 20 repetitions of the dead-lift with 10 kg on an Olympic bar. This was done on two separate occasions, once whilst wearing a belt and once without the belt. The crosssectional area of the L3-L4, L4-L5 and L5-S1 discs was estimated using the anthropometric procedure of Colombini et al. (1989). Shrinkage without the belt was 4.08+ 1.28 mm compared to 2.08 + 0.05 mm with the belt: corresponding values for perceived exertion were 16.2 + 1.6 and 13.4 + 1.3. It was concluded that wearing a weightlifter's belt was effective in reducing spinal loading during multiple repetitions of the dead-lift. The magnitude of shrinkage incurred was related both to body mass and lumbar disc area. The decrease in shrinkage associated with wearing a belt was significantly related to body mass but not to estimated lumbar disc area.

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7. Running and jumping 7.1 Running exercises Running, particularly on road surfaces, induces repetitive loading of the spine. Shrinkage in experienced and novice runners exercising on a treadmill at 12.2 km.h"1 for 30 min was examined by Leatt et al. (1986). Loss of stature amounted to 2.35 mm for the experienced group and was 3.26 mm for the other, the difference being nonsignificant. The experienced runners did a further 19 km at 14.6 km.h"1 and lost another 7.79 mm on average. It appeared that the duration of the run was an important factor. Effects of running continuously at 10 km.h'1 for 40 min have been compared with those due to alternating a fast and slow pace regularly over the same time and covering the same overall distance. The pace fluctuated between jogging at 7 km.h"1 and 21 km.h"1 sprints. No significant difference was found between the intermittent and the continuous running in terms of spinal shrinkage, once the distance and duration of exercise were matched (Reilly et a/., 1988). The influence of running intensity on shrinkage was examined by Garbutt et al. (1989). Five male runners did three 30-min runs at 70%, 85% and 100% of their competitive marathon pace. In the first 15 min, mean losses of stature were 4.25, 3.37 and 3.97 mm for the intensities increasing from half-marathon to 10-km race pace. The influence of the quality of the running shoe on shrinkage may be important but this has yet to be investigated. In a subsequent study, Garbutt et al. (1990) examined the effect of three running speeds on two groups of runners, one with chronic low-back pain. The two groups of seven male marathon runners exercised at 70%, 85% and 100% of their marathon race pace for 30 min on separate occasions. Before and after exercise the subjects were seated for 20 min with the lumbar spine supported. Stature was measured before preexercise sitting, before running, after 15 min of running, after 30 min of running and after post-exercise sitting. There were no significant differences in the responses to the three running regimens between the groups. Shrinkage was significantly greater in the first 15 min, being 3.26 (± 2.78) mm compared with 2.12 (± 1.61) mm for the second half of the run. The faster the running speed, the greater was the resultant shrinkage. The 70%, 85% and 100% conditions caused 3.37 (± 2.38), 5.10 (± 1.90) and 7.69 (± 3.69) mm of shrinkage respectively. These observations suggest that in this group of runners who were able to maintain their training despite continuing back pain, low-back pain was independent of the shrinkage induced by running. Further research was recommended to determine the effects of longer duration runs on spinal shrinkage. Dowzer et al. (1998) used spinal shrinkage to evaluate the benefits of deep-water running in reducing impact loading on the skeleton. Running in deep water caused significantly lower shrinkage (2.92 mm) than running in shallow water (5.51 mm) when the feet touch the swimming pool floor, or running on a treadmill (4.59 mm). These values were incurred over 30 min, but the higher rates of shrinkage were found in the first 15 min in all the conditions. 7.2 Jumping exercises Jumping and bounding exercises have been increasingly implemented in training regimens to develop leg power. Landing from such exercises induces high impact

T. Reilly / Measurement of Spinal Loading: Shrinkage

forces which the human body must seek to absorb. The intervertebral disc is the principal shock absorber of the spine responsible for dissipating these high forces. Shrinkage measurements have been employed to study the spinal loading resulting from such jumping and bounding exercises. A regimen of ten sets of five standing broad jumps with 15-s recovery between each set, lasting on average 6.7 min, was found to cause a mean loss in stature of 1.7 mm (Boocock et al., 1988). To assess the potential of unloading the spine pre-exercise, thereby increasing the discs' functional ability to absorb compressive loading, a 10-min period of gravity inversion was undertaken prior to the same exercise period. Inverting the subject at 50° has been found to increase stature more than a 90° inclination, which in turn was superior to the Fowler position (Leatt et al, 1985). The unloading period caused a mean increase in stature of 2.7 mm and the resulting exercise period when performed immediately after inversion induced twice the magnitude of shrinkage, 3.5 mm. It was concluded that the benefits gained by spinal unloading pre-exercise are shortlasting. Similarly, drop-jumping exercises, which involve athletes dropping from a predetermined height and performing a rebound jump immediately on landing, have been noted to induce shrinkage. Five sets of five drop-jumps from a height of 1 m, rebounding over a hurdle 0.5 m high, caused a mean loss in stature of 1.74 mm (Boocock et al, 1990). On this occasion, post-exercise unloading was investigated with a 20-m gravity inversion period directly following the exercise session. This inversion period caused an increase in stature of 5.18 mm compared with 0.76 mm from a standing period of similar duration. Stature was maintained for a further 40 min in which subjects stood. During the 40 min following inversion there was a rapid loss in stature of 4.07 mm. For the session involving standing post-exercise this same period caused little alteration in stature, 0.04 mm. It was noted that 30 min into this 40-min recovery period there was no significant difference for stature alterations between the two experimental conditions. It was again concluded that the effects of unloading are only short-lived. Further, it should be recognised that in some people a rapid regain in stature on unloading may adversely affect the dynamic response characteristics of the spine. If major exertion is undertaken immediately the restperiod is ended, a brief warm-up may be advisable. Fowler et al (1994) compared the effects of drop-jumping with an 8.5-kg load added in a weighted vest. Shrinkage of 0.62 mm in unloaded drop-jumping was increased to 2.14 mm when the weighted vest was added. Furthermore, the rate of force loading rose from 20742 N.s"1 when the weighted vest was used. The results reflected the greater physical stress of loaded drop-jumping compared to the same exercise without external load. Plyometric exercises such as drop-jumping give rise to high impact forces and therefore a high spinal loading (Boocock et al, 1990). Since this form of plyometric exercise is potentially injurious to the back, alternative modes of exercise that reduce this risk but provide the same stretch-shortening stimulus for muscle training is discernible. The pendulum swing provides such an alternative, whereby the athlete is positioned seated in a swing and directly in front of a vertical rebound surface. The athlete swings forwards and backwards on the pendulum, rebounding against this vertical surface. Fowler et al. (1995) showed that the device offers a significant training stimulus. Later the same group showed that the pendulum swing reduces the loading of the spine compared to drop-jumping exercises (Fowler et al, 1997). Based on lower shrinkage results and lower peak forces, it was concluded that the pendulum

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exercises pose a lower injury potential to the back than do drop-jumps performed from a typical height of 28 cm.

8. Other applications to physical activity There are many types of physical activity, whether in recreational or occupational contexts, where there is a high prevalence of back pain. Common among these is loading on the spine, irrespective of whether imposed by manual handling, weightlifting and carrying, twisting or working too long in an inappropriate posture. Golf is a recreational activity where players carry their golf clubs around the course. Wallace and Reilly (1993) simulated an 18-hole round of golf in a laboratory study. Three conditions investigated were i) walking the course without playing; ii) walking and playing (without bag); iii) walking and playing carrying an 8-kg golf bag. The walking condition caused a smaller spinal shrinkage (3.58 mm) than playing (4.98 mm) and playing combined with carrying the golf bag (5.82 mm). It was suggested that the high incidence of low-back pain in golf players may be associated not only with compressive loading but also with high shear forces produced during the golf swing. In view of the responsiveness of spinal shrinkage to load carrying, the technique has been employed in evaluating new mail-bag designs for postal deliveries. Parsons et al. (1994) compared three new designs with the existing pouch mail-bag in laboratory-based and field trials. The use of spinal shrinkage was combined with biomechanical, physiological and perceptual (subjective) responses. The combination of techniques was useful in interpreting the overall results and in highlighting the particular benefits of the individual designs. Spinal loading is implicated in the aetiology of back injury in cricket. Reilly and Ghana (1994) used spinal shrinkage to identify specific consequences for the spine of fast bowling. Bowling every 30 s for 30 min caused a shrinkage of 2.30 mm compared to 0.29 mm when a run-up without a delivery was employed. The results indicated that the delivery rather than the run-up is the main cause of spinal shrinkage in cricket bowling. A gravity inversion regimen pre-exercise was found to have a likely protective role in such practice conditions. Field invasive games such as hockey make unique physiological and physical demands on players. Playing and dribbling the ball are usually executed in a position of spinal flexion. Evidence of the physical strain on the spine during field hockey was provided by Cannon and James (1984) who reported that over a 4-year period 7.6% of patients referred to a clinic for athletes suffering from back pain were hockey players. Reilly and Seaton (1990) observed an average shrinkage rate of 0.4 mm.min"1 in players dribbling a hockey ball in a laboratory simulation, a value greater than previously reported for other activities. They concluded that the peculiar postural requirements of the game caused physiological strain (indicated by oxygen consumption and heart rate) and spinal loading in excess of orthodox locomotion. Later Reilly and Temple (1993) demonstrated that an enhanced crouched position when dribbling accentuated the subjective and physical strain on the spine. Their observations suggested that the strength of the back muscles may have a protective function in such conditions. Many current guidelines for lifting in industrial work are tailored to static and sagittally symmetric postures, yet the majority of tasks associated with manual materials handling have asymmetric components. There is evidence that low-back

T. Reilly /Measurement of Spinal Loading: Shrinkage

disorders are related to lateral bending, axial twisting and awkward postures (Marras et al., 1993). Au et al. (2001) analysed the spinal shrinkage due to repetitive exertions confined to each of three separate axes (twist, lateral bend, flexion). The experiment was performed twice with small technique modifications in the twisting task (and thus two data collections were performed). Subjects performed each task for 20 min at 10 repetitions min"1, where stadiometer measurements of standing height were taken prior to and immediately following the 20-min exertion. The twisting task demonstrated significant spinal shrinkage (1.81 and 3.2 mm in the two experiments) while no clear effect emerged for the other two tasks. These data suggest that repetitive torsional motions impose a larger cumulative loading on the spine when compared with controlled lateral or flexion motion tasks of a similar moment. 9. Overview Spinal shrinkage as indicated by computer-aided precision stadiometry has been employed in a range of contexts as an index of the load on the spine. This use has focussed on activities in which there is an apparent risk of musculoskeletal disease. These circumstances have included occupational settings and recreational or habitual activities. Precision stadiometry has been applied also with a view to accomplishing an ergonomic re-design of the work-place. Such applications have included experimental and biomechanical analyses of industrial seat design (Eklund and Corlett, 1986) and evaluation of board sailing harnesses (Reilly et al, 1993). The technique has also been used in monitoring recovery of the spine when loading is released. Various possibilities for accelerating the recovery of the spine during its unloading have been employed. These include adoption of the Fowler position, a seated recovery or use of gravity inversion devices with the subject suspended by the ankles (Leatt et al., 1985). The conventional approach towards relieving musculoskeletal strain is to examine the ratio between work and recovery breaks. Within the current Biomed IV project, the optimisation of the work to rest ratio is a key topic of investigation. References Althoff, I., Brinkmann, P., Forbin, W., Sandover, J. and Burton, K. (1992). An improved method of stature measurement for quantitative determination of spinal loading. Spine, 17, 682-693. Au, G., Cook, J. and McGill, S. M. (2001). Spinal shrinkage during repetitive controlled torsion, flexion and lateral bend motion. Ergonomics, 44, 373-381. Boocock, M. G., Reilly, T., Linge, K. and Troup, J. D. G. (1986). Fine measurements of stature for measuring spinal loading. In: Kinanthropometry III (eds T. Reilly and J. Watkins), pp. 98-103. London: E.and F. N. Spon. Boocock, M. G., Garbutt, G., Reilly, T., Linge, K. and Troup, J. D. G. (1988). The effects of gravity inversion on exercise-induced spinal loading. Ergonomics, 31, 1631-1637. Boocock, M. G., Garbutt, , G., Linge, K., Reilly, T. and Troup, J. D. G. (1990). Changes in stature following drop-jumping and post-exercise gravity inversion. Medicine and Science in Sports and Exercise, 22, 385-390. Bourne, N. D. and Reilly, T. (1991). Effect of a weightlifting belt on spinal shrinkage. British Journal of Sports Medicine, 25, 209-212. Cannon, S. R. and James, S. E. (1984). Back pain in athletes. British Journal of Sports Medicine, 18, 159-164.

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Colombini, D., Occhipinti, E., Grieco, A. and Faccini, M. (1989). Estimation of lumbar disc area by means of anthropometric parameters. Spine, 14, 51-55. Corlett, E. N., Eklund, J. A. E., Reilly, T. and Troup, J. D. G. (1987). Assessment of workload from measurement of stature. Applied Ergonomics, 18, 65-71. Dowzer, C. N., Reilly, T. and Cable, N. T. (1988). Effect of deep and shallow water running on spinal shrinkage. British Journal of Sports Medicine, 32,44-48. Eklund, J. and Corlett, E. N. (1984). Shrinkage as a measure of load on the spine. Spine, 9, 189-194. Eklund, J. A. E. and Corlett, E. N. (1986). Experimental and biomechanical analysis of seating. In: The Ergonomics of Working Postures: Models, Methods and Cases. London: Taylor and Francis. Eklund, J. A. E., Ortengren, R. and Corlett, E. N. (1987). A biomechanical model for evaluation of spinal loads in seated work tasks. In: Biomechanics X-B (ed. B. Jonsson). Champaign, III: Human Kinetics. Fitzgerald, J. G. (1972). Changes in spinal stature following brief period of shoulder loading. Institute of Aviation Medicine, Report No. 514, Famborough. Foreman, T. K. and Troup, J. D. G. (1987). Diurnal variation in spinal loading and the effects on stature: a preliminary study of nursing activities. Clinical Biomechanics, 2,48-54. Fowler, N. E., Lees, A. and Reilly, T. (1994). Spinal shrinkage in unloaded and loaded drop-jumping. Ergonomics, 37, 133-139. Fowler, N. E. Trzaskoma, Z., Wit, A., Iskra, L. and Lees, A. (1995). The effectiveness of a pendulum swing for the development of leg strength and counter-movement jump performance. Journal of Sports Sciences, 13, 101-108. Fowler, N., Lees, A. and Reilly, T. (1997). Changes in stature following plyometric drop-jump and pendulum exercises. Ergonomics, 40,1279-1286. Garbutt, G., Boocock, M. G., Reilly, T. and Troup, J. D. G. (1989). The effect of running speed on spinal shrinkage. Journal of Sports Sciences, 1,11. Garbutt, G., Boocock, M. G., Reilly, T. and Troup, J. D. G. (1990). Running speed and spinal shrinkage in runners with and without low back pain. Medicine and Science in Sports and Exercise, 22, 769-772. Kazarian, L. E. (1975). Creep characteristics of the human spinal column. Orthopaedic Clinics of North America, 6, 3-18. Koeller, W., Funke, F. and Hartman, F. (1984). Biomechanical behaviour of human invertebrate discs subjected to long lasting axial loadings. Biorheology, 21, 175-186. Kramer, J. (1985). Dynamic characteristics of the vertebral column, effects of prolonged loading. Ergonomics, 28, 95-97. Leatt, P., Reilly, T. and Troup, J. D. G. (1985). Unloading the spine. In: Contemporary Ergonomics 1985 (ed. D. Oborne), pp. 227-232. London : Taylor and Francis. Leatt, P., Reilly, T. and Troup, J. D. G. (1986) Spinal loading during circuit weight-training and running. British Journal of 'Sports Medicine, 20, 119-124. Marras, W. S., Lavender, S. A., Leurgens, S. E., Rajulu, S. L., Allread, W. G. and Fathallah, F. A. (1993). The role of dynamic three-dimensional trunk motion in occupationally-related low-back disorders: the effects of workplace factors, trunk position and trunk motion characteristics on risk of injury. Spine, 18, 617-628. Marras, W. S., Lavender, S. A., Leurgens, S. E., Fathallah, F. A., Ferguson, S. A., Allread, W. G. and Rajulu, S. L. (1995). Biomechanical risk factors for occupationally related low-back disorders. Ergonomics, 38, 377-410. McGill, S. M., Van Wijk, M. J., Axler, C. T. and Gletsu, M. (1996). Studies of spinal shrinkage to evaluate low-back loading in the workplace. Ergonomics, 39, 92-102. Parsons, C., Atkinson, G., Doggart, L., Lees, A. and Reilly, T. (1994). Evaluation of new mail delivery bag design. In: Contemporary Ergonomics 1994 (ed. S. A. Robertson), pp. 236-240. London: Taylor and Francis. Reilly, T., Tyrrell, A. and Troup, J. D. G. (1984). Circadian variation in human stature. Chronobiology International, 1, 121-126. Reilly, T., Grant, R. Linge, K. and Troup, J. D. G. (1988). Spinal shrinkage during treadmill running. Abstarcts: New Horizons in Human Movement Vol. Ill, p. 142, Cheonan: SOSCOC. Reilly, T. and Peden, F. (1989). Investigation of external weight loading in females. Journal of Human Movement Studies, 17, 165-172. Reilly, T. and Seaton, A. (1990). Physiological strain unique to field hockey. Journal of Sports Medicine and Physical Fitness, 30, 142-146. Reilly, T., Boocock, M. G., Garbutt, G., Troup, J. D. G. and Linge, K. (1991). Changes in stature during exercise and sports training. Applied Ergonomics, 22, 308-311.

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Reilly, T., Brymer, E. and Townend, M. S. (1993). An ergonomic evaluation of boardsailing harnesses. In: Contemporary Ergonomics 1993 (edited by E. J. Lovesey), pp. 445-450. London : Taylor and Francis. Reilly, T. and Temple, J. (1993). Some ergonomic consequences of playing field hockey. In: Contemporary Ergonomics (ed. E. J. Lovesey), pp. 441-444. London: Taylor and Francis. Reilly, T. and Ghana, D. (1994). Spinal shrinkage in fast bowling. Ergonomics, 37, 127-132. Reilly, T., and Davies, S. (1995). Effects of a weightlifting belt on spinal loading during performance of a dead-lift. In: Sport, Leisure and Ergonomics (edited by G. Atkinson and T. Reilly), pp. 136139. London: Taylor and Francis. Tyrrell, A. R., Reilly, T. and Troup, J. D. G. (1985). Circadian variation in stature and the effects of spinal loading. Spine, 10,161-164. Van Dieen, J. H., De Looze, M. P. and Hermans, V. (2001). Effects of dynamic office chairs on trink kinematics, trunk extensor EMG and spinal shrinkage. Ergonomics, 44, 739-750. Wallace, P. and Reilly, T. (1993). Spinal and metabolic loading simulations of golf play. Journal of Sports Sciences, 11,511-515. Wilby, J., Linge, K., Reilly, T. and Troup, J. D. G. (1987). Spinal shrinkage in females: circadian variation and the effects of circuit weight-training. Ergonomics, 30,47-54.

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Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

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EPIDEMIOLOGY: MUSCULOSKELETAL PROBLEMS IN BELGIAN NURSES Evert Zinzen Vrije Universiteit Brussel Dept. Experimental Anatomy Laarbeeklaan 103, 1090 Brussels Belgium

Abstract The purpose of this chapter is to give an overview of all epidemiological aspects of the nursing profession in Belgium and relate them to musculoskeletal problems in general and to low-back problems (LBP) in particular. To achieve this goal, a whole new booklet composed of different existing validated questionnaires was used. The reliability and validity of this new measuring instrument emerged as very good. About 270 questions were analysed regarding professional items, health items (physical and psychological), musculoskeletal items, work-place items and personal items. A lot of variables showed a relation with low-back problems, leading to the conclusion that back pain has a multiplicity of causes and needs a multidisciplinary approach in prevention. This multiplicity makes it also impossible to define LBP as a professional disease.

1. Introduction and purpose When thinking of musculoskeletal problems in nursing personnel, low-back problems (LBP) immediately come to mind. This is not a surprise since these problems were already being investigated in the 16th century. It is commonly accepted that 50 to 80% of the population suffers at least once from LBP in their lifetime. Many studies have shown that nurses in particular are at high risk (Dehlin et al., 1976; Videman et al., 1984; Leighton and Reilly, 1995). The only study found on hospital nurses in Belgium mentions a lifetime prevalence of 65% for males and 73% for females (Stappaerts, 1989a and 1989b). Difficulties in comparing studies may arise since definitions of low-back problems may differ and moreover the incidence or prevalence rates often vary. Therefore it is important to clarify the research area by giving clear definitions.

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Some research teams have used objective criteria such as bulging discs, bone deformations, and so on to classify patients (e.g. Dehlin et al., 1976) or symptom classifications such as made by the "Quebec Task Force" (Spitzer et al., 1987). These ways of defining low-back problems are very useful when working in a patient surrounding and will certainly help to state a diagnosis and provide the necessary information for a treatment. However, in 50 to 80% of LBP cases the problem disappears without intervention in 7 to 35 days and in a large amount of the cases there is no pathological reason for the problems (Buckle, 1987; Spitzer et al., 1987; Frymoyer and Andersson, 1991; Oostendorp et al., 1997). This means that in epidemiological studies, the use of these kinds of definitions will not include the so-called "idiopathic" back problem sufferers. There is not one "golden" definition of low-back problems. The only constant factor is pain and that is in itself a very subjective item (Janzen, 1981; Anderson, 1986; Buckle, 1987; Pope et al., 1991). That way it will always be impossible to validate LBP objectively and the problem should therefore be approached in a pragmatic way (Wood and Badley, 1980). Since the purpose of this research is to get a total overview of the epidemiology of musculoskeletal problems, LBP in particular, the following definition is used throughout this chapter: "having experienced discomfort such as acute pain, stiffness, cramps, chronic pain or other discomfort which has lasted more then one day in the low-back region ". The second purpose of this work is to determine if LBP can be considered as a "professional disease". To comply with Belgian law, LBP must be solely due to work-related influences.

2. Literature overview 2.1 Relation between work circumstances and low-back problems It is generally accepted that musculoskeletal problems in the work-place are often related to acute or chronic overload injuries including factors such as age, tiredness and psychosocial stressors. The musculoskeletal problem will arise when the load/loadabilitiy equilibrium of the human body is disturbed (Zijlstra, 1989; Pope et al., 1991). According to Biering-Sorenson (1985) overload injuries related to lifting patients in a hospital situation can explain for 42% of LBP in nursing personnel. Others are more careful but all agree that these kinds of overload injuries are important contributors to LBP in nursing personnel (Abenheim and Suissa, 1987; Andersson, 1990, Frymoyer and Andersson, 1991). Bad postures during the work tasks are described as having a negative influence on LBP also. Engels and co-workers (1994) used the "Ovako Working posture Analysis System" or OWAS to categorise the postures in nursing personnel. They found that for about 20% of the time nurses were in dangerous postures. It was remarkable that these dangerous postures occurred not only during patient-related tasks but also during administrative tasks. Other studies have indicated that the most heavy tasks in descending order for nurses are related to helping the patients in and out of bed, nursing the patient in bed (washing, putting bandages), tasks at the bed without a patient (putting new sheets on), medical/technical tasks (preparing pills, infusions, and so on) and administration (Stobbe

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et al., 1988; Garg et al., 1992; Knibbe and Friele, 1996; Caboor et al, 1997). These heavy tasks are performed most frequently in the Orthopaedics Department, or in the General Medicine department and in the Operation Room (Leighton and Reilly, 1995). Chaffin and co-workers (1991) produced a classification protocol to determine the heaviness of a job by the frequency and the load workers have to lift. According to this table, the nursing profession is completely excluded since very heavy work was defined as lifting (once) 50 kg or lifting (frequently) 25 kg. Although Frymoyer et al. (1980), De Gaudemaris et al. (1986) and Riihimaki et al. (1989) found a relation between the prevalence of LBP and the heaviness of the nursing job, Bigos et al. (1992) and Porter et al. (1989) could not confirm this relationship. Skovron et al. (1987a and b) concluded that there must be other factors (in and outside the work-place) causing low-back problems. Williamson and co-workers (1994) looked at the influence of long working shifts on LBP, Kurumatani et al. (1994) discussed the alternation of night and day shifts and Ryden et al. (1989) investigated the differences in prevalence rates of LBP in morning-, evening and nightshifts. They all came basically to the same conclusion : it is important to avoid tiredness since being tired increases the risk of LBP. Work satisfaction is another factor often mentioned in the literature. A low level of it would increase the risk of LBP (Taylor, 1968; Bergenudd and Nilsson, 1988; Bigos et al., 1992). Psychological factors such as hysteria, hypochondriasis, somatising and depression are according to Andersson and Pope (1991) and Southwick and White (1983) important in the development and healing of LBP. Waddell et al. (1993) and Main and Waddell (1991) pointed out that fear avoidance beliefs towards work and physical activity are very high among LBP sufferers. They also noted that LBP patients often possessed bad coping strategies. The "Pain, Activity and Work" questionnaire has proven that LBP-sufferers are more negative about pain, work and activity (Burton et al., 1997). Battie et al. (1989) concluded from their study in the Boeing factory that psychological factors are a much greater risk in the development of LBP than purely physical factors. Other work-circumstance factors related to LBP, but more rarely mentioned in literature, are the patients/nurse ratio (Larese and Fiorito, 1994) and the distance between home and the hospital (Caillard et al., 1987). 2.2 Relation between personal factors and low-back problems Age is one of the most often discussed personal factors in relation to LBP. In general most investigators support a bimodal model with a high incidence of LBP between the age of 15 and 24 years and a second episode between the ages of 35 and 55 (Nachemson, 1971; Biering-Sorenson, 1982; Svensson and Andersson, 1983; Abenheim and Suissa, 1987). In nursing personnel the first incidence peak is located around 20 years and could be explained by the sudden increase of work pressure which nurses experience on leaving school and starting at the work-place (Kaur and Pedersen, 1986; Feldstein et al., 1990 and 1993). The second peak for nurses lies between the age of 50 and 58 years and could be explained by a progressive degeneration of the invertebral discs (Dehlin et al., 1976; Hefferin and Hill, 1976; Feldstein et al., 1990 and 1993). Most authors have failed to find a relation between gender and LBP (Horal, 1969; Nachemson, et al., 1979, Svensson and Andersson, 1982; Valkenburg and Haanen,1982).

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On the other hand, it is noted that males undergo surgery more often for discal hernias than females (Spangfort, 1972; Kelsey and Ostfeld, 1975). In Belgian nurses Stappaerts (1989a and b) reported a higher lifetime prevalence of LBP for males (73%) than for females (65%), although no explanation for this difference was given. This finding is in contradiction with the fact that according to Frymoyer et al. (1980) females have a higher risk for LBP during pregnancy, menstruation and menopause. Neither Stubbs et al. (1984) nor Videman et al. (1984) could confirm this relation. Kurumatani and co-workers (1994) stated that sleep deprivation in females and males with small children increases and therefore so does the risk for LBP. Mundt et al. (1993) and Videman et al. (1984) even added that frequent lifting of small children (often with extended knees and a round back) increases the risk for LBP by four times. Some authors mention a good level of physical fitness as a preventor of LBP (Nachemson, 1983; Haldeman, 1990). Most of the studies, however, did not manage to confirm a relation between fitness and LBP (Harber et al., 1987; Leighton and Reilly 1995). Although positive effects of physical fitness on the prevention of LBP are hard to prove, it remains without question a good means of preventing cardiovascular diseases and should be promoted that way. Smoking is another questionable factor. It is relatively clear that smoking increases the risk for LBP (and for many other diseases) but it is difficult to explain why. Some authors considered that the typical cough of smokers increases the intradiscal pressure (BieringSorenson and Thomson, 1986; Haldeman, 1990; Mundt et al., 1993). Others hypothesised that it is more the way of living of smokers - in general less healthy - (Owen and Damron, 1984; Deyo and Bass, 1989), or a reduced blood flow in the end plates caused by nicotine (Frymoyer et al., 1983). The relative risk rate for LBP due to smoking is fairly low (1 in 5) according to Deyo and Bass (1989) and other research teams could not prove a relation between smoking and LBP (Troup et al, 1987; Ryden et al., 1989). Stubbs and Buckle (1984) observed a relation between LBP and musculoskeletal problems in other body regions. Dehlin et al. (1976) and Mandel and Lohman (1987) reported a clear relation between LBP and the incidence of cervical and thoracic problems. Other more rarely cited LBP-related factors found in the literature are : i) a history of LBP (Troup et al., 1987; Yenning et al., 1987; Ryden et al, 1989); ii) high flexibility and low isometric endurance of the trunk musculature (BieringSorenson, 1984); iii) the use of narcotics (Ryden et al, 1989); iv) living single (Gyntelberg, 1974; Pottier and Estryn-Behar, 1980); v) low level of religion (in Israel) (Magora, 1970a and 1970b) vi) LBP in the family (Owen and Damron, 1984) vii) frequent headaches (Harber et al, 1987)

3. Methodology The section above gives an overview of factors related to LBP. It is certainly not pretended to be complete. Nevertheless, it is almost inevitable to conclude that very many factors

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45

showed, in some study and to some degree, a relation with LBP. To cover for our study as many variables as possible, a booklet of different validated and reliable questionnaires was composed. The core of this booklet was the questionnaire used in the "Study of Musculoskeletal Pain in Nursing Personnel" by Skovron et al. (1987a). This was already a combined questionnaire derived from the "Head Nurse Scale", the "Quality of Employment" and the "Work Apgar" questionnaires. In addition the "Pain Locus of Control (PLC)" (Main and Waddell, 1991), the "Coping Strategies Questionnaire (CSQ)" (Rosenstiel and Keefe, 1983; Main and Waddell, 1991), the "Modified Zung Depression Inventory (MZDI)" (Main and Waddell, 1984) and the "Fear-Avoidance Beliefs Questionnaire (FABQ)" of Waddell et al. (1993) were added. These original English questionnaires were carefully translated in the presence of K. Burton and T. Symonds of the Spinal Research Unit of the University of Huddersfield (UK). The Dutch VOEG questionnaire (questionnaire directed towards general health) and questions related to sleeping habits and clothing in the work-place were finally added. In this way a new and original multidisciplinary measuring instrument was created, meaning that reliability and eventually validity tests should be repeated. Therefore Kappa values, ANOVA with paired Friedman tests and, where appropriate, intra-class correlation coefficients were calculated. Furthermore Cronbach alpha values were calculated to measure the internal consistency of the questionnaire. These data were calculated on the responses of 435 nurses who had answered the questionnaire twice within a six-month interval. For the actual analysis, 1783 booklets were distributed in 4 different Flemish (Belgian) hospitals. Twelve hundred and sixteen booklets (267 from male and 949 from female nurses) were returned and sufficiently filled in to analyse. Descriptive data of the participating nurses can be found in Table 1. Table 1. Descriptive data (+ SD) from the investigated nursing population.

Mean age

Mean body mass

Mean Height

34.0 ± 7.8 year

64.5 ± 10.9 kg

168.5 ± 8.2 cm

Six different experimental groups were determined for analysis. A group of nurses with a lifetime prevalence of LBP (L-LBP) was compared with the group of nurses who never experienced LBP; an annual prevalent group (A-LBP) of nurses was compared with nurses who had not experienced a spell of LBP during the last year and a point prevalent group (P-LBP) was compared with nurses who did not experience LBP at the moment of filling in the questionnaire. Comparisons were done by means of Chi-square, ANOVA or Kruskal-Wallis tests where appropriate.

4. Results 4.1. Reliability According to Main and Waddell (1991) a Kappa-value greater then 0.60 means that there exists a substantial concordance between the repeated measures. A kappa-value

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E. Zinzen /Epidemiology: Musculoskeletal Problems in Belgian Nurses

between 0.41 and 0.59 means an average concordance, a value between 0.21 and 0.40 stands for a moderate concordance while a value lower than 0.21 means that there is no significant concordance between the results of the two measures. Table 2 displays the Kappa-values found from our questionnaire. Bearing in mind that there was a 6-month time interval between the two tests and that the 5.9% questions (N = 4) with insufficient concordance were all questions where except for 3 or 4 respondents all other nurses answered in the same direction, we can safely state that the results of the questions with dichotomous answers are reliable. Table 2. Kappa-values of the dichotomous variables. Kappa

Percentage of questions

>0.60

41.2%

0.41-0.59

29.4%

0.21-0.40

23.5%

<0.21

5.9%

For the questions where the answers were continuous variables, a paired ANOVA or a paired Friedman test was used (depending on whether the data were parametrically distributed or not). For the 101 questions submitted to this test, we found in the re-test 14 significantly different answers. Differences were related to the time interval between tests or were smaller then the measurement error. The intra-class correlation coefficients were always higher than 0.75 for these 14 questions. It was concluded that test-retest reliability of the questionnaire was high. In addition to the test-retest reliability, the internal consistency of the sub-questionnaires was calculated using Cronbach's alpha value. It was concluded that the Cronbach alpha value for the different sub-questionnaires ranged between 0.81 and 0.98 which can be considered to have a very high internal consistency (see Table 3). Table 3. Cronbach Alpha of the sub-questionnaires. Sub-questionnaire

Cronbach Alpha (N=1216)

VOEG (General health)

0.92

Modified Zung Depression Index (MZDI)

0.81

Pain Locus of Control (PLC)

0.96

Fear Avoidance Believes Quest (FABQ)

0.98

Coping Strategies Quest (CSQ)

0.95

Work Apgar

0.82

4.2. Validity Due to the test set-up it was impossible to perform extensive validity tests. However, all questions were checked on impossible answers and some sub-questionnaires were compared with a similar study of Symonds et al. (1994) of workers in light industry. These

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47

sub-questionnaires were the MZDI, the Work Apgar and the different scores of the PLC, FABQ and CSQ. Results were obviously different between our study and that of Symonds and co-workers but were clearly in the same direction. Together with the fact that the questionnaires in the English language were considered to be valid, our booklet was considered a valid instrument too. 4.3. Professional items The participating nurses were mainly highly educated and were working in a position comparable with the studies they had done. Most of them were working full-time in 8-hour working shifts. They changed twice per week between morning, evening and night shifts without using a standard rotation method. In seven days on average, four shifts were performed. About 44% of the responders were working in the departments considered as heavy duty, while 26% was working on "light duty" departments. Table 4 gives the variables with a "positive" relation to the different prevalence rates of LBP, meaning that the value found in the LBP sufferers group was significantly higher then in their control groups. Table 5 provides the same information but here we find the variables with a significantly lower value for the LBP groups. Table 4. Professional variables positively related with LBP. Variable

L-LBP

A-LBP

P-LBP

Time spent in current working position

X

X

X

Time started with the nursing profession

X

X

Amount of days worked in the past 7 days

X

Being a hospital assistant

X

Being a nursing aid

X

Had a lower education

X

Legend: L-LBP = lifetime prevalence; A-LBP = annual prevalence; P-LBP = point prevalence Table 5. Professional variables negatively related with LBP. Variable Working as a high level nurse Being a nursing aid

L-LBP

A-LBP

X

P-LBP X

X

Workload

X

Average amount of hours worked/week

X

Time spent on evaluating patients

X

Had a high education

X

Legend: L-LBP = lifetime prevalence; A-LBP - annual prevalence; P-LBP = point prevalence

Back problems are clearly related to the time working as a nurse and are probably related to the level of employment. The longer the nurses are working and the lower the level of employment is, the more LBP is experienced.

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4.4. Health items On average the Belgian nursing personnel can be considered as healthy (low score on the VOEG questionnaire). Somewhat less then half of the responders stated they had smoked sometime in their life. Only 27% were still smoking at the time of filling in the questionnaire. On average they smoked 11 cigarettes a day; 59% of all nurses who had ever smoked quit smoking at the average age of 26.5 years or after smoking for about 9 years. About 80% of the nurses drank alcoholic beverages between once a week and once a month. Only 6.4% of the responders drank alcohol every day. Most of the female nurses have not been pregnant. Those who had been pregnant had on average 2 children. At the time of completing the questionnaire 3.3% ,of the female nurses was pregnant (and still working), 47% complained of menstrual cramps and only 5.5% had reached the menopause. Table 6. Health variables positively related with LBP. Variable

L-LBP

A-LBP

P-LBP

History of smoking

X

X

Amount of pregnancies

X

X

Amount of children

X

X

Amount of deliveries

X

Having menstrual cramps

X

Reached Menopause

X

Frequency of alcohol consumption Level of depression (MZDI)

X X X

X

X

X

Legend: L-LBP = lifetime prevalence; A-LBP = annual prevalence; P-LBP = point prevalence Table 7. Health variables negatively related with LBP. Variable General health

L-LBP

A-LBP

P-LBP

X

X

X

Frequency of alcohol consumption

X

Legend: L-LBP = lifetime prevalence; A-LBP = annual prevalence; P-LBP = point prevalence

Table 6 and 7 show that nurses with LBP were less healthy, more depressive and had a history of smoking. The female nurses with LBP had more pregnancies and children and complained more of menstrual cramps. The relation between alcohol and LBP is somewhat unclear: a higher frequency of alcohol intake was seen in the A-LBP group while a lower frequency of alcohol intake can be noted in the P-LBP nurses.

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49

4.5. Musculoskeletal items About 52% of the responders experienced musculoskeletal problems in the past year. They believed the work circumstances were the cause of this problems. Only 3% (N=34) of the nurses changed department because of these problems. On average the nurses stayed 4 days at home in the past year due to a musculoskeletal problem. Musculoskeletal problems in the nursing population investigated occurred most in the lower back (53.3%) and in the neck region (27.0%). These areas were followed by the shoulders, high back, hips and knees (each ±10%). Nurses with musculoskeletal problems described their pain as very moderate in the best circumstances and as moderate in the worst circumstances. At the time of filling in the questionnaire, they experienced almost no pain. Nearly 8% of the nurses in this study always experienced pain related to a musculoskeletal problem, but most of them had days without any pain. Only 14% were very passive about their pain and believed that nothing could help them, although the results of the Pain Locus of Control (PLC) questionnaire indicated that in general nurses trusted that medication and physicians can help to reduce the pain. In spite of this indication, only 13.2% of the nurses with musculoskeletal problems visited the company physician or a general practitioner. The most frequent diagnoses were arthroses, overload injuries (muscle ruptures, stretched ligaments). Although only 13.2% of these nurses visited a physician, almost 23% of them was following treatment. The most frequent treatments were physiotherapy, medication and rest. The level of pain was lowest before going to work, increased a bit during work and reached a moderate level after work. Although work seemed to increase the pain, the score on the "Fear Avoidance Beliefs Quest" towards work was rather low. Physical activity on the other hand was feared and more avoided. The pain felt was often associated with lifting. Bending forward, standing, rotation of the trunk, pushing and sitting were not causing so much pain. The coping strategies the nurses were using can be considered as being good: they were not ignoring their pain but would try to overcome it in a realistic level and not by praying or hoping. They certainly did not catostrophyse their pain, nor would they adapt their lifestyle to the pain. Low-back problems occurred mainly in the past year and were caused at work as well as outside the work-place. Nurses with low-back problems more often changed departments due to their problem and were also more on sick leave than their LBP-free colleagues. The pain that LBP-sufferers felt was more persistent and of a higher level than what nurses with other musculoskeletal problems felt. They also feared and avoided more physical activity and work and would perform more pain behaviours. Except for the "annual prevalence LBP" group, the nurses with LBP tended to catastrophyse their problem more than their colleagues with other problems. The coping strategies of the 'point prevalence LBP group' were significantly worse but they would seek more help of physicians than their non-PLBP colleagues. Obviously nurses with LBP have more pain in their back than in their legs.

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Table 8. Musculoskeletal variables positively related with LBP. L-LBP

A-LBP

P-LBP

Problems were caused by the job

X

X

X

Problems were caused the last year

X

X

X

Problems were caused by factors outside the job

X

X

X

Changed of department due to musculoskeletal problems

X

X

X

Sick leave

X

X

X

Musculoskeletal problems in other body regions

X

X

X

Pain level in the worst circumstances

X

X

X

Pain level now

X

X

X

Experiencing always pain

X

X

X

Resting

X

X

X

Variable

Pain levels during and after work

X

X

X

Pain is related with all questioned postures

X

X

X

PLCB15 : Pain responsibility

X

X

X

FABPhys : Fear Avoidance for physical activity

X

X

X

FABWork : Fear avoidance for work

X

X

X

CSQ : Pain behaviours

X

X

Painlevel in the best circumstances

X

X

CSQ catastrophysing

X

X

Sometimes no pain

X

X

Amount of days of sick leave

X

Experiencing alternate pain

X

Painlevel before work

X

Painlevel is not changing

X

Visit and diagnosis by a general practitioner

X

Visit and diagnosis by a company physician

X

Treatment for musculoskeletal problems

X

CSQ : diverting attention

X

CSQ : ignoring pain sensation

X

CSQ: self statements

X

CSQ : increasing physical activity

X

CSQ praying and hoping

X

Legend: L-LBP = lifetime prevalence; A-LBP = annual prevalence; P-LBP = point prevalence Table 9. Musculoskeletal variables negatively related with LBP. Variable More pain in the legs then in the back

L-LBP

A-LBP

X

X

Sometimes no pain Legend: L-LBP = lifetime prevalence; A-LBP = annual prevalence; P-LBP = point prevalence

P-LBP

X

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4.6. Work-place items Most of the nurses investigated were satisfied with their job and their colleagues but still found their job mentally demanding. They had to perform a lot of precision jobs and they felt that the work-place only in half of the time was satisfying to perform their tasks. Half of the time patients were lifted alone (without help) and the other half of the time lifting happened with two people. Mechanical aids were almost never used. About 67% of the nurses were educated in lifting techniques. Only 40% of them found this education sufficient. Nurses were satisfied with the light intensity, the level of noise, the intensity of smells, the risk of exposure to toxic chemicals and/or liquid medication, the risk of getting hurt whilst helping patients, the risk of sliding or falling and the surrounding temperature. They are in general not exposed to vibrations or radiation but considered the risks for cuts and needle wounds and contamination by human excrement or medical material to be high. The office of the nurses was considered to be adapted to the work but the patient room was considered as too small to be able to move. The distance between the nursing office and the most distant patient room was considered as being far. The uniform consists most of the time of trousers and blouse, although the typical skirt is also often worn. Pumps or clogs are the most popular footwear. Table 10. Work-place variables positively related with LBP. L-LBP

A-LBP

P-LBP

Lifting alone

X

X

X

Risk for cut and needle wounds

X

X

Risk to gut hurt whilst helping patients

X

X

Variable

Risk for contamination

X

Wearing trousers and blouse

X

Legend: L-LBP = lifetime prevalence; A-LBP = annual prevalence; P-LBP = point prevalence Table 11. Work-place variables negatively related with LBP. L-LBP

A-LBP

P-LBP

Optimal work circumstances

X

X

X

Lifting with help

X

X

Room in the nursing office

X

X

Variable

X

Job satisfaction Sufficient education in lifting techniques

X

X

Room in the patient rooms

X

Wearing a skirt

X

Legend: L-LBP = lifetime prevalence; A-LBP = annual prevalence; P-LBP - point prevalence

Nurses with LBP were lifting significantly more alone and significantly less with help than their colleagues with no LBP. They also believed that their work-circumstances were less optimal and they felt a greater risk for cuts and needle wounds or of getting hurt by

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helping patients. They also were less satisfied with their job. In the annual prevalence group more nurses wore trousers and blouse and fewer wore a skirt. 4.7. Personal items The average families of the investigated nurses consisted of 3 persons; however, families of 2 and 4 persons were the most frequent. About 75% of the nurses did not have children younger then 5 years and about 50% of them were mainly responsible for the children when they were not working. Nurses performed about 6 lifts per day of children in the family surrounding. Almost 60% of them were actively involved in sports and about 13% had a physically active hobby. On average the nurses spend each time about 2 hours, 6 times per month, 10 months per year at their leisure activity. Cleaning in the house takes about 7 hours/week, shopping ± 3 hours, cooking ± 6 hours, repairing or making home improvements about 2 hours/week and 3 hours are spent in travelling between home and work. Table 12. Personal variables positively related with LBP. Variable

L-LBP

Date of birth

X

Weight

X

Responsibility for children < 5 year

X

Amount of persons demanding attention in the family

X

Responsibility for persons in the family

X

A-LBP

P-LBP X

X

Gender (more males)

X

Length

X

Time spent to cleaning

X

Time spent to cooking

X

Legend: L-LBP = lifetime prevalence; A-LBP = annual prevalence; P-LBP = point prevalence

Nurses with LBP were generally older and heavier than their colleagues without LBP. Responsibility in the family seemed only important for the 'life prevalence LBP' group of nurses whilst more males and taller nurses experienced LBP the past year. Nurses who were experiencing pain at the time of filling in the questionnaire were spending significantly more time in cleaning and cooking.

5. Discussion 5.1. Professional items Results indicate that the investigated nurses were mostly younger then 40 years (on average 34 years) and that the risk for LBP increases with age. The age distribution is very similar

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53

to what is found in other countries (Ryden et al. (USA), 1989; Larese and Fiorito (Italy), 1994; Leighton and Reilly (UK), 1995; Knibbe and Friele (Holland), '1996). The increase in prevalence of LBP with age was also found by Stubbs et al. (1985) whilst Skovron et al. (1987a) found an inverse relation and Mandel and Lohman (1987) did not found any relation at all. Feldstein et al. (1990 and 1993), Hefferein and Hill (1976) and Dehlin et al. (1976) have found in their studies two age-related peaks of prevalence of LBP : these were at the start of the nursing profession and between the age of 50 to 58 years. More than 85% of the nurses in our investigation had not reached the age of 40, explaining why we could certainly not notice the second peak. On the other hand it is impossible to confirm the existence of the first peak since the prevalence rates were increasing with an increase in age. Haldeman (1990) showed that with increasing age there will be an increasing amount of pathologies resulting after a certain time in an increase of symptoms. Since most of the nurses were rather young, it can be hypothised that the pathology (without symptoms) starts at the beginning of the nursing profession and that the work-circumstances of the nurses are negatively influencing the time between the occurrence of the pathology and the symptoms resulting in the earlier occurrence of LBP. This hypothesis gains strength from the fact that results of this study showed that the time being a nurse is related with the prevalence of LBP. Videman et al. (1984), Harber et al. (1985), Jensen (1987), Yenning et al. (1987) and Dehlin et al. (1976) reported that those using nursing aids are at higher risk for the development of LBP. The results of our study indicate, however, no clear relation, with the exception of the point prevalence group, between education level or the level of employment and the prevalence of LBP. Probably that is also the reason why only a few nurses take time to study. The exception in the point prevalence group gives the impression that the LBP-episodes are probably not too painful and not too long in duration because apparently after a while they are forgotten since they are not mentioned anymore in the annual or lifetime prevalence groups. The value of this relation in the point prevalence group can therefore be questioned. An unsuspected non-relation was found between how the work is performed (amount of shifts per week, morning, evening or night shifts, amount of double shifts, amount of changes in shift, amount of working hours of the shift, workload of the department) and the prevalence of LBP. This is contrary to what was expected and to the results of Ryden et al. (1989), Minors et al. (1994) and Kurumatani et al. (1994). These researchers, however, were the only ones found in the literature who had also investigated these relations. The main difference between their studies and ours is that their experimental groups consisted only of nurses working in those departments which were considered as having a very high workload. Our study incorporates nurses of all departments and displays an average result for the "average" nurse. 5.2. Health items Results of the VOEG questionnaire, indicating the level of general health, are clearly related with the investigated prevalence rates : the lower the general health is, the higher the prevalence rates are. This is completely in agreement with the results of others (Wolkind, 1974; Frymoyer et al., 1980; Southwick and White, 1983; Main et al., 1984; Deyo and Bass 1989; Ryden et al., 1989; Haldeman, 1990; Andersson and Pope (1991) and Burton et al., 1997), although they incorporated also the concept of psychological health in their results. Evaluating the level of depression (MZDI) of our investigated nurses, it can be noticed that a higher level of depression strongly relates to the three investigated

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E. Zinzen /Epidemiology: Musculoskeletal Problems in Belgian Nurses

prevalence rates. This leads to the conclusion that both physical and psychological health are related to LBP. Regarding alcohol consumption and smoking, no clear relation with LBP was found in our study. However, it is hypothised that alcohol consumption and smoking are a part of a unhealthy lifestyle and will have their influence on general health which is itself strongly related with LBP. Gynaecological problems such as menstrual cramps and menopause and also pregnancy seem to be related to the prevalence of LBP. These are, however, temporarly problems. One could argue that by adding these risks, female nurses are more likely to develop LBP than male nurses. The contrary, however, is true. Males experience more LBP than females which compensates for the influence of gynaecological problems and pregnancy on LBP. The results found in this study are very similar to the results of Frymoyer et al. (1980 and 1983), Svensson and Andersson (1983), Biering-Sorenson (1986), Heliovaara (1988), Deyo and Bass (1989), Haldeman (1990) and Mundt et al. (1993). 5.3. Musculoskeletal items The nurses with LBP believed more than their problem-free colleagues that their musculoskeletal problems were caused at the work-place. This is not new and certainly not unexpected but they also experienced more musculoskeletal problems outside the workplace indicating that the work-place alone can not be responsible for all their problems. On the other hand the musculoskeletal problems experienced were not so bad since only about 50% of the nurses consulted a physician and only 13% consulted the industrial medical officer. This also indicates that nurses do not trust their industrial physician as he often is a member of the hospital board. The authors believe that the industrial physician should perform some "image building" and gain more trust since he/she is the one closest to the work situation and should be the one first consulted. In the cases where a physician was consulted, we noticed that the most back-related problems were discal hernia, acute lumbago, scoliosis and ideopathic low-back pain. The most frequent treatments prescribed were physiotherapy, medication and rest. These findings correspond with the results of Harber et al. (1985). The fact that rest is still the third most important treatment for nonspecific LBP is much contestated by different authors. Malmivaara et al. (1995) stated that one should keep moving within the limits of pain and showed that the healing results were much better than those obtained by rest and even better then by performing mobilising exercises for the back. A little unexpected was the fact that almost no nurses (3%) changed department due to LBP, although this result can be biased by nursing personnel who left the hospital. Extra demand at the hospital board revealed that not many nurses were leaving the hospitals; most of the time they were re-located. The hospitals in Belgium are trying very hard to keep their personnel since there is for some years a lack of nurses. In general, it is concluded that on average each nurse stays 2.5 days/year at home due to LBP what is much less then what Pettier and Estryn-Behar (1980) found in France (22 days/year). This result indicates again that the LBP experienced in the Belgian hospitals is most of the time not so bad. The most frequently experienced musculoskeletal problems were LBP followed by neck problems, problems in the shoulders region, at the higher back and much less in the extremities. It has also been noticed in other occupations that LBP is the most common

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musculoskeletal problem (Svensson and Andersson, 1982; Grieco et al., 1989 and Ryan, 1989). It is remarkable that nurses with LBP were experiencing also much more musculoskeletal problems in other body regions. Maybe this can be explained by the fact that these nurses have in general a lower loadability and a lower pain threshold. All investigated pain levels were higher for the different low-back pain groups, although it almost never exceeded a "moderate" level. Lifting induces, according to the nurses investigated, the most musculoskeletal problems followed by forward bending, standing, rotations of the trunk, pushing and sitting. These findings are on the same lines as found by others (Magora, 1972; Dehlin and Lindberg, 1975; Raistrick, 1981; Luttman et al, 1983; Kelsey et al., 1984; Yenning et al., 1987; Pope, 1988; Mundt et al., 1993; Marras et al., 1995 and Van Dieen et al., 1996) Nurses with musculoskeletal problems were more convinced that physicians and medication would help to control their pain than were their pain-free colleagues. This finding is similar to what Symonds et al. (1994) observed in a biscuit factory and Main and Parker (1989) reported in a normal population. Main and Waddell (1991) indicated that catastrophysing is highly related to the occurrence of LBP, although this study does not quite confirm this finding. From the Coping Strategies Questionnaire it was the item "Pain behaviours" that mainly showed a relation with LBP, although all other sub-items were also moderatly related. Together with poor coping strategies, the nurses with LBP showed a rather great fear and avoidance behaviour towards work and physical activities as was also found by Symonds et al. (1994) and Waddell et al. (1993). They indicate that a proper prevention campaign with explanation about the problems can reduce this fear avoidance behaviour and so reduce the amount of sick leave. Summarising this sub-item of the questionnaire, one could conclude that nurses with LBP have more negative attitudes, consider more their work as responsible for their problems, experience more musculoskeletal disorders in other body regions, can cope less with pain, experience a higher pain level, will ask more frequently for medical help and fear and avoid more work-situations and physical activities than their colleagues without LBP. 5.4. Work-place items Except for the lifetime-prevalent LBP nurses, the job satisfaction was lower when LBP was experienced. This was found also by Taylor (1968), Westrin (1970), Magora (1973b), Bergenudd and Nilsson (1988) and Minors et al. (1994). Symonds et al. (1994), however, could not prove a relationship between job satisfaction and LBP in a biscuit factory whilst Skovron (1987a) to her own surprise found an inverse relationship in nurses. These contradictory results found in the literature may be explained by a selection bias. One could also formulate the hypothesis that the items measured by the Work APGAR tool are more situated in the present as illustrated by the fact that the lifetime prevalent group was not less satisfied. Aspects such as social contact and daily stress are strongly time-related and often forgotten after a while and could explain the differences in results. On the other hand the nurses were convinced that lots can be done to their work circumstances such as providing more space in the patients' room and in the nurses' office, reducing the risk of cuts and needle wounds and the risk of getting hurt whilst helping patients. It was remarkable also that nurses already suffering from LBP lifted more patients alone than their pain-free colleagues.

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From all these statements one could get the impression that the LBP group of nurses consisted of "complainers". On first sight, all these aspects (except for lifting alone) were not expected to influence the onset of LBP strongly. In the light of prevention, however, it is felt that appropriate actions can be undertaken. As regards to lifting alone, the authors are convinced that a "non-lifting" policy as used in the UK is the golden standard. If lifting has to be done, then it should be done with as little effort as possible (Nachemson, 1971; Frymoyer et al, 1980; Breen and Lloyd, 1985; Harber et al., 1985 and 1988a; Stubbs et al., 1985; De Gaudemaris et al., 1986; Riihimaki et al., 1989; Ryden et al., 1989; Stappaerts, 1988 and 1989a and 1989b; Garg et al, 1991; Pheasant et al., 1991; Pope et al., 1991; and lots of others). The presence of lifting aids was not investigated in this study but it is generally accepted that they will reduce the efforts necessary for lifting manually although Garg et al. (1991 and 1992) questioned the quality and the usefulness of some equipment. Our own research team has proven that beds adjustable in height reduce compression and shear forces at the L5/S1 segment, provide less muscle activity and allow nurses to move their backs more in a safe way compared to beds with a standard height (de Looze et al., 1994; Caboor et al., 2000). Another aspect is the education in using lifting aids as well as in lifting skills. Only 67% of the nurses investigated had any training in lifting and only 40% of them considered this training as sufficient. This fact was not only mentioned by the nurses since also Feldstein et al. (1990 and 1993) and Van Hoof (1988) came to the same conclusion by investigating the quality of the education nurses get. They stressed the value of a good education in lifting at the school level. It is remarkable that only the lifetime-prevalent LBP nurses consider their lifting education worse than their pain-free colleagues. A real explanation for this is not so clear. In general it is believed that wearing trousers and blouse permits the nurses to move freely while a skirt reduces the range of motion of the legs (Stubbs et al., 1985; Jaeken, 1986). Only the 'annual prevalent' nurses seem to have understood this reasoning. 5.5. Personal items Nurses with LBP seem to be older then their pain-free colleagues. Detailed analysis of the results did not reveal a bimodal model as suggested by some authors (Nachemson, 1971; Biering-Sorenson, 1982; Svensson and Andersson, 1983 and Abenheim and Suissa, 1987). Therefore it is suggested that possibly only the progressive degeneration of the discs is responsible for the LBP experienced. Furthermore, the nurses with LBP were somewhat heavier than their colleagues without LBP. Calculation of the BMI gives a result of 23.4 for the male nurses and 22.8 for the female nurses, meaning that the nurses on average were certainly not obese. Deyo and Bass (1989), however, stated that overweight is almost always present before the onset of LBP. Our study has not looked into this aspect but results could point in that direction. The fact that 'annual prevalent LBP' nurses were taller could also play a role in their weighing more. For the lifetime-prevalent LBP group, responsibility and giving attention to members in the family was an item related to LBP. Possibly this has to do with the extra lifting which needed to be performed by taking care of these persons. Why only the lifetime-prevalent group brought these items forward is not clear. Only the 'point-prevalent LBP' nurses spent more time in cleaning and cooking than their colleagues who were not experiencing LBP for the moment. Possibly the explanation

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for this result can be found in the fact that these nurses were also working more part-time and simply had more time to spend in these activities. Gender only played a role in the 'annual prevalence LBP' group where more males in comparison with females were suffering from LBP. This is in accordance with the results of Stappaerts (1989a and b) gathered in another Belgian hospital. The fact that only in the annual prevalent group does gender emerge could indicate that it is not playing a large role in the onset of LBP as was already stated by the majority of authors consulted (Horal, 1969; Nachemson, et al., 1979, Svensson and Andersson, 1982; Valkenburg and Haanen, 1982). A remarkable non-relation was found between time spent in physically active leisure and the occurrence of LBP. This observation is possibly due to the fact that about seventy means of leisure time were mentioned by the nurses and that the research team had made an arbitrary choice to classify them as highly physically active, moderate or not physically active. On the contrary several studies can be cited explaining the benefits of being physically active in relation to LBP (Frymoyer et al., 1983; Harber et al., 1987; Porter et al., 1989; Burton et al., 1989; and Leighton and Reilly, 1995) 6. Conclusions It would be difficult to summarise all the epidemiological aspects and LBP-related items found in this study. Some influential factors were already found in the literature, some are new, some can be explained, others can not. It has to be clear that this study could only establish a relationship with LBP and could not prove causality. This makes it difficult to draw inferences towards prevention. As to Belgian law which states that a professional disease should have only a causal relation with work-related factors, it can be concluded that LBP can not be considered as a professional disease since so many variables were found outside the work-place also. Another question which still remains is: "are these variables which are related to LBP all equally responsible for LBP or are some items more responsible than others?" At this point, it is impossible to say. In this chapter the main purpose was to be descriptive about epidemiological aspects of the nursing profession and in our impression this has been achieved. The importance of the items found and the implication of these results for the development of a primary preventative model are emphasised later in Chapter 15. References Abenheim, L.L.and Suissa, S. (1987). Importance and economic burden of occupational back pain: a study of 2500 cases representative of Quebec. Journal of Occupational Medicine, 29, 670-674. Anderson, J.A.D. (1986). Epidemiological aspects of back pain. J. Soc. Occup. Med. 36, 90-94. Andersson, G.B.J. (1990). Epidemiology of spinal disorders. In: The Adult Spine: Principles And Practice (ed. J.W. Frymoyer). New York: Raven Press. Andersson, G.B.J. and Pope, M.H. (1991). The patient. In: Occupational Low Back Pain: assessment, treatment and prevention (eds. M.H. Pope, G.B.J. Andersson, J.W. Frymoyer and D.B. Chaffin), pp. 132147, St. Louis: Mosby-Year Book. Battie, M.C., Bigos, S.J., Fisher, L.D., Hansson, T.H., Jones, M.E. and Wortley, M.D. (1989). Iso-metric lifting strength as a predictor of industrial back pain reports. Spine, 14, 851-855. Bergenudd, H. and Nilsson, B. (1988). Back pain in middle age: occupational workload and psychologic factors : an epidemiologic survey. Spine, 13, 58-60.

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Biering-Sorenson, F. (1982). Low back trouble in a general population of 30-,40-,50-, and 60-year old men and women: study design, representativeness, and basic results. Dan. Med.Bull. 29, p.289. Biering-Sorensen, F. (1984). Physical measurements as risk indicators for low-back trouble over a one-year period. Spine, 2, 106-119. Biering-Sorensen, F. (1985). Risk of back trouble in individual occupations in Denmark. Ergonomics, 28, 51-60. Biering-Sorenson, F. and Thomson, C. (1986). Medical, social and occupational history as risk indicator for low back trouble in a general population. Spine, 11, 720-725. Bigos, S.J., Battie, M.C., Spengler, D.M., Fisher, L.D., Fordyce, W.E., Hansson, T., Nachemson, A.L., and Zeh, J. (1992). A longitudinal, prospective study of industrial back injury reporting. Clin. Orthop, 279, 21-34. Breen, A.C. and Lloyd, S.G. (1985). A study of back pain in nurses. European Journal of 'Chiropractic, 33, 3-7. Buckle, P. (1987). Epidemiological aspects of back pain within the nursing profession. International Journal of Nursing Studies, 24, 319-324. Burton, A.K., Tillotson, K.M. and Troup, J.G.D. (1989). Prediction of low-back trouble frequency in a working population. Spine, 4, 939-946. Burton, A.K., Symonds, T.L., Zinzen, E., Tillotson, K.M., Caboor, D., Van Roy, P. and Clarys, J.P. (1997). Is ergonomic intervention alone sufficient to limit musculoskeletal problems in nurses ? Occupational Medicine, 471, 25-32. Caboor, D., Zinzen E., Van Roy, P., and Clarys, J.P. (1997). Job evaluation using a modified DelphiSurvey. Proceedings S.A.S.P. Int. Congress, Cape Town, pp.56-60. Caboor D.E., Verlinden M.O., Zinzen E., Van Roy, P., van Riel M.P., and Clarys J.P. (2000). Implications of an adjustable bed height during standard nursing tasks on spinal motion, perceived exertion and muscular activity. Ergonomics, 43, 1771-1780. Caillard, J.F., Czernichow, P., Doucet, E., Jamoussi, S., Rebai, D., Julien, F., and Proust, B. (1987). Le risque lombalgique professionnel a I'hopital: etude au centre hospitalier regional de Rouen. Archives des Maladies Professionnelle, 48, 623-627. Chaffrn, D. B., Andersson, G. B. J., Pope, M. H. and Nordin, M. (1991). Work-place evaluation. In: Occupational Low Back Pain: assessment, treatment and prevention, (eds. M. H. Pope, G. B. J. Andersson, J. W. Frymoyer and D. B. Chaffin), pp. 44-70. St. Louis: Mosby Year-Book,. De Gaudemaris, R., Blatier, J.F., Quinton, D., Piazza, E., Gallin-Martel, C., Perdrix, A. and Mallion, J.M. (1986). Analyse du risque lombalgique en milieu professionnel. Rev. Epidem. et Sante Publ., 34, 308317. Dehlin, O. and Lindberg, B. (1975). Lifting burden for a nursing aide during patient care in a geriatric ward. Scandinavian Journal of Rehabilitation Medicine, 1,65-72. Dehlin, O., Hedenrud, B. and Horal, J. (1976). Back symptoms in nursing aides in a geriatric hospital: an interview study with special reference to the incidence of low-back symptoms. Scandinavian Journal of Rehabilitation Medicine, 8,47-53. de Looze, M., Zinzen, E., Caboor, D., Heyblom, P., van Bree, E., Van Roy, P., Toussaint, H.M. and Clarys J.P. (1994). Effect of individually chosen bed-height adjustments on the low-back stress of nurses. Scandinavian Journal of Work, Environment and Health, 20,427-434. Deyo, R.A. and Bass, J.E. (1989). Lifestyle and low-back pain: the influence of smoking and obesity. Spine, 14, 501-506. Feldstein, A., Vollmer, W. and Valanis, B. (1990). Evaluating the patient-handling tasks of nurses. Journal of Occupational Medicine, 32, 1009-1013. Feldstein, A., Valanis, B., Vollmer, W., Stevens, N. and Overton, C. (1993). The back injury prevention project: pilot study: assessing the effectiveness of back attack, an injury prevention program among nurses, aides, and orderlies. Journal of Occupational Medicine, 35, 114-120. Frymoyer, J.W. and Andersson, G.B.J. (1991). Clinical Classification. In: Occupational Low Back Pain: assessment, treatment and prevention, (eds. M. H. Pope, G. B. J. Andersson, J. W. Frymoyer and D. B. Chaffin), pp. 44-70. St. Louis: Mosby Year-Book. Frymoyer, J.W., Pope, M.H., Costanza, M.C., Rosen, J.C., Goggin, J.E. and Wilder, D.G. (1980). Epidemiologic studies of low-back pain. Spine, 5,419-423. Frymoyer, J.W., Pope, M.H., Clements, J.H., Wilder, D.G., MacPherson, B. and Ashikaga, T. (1983). Risk factors in low-back pain: an epidemiological survey. Journal of Bone and Joint Surgery, 65-A, 213-218. Garg, A., Owen, B., Seller, D.and Banaag, J. (1991). A biomechanical and ergonomic evaluation of patient transferring tasks: bed to wheelchair and wheelchair to bed. Ergonomics, 34, 289-312.

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Garg, A., Owen, B.D. and Carlson, B. (1992). An ergonomic evaluation of nursing assistants job in a nursing home. Ergonomics, 35, 979-995. Grieco, A., Occhipinti, E., Columbini, D., Menoni, O., Bulgheroni, M., Frigo C and Boccardi, S. (1989). Muscular effort and musculo-skeletal disorders in piano-students: electromyographic, clinical and preventive aspects. Ergonomics, 32, 697-716. Gyntelberg, F. (1974). One year incidence of low back pain among male residents of Copenhagen aged 40 59. Dan. Med. Bull, 21, 30. Haldeman, S. (1990). Failure of the pathology model to predict back pain. Spine, 15, 718-724. Harber, P., Billet, E., Gutowski, M., Soo Hoo, K., Lew, M. and Roman, A. (1985). Occupational low-back pain in hospital nurses. Journal of Occupational Medicine, 27, 518-524. Harber, P., Billet, E., Lew, M. and Horan, M. (1987). Importance of non-patient transfer activities in nursing-related back pain. I. Questionnaire survey. Journal of Occupational Medicine, 29, 967-970. Harber, P., Billet, E., Shimozaki, S. and Vojtecky, M. (1988a). Occupational back pain of nurses: special problems and prevention. Applied Ergonomics, 19, 219-224. Hefferin, E.A. and Hill, B.J. (1976). Analysing nursing's work-related injuries. American Journal of Nursing, 76, 924-927. Heliovaara, M. (1988). Epidemiology of sciatica and herniated lumbar intervertebral disc. Helsinki, Finland: Research Inst.for Social Security, 1-147. Horal, J. (1969). The clinical appearance of low back disorders in the city of Gothenburg, Sweden. Acta Orthop Scand, Suppl, 1, p.l 18. Jaeken, G. (1986). De verpleegster heft drie ton per dag. Verpleegkundigen en Gemeenschapszorg, 5, 263265. Janzen, R. (1981). Schmerzanalyse, als Wegweiser zur Diagnose. Stuttgart. Jensen, R.C. (1987). Disabling back injuries among nursing personnel: research needs and justification. Research in Nursing & Health, 10, 29-38. Kaur, B. and Pedersen, H. (1986). Mind your backs! Nursing Times, 16,45-47;. Kelsey, J.L. and Ostfeld, A.M. (1975). Demographic characterestics of persons with acute herniated lumbar intervertebral disc. J Chron Disease, 28, p.37. Kelsey, J.L., Githens, P.B., White, A.A. 3d., Holford, T.R., Walter S.D., O'Connor, T., Ostfeld, A.M., Weil, V., Southwick, W.O. and Calogero, J.A. (1984). An epidemiologic study of lifting and twisting on the job and risk for acute prolapsed lumbar intervertebral disk. J. Orthop. Research, 2, 61-66. Knibbe, J.J. and Friele, R.D. (1996). Prevalence of back pain and characteristics of the physical workload of community nurses. Ergonomics, 39, 186-198. Kurumatani, N., Koda, S. and Nakagiri, S. (1994). The effects of frequently rotating shiftwork on sleep and the family life of hospital nurses. Ergonomics, 37, 995-1007. Larese, F. and Fiorito, A. (1994). Musculoskeletal disorders in hospital nurses: a comparison between two hospitals. Ergonomics, 37, 1205-1211. Leighton, D.J. and Reilly, T. (1995). Epidemiological aspects of back pain: the incidence and prevalence of back pain in nurses compared to the general population. Journal of Occupational Medicine, 45, 263-267. Luttmann, A., Laurig, W. and Gencoglu, M. (1983). Ermittlung von Riviergrossen bei der Hausmullabfuhr unter Berucksichtigung der Beanspruchung der Beschaftigten. Zentralblatt fur Arbeitzmedizin, Arbeitsschutz, Prophylaxe und Ergonomie, 33, p49. Magora, A. (1970a). Investigation of the relation between low back pain and occupation. Ind. Med., 39, 465 -471. Magora, A. (1970b). Investigation of the relation between low back pain and occupation: 2. Work History. Ind. Med., 39, 504-510. Magora, A. (1972). Investigation of the relation between low back pain and occupation. Ind. Med., 41, 5-9. Magora; A. (1973b). Investigation of the relation between low back pain and occupation.5. Psychological aspects. Scandinavian Journal of Rehabilitation Medicine., 5, p. 191. Main, C.J. and Parker, H. (1989). Pain management programmes. In: Back Pain: New Approaches to Rehabilitation and Education, (eds. M. Roland and J. Jenner), Manchester U.K.: Manchester University Press. Main, C. J. and Waddell, G. (1984). The detection of psychological abnormality in chronic low back pain using four simple scales. Current Concepts in Pain, 2, 10-15. Main, C. and Waddell, G. (1991). A comparison of cognitive measures in low back pain: statistical structure and clinical validity at initial assessment. Pain, 46,287-298.

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Malmivaara, A., Hakkinen, U., Aro, T., Heinrichs, M.L., Koskenniemi, L., Kuosma, E., Lappi, S., Palohelmo, R., Servo, C., Vaaranen, V. and Hernberg, S. (1995). The treatment of acute low back pain: bedrest, exercises, or ordinary activity ? The New England Journal of Medicine, 332, 351 - 355. Mandel, J.H. and Lohman, W. (1987). Low back pain in nurses: the relative importance of medical history, work factors, exercise, and demographics. Research in Nursing & Health, 10, 165-170. Marras, W.S., Lavender, S.A., Leurgans, S.E., Fathallah, F.A., Ferguson, S.A., Allread, W.G. and Rajulu, S.L. (1995). Biomechanical risk factors for occupationally related low back disorders. Ergonomics, 38, 377-410. Minors, D.S. Healy, D. and Waterhouse, J.M. (1994). The attitudes and general health of student nurses before and immediately after their first eight weeks of nightwork. Ergonomics, 37, 1355-1362. Mundt, D.J., Kelsey, J.L., Golden, A.L., Pastides, H., Berg, A.T., Sklar, J., Hosea, T. and Panjabi, M.M. (1993). The Northeast Collaborative Group on Low Back Pain. An epidemiologic study of nonoccupational lifting as a risk factor for herniated lumbar intervertebral disc. Spine, 18, 595-602. Nachemson, A.L. (1971). Low back pain: its etiology and treatment. Clin. Med., January, 18-24. Nachemson, A. (1983). Work for all: for those with low back pain as well. Clinic. Orthop. and Rel. Res., 17, 77-85. Nachemson, A.L., Schultz, A.B. and Berkson, M.H. (1979). Mechanical properties of human lumbar spine motion segments: influences of age, sex, disc level, and degeneration. Spine, 4, 1-7. Oostendorp, R.A.B., Warns H.W.A. and Hendriks H.J.M. (1997). Fysiotherapie en lagerugpijn, een nieuw paradigma. Ned. T Fysiother, 107, 102-110. Owen, B.D. and Damron, C.F. (1984). Personal characteristics and back injury among hospital nursing personnel. Research in Nursing and Health, 7, 305-313. Pheasant, S., Holmes, D. and Stubbs, D. (1991). Back pain in nurses: some ergonomic studies. Contemporary Ergonomics (edited by E. J. Lovesey), pp.323-327. London: Taylor and Francis. Pope, M.H. (1988). Concepts in the prevention of occupational low back pain. Contemp. Orthopaedics, 17, 43-54. Pope, M.H., Andersson, G.B.J. and Chaffin, D.B. (1991). The work-place. In: Occupational Low Back Pain: Assessment, Treatment and Prevention, (eds. M.H. Pope, G.B.J. Andersson, J.W. Frymoyer and D.B. Chaffin), pp.117-131. St. Louis: Mosby Year-Book. Porter, R.W., Adams, M.A. and Hutton, W.C. (1989). Physical activity and the strength of the lumbar spine. Spine, 14, 201-203. Pettier, M. and Estryn-Behar, M. (1980). L'ergonomie du travail infirmier. Le Travail Humain, 43, 121153. Raistrick, A. (1981). Nurses with back pain: can the problem be prevented? Nursing Times, 14, 853-856. Riihimaki, H., Tola, S., Videman, T. and Hanninen, K. (1989). Low-back pain and occupation: a crosssectional questionnaire study of men in machine operating, dynamic physical work, and sedentary work. Spine, 14, 204-209. Rosenstiel, A.K. and Keefe, F.J. (1983). The use of coping strategies in chronic low back pain patients: relationship to patient characteristics and current adjustment. Pain, 17, 33-44. Ryan, G.A. (1989). The prevalence of musculo-skeletal symptoms in supermarket workers. Ergonomics, 32,359-371. Ryden, L.A., Molgaard, C.A., Bobbitt, S. and Conway, J. (1989). Occupational low-back injury in a hospital employee population : an epidemiologic analysis of multiple risk factors of a high-risk occupational group. Spine, 14, 315-320. Skovron, M.L., Mulvihill, M.N., Sterling, R.C., Nordin, M., Thougas, G., Gallacher, M. and Speedling, J. (1987a). Work organization and low back pain in nursing personnel. Ergonomics, 30, 359-366. Skovron, M.L., Nordin, M., Sterling, R.C. and Mulvihill, M.N. (1987b). Patient care and low back injury in nursing personnel. In: Trends in Ergonomics/Human Factors 4, (ed. S.S. Asfour), pp.855-862, NorthHolland: Elsevier Sciences. Southwick, S.M. and White, A.A. (1983). The use of psychological tests in the evaluation of low-back pain. Journal of Bone and Joint Surgery, 65A, 560-565. Spangfort, E.V. (1972). The lumbar disc herniation. Acta Orthop. Scand. Suppl. I,p.l42. Spitzer, W.O., Leblanc, F.E., Dupuis, M. et al. (1987). Scientific approach to the assessment and management of activity-related spinal disorders: a monography for clinicians. (Report of the Quebec Task Force on spinal disorders). Spine, 12, Suppl.7, S1-S59. Stappaerts, K.H. (1988). Lage rugpijn bij verplegenden. Tijdschrift voor ziekenverpleging; 42, 651-655. Stappaerts, K. (1989a). Lage rugpijn: een onderzoek bij verplegenden en richtlijnen voor preventie. In: Hermes, Leuven: KUL, pp.7-34.

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EPIDEMIOLOGY OF MUSCULOSKELETAL DISORDERS IN A SAMPLE OF BRITISH NURSES AND PHYSIOTHERAPISTS Caryl Beynon and Thomas Reilly Research Institute for Sport and Exercise Sciences Liverpool John Moores University Henry Cotton Campus 15-21 Webster Street, Liverpool, L3 2ET United Kingdom Abstract: The prevalence of back pain in nurses is well documented but nurses' experience of other musculoskeletal disorders is less well explored. Musculoskeletal disorders of physiotherapists have also been somewhat ignored. Using a questionnaire the first phase of the study aimed to quantify the musculoskeletal disorder experienced by a sample of hospital based nurses and physiotherapists and make comparisons between the two occupational groups. Chi squared and logistic regression analyses were performed on the data to identify which factors were associated with the presence or absence of musculoskeletal symptoms and then more specifically back pain. The second, prospective stage of the study considered data from nursing and physiotherapy staff presenting at an Occupational Health Department with a musculoskeletal disorder. Subjective data regarding the cause of symptoms, diagnoses and prognoses are presented. In combination, the two phases of the study indicated that occupational, organisational, personal and psychosocial factors were associated with musculoskeletal disorders and back pain.

1. Introduction A wealth of epidemiological research considering back disorders has been conducted with various results on the problem being quoted. Variation between studies is due to a number of factors: these include how back pain is defined, the methodology employed, the specific population considered, participant recall and non-response bias (Papageorgiou et al., 1995). There have been numerous studies of the prevalence of back pain in British nurses but these are often likely to be under-estimates, with minor problems going undetected and seen by the nursing staff as an inherent occupational risk. Prevalence rates in particular are underestimated, especially if the information is acquired from employee service data (Harber et al., 1985) or accident reports (Stubbs et al., 1983). Despite this potential under-estimation, nursing is frequently cited as an occupation with a high risk of back problems (Guo et al., 1995; Hildebrandt, 1995), constituting a huge

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financial burden and long periods of sickness absence from work. Reviewing the literature, Larese and Fiorito (1994) quoted annual prevalence rates of between 35% and 52%, being consistently higher than the general population (Pheasant and Stubbs, 1992), and comparable to rates found among workers in heavy industry (Larese and Fiorito, 1994). Buckle (1987) estimated the cost of the problem at 764,000 lost working days per year. Harber et al. (1985) and Stubbs et al. (1983) quoted similar figures. Whilst there has been a plethora of studies concerning back pain within the nursing profession, this area of research is rarely expanded to include other anatomical sites where musculoskeletal problems may be evident. A questionnaire survey of staff in four nursing homes in The Netherlands in which a 95% response rate was obtained reported musculoskeletal symptoms in various anatomical areas. Whilst 43% had low-back pain symptoms, 30% had arm or neck complaints (mostly in the shoulder) and 16% had leg complaints (mostly in the knee) (Engels et al, 1996). Anatomical areas other than the back are therefore also affected. While a wealth of information regarding musculoskeletal problems in nurses exists, physiotherapists are often neglected in research, possibly because it is assumed that they have superior understanding of body mechanics and in particular back protection (Molumphy et al., 1985). Despite the highlighted sample design bias (considering only graduates of the University of Iowa's Physical Therapy Programme), Bork et al. (1996) found 61% of the 928 physiotherapist respondents experienced work-related musculoskeletal problems in at least one anatomical site, with 45% of these concerning the lower back. It was also indicated that one third of the physiotherapists complained of wrist and hand symptoms. This figure compares to 29% of 500 registered physical therapists suffering low-back pain for more than three days (Molumphy et al., 1985) and an annual prevalence of 38% shown by Scholey and Hair (1989). In order to quantify the prevalence of various musculoskeletal disorders and to enable comparisons to be made between the nursing and physiotherapy professions, comprehensive epidemiological work must be undertaken. This is often achieved by use of a questionnaire. Considering the neck, shoulder and thoracic region of the spine, Bjorksten et al. (1999) compared questionnaire responses relating to musculoskeletal symptoms with clinical diagnoses. The authors concluded that the questionnaire was a valid assessment tool. The aim of this work was to quantify the musculoskeletal problems experienced by nurses and physiotherapists and identify some of the factors associated with these symptoms. 2. Methodology The epidemiological work consisted of a retrospective and a prospective study. 2.1 Retrospective Study Two questionnaires were designed for the purpose of the study. The questionnaires for nurses and physiotherapists were fundamentally identical to allow valid comparisons to be made between the two occupations. Musculoskeletal disorders were defined as 'injuries or diseases of the musculoskeletal system which may be attributed to work and are characterised by symptoms of pain, numbness or inflammation'. Diagrams of the front and back of the body were included for respondents to indicate the site of their symptoms.

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The Nursing Personnel Questionnaire The questionnaire consisted of four sections and 45 questions. Some questions had multiple sub-sections. There was also an additional sheet attached for respondents suffering from more than one musculoskeletal disorder. The four sections detailed 1) general information relating to job characteristics; 2) prevalence of musculoskeletal disorders, symptoms, effect on nursing activities and treatment; 3) work activities and opinions on the work environment, including work psychosocial profile (happiness at work, self-perceived job competency, job aspirations, job satisfaction, work pressure and happiness outside work); 4) personal data (age, height and so on). The second section could be ignored by those not suffering from any musculoskeletal problems. The Physiotherapist Questionnaire This questionnaire consisted of the same four sections and included 46 questions in total. Slight alterations were made to the third section after consultation with a senior physiotherapist, and this consultation resulted in the inclusion of an additional question relating to the adoption of bent/stooped postures. All other sections were identical to the nursing questionnaire. Sample Altogether, 5029 questionnaires were distributed, 4235 to nurses and 794 to physiotherapists. The nurses were recruited from 7 hospitals within the Merseyside area but, in order to obtain an adequate sample, the physiotherapists were selected from 20 hospitals within a larger geographical radius. Nurses and physiotherapists of all grades and specialities were requested to complete the form, irrespective of whether or not they were suffering, or had previously experienced, any musculoskeletal symptoms. Distribution Questionnaires were sent by normal mail or delivered by hand to the head manager, the superintendent physiotherapist or the personnel department depending on the wishes of each hospital, and the number of questionnaires involved. It was not possible to standardise the distribution. The individual recipient was then responsible for distributing the questionnaires to various departments and wards to obtain a cross-section of the nursing/physiotherapy personnel. Each questionnaire, once completed, could be returned to the distributor to be forwarded en masse, or could be returned independently in an attached addressed envelope. The questionnaire was totally confidential so it was not possible to follow up those individuals who had not completed the questionnaire. 2.2 Analysis of data Data were analysed using the statistical software SPSS (version 6.01). To establish the relationship between two or more categorical variables, chi-squared analyses were used. Logistic regression analysis was used to identify risk factors associated with musculoskeletal disorders (i.e. presence or absence). Initially, those variables most likely to be significantly related to the presence of symptoms were added into the logistic regression analysis. The variables with the least significance were discarded from the analysis and replaced with other variables. All variables were entered into the analysis and discarded if non-significant. In the case of two similar, possibly related variables (for example self-perceived pressure at work and happiness at work), both were entered independently and in combination. If the

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variable remained significant independently and in combination, it remained in the model. Changes in the level of significance for each variable indicated which one was most strongly related to the presence of symptoms. 2.3 Prospective Study The number and details of the participants within this study could not be estimated in advance. The sample group consisted of nurses and physiotherapists presenting at an Occupational Health Department of an N.H.S. Trust with a musculoskeletal disorder and was therefore entirely dependent on the number of individuals affected and their willingness to chose this department as their site of treatment. The definition used to determine inclusion in the study was broad but covered musculoskeletal disorders of any anatomical area which could be attributed to work. Individuals who presented at the Occupational Health Department were given a full clinical examination by the Occupational Health Physician and any patients suffering musculoskeletal problems were noted. Inclusion in the study was therefore left to the discretion of this physician and the information collected was obtained after a full clinical examination. Data collection Case studies of individuals suffering severe musculoskeletal symptoms (serious disorders requiring active treatment and resulting in an inability to continue work) were recorded and their progress followed over a 12-month period. Information included a clinical diagnosis and the treatment initiated, the severity of the problem and sickness absence and the perceived cause of the injury. Information from patient records was transferred onto a data collection sheet through consultation between researcher and physician to maintain confidentiality and avoid any compromise of patient records. Secondly, the number of individuals consulting the Occupational Health Department was recorded over a one-month period to ascertain the number of people using this practitioner as the mode of treatment. Some details relating to the location of the disorder and the perceived cause were also recorded.

3. Results 3.1 Retrospective Study Responses to Cross-Sectional Questionnaire A response rate of 44% (n=349) was obtained for the survey of physiotherapists; the questionnaire was completed by 19.3% (n=813) of the nursing personnel sampled. Sixty-four of the questionnaires returned were unsuitable for analysis due to incorrect completion or they included domiciliary nursing. The sample characteristics of both populations are shown in Table 1. There was no significant difference between the percentage of males and females in the nursing and physiotherapist groups (p>0.05). There was no significant difference between the ages of nurses and physiotherapists (p>0.05). The height and body mass both differed significantly between the nurses and the physiotherapists. Physiotherapists tended to be taller and centred around 55-65 kg compared to nurses who were shorter and had a wider body mass range (both p<0.05).

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Table 1. Sample characteristics of questionnaire respondents (mean ± standard deviation).

(mean) (SD (male) (female) (mean) (SD) (mean) (SD)

Age (years)

Sex Height (cm) Mass (kg) Sample size

Nurses 36.5 9.1 67 705 164 8.4 66.0 12.9

Physiotherapists 33.5 9.7 33 292 166 13.1 64.0 9.5

774

325

Epidemiology of musculoskeletal disorders The annual prevalence of musculoskeletal disorders of various locations for nurses and physiotherapists combined was 49%. The point prevalence was 20.7%. Almost half of those (42.2%) who had suffered symptoms in the past year were therefore exhibiting symptoms at the time of the questionnaire. Respondents indicated the site of musculoskeletal symptoms on an anatomical diagram. These sites were grouped into specific areas for analysis; for example, low back, buttocks, hips, pelvis and upper legs were included in one category. The anatomical areas and corresponding percentage of nurses and physiotherapists who had experienced symptoms in the past year are shown in Figure 1. HI Low-back, buttocks, pelvis, hips, upper legs

13%

• Neck, shoulder, upper/mid back, upper arm, chest 46o/0

j D Wrist, hand, forearm, elbow, fingers D Knee, lower limb

I Torso: whole body area

21%

0 Other, not stated, diverse body regions

Figure 1. Percentage of nurses and physiotherapists who suffered musculoskeletal disorders in each anatomical area.

There was no significant difference in the relative percentages of nurses and physiotherapists who had suffered a musculoskeletal disorder during the past year (p>0.05). The location of disorders did differ significantly (p<0.05) between the two samples. Physiotherapists experienced more symptoms relating to the wrist, fingers, hand and forearm, knee and lower limb (p<0.05).

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Anthropometric, demographic, and social variables There was no significant difference in height or body mass between those suffering and those not suffering musculoskeletal symptoms. There was also no difference concerning smoking habits, how many units of alcohol they consumed in the average week and their perceived fitness level. There was no significant difference between the ages of nurses and physiotherapists in the sample and an approximately equal percentage of nurses and physiotherapists reported a musculoskeletal disorder (p<0.05). Participants were grouped into six categories according to their age. Age was found to have a significant effect on the reporting of musculoskeletal disorders (p<0.05). Nurses and physiotherapists showed a significantly higher percentage of musculoskeletal disorders between the ages of 30 and 59 than above or below this range (seven subjects being of over 60 despite this being the recognised retirement age). The prevalence of musculoskeletal symptoms was proportionately the greatest for those staff aged between 50 and 59 years. Absence from work Absence from work due to musculoskeletal symptoms at any time during their working life was indicated by 25% of respondents. In the past year, the mean number of days to be taken off was 1.5 (± 14), but five of the participants had taken more than one hundred days off work, with the maximum duration of absence being 335 days. In total, musculoskeletal disorders accounted for 19% of all absences from all respondents within the previous years. Perceived causes Regarding their lifetime experiences, 36.4% of respondents with musculoskeletal symptoms could recall a specific causal incident. For 66.7%, the cause indicated was patient handling and lifting. Similarly, of those personnel who attributed their symptoms to continued exposure to a stressor, patient handling and lifting was implicated by 51.3% of respondents. Medical consultation Respondents were asked to indicate from whom treatment for their musculoskeletal disorder had been received. A general practitioner was consulted by 29% of respondents, a physiotherapist by 9% and these two practitioners in combination by 11%. Other sources of advice included consultant/specialists, complementary therapists (e.g. acupuncturist, chiropractic, osteopath), the occupational physician, the Accident and Emergency department or combinations of these. A significantly smaller proportion of physiotherapists consulted a medical practitioner regarding their musculoskeletal disorder than nurses did (p<0.05). Treatment The main treatment prescribed for musculoskeletal disorders was physiotherapy (31%), followed by medication (22%) and these modalities in combination (16%). Surgery had been required by only 3.5% of sufferers and rest alone had been the therapy prescribed for 3% of respondents. Those using complementary therapy (e.g. acupuncture, chiropractic, osteopathy) alone numbered 2%, although 8% had received complementary therapy in combination with other treatment. Following treatment, the symptoms had become less severe for 64% of respondents and 22% had indicated that the musculoskeletal disorder had disappeared. There was no significant difference between the number of physiotherapists and the number of nurses receiving treatment for their musculoskeletal disorders despite fewer physiotherapists consulting a medical practitioner, because more physiotherapists relied on self-treatment, or informal treatment from a colleague.

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Occupational adaptation Symptoms had forced 4% of sufferers to change job/specialities. Over half (56%) of all sufferers had modified the way they performed their tasks to alleviate any discomfort. The main ways of modifying their tasks were to change their technique/posture (23%), to avoid (where possible) carrying out specific problematic tasks (18%) and to seek assistance, either from staffer patients (12%). Again the main tasks in which changes were implemented were chiefly concerned with lifting or transferring patients and equipment (54%), but 13% of respondents stated they found 'all tasks' to be problematic and require changes in the way they were performed. Suitability of-work environment The working environment was deemed to be unsuitable by 40% of respondents. Personnel perceived the main problems to be i) a poorly designed work area or space constraints (61%) and ii) unsuitable equipment. The regular performance of overhead tasks was indicated by 40% of the whole sample, with cupboards/shelving (33%) and medical attachment (21.5%) cited as the main reasons for this action. Lifting and patient handling It was indicated by 92% of nurses that they were involved in the lifting and handling of patients. Three quarters (n=380) of those individuals carried out less than 10 manual transfers per shift without the use of any assistive devices, and one-quarter (n=127) carried out more than 10 transfers, with the maximum per shift indicated as 60. This value was comparable to the number of lifts that physiotherapists performed without the use of assistive devices (77% less than 10 per shift and 23% more than 10 per shift). The reasons given for not always using assistive devices differed between the nurses and physiotherapists. Nurses indicated that assistive aids were not always available/appropriate (49%) or not required (42%). Physiotherapists also rated these reasons highly, 21% and 31% respectively, but 28% of respondents felt the main reason was that lifting and manually transferring patients were part of the rehabilitation process, with patients encouraged into normal functioning requiring manual assistance in movement. Predictive variables for musculoskeletal disorders The results of the logistic analysis are given in Table 2. The risk of incurring a musculoskeletal disorder increased by 6% for every unit increase in perceived work pressure, and by 13% when the staff felt their work often involved repetitive tasks. Specialties with high risk and low risk were identified and are illustrated in Table 4 and Table 6 for nurses and physiotherapists respectively. Table 2. Variables in overall logistic equation for musculoskeletal disorders (nurses and physiotherapists combined).

S.E. B Df Variable Perceived work pressure 0.062 0.014 1 1 Performance of repetitive tasks -0.140 0.067 1 Work specialty -0.323 0.068 Constant -1.357 0.314 1 All variables except work specialty are all arbitrary units. 'B' are the coefficients of the logistic regression model (Norusis,

P< 0.000 0.038 0.000 0.000

1994).

Esp(B) 1.064 0.870 0.724

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Predictive variables for musculoskeletal disorders in nurses Logistic regression analysis considering nurses only is given in Table 3. Table 3. Variables in logistic equation for musculoskeletal disorders (nurses only). Variable B S.E. df Exp(B) P< Perceived work pressure 1 0.000 1.069 0.066 0.017 Work specialty* 1 0.000 Specialty (1) 2 0.000 0.540 -0.617 0.123 1 Specialty (2) 0.380 0.906 0.112 -0.098 1 Age (years) 1.031 0.001 0.031 0.009 1 Constant 0.000 -2.451 0.489 * Initial logistic regression analysis indicated specialties below -0.04, between -0.04 and +0.04 and above +0.04. These 3 groups were used in subsequent analysis.

The risk of nursing staff suffering musculoskeletal disorders increased by 7% for every unit increase in perceived work pressure, and 3% for each yearly increase in age. A low risk group of specialties was identified and nurses working in these specialties were 46% less likely to incur symptoms than those in the other included specialties. This is shown in Table 4. Table 4. Low and high risk specialties for musculoskeletal disorders in nurses only. High risk specialties General medicine Orthopaedics Theatre/recovery Intensive care Accident and emergency Oncology E.N.T. Plastics/burns Rheumatology Spinal injuries Respiratory care Rehabilitation Coronary care Midwifery/obstetrics/gynaecology Renal/urology

Low risk specialties Surgery Paediatrics Care of the elderly Psychiatry/mental health Out patients Dermatology Haematology

Predictive variables for musculoskeletal disorders in physiotherapists The logistic regression analysis considering physiotherapists only is given in Table 5. Table 5. Variables in logistic equation for musculoskeletal disorders (physiotherapists only). Variable Regular stooped posture Work specialty Constant

B -0.267 -0.614 -0.536

S.E. 0.117 0.214 0.215

df 1 1 1

P< 0.023 0.004 0.013

Exp(B) 0.766 0.541

Those physiotherapists whose work required the regular adoption of stooped positions were 23% more likely to suffer musculoskeletal symptoms than those who answered 'no' to this

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question. Those personnel working in the identified high risk specialties had a 46% greater likelihood of incurring musculoskeletal symptoms. These specialties are listed in Table 6. Table 6. High and low risk specialties for musculoskeletal disorders in physiotherapists. High risk specialties General medicine Paediatrics Orthopaedics Care of the elderly Psychiatry/mental health Out-patients Bums and plastics Midwifery/obstetrics/gynaecology Neurology Rheumatology Respiratory care Rehabilitation Musculoskeletal

Low risk specialties Surgery Intensive care Accident and emergency Oncology Coronary care Spinal injuries

In all the above analyses, the anthropometric data had no significant predictive value. Age, smoking, alcohol consumption and fitness level also were not significant indicators. The number of lifts performed did not have overall significance when the nurses and physiotherapists were considered independently. The number of lifts performed by nurses and the years in the job showed some significance, but this result was not independent, with the significant effect of one variable being eliminated when the other was included. The age of the nurse remained a significant predictor in all analyses, so was deemed to be a more important indicator than the number of years in the job. Predictive variables for low-back pain (Nurses and physiotherapists combined) The logistic analysis is given in Table 7. Table 7. Variables in logistic equation for low back pain (nurses and physiotherapists combined). Variables % of time on feet in shift Perceived work pressure Job aspiration/motivation Perceived work happiness Constant

B. -0.012 -0.075 0.121 -0.025 3.275

S.E. 0.005 0.017 0.029 0.010 0.556

df 1 1 1 1 1

P< 0.013 0.000 0.000 0.016 0.000

Exp(B) 0.989 0.928 1.129 0.976

The risk of nursing and physiotherapy staff suffering from low-back pain increased by 1% for every percent increase in the time they spent on their feet during the course of an average shift. The psychological well-being of the individual also had predictive qualities. The risk increased by 7% for each unit increase in work pressure, and by 2.5% for each unit increase in work happiness. Conversely, the risk decreased by 13% for each unit increase in job aspiration.

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Predictive variables for low-back pain (Nurses only) The results of the logistic regression analysis are given in Table 8. Table 8. Variables in logistic equation for low-back pain (nurses only). Variables Job aspiration/motivation % of time on feet in shift Perceived work happiness Perceived work pressure Constant

B. 0.125 -0.016 -0.028 -0.094 4.163

df 1 1 1 1 1

S.E. 0.035 0.007 0.012 0.021 0.750

P< 0.000 0.013 0.023 0.000 0.000

Exp(B) 1.134 0.984 0.972 0.910

The risk of the nurses suffering from low-back pain decreased by 13% for every unit increase in job aspiration. The risk increased by a small percent with increased time spent by the nurses on their feet, increased happiness at work and increased job pressure. Predictive variables for low-back pain (Physiotherapists only) The results of the logistic analysis are shown in Table 9. Table 9. Variables in logistic equation for low-back pain (physiotherapists only). Variables Work specialty Specialty (1) Specialty (2) Constant

B.

0.717 0.208 1.711

S.E.

df

0.415 0.275 0.227

2 1 1 1

P< 0.000 0.084 0.449 0.000

Exp(B) 2.048 1.231

The only risk variable of predictive value for low-back pain in physiotherapists was the specialty in which they worked. In the above analyses of low-back pain, the anthropometric data and the variables considering the psychosocial status of the individual outside work again had no predictive value. Carrying out manual lifts and the number of manual lifts performed by the nurses and physiotherapists also were not significant indicators of the prevalence of low-back pain.

3.2 Prospective Study In August 1997, all individuals visiting the department with musculoskeletal disorders were recorded for the study, totalling 9 nursing staff and 2 physiotherapists. The characteristics of these 11 are given in Table 10. It was indicated by the participating Occupational Health Physician that this constituted a typical month in the department, in terms of the number of individuals presenting with musculoskeletal disorders and the types of problems experienced. It was not possible to keep detailed accounts of all musculoskeletal injuries being presented at the Occupational Health Department within the 12-month period due to the increased work load this would incur for the Occupational Physician. Information was collected on seven patients with severe problems and their treatment and progress were followed as case studies. The sample characteristics are presented in Table 11.

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Table 10.

Characteristics of individuals consulting the Occupational Health Department in August 1997. Job title

Musculoskeletal Disorder

Perceived Cause

Radiographer

Low-back pain and sciatica

Lifting patient

Radiographer

Low-back pain and sciatica

Lifting equipment

Healthcare Assistant Senior Enrolled Nurse Senior Enrolled Nurse Senior Enrolled Nurse Sister

Fractured scaphoid on left wrist Rotator cuff aggravation

Trapped hand in cot side

Rotator cuff aggravation

Lifting

Rotator cuff aggravation

Lifting

Cervical spondylosis

Lifting

Staff Nurse

Cervical spondylosis

Lifting

Staff Nurse

Cervical spondylosis

Lifting

Physiotherapist

Neck injury

Lifting patient

Physiotherapist

Low-back pain and left-sided sciatica

Lifting

Lifting

Table 11. Sample characteristics of case study subjects. Ref no.

Job title

Specialty

Age Sex

Disorder

1

Auxiliary

Orthopaedic

28

Female

2

Auxiliary

Orthopaedic

32

Female

3

S.E.N.

Out-patients

49

Female

4

R.G.N.

Renal Unit

26

Female

5

R.G.N.

Elderly

38

Female

6

Radiographer

Radiography

37

Female

7

Auxiliary

Orthopaedic

41

Female

Lumbar spondylosis, L3, L4, L5, L5/S 1 , S 1 nerve root entrapment = low back pain and sciatica Lumbar spondylosis, L3, L4, L5, L5/S 1 = low back pain and left sided pain Nerve root narrowing, C4, C5, C6 = neck pain and bilateral brachialgia Narrowing at L5/S1 = low back pain, right sided sciatica, loss of ankle flexion L5/S 1 disc prolapse; S 1 nerve root narrowing = low back pain and sciatica C5 C6 disc protrusion = restricted cervical movement and brachialgia Lumbar/sacral spondylosis = left sided sciatica

S.E.N. = State enrolled nurse R.G.N. = Registered general nurse

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Location ofmusculoskeletal disorders The highest number of problems concerned the lower back, with patients usually suffering additional sciatic symptoms. The second most commonly injured area was the neck, with 2 of the 6 individuals also suffering brachialgia. Three staff had shoulder disorders and the final subject had a fractured scaphoid. Absence from work All subjects who had visited the Occupational Health Department in August had had a period of time off work. The average time of sickness absence for the stated neck and shoulder injuries was approximately one month. However, the physician estimated that the physiotherapist with low-back pain and left-sided sciatica would be absent from work for anything up to one year depending on the response to treatment. Considering the seven case studies, the Occupational Health Physician was asked to record the number of days off work so far, due to the musculoskeletal disorder. This number ranged from 153 days for subject 3 to 335 days for subject 4. Absence from work was continuous for all subjects with the exception of subject 1 who returned to work between two periods of sick leave. Treatment and outcomes All injuries were new problems, with the exception of the physiotherapist with low-back pain and sciatica which was an old recurring problem. Assuming that August was a typical month, it can be deduced that 120 new cases are presented at the Occupational Health Department each year. All subjects who visited in August were treated at the Occupational Health Department with physiotherapy. The treatment initiated for the case studies and the outcome of that treatment are given in Table 12. Of the 7 individuals, it can be seen that 3 had to be retired from nursing and this was the likely outcome for the fourth nurse whilst the remaining 3 continued to work having had symptoms relieved. Table 12. Treatment and outcomes for the case study subjects. Ref no.

Diagnosis

1

MRJ scan

2

MRI scan

3

MRI scan

Initial Treatment Epidural injections Physiotherapy

Epidural injections 4 CT lumbar Physiotherapy scan and rest Rest, awaiting 5 MRI scan surgery Rest, awaiting 6 MRI scan surgery 7 MRI scan Rest, not suitable for surgery MRI = Magnetic Resonance Imaging CT = Computerised Tomography

Follow Up

Follow Up

Retired from nursing Changed to specialty with no lifting Pain free and back to Work Retired form nursing

No problems

Discectomy. Still severe sciatica. Off work Discectomy. Back to work, symptom free Retired from nursing

Likely to be retired from nursing

No problems

Perceived causes The majority of subjects attributed their symptoms to lifting activities. Of the case study subjects, 6 indicated a single lift as the cause, and subject 6, the radiographer, felt the injury was attributed to the cumulative effects of lifting heavy equipment over a number of years.

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Lifting of both patients and equipment was therefore given as the cause of the injuries in all but one case.

4. Discussion Response rate for the retrospective study The questionnaires were distributed to head managers, the superintendent physiotherapist or the personnel department. This targeted individual was then responsible for forwarding the questionnaires to various heads of specialties and from there to the staff. It was not possible to quantify those questionnaires which had been sent to the hospital but not distributed to the staff due to questionnaires being lost or left over resulting from over-estimation of the number of staff in each specialty. It is therefore possible that fewer questionnaires than stated actually reached staff, partially accounting for the seemingly low response rate from the nurses. Financial restriction dictated that enclosing pre-pain envelops for the return of questionnaires was not possible and staff may have been reluctant to return the completed questionnaire to their manager. Prevalence of musculoskeletal disorders and sickness absence The questionnaire indicated that the annual prevalence of musculoskeletal disorders was 49% and the point prevalence was 20.7%. An annual prevalence and point prevalence of 38% and 14% respectively have been reported by Scholey and Hair (1989) for low-back pain in physiotherapists. Figures relating to other areas of the body affected by musculoskeletal disorders are harder to find and vary greatly according to the methodology employed. Ten new musculoskeletal cases were presented at the Occupational Health Department in the month considered, giving approximately 120 new cases each year. Re-occurring problems further increase the number of individuals being treated for a musculoskeletal complaint. The retrospective questionnaire reported that only 10% of sufferers consulted the Occupational Health Department in conjunction with other practitioners and that only 0.4% consulted the department as their only mode of treatment. The 120 new cases reported in the prospective study may only constitute a small part of the musculoskeletal problem. The literature suggests nursing is a profession with a high risk of back problems (Hildebrandt, 1995) but the results of the retrospective study indicate that nurses are at a high risk of musculoskeletal disorders in general. There was no significant difference in the relative percentage of nurses and physiotherapists who had suffered symptoms during their working life, indicating the problem is of the same magnitude in the physiotherapy staff as nursing staff, despite physiotherapists being an occupational group seldom studied (Molumphyefa/.,1985). Symptoms in the lower back, buttocks, pelvis, hips and upper legs accounted for the majority of problems, 46.3%. Physiotherapists were found to suffer significantly more symptoms than nurses relating to the wrist, fingers, hand and forearm and the knee and lower limb. This observation confirmed the findings of Bork et al. (1996) that nearly one third of the physiotherapists studied complained of wrist and hand symptoms. These symptoms were thought to be associated with prolonged manual therapy, for those involved in the most hours of manual therapy activities showed higher prevalence rates. The magnitude of the problem is evident when sickness absence is considered. Of the questionnaire respondents suffering musculoskeletal symptoms, 25% had indicated time off work, and musculoskeletal disorders accounted for 19% of all sickness absences of all staff surveyed within the previous year. Considering individual cases, the prospective study

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indicates potentially long periods of absence from work following a serious musculoskeletal disorder. Three of the seven case studies were retired from nursing and one further nurse was likely to leave the profession in the near future as discectomy had failed to eliminate her severe sciatica. Risk factors -within the profession Regarding the lower back alone, Ready (1993) identified certain high risk nursing wards as being associated with the greatest risk of injury. Vasiliadou et al. (1995) and Owen (1986) showed the risk of injuries was greater in specialities requiring the performance of physically demanding tasks. However, Harber et al. (1985) indicated no such difference believing that nurses with symptoms would 'select' themselves out of particularly detrimental roles, and that all nursing carried some 'dangerous' component. High and low risk specialties were identified in the retrospective study, with nurses and physiotherapists being at a significantly higher risk of suffering musculoskeletal disorders if working within one of the high risk groups. Considering only the nurses, those working in surgery, care of the elderly, paediatrics, psychiatry/mental health, out-patients, dermatology and haematology were 46% less likely to incur symptoms than staff working in other specialties. All other specialties were considered higher risk. Considering only physiotherapists, low risk specialties were surgery, intensive care, accident and emergency, oncology, coronary care and spinal injuries and again staff were 46% less likely to suffer symptoms when working in these areas. Despite some specialties being identified as high risk for both nursing and physiotherapist staff, the differences between the groups reflect the heterogeneous nature of the two occupations. Caution should be exercised in relating the results of nurses to healthcare personnel in general. Specialties concerned with mobile patients, for example dermatology, haematology and out-patients, may be expected to feature in the low risk group with minimal staff assistance being required. The varied nature of those specialties constituting the high risk group also indicate the magnitude of the musculoskeletal problem, as it is not only in the departments where increased manual handling may occur where nursing and physiotherapy staff are at risk. This finding supports the view that it is not patient handling alone that constitutes a risk for the onset of musculoskeletal symptoms. Harber et al. (1987) found that nurses actually performed more non-patient contact actions than patient contact actions and were frequently required to lift, pull, push and manipulate other objects often weighing more than 27.3 kg. While speciality appeared to be an important risk factor, the grade of work did not have significant influence on musculoskeletal prevalence with all grades being equally affected. This observation contradicts results of McGuire et al. (1995) who concluded that more untrained (auxiliary) nurses had time off work than other groups because this group was engaged more in 'heavy' work and increased manual handling. Mercer (1979, cited by Stubbs et al., 1983), showed nurses to have a short stay occupational profile, with 37% of the nurses studied being in their current post for less than one year. When correlating musculoskeletal disorders with speciality or grade, the cumulative effects of previous work may therefore be a cumulative factor and can not be ignored. Longitudinal research work may help to overcome this problem. The number of years working within the healthcare profession had previously been highlighted as significant. Specifically referring to back pain, Adams (1996) stated that newly qualified/trained nurses were most at risk from injuries because their intervertebral discs had had insufficient time to 'catch up' with strengthening muscle and bone. It could therefore be argued that an initial period of physical training and strengthening is required

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before staff have increased protection from symptom onset. Pain in the arm and neck has also been associated with the number of years in the job (Engels et al., 1996). Leg and back pain was not associated with years at work but this finding may be due to the 'healthy worker effect', with those suffering leg and back pain leaving the profession because their symptoms are more debilitating (Engels et al., 1996). Other researchers have found no association between the number of years in the healthcare profession and pain in the neck and shoulders, but there was a 'tendency' towards an association between years of work and low-back pain (Ahlberg-Hultenef a/., 1995). The number of years working in the profession did not have a significant predictive value for annual prevalence, but the age of symptomatic and asymptomatic individuals was significantly different (p<0.05). Nurses and physiotherapists showed a higher percentage of musculoskeletal disorders between the ages of 30 and 59, and particularly between 50 and 59 than staff at the higher or lower age spectrum. The logistic analysis also highlighted age as a significant risk factor for the prevalence of musculoskeletal disorders in the nursing group only, with nurses having a 3% increase in risk for each yearly increase in age. The above analysis would appear to suggest the importance of the relationship of work and a physiological ageing response to be responsible for the occurrence of symptoms, with time spent working in the job having less relevance. Vertebral discs are known to weaken with time (Hsiang et al, 1997). If this was true, it would be expected that the over-60 category would have more individuals with, than without musculoskeletal problems, which was not shown. This finding may be due to the limited number of subjects within this age category, poor recall of distant memories required when completing the questionnaire, or potentially the "healthy worker" effect in which individuals susceptible to musculoskeletal problems had left the profession before reaching the age of 60, leaving only those with low susceptibility within this age category. Medical consultation and treatment profiles Only 29% of sufferers had consulted a medical practitioner concerning their musculoskeletal disorder. The Royal College of Nursing (1979) (cited by Stubbs et al., 1983) is quoted as saying that back pain "has been and still is regarded as an occupational hazard of nursing" It would appear that this view still prevails, with few nurses and physiotherapists seeking help. The general practitioner (G.P.) was the service most often used, followed by a physiotherapist and these two methods in combination. The hospital occupational health department was rarely visited as the only source of treatment, but was more often used in combination with other methods. Complementary therapy (e.g. acupuncturist, chiropractic, osteopath) appeared to be an attractive alternative for many sufferers. A significantly smaller number of physiotherapists compared to nurses consulted a medical practitioner (p<0.05). It is conceivable that many physiotherapists rely on selftreatment or treatment from a colleague on a more informal basis than formally visiting a practitioner, having the knowledge and expertise to do so. In such cases, a medical practitioner may only be consulted in more severe cases. The questionnaire indicated that physiotherapy was the major treatment prescribed, followed by medication and the two in combination. Commonly, individuals took analgesics to reduce the pain without seeing the doctor and returned to work with no sickness absence. Surgery had actually been required by 3.5% of respondents. There was no significant difference in the number of nurses and physiotherapists receiving treatment (p<0.05), confirming the premise that physiotherapists often rely on self-treatment. Treatment seems to be successful in most cases, with 64% of respondents indicating their symptoms were less severe, and 22% indicating they had disappeared completely following treatment. The

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remaining 14% constitutes those individuals with chronic and recurring problems and indicates the problem faced in treatment of a group of disorders where a cure is still not available and physiological cause unknown. Physiotherapy was also used to treat the case studies of the prospective study. However, these individuals represent the serious end of the spectrum of musculoskeletal disorders with two of the seven requiring epidural injections and two others awaiting surgery. Precipitating factors (Physical) Considering individuals' experiences of musculoskeletal disorders, 36.4% of respondents suffering musculoskeletal symptoms could recall a specific causal incident. Of these individuals, patient handling and lifting was stated as the cause by 66.7%. Of those personnel who could not attribute their symptoms to a single incident, but rather to continued exposure to a stressor, patient handling and lifting was implicated by 51.3%. All but one individual (n=17) presenting at the Occupational Health Department cited lifting as the cause of their musculoskeletal complaint. Patient handling is frequently cited as the most common cause precipitating a period of low-back pain in both nursing (Jensen, 1990) and physiotherapy (Bork et al, 1996). Subjective ratings from nurses have been taken which indicate that patient handling and transferring tasks have the highest stress scores, both in terms of the hardest and most frequent tasks (Owen and Garg, 1989; Smedley et al, 1995). There has been little attention given by researchers to the role of lifting and patient handling and the onset of other musculoskeletal disorders and this present study failed to draw a connection between these types of task and musculoskeletal problems. Of the nursing group, 92% indicated that they were involved in 'patient lifting/manual handling'. Considering both nurses and physiotherapists, approximately three-quarters of those involved carried out less than 10 manual lifts per shift without the use of assistive devices and about one-quarter carried out more than 10 per shift. A multitude of assistive devices has recently been introduced into hospitals to reduce the physical effort of manual handling (Bell et al., 1979). Again, numerous reports have advocated the benefits of such devices (Hofmann et al., 1994; Smedley et al., 1995; Zhuag et al, 1999), but this current work demonstrates manual handling still occurs. Nurses indicated that assistive aids were not always available/appropriate (49%) or not required (42%). Physiotherapists highlighted the same reasons as being important, 21% and 31% respectively, but 28% of respondents felt the main reason was that manual handling was an important part of patient rehabilitation, patients being encouraged to bear weight while getting manual assistance from the physiotherapist. McGuire et al (1995) showed similar results, with 60.5% of the respondents to the nursing questionnaire admitting not using aids in all appropriate situations. The main reason was unsuitability to the task. This would appear to suggest that the installation of aids and the training of staff are not necessarily sufficient, and that the situation must be considered more closely to ensure aids are appropriate for the varying demands of the departments and that staff are able to see their value. Garg et al. (1992) showed that transfers using mechanical hoists were slower than manual transfers, requiring an extra 65 minutes per shift, or 14% of the work shift, to perform the same work tasks. The additional time required when using aids can only be compensated for by increased staffing levels. Despite the focus of much research on lifting and patient handling and its accepted detrimental effect, the retrospective study failed to identify lifting as having a predictive value for the onset of musculoskeletal disorders when the associated factors were entered into the logistic regression analysis. The number of lifts performed was entered into the analysis

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of both general musculoskeletal disorders and low-back pain specifically, and failed to yield significant results. The number of lifts per shift performed by nurses only and the years in the job showed some predictive significance for musculoskeletal disorders in general, but this result was not independent, with the significance of one variable being eliminated when the other was included. As mentioned, age remained a significant predictor in all analyses, so was deemed more important than these two associated factors. It is conceivable that lifting and manual handling have become popularly accepted causes of back injuries such that healthcare personnel and researchers alike have until now seen no cause to explore these factors in more detail or other potential causes. Garg et al. (1991) showed that pulling the patient with a sling or belt resulted in significantly lower forces in the erector spinae and compressive forces at L5/S1 compared to lifting. In many analyses, this activity would still be labelled manual handling so the precise detrimental actions/methods of handling could not be ascertained. Static actions (defined here as being postures held for more than 30 seconds) have been shown to occur in nursing almost as commonly as dynamic actions. The association between cumulative stress from the maintenance of static postures and back pain was demonstrated by Kumar (1990) with job assessments showing load to be greater in back pain sufferers than non-sufferers. Interestingly, this research showed those physiotherapists whose work regularly required the adoption of stooped positions were 23% more likely to suffer musculoskeletal symptoms than those who gave a negative response to this question. This was the only variable showing predictive value for the physiotherapy group except for the specialty in which they worked. Garg et al. (1992) indicated that many nursing tasks required bent-over postures and ensuing fatigue of back muscles. It was suggested that transferring a patient immediately afterwards could be especially detrimental. This question was not included within the questionnaire for nurses as it was deemed more specific to physiotherapy work than nursing tasks, so comparisons can not be drawn. It is nevertheless interesting to identify its relative importance among the physiotherapists compared to the lack of statistical significance shown by the lifting variables. Staff members who felt their work often required the performance of repetitive tasks were 13% more likely to suffer a musculoskeletal disorder than those who answered 'no' to this question. In this case, repetition is unlikely to mean highly repetitive tasks with a short task cycle (for example assembly line work where task cycles can be approximately 30 seconds). It is more likely to mean the repeated performance of a task throughout the day, such as stripping and re-making beds, toileting patients or re-dressing wounds. The association between repetition of tasks and musculoskeletal disorders may therefore be due to some 'dangerous' component of the tasks that is being repeated. Repeatedly assisting patients to the toilet involves manual handling and dressing wounds involves static trunk flexion, both of which increase the risk of suffering a musculoskeletal disorder. When considering the working environment, 40% of respondents deemed it to be unsuitable for the completion of required tasks. The main problem cited was a poorly designed work area or space constraints (61%). Bathrooms, especially in older hospitals, are often cramped because considerable amounts of equipment, including a hoist, are required in a small space. The problem of space has been reported in other studies (Engels et al, 1996), with limited space between the beds being reported by 41% of questionnaire respondents. Lack of space compounds the problems of lifting and handling patients because an optimum lifting positions can not be assumed, and trunk twisting becomes increasingly necessary (Blue, 1996). It is important to recognise the need to address design of space and equipment, not just implement lifting devices that are not appropriate to the situation (Garg et al., 1992).

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As mentioned, the other potential precipitating factor regarding the physiotherapy staff was the involvement in manual therapy. Bork et al. (1996) believed this to be responsible for the increased percentage of musculoskeletal problems relating to the wrist and hands. Physiotherapists had significantly more problems in this anatomical area than the nurses, and the subsequent ergonomic risk assessment of the work environment should shed light as to the possible causes of this finding. Low-back pain in the nursing personnel was significantly associated with the percentage of time on the feet within a working shift. This was not significant when musculoskeletal disorders in general were considered, so prolonged standing must be somehow detrimental to the back only. Prolonged standing/walking, may increase the rate of natural spinal shrinkage; shrinkage refers to the process by which fluid is expelled from the nucleus pulposus when the compressive loads on the discs exceed the interstitial osmotic pressures of the discs' tissues (Helander and Quance, 1990; Van Diee'n and Toussaint, 1993). The result is damage to the end-plates, leading to irreversible loss in disc height (Stalhammar et al., 1989), further disc degeneration and stiffness. Bulging on the annulus decreases the distance to nerve roots and increases the probability of nerve root pressure and pain (Eklund and Corlett, 1984). Prolonged standing is likely to accentuate this process, and the situation will be compounded if the individual increases the compressive forces acting on the spine by undertaking further physical activity or adopting postures that load the spine. Alternatively, prolonged standing results in strain on ligaments, with the accompanying muscular contraction leading to fatigue, strain and discomfort (Blue, 1996). Spinal loading may potentiate back pain, but the resultant spinal shrinkage can quickly be reversed with the initiation of rest periods where the spine will be unloaded, with offloading being inversely related to loss of stature (Foreman and Troup, 1987). Gains in stature are very rapid at the beginning of rest periods so even short, frequent breaks would be beneficial to aid metabolism of the spine (Stalhammar et al., 1989 and 1992). Eklund and Corlett (1984) showed that lying down and the Fowler position induced greatest increases in stature compared to other postures. Taking short but frequent breaks and lying down for a period whilst at rest may be beneficial, if possible, in reducing back pain in the nursing staff. It may also be beneficial for the nurses to perform tasks sitting down where possible. Such measures may help reduce the likelihood of back pain associated with spinal shrinkage. Precipitating factors (Psychos octal) As musculoskeletal disorders are multi-factorial in nature, it is no longer adequate to consider only the biological and biomechanical aspects of the occupation. An increased focus on psychosocial characteristics of the individual, both relating to work and general life, is essential if the whole picture is to be understood. Cox (1993) defined psychosocial hazards as 'aspects of job content, work organisation and management and of environmental, social and organisational conditions which have the potential for psychological and physical harm'. Work was felt to be a stressor when the demands could not be matched by the individual's capabilities, especially when the individual has little control and support. This present study indicated that the psychological variables proved to be the most useful set of factors in predicting those individuals likely to report both musculoskeletal disorders and low-back pain specifically. Work pressure was especially important, having significance in the overall analysis of musculoskeletal disorders and low-back both for all subjects and when nurses were analysed independently. The risk of incurring a musculoskeletal disorder increased by 7% for nurses with every unit increase in work pressure, and the risk of sustaining an injury to the low-back region increased by 9%. These results were highly

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significant. This variable had no predictive value for the physiotherapists, again highlighting the danger of generalising nursing results to other healthcare professionals. The importance of the psychological factors has been reported in other studies (Engels et al, 1996). Multivariate analysis indicated that aspects of work pressure were associated with all three musculoskeletal disorders studied but ergonomic aspects (i.e. poor layout of ward, nonheight adjustable beds and so on) were not. However, Engels et al. (1996) also reported that musculoskeletal disorders were associated with physical work load, so the psychological factors were not solely responsible for the presence of symptoms. Psychological demands, such as are implicit in high work load and high work pressure, may be associated with emotional states such as stress and worry, thought to cause an increase in adrenaline hormone levels and increased muscle tension through calcium mediated muscle contractions. Ohlsson et al. (1994) related work overstrain and resultant muscle tension to disorders of neck and upper limb in females working in the fishing industry. Leino and Hanninen (1995) reported similar results when mental overstrain was considered in workers in the metal industry. Physiotherapists were used to eliminate subjective findings and inter-subjectivity. The authors found no association between musculoskeletal disorders and physical work load and concluded that the psychosocial factors were more related to morbidity than physical factors. The stress induced theory would only account for muscular pain and not pain relating to the skeletal or nervous systems Staff with increased perceived work pressure may be more likely to perform tasks hurriedly, possibly resulting in accidents or falls and musculoskeletal problems. Of those nurses and physiotherapists who could recall a specific causal incident, 7.5% indicated a fall to be responsible. Staff working hurriedly may also be less likely to take the extra time involved in the implementation of assistive devices and therefore move patients manually. The extra time involved in using assistive aids was the reason given for lifting manually by only 1.2% of nurses and the same percentage of physiotherapists. However, it may only take one manual patient transfer to damage vertebral structures. Job aspirations and happiness at work also were seen to be significant indicators for lowback trouble for the nursing population. Those nurses with the higher job aspirations were less likely to suffer low-back pain. It may be that nurses highly motivated to move up the professional hierarchy would be less likely to notice slight musculoskeletal problems with more of their time devoted to improving their nursing skills. Alternatively, nurses already suffering symptoms which they perceived to be work related may be more disillusioned with the occupation and less motivated to improve their job status. Increased happiness at work was related to an increased risk of nursing staff suffering low-back pain, although this variable was not as highly significant in the analysis as work pressure or the percentage of time spent on the feet. It is possible that 'happiness' refers to mood state in which nurses could be more care-free and more vulnerable to musculoskeletal damage as a consequence of lack of concentration for personal welfare. Finally, caution must be exercised in attributing causation from results of the logistic analyses. It is just as conceivable that respondents have low job aspirations and little desire to move up the professional hierarchy because a musculoskeletal disorder is reducing their enjoyment of their job, as it is that low aspirations may be a predictive cause of symptoms. This possibility is true for perceived work pressure, with musculoskeletal problems being responsible for, or a result of, increased work pressure. Longitudinal work should assist in determining the direction of the causal chain. In addition to individual psychological variables, personal characteristics and social background are thought to be equally important in the potential development of musculoskeletal symptoms. The incidence of certain musculoskeletal disorders is reported

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to be higher in females than males (Bernard et al., 1994; Ekberg et al, 1994; Hagberg et al., 1995). Additionally, height, strength/fitness and body mass (in terms of obesity) have also been thought to increase the risk of occurrence (Arad and Ryan, 1986; Frymoyer and CatsBaril, 1987; Makela et al., 1993), but the evidence is far from conclusive. Engels et al. (1996) reported no relation between self-reported musculoskeletal complaints in nurses and gender, body mass index and height. When entered into the logistic regression analysis of this study, gender and anthropometric data were not significantly associated with the presence of symptoms. Other factors thought to be associated with increased musculoskeletal problems are smoking (Niedhammer et al, 1994), alcohol consumption (Ready et al, 1993) and mechanical vibration (Neidhammer et al, 1994). When considering the connection between smoking and vibration to musculoskeletal disorders, conclusive evidence is somewhat lacking and again, the cross-sectional design of many studies makes the attribution of causality impossible. The social and individual factors examined in the present study failed to show any predictive value. Smoking, alcohol consumption, fitness level, commuting distance and suffering from metabolic diseases were all entered into the logistic equation and all failed to show any significant results to support a positive connection. In the case of smoking, Owen (1986) found no difference between smokers and non-smokers and back pain, but the injured group smoked on average 23 cigarettes per day and the non-injured smoked only 10 per day. The detrimental effects may therefore be attributed to the amount smoked and this work only considered yes/no responses to smoking. Happiness outside work was also not significantly related to the presence/absence of a musculoskeletal disorder or low-back pain. 5. Conclusions The annual prevalence of musculoskeletal disorders in nurses and physiotherapists was 49%. Symptoms relating to the lower back, buttocks, pelvis, hips and upper legs accounted for the majority of problems in the questionnaire. The lower back was also the anatomical area most affected by those presenting at the Occupational Health Department. Whilst both nurses and physiotherapists suffered considerable back-pain, physiotherapists suffered significantly more symptoms relating to the wrists, hands, fingers and forearm, knees and lower limb. When the cause of symptoms was considered, patient handling and lifting was identified as the main perceived cause of musculoskeletal disorders, both in the retrospective and prospective studies. However, the number of lifts performed each shift failed to predict the prevalence of low-back pain and it is likely that manual handling is required in most aspects of nursing and physiotherapy. Evaluating exactly which manual handling tasks are responsible for symptoms is required. Physiotherapists suffered musculoskeletal symptoms if their work regularly required the adoption of stooped postures. Nurses who spent longer time on their feet during the course of their shift were more likely to have back problems and nurses who stated a high perceived work pressure had a higher musculoskeletal and low-back pain prevalence.

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Hsiang, S.M., Brogmus, G.E. and Courtney, T.K. (1997). Low back pain (LBP) and lifting technique - a review. International Journal of Industrial Ergonomics, 19, 59-74. Jensen, R.C. (1990). Back injuries among nursing personnel related to exposure. Applied Occupational and Environmental Hygiene, 5, 38-45. Kumar, S. (1990). Cumulative load as a risk factor for back pain. Spine, 15, 1311-1316. Larese, F. and Fiorito, A. (1994). Musculoskeletal disorders in hospital nurses: A comparison between two hospitals. Ergonomics, 37, 1205-1211. Leino, P.I. and Hanninen, V. (1995). Psychosocial factors at work in relation to back and limb disorders. Scandinavian Journal of Work, Environment and Health, 21, 134-142. Makela, M., HeliOvaara, M., Sievers, K., Knekt, P., Maatela, J. and Aromaa, A. (1993). Musculoskeletal disorders as determinants of disability in Finns aged 30 years or over. Journal of Clinical Epidemiology, 46, 549-559. McGuire, T., Ainslie, A. and Dewar, B.J. (1995). An assessment of moving and handling practices among Scottish nurses. Nursing Standard, 9, 35-39. Molumphy, M., Unger, B., Jensen, G.M. and Lopopolo, R.B. (1985). Incidence of work-related low back pain in physical therapists. Physical Therapy, 65, 482-486. Niedhammer, I., Lert, F. and Marne, M.J. (1994). Back pain and associated factors in French nurses. International Archives of Occupational and Environmental Health, 66, 349-357. Norusis, M.J. (1994). SPSS Advanced Statistics 6.1. Chicago: SPSS Inc. Ohlsson, K., Hansson, G.A., Balogh, I., Stromberg, U., Palsson, B., Nordander, C., Rylander, L. and Skerfving, S. (1994). Disorders of the neck and upper limbs in women in the fish processing industry. Occupational and Environmental Medicine, 51, 826-832. Owen, B.D. (1986). Personal characteristics important to back injury. Rehabilitation Nursing, 11, 12-16. Owen, B.D. and Garg, A. (1989). Patient handling tasks perceived to be most stressful by nursing assistants. In: Advances in Industrial Ergonomics and Safety 1 (edited by A. Mital), pp. 775-781. London: Taylor and Francis. Papageorgiou, A.C., Croft, P.R., Ferry, S., Jayson, M.I.V. and Silman, A.J. (1995). Estimating the prevalence of low back pain in the general population. Spine, 20, 1889-1894. Pheasant, S. and Stubbs, D. (1992). Back pain in nurses: epidemiology and risk assessment. Applied Ergonomics, 23, 226-232. Ready, A.E., Boreskie, S.L., Law, S.A. and Russell, R. (1993). Fitness and lifestyle parameters fail to predict back injuries in nurses. Canadian Journal of Applied Physiology, 18, 80-90. Scholey, M. and Hair, M. (1989). Back pain in physiotherapists involved in back care education. Ergonomics, 32, 179-190. Smedley, J., Egger, P., Cooper, C. and Coggon, D. (1995). Manual handling activities and risk of low back pain in nurses. Occupational and Environmental Medicine, 52, 160-163. Stalhammar, H.R., Leskinen, T.P.J., Rautanen, M.T. and Troup, J.D.G. (1989). Body height changes and perceived exertion in self-paced and fixed-paced work and during recovery. In Proceedings of the Third Biomechanics Seminar (edited by C. Hogfors), pp. 124-135. Stalhammar, H.R., Leskinen, T.P.J., Rautanen, M.T. and Troup, J.D.G. (1992). Shrinkage and psychophysical load ratings in self-paced and force-paced lifting work and during recovery. Ergonomics, 35, 1-5. Stubbs, D.A., Buckle, P.W., Hudson, M. P., Rivers, P.M. and Worringham, C.J. (1983). Back pain in the nursing profession. 1. Epidemiology and pilot methodology. Ergonomics, 26, 755-765. Van Diee'n, J.H., and Toussaint, H.M. (1993). Spinal shrinkage as a parameter of functional load. Spine, 18, 1504-1514. Vasiliadou, A., Karvountzis, G.G., Soumilas, A., Roumeliotis, D. and Theodosopoulou, E. (1995). Occupational low-back pain in nursing staff in a Greek hospital. Journal of Advanced Nursing, 21, 125-130. Zhuag, Z., Stobbe, T.J., Hsiao. H., Collins, J.W. and Hobbs, G.R. (1999). Biomechanical evaluation of assistive devices for transferring residents. Applied Ergonomics, 30, 285-294.

Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

ELECTROMYOGRAPHY IN OCCUPATIONAL ACTIVITIES J. P. Clarys(1) and T. Reilly(2)

(1) Department of Experimental Anatomy, Vrije Universiteit Brussel, Belgium (2) Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, UK

Abstract: The improvement of electromyographic (EMG) devices for the detection of electric potentials produced in voluntary complex movements and the evolution of methodological approaches to data acquisition and computerised analysis of patterns of activity are responsible for the increased applications of EMG in bioengineering, rehabilitation, sport and occupational biomechanics, physiology, zoology and ergonomics. Examples of these uses of EMG in ergonomics are highlighted in this review. The method is most effective when combined with other indices of task load and physiological strain.

1. Introduction The usual aim of an ergonomic investigation is to analyse the occupational or sport environment in order to improve the conditions in the environment in question. The ergonomist may need information about human responses to particular working environments, which can be obtained by basic physiological methods. These responses are an obvious prerequisite for an ergonomist seeking to make recommendations about re-designing the task in question or altering the environment, at least when results of basic research are already available. On the other hand it is not equally obvious to the basic researcher to base his or her experiments on the needs of the practising ergonomist or to present results in such a way that they are applicable or even understandable to the ergonomist. Sometimes, basic research investigations will provide a result which is of limited value to the ergonomist, simply because it is not obvious how to apply the results in a practical situation (Jonsson andNilsson, 1979). In ergonomics, electromyography (EMG) is usually one tool amongst other measuring instruments to complete the scientific information needed to provide the best possible working environment. Within this context, and although there are several fundamental differences between basic research and ergonomic applications, there are many similarities between the 'work' and 'sport' environments, especially where there is a concern for 'human versus equipment' issues.

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Muscle activity can be detected by a technique known as electromyography (EMG). When a skeletal muscle fibre is activated, a wave of electrical depolarisation, referred to as an action potential, travels along the surface of the fibre. All of the muscle fibres in a single motor unit will be activated together. Needles or thin wires inserted into the muscle will detect the electrical signals produced. The intensity of the signal recorded by EMG is a measure of the number of motor units which are active. Electrodes placed on the skin surface over the underlying muscle are also used to record muscle activity, in which case the method is referred to as surface EMG (Fig. 1). DATA PROCESSING SYSTEM ANALYSIS QUALITATIVE

Figure 1. Different steps of the EMG data acquisition and analysis process.

2. Telemetric, on-line and remote registration approaches Over the years, the improvement of devices for registering the EMG signal and the evolution of methodological approaches to both EMG data acquisition and computerised pattern analysis have been valuable for bio-engineers, physiotherapists, sports biomechanicists, ergonomists, electrophysiologists, and eventually for trainers and coaches also. Since the end of the 1960s there has been a development in miniaturised telemetric devices for monitoring complex human movements remotely. Especially for kinesiological purposes, the telemetric devices have recently been changed from two-channel registrations to eight-channel systems. There are obvious and numerous advantages to telemetric measurement of muscular activity, although some difficulties may be encountered in field circumstances. For example, it is difficult to link more than two or three transmitters in parallel due to the limited free radio wave possibilities at present. Secondly, since the beginning of the research employing EMG, breaks in transmission, atmospheric conditions, statics or other disturbances have never been truly controllable (Clarys et al., 1988).

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In order to measure muscle activity in complex sports movements in the laboratory or field studies, different features are taken into consideration: (i)

(ii)

(iii) (iv)

The EMG data acquisition system with its electrodes should allow total freedom of movement for the subject - in other words, movements without additional resistance. The set-up should allow adaptation to the characteristics of the field and movement circumstances, in different situations, and be applicable to activities such as swimming, skiing, archery, cycling and so on in sport, and to the working environment of health-care professionals. It should accommodate long-term activity and movement over large distances and allow continuous measurements (up to tape limits). It should be possible to monitor six to twelve muscles (at least) simultaneously. The combined registration and data acquisition set-up should be user-friendly.

A multichannel FM recorder, 'active' electrodes, a regulation-amplification unit and different synchronisation modes were integrated into one system with different possibilities in order to allow such a combination. This integration was done in both a 'conventional on-line' and 'remote' configuration (Clarys and Public, 1987). The advantage of the active electrode over the classic passive electrode is that it decreases erroneous registrations. This feature has become important since we have found that, despite thorough precautions (different taping and plastic varnish for protecting the electrodes), water does decrease the detectable electrical output of human muscle. In other words, an imaginary identical intensity will produce more electricity in the air than in the water. The implications for using EMG in aquatic environments have been reviewed elsewhere (Clarys, 1985).

3. Critical appraisal of EMG studies, its limitations and hazards Most activities in sport and occupational settings involve complex movement patterns often complicated by external forces, impacts and the equipment used during the movement. An electromyogram (or its derivatives) is the expression of the dynamic involvement of specific muscles within a determined range of that movement. The integrated EMG of that same pattern (iEMG) is the expression of its muscular intensity. However, intensity is not always related to force. For a review of EMG and force related to voluntary effort and isometric conditions, the reader is referred to the various literature sources (e.g. Clarys et al., 1988). Mostly surface EMG is used to investigate the activity of a series of muscles, seldom just one or two. The choice of these muscles is based either on practical knowledge of the skill or on the basic anatomy literature. The functional EMG literature and early specific EMG work are rarely referred to. Scientists working in sport and occupational contexts tend to measure EMG using surface electrodes. Skeletal muscles do not always stay in the

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same place during complex dynamic (sometimes ballistic) movements and the entire muscle belly may not be under the skin, but covered by parts of other bellies or tendons and subcutaneous adipose tissue (that is variable both in its composition and volume). It is important to note that the selection of muscles for surface EMG (SEMG) measurement requires careful consideration. Some of these choices can lead to erroneous registration, sometimes without being noticed by peer reviewers. Various researchers have placed surface electrodes on the M. sartorius, M. gracilis, and M. teres major (see Clarys, 2000). Measuring the SEMG of these muscles under static conditions creates little or no problems, but under complex dynamic conditions the sartorius and gracilis muscles disappear from under the electrodes as does M. teres major, especially during arm motion above 90° abduction. It is therefore uncertain which muscles have contributed to the EMG patterns presented. Other research groups have selected for their studies M. extensor carpi radialis brevis. This muscle has a very small superficial 'strip' accessible under the skin. The EMGs of this muscle are dubious and may give more information about M. extensor digitorum. The same problem arises when measuring M. semimembranosus (under M. semitendinosus), although the superficial muscle belly parts are greater in size than is the case with M. extensor carpi radialis brevis; the combination of displacement of the superficial M. semitendinosus with a lack of functional surface again gives different information from that which is expected (e.g. the cross-talk phenomenon). Use of wire electrodes does not necessarily have this problem, although measuring M. subscapularis in this way - especially during front crawl in swimming and during arm swing movements, for example, - is questionable. This point of view of the anatomist who is confronted with these situations in the dissection room and palpation classes should not be discounted. The competent anatomist will not select M. sacrospinalis, but instead chooses M. erector spinae for measurement. One group, however, reported measuring the EMG of M. tibialis posterior during skiing with unipolar active surface electrodes. Clarys (2000) assumed that this was a printing error. On the other hand we must accept that the most direct view of muscle activity is provided by wire electrodes inserted into the muscle of interest. The electrodes and techniques are standard for applying wire electrodes. Adjacent muscles in the same limb segment can easily be differentiated by the appropriate use of wire electrodes. Most ergonomists prefer surface electrodes because of their ease of use and the comfort provided for the subject. Each technique has its place, but the selection of technique should be made by a clear understanding of what data are required to assist in clarifying the clinical decision, not by which of the two techniques is more convenient or comfortable. The next concern is how to deal with variability of these data. There are several types of variability: • • •

That which occurs within the same muscle between repetitions of the same activity (on a cycle to cycle basis), That which occurs between tests made on the same patient/subject and muscle but on different occasions, That which occurs in the relationship between muscles,

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•

That which occurs patients/subj ects.

between

muscle

groups

in

different

Various approaches have been applied in localising the site of detection of the electrode on the skin: (1) over the motor point; (2) equidistant from the motor point; (3) near the motor point; (4) on the mid-point of the muscle belly; (5) on the visual part of the muscle belly; (6) at standard distances of osteological reference points (anthropometric landmarks); and (7) with no precision at all with respect to its placement (Clarys, 2000). The effects of electrode location on muscle fibre conduction velocity and median frequency estimates have been discussed in the SENIAM (SEMG for non-invasive assessment of muscles) publications (see Clarys, 2000). The most reliable and most stable EMG values are to be obtained from the muscle belly area between the motor point and the most distal tendon. It follows that the position of the detection electrode must be chosen very carefully in order to minimise errors. Motor points are often located at the borders of muscles if projected to the skin, since other muscles or tendons cover part of those muscles. The motor point moves according to the level of contraction and the complexity of the movement, and so locating the detection electrode over, near or equidistant from the motor point must be avoided. The motor point in certain muscles can disappear beneath another muscle. In other words, the region has to be large enough to accommodate the electrode. For complex skills in sport and occupational contexts, the muscle belly shortens in the proximal direction during concentric contractions and the electrode on the skin is relocated to a position over the distal tendon. It is proposed therefore to place the electrodes over the visual mid-point of the 'contracted' muscle (Clarys, 1985). In addition to localising the electrode in its proper place on the skin over a muscle, it is important also to pay attention to the orientation of the electrode with respect to the muscle fibres. Bipolar surface electrodes have two detection surfaces. For optimal results, the two detection surfaces should be oriented so that the line between them is parallel to the muscle fibres (Clarys, 2000). In some skeletal muscles, neither of these conditions is satisfied; in such cases it is advisable to place the electrode in such a way that the line between the detection surfaces points to the origin and the insertion of the muscle. This orientation provides for consistent landmarks, so that the future placement of the electrode will have near-similar orientations and reduce the variation in SEMG signal among the myoelectric measurements obtained from different muscle contractions. Following the criteria of the International Society of Kinesiological Electromyography, SENIAM and the Journal of Electromyography and Kinesiology, it is recommended to report the upper cut-off frequency, the lower cut-off frequency and the type of filter used in the amplifiers. If a DCcoupled amplifier is used, the input impedance and input current should also be reported (Clarys, 2000). The type and material of the electrodes, the space between the contacts, the site and the preparation of the skin should also be documented. With respect to the processing of data, it is important to mention not only the use of raw EMG, iEMG, linear envelope, mean rectified EMG (MREMG), but also average EMG or ensemble average, together with the

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synchronisation system and the normalisation technique used, such as normalised to MVC or to 50% of the average of three MVCs, or to the highest peak (per movement or per subject) or to the mean of the subject ensemble average. The linear envelope is the qualitative expression of the rectified and eventually averaged signal. Within a window choice, this linear envelope can be smoothed, independent of its purpose. It should equally be clear that once smoothing is started, integration is no longer possible and it is unwise to use 'intensity' or 'activity level' in this case. Integration refers to the surface under the non-smoothed but rectified signal, to express the phenomenon of 'muscular intensity'. No two EMG profiles that result in the same action are ever identical because of the change in the actual motor units controlling the activity. Due to this known variability of the EMG signal, not only between subjects but also between different trials, different normalisation techniques have been developed to reduce variability. In general, the EMG of maximum effort or the highest EMG value has been selected as the normalising factor. In the main, the subject is asked to perform a maximal voluntary contraction (MVC) of the muscle (groups) being studied. This amplitude, either raw or rectified, is then used as a reference value (e.g. 100%). The use of the MVC reference is acceptable in all static applications. For all dynamic activities the use of an isometric reference is questionable. Several investigators have recently reported EMG values in dynamic activities that exceeded the maximal isometric effort (Clarys, 2000). Therefore, other normalisation techniques have been developed in kinesiological EMG, e.g. normalisation to the highest peak activity in dynamic conditions, to mean integrated EMG (ensemble average), to EMG per unit of measured force (net moment), and so on. In an extensive review of sport specific and ergonomic studies using EMG, the missing information mostly concerned the issue of normalisation. In the majority of both sport and occupational studies in which a normalisation technique is mentioned, the MVC technique has been used. This approach, however, is unreliable in all dynamic situations for several reasons (see Clarys, 2000): • • •

different maxima may be observed within the same subject repeating at different occasions the same 'maximal' but isometric effort; different maxima are observed at different angles of movement, both in eccentric and concentric movement modes; and additionally, the question of linearity may arise when the values measured during isotonic dynamic-ballistic-complex sports movements (or heavy lifting tasks) exceed the 100% MVC. For example, Clarys et al. (1983) found dynamic percentages in swimming up to 160%, while Jobe et al. (1984) reported up to 226% of MVC in baseball pitching.

It seems reasonable to suggest that a statically obtained EMG, such as MVC, cannot be an appropriate reference for dynamic EMG. In other words, most problems disappear when the proper normalization techniques are used. The data must be standardized for the cycle time and the amplitude. Several types of amplitude normalization are in use. All of them work. The important thing

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is to choose a normalization technique, apply it religiously, compare the reported results with your clinical estimate of the patient's or subject's performance and adjust either your perception of performance or the EMG technique to achieve agreement between the EMG and actual performance.

4. Electromyography and muscle actions In isometric work, the EMG signal is proportional to the force generated by muscle actions. Under dynamic conditions, the relationship is not so simple due to the changing force-torque characteristics at different phases of the movement. In very fast, ballistic-type motions, the EMG signal demonstrates alternating bursts of activity in both agonist and antagonist muscles. In such movements the EMG is triphasic in activity (McArdle et al., 1996). A first burst of EMG activity is evident in the agonist, followed by signals from the antagonist whilst the agonist becomes electrically silent before finally there is another burst of activity from the agonist. The first burst of activity from the agonist represents the propulsive force that initiates limb motion whereas the first activity in the antagonist concludes with deceleration of the limb. The second phase of activity in the agonist determines the final positioning of the limb. During eccentric muscle actions, the tension generated can exceed that during isometric action which in turn is greater than during a concentric action when the same muscle shortens in length. Despite the high EMG activity during an eccentric action, the energy expended may be quite low since fewer motor units may be recruited. It is during eccentric muscle actions that muscle damage may occur. Leakage of creatine kinase through the muscle membrane into the blood is evident following eccentric work and the ensuing soreness peaks 48-72 hours later. The phenomenon of 'delayed onset muscle soreness' may also be linked to an inflammatory response due to micro-trauma within the muscle and its connective tissue. The damage occurs due to the forces involved in stretching the muscles which are resisted by the contractile components. Eccentric actions are dominant in weight lowering activities compared to the predominance of concentric (and isometric actions) in lifting activities. Both lifting and lowering components, as well as carrying, are incorporated into the physical tasks of many health-care personnel. The electromyographic activity can be seen as a neuromuscular response to match the biomechanical requirements. The EMG signal information can be used in different ways depending on the question at issue. A basic question is whether we are interested in forces and torques (biomechanics) or muscle activation (physiology). Both approaches have ergonomic relevance. However, an investigator should decide which approach is the most suitable for the actual question at issue since the chosen approach is closely linked to the choice of calibration strategy and interpretation of results (Hagg, 1997). If we are interested in forces and torques, we have to establish a calibration curve between SEMG and force or torque (Mathiassen et al., 1995). This relationship involves several error sources which too often have been overlooked. With this biomechanical approach, fatigue effects are considered as confounders since they alter the EMG-force relationship.

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The physiological approach can be subdivided into general muscle activation and specific fatigue studies. The RMS or rectified low-pass filtered SEMG is a good estimator of the degree of muscle activation. When studying the electrical activity as such we reduce the scope to the muscle itself even if this approach can give valuable information in, for example, functional biomechanical studies. We also eliminate the error sources associated with the force-EMG relationship (Hagg, 1997). The increase in amplitude due to fatigue can be interpreted as an increased muscle activation even if a minor part of it can be attributed to a decrease in action potential velocity (Lindstrom et al., 1977). Another contributing source which should be considered is the psychogenically related muscular activity which is non-functional from a biomechanical point of view (Wasrsted and Westgaard, 1996; Hagg, 1997). Electromyography has been used to assess the muscles engaged in particular activities. The EMG pattern can also help to show the relative involvement of individual muscles in the task in hand. A change in the integrated EMG may indicate increased motor unit recruitment, as might occur when the motor units previously engaged begin to fatigue. The technique may also be used in biomechanical modelling; for example, Marras and Granata (1997) developed and EMG-assisted model to assess spinal loading during dynamic lifting. Norlander et al. (2000) focused on low-threshold type 1 muscle fibres presumed to be vulnerable in contractions of long duration: this group of muscle fibres is known as the Cinderella fibres - 'first up, last to bed'. These authors studied female hospital cleaners, female office workers and male office workers during one working day. The frequency of periods of muscle rest (EMG gaps) was derived, since a low gap frequency is known to be a risk factor for musculoskeletal disorders. Electrical activity was monitored in bilateral trapezius muscles using the standard Ag/AgCl surface electrodes. Separate analyses were conducted for nine different work tasks. The cleaners had a higher prevalence of neck/shoulder myalgia and were found to have much less muscular rest than the office workers. There was a wide range of muscular rest within the same work task. Office workers with a high subjective muscular tension had higher values of muscular rest and a higher gap frequency than those without such a tendency. Gap frequency did not differ between the two occupational groups. It is possible that the work tasks studied were not the most suitable for studying the effect hypothesised.

5. Electromyography in assessment of task demands Electromyography has been used extensively as a variable in a range of ergonomics investigations, including the assessment of muscle coordination. Recent examples have included studies of static and dynamic lifting tasks (Yates and Karkowski, 1992), fatigue during repetitive light work (Nakata et al., 1992), excessive drafts on shoulder muscles (Sundelin and Hagberg, 1992), typewriting and keyboard use (Fernstrom et al., 1994), effects of precision and force demands in manual work (Milerad and Ericson, 1994), symmetric and asymmetric lifting tasks in restricted postures (Gallagher et al., 1994), verifying spinal and abdominal muscle activity during garden raking (Kumar, 1995) and during repetitive lifting tasks (Kim and Chung, 1995),

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assessing the load on upper M. trapezius in jet pilots (Harms-Rindahl et al., 1996), monitoring the influence of the operating technique on muscular strain (Luttmann et al., 1996a) and muscular fatigue of surgeons in urology (Luttmann et al., 1996b). According to Baten (1998), alternative methods are developed to enable ambulatory application. One of them uses back extensor SEMG signals in combination with 3D low-back angle data assessed with an Isotrack system with the transmitter placed at the sacrum and the receiver at the skin above vertebra T10 (Dolan and Adams, 1993). Another fully ambulatory method applies 3D inertial movement sensor modules which assess full absolute 3D kinematics of the body segments in combination with back extensor SEMG signals, both recorded with a portable data acquisition system (Baten, 1998). Both methods require a set of calibration recordings in which the relation between SEMG and spinal extension moment (2D) is determined under different kinematic conditions. In the first case the kinematics taken into account comprise the back angle plus a general correction factor for the contraction velocity. In the second system full body segment kinematics are included in an automatic calibration applying artificial neural network technology (Baten, 1998). A more conventional use of EMG in ergonomics was recently provided by Anton et al. (2001). They examined the effect of overhead drilling tasks on EMG activity and shoulder joint movement, work-related musculoskeletal disorders of the shoulder joint being common in the construction and manufacturing tasks. Close, middle and far reach positions were examined whilst the subjects worked from a standing posture on either a lower or a higher step of a stepladder. Root mean square (RMS) amplitude of EMG activity from anterior deltoid, biceps brachii and triceps brachii muscles was used to determine muscular load. Digital video was employed to determine shoulder joint movement using 2-D static link segment modelling in the sagittal plane. It was found that movement increased monotonically with RMS amplitude. The findings confirmed that workers performing overhead tasks should work close to their body in order to minimise shoulder forces. A further illustration of how EMG can complement other investigative tools was provided by van Dieen et al. (2001). They focused on seated work which has been shown to constitute a risk factor for low-back pain. In order to evaluate the potential health effects with respect to the low back of office chairs with a moveable seat and back rest, trunk kinematics, EMG activity of erector spinae muscles, spinal shrinkage, and local discomfort were assessed. Three chairs were used, one with a fixed seat and back rest, one with a seat and back rest moveable in a fixed ratio with respect to each other, and another with a freely moveable seat and back rest. Trunk kinematics and EMG of the erector spinae were strongly influenced by the task performed but not by the type of chair. The results imply that dynamic office chairs offer a potential advantage over fixed chairs but the effects of the tasks on the indicators of trunk load investigated were more pronounced than were the effects of the chair.

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6. Overview In this chapter, some background and a rationale for use of electromyography (EMG) in an ergonomics context have been provided. More comprehensive reviews of the technique (e.g. Clarys, 2000) and its applications (Clarys et al., 1988) have been published elsewhere. In this review some examples of the use of EMG in occupational activities, especially those in which risk of musculoskeletal disorders have been highlighted, are given. It is clear that the utility of EMG is increased when it is used alongside other methods such as film analysis, force measurements or spinal shrinkage. Its value is enhanced when combined with these other methods, particularly when exploring multifactorial causes of work related musculoskeletal complaints.

References Anton, D., Shibley, L. D., Fethke, B., Hess, J., Cook, T. M. and Rosecrance, J. (2001). the effect of overhead drilling on shoulder movement and electromyography. Ergonomics, 44, 489-501. Baten, C.M. (1998). Surface EMG as a tool for analyzing work related musculoskeletal disorders. In: Surface Electromyography Application Areas and Parameters; Proceedings of the third general SENIAM workshop, Aachen, Germany, p. 121. Clarys, J. P. (1985). Hydrodynamics and electromyography: ergonomic aspects in aquatics. Applied Ergonomics, 16, 11-24. Clarys J. P. (2000). Electromyography in sports and occupational settings: an update on its limits and possibilities. Ergonomics, 43,1750-1762. Clarys, J. P. and Public, J. (1987). A portable EMG data acquisition system with active surface electrodes for monitoring kinesiological research. In: Biomechanics X (ed. B. Jonsson), pp. 233-239. Champaign 111: Human Kinetics. Clarys, J. P., Cabri, J., De Witte, B., Toussaint, H. de Groot, G., Huying, P. and Hollander, P. (1988). Electromyography applied to sport ergonomics. Ergonomics, 31, 1605-1620. Clarys, J. P., Massez, C., van den Broeck, M., Piette, G. and Robeaux, R. (1983). Total telemetric surface of the front crawl. In: Biomechanics VIII-B. International Series on Biomechanics, Vol 4B (edited by H. Matsui and K. Kobayashi), pp. 951-958. Champaign, 111: Human Kinetics. Dolan, P. and Adams, M.A. (1993). The relationship between EMG activity and extensor moment generation in the erector spinae muscles during bending and lifting activities. Journal of Biomechanics, 26,513-522. Fernstrom, E., Ericson, M. O. and Malker, H. (1994). Electromyographic actvivity during typewriter and keyboard use. Ergonomics, 37,477-484. Gallagher, S., Hamrick, C. A., Love, A. C. and Marras, W. S. (1994). Dynamic biomechanical modelling of symmetric and asymmetric lifting tasks in restricted postures. Ergonomics, 37, 1289-1310. Hagg, G.M. (1997). Topical issues in ergonomics related to surface EMG. In: European Applications of Surface Electromyography, Proceedings of the second general SENIAM workshop, Stockholm, Sweden, pp. 3-9. Harms-Rindahl, K., Ekholm, J., Schuldt, K., Linder, J. and Ericson, M. O. (1996). Assessment of jet pilots' upper Trapezius load calibrated to maximal voluntary contraction and a standardised load. Journal of Electromyography and Kinesiology, 6, 67-72. Jobe, W. Tibone, E., Perry, J. and Moynes, D. (1984). An EMG analysis of the shoulder in throwing and pitching. American Journal of Sports Medicine, 11, 3-5. Jonsson, B. and Nilsson, T. (1979). EMG fatigue effects and recovery of endurance in forearm muscles. Proceedings of the 4th Congress International Society of Electrophysiological Kinesiology (ed. C. J. DeLuca). Boston, pp. 98-99.

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Jorge, M. and Hull, M. L. (1983). Preliminary results of EMG measurements during bicycle pedalling. In: Biomechanics Symposium. ASME vol. 56, pp. 27-30. New York: American Society of Mechanical Engineers. Kim, S. H. and Chung, M. K. (1995). Effects of posture, weight and frequency on trunk muscular activity and fatigue during repetitive lifting tasks. Ergonomics, 38, 853-863. Kumar, S. (1995). Electromyography of spinal and abdominal muscles during garden raking with two rakes and rake handles. Ergonomics, 38, 1793-1804. Lindstrom, L., Kadefors, R. and Petersen, I. (1977). An electromyographic index for localized muscle fatigue. Journal of Applied Physiology, 43,750-754. Luttmann, A., Sokeland, J. and Laurig, W. (1996a). Electromyographical study on surgeons in urology I. Influence of the operating technique on muscular strain. Ergonomics, 39, 285-297. Luttmann, A., Jager, M., Sokeland, J. and Laurig, W. (1996b). Electromyographical study on surgeons in urology II. Determination of muscular fatigue. Ergonomics, 39, 298-313. Marras, W. S. and Granata, K. P. (1997). The development of an EMG-assisted model to assess spine loading during whole-body free-dynamic lifting. International Journal of Electromyography and Kinesiology, 7, 259-268. Mathiassen, S.F., Winkel, J. and Hagg, G.M. (1995). Normalizationof surface EMG amplitude from the upper trapezius muscle in ergonomic studies - a review. Journal of Electromyography and Kinesiology, 5, 195-226. McArdle, W. D., Katch, F. I. and Katch, V. L. (1996). Exercise Physiology: Energy, Nutrition and Physical Performance. (4th Edition). Baltimore: Williams and Wilkins. Milerad, E. and Ericson, M. O. (1994). Effects of precision and force demands, grip diameter and arm suppport during manual work: an electromyographic study. Ergonomics, 37, 255264. Nakata, M., Hagner, I. and Jonsson, B. (1992). Perceived musculoskeletal discomfort and electromyography during repetitive light work. Journal of Electromyography and Kinesiology, 2, 103-111. Norlander, C., Harisson, G. A., Rylander, L., Asterland, P., Bystrom, J. U., Ohlsson.K., Balogh, I. and Skesfuing, S. (2000). Muscular rest and gap frequency as EMG measures of physical exposure: the impact of work tasks and individual related factors. Ergonomics, 43, 1904-1919. Sundelin, G. and Hagberg, M. (1992). Effects of exposure to excessive drafts on myoelectric activity in shoulder muscles. Journal of Electromyography and Kinesiology, 2, 36-41. Van Dieen, J. H., de Looze, M. P. and Hermans, V. (2001). Effects of dynamic office chairs on trunk kinematics, trunk extensor EMG and spinal shrinkage. Ergonomics, 44, 739-750. Wsersted, M. and Westgaard, R.H. (1996). Attention-related muscle activity in different body regions during VDU work with minimal physical activity. Ergonomics, 39,661-676. Yates, J. W. and Karkowski, W. (1992). An electromyographic analysis of seated and standing lifting tasks. Ergonomics, 35, 889-989.

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THE IMPLEMENTATION OF ADDITIONAL SOFTWARE FOR 3-D ANALYSIS OF COUPLED MOTION IN THE CERVICAL SPINE BY MEANS OF AN ELECTROMAGNETIC TRACKING DEVICE P. Van Roy, J. P. Baeyens, R. Lanssiers, A. Vermoesen, D. Caboor, E. Zinzen, M. Verlinden and J. P. Clarys Vrije Universiteit Brussel Department of Experimental Anatomy Laarbeeklaan 103, 1090 Brussels Belgium

Abstract. New software was implemented to facilitate the control, the treatment and the organisation of the output stream of 3-D kinematic results, obtained with an electromagnetic tracking device (Flock of Birds) in a rehabilitation context. The creation of a number of user friendly menus provided easy file management in recording real time readings of discrete motion sequences. Software based adaptations of the reference frames allowed for the registration of relative data between the receivers, thereby starting from zero values, comparable to the neutral-zero method in clinical goniometry. With the implementation of a function "recalculate", a posteriori manipulation of the technical reference frames offered useful applications to avoid gimbal lock artefacts, to align the reference frames and to adopt them to the standardisation proposal of the International Society of Biomechanics (ISB). The software further provided simultaneous graphical display of the Euler angles in one window, and simultaneous graphical display of the translation components in another. The output data are saved in a format, which can be exported to current spreadsheets. The simultaneous graphical display of the axial rotation of the cervical spine and the associated components of lateral bending and/or flexion/extension in young and healthy volunteers, allowed good insight into the time characteristics of coupled motion. Most of the graphs showed the traditionally described ipsilateral coupled lateral bending. However, amplitude and shape of the curves revealed substantial inter-individual differences in amplitude and timing of coupled motion. Left-right differences were obvious in many graphs. The presence of substantial functional variation in coupled motion of the cervical spine in young volunteers without complaints must warn us not to jump to conclusions.

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1. Introduction: context and aims of developing additional software In recent decades, the growing support for 3-D joint motion analysis has led to an expansion of commercially available systems to record 3-D kinematics. Besides computerised goniometer systems and video-based or opto-electronic equipment, electromagnetic tracking devices have been increasingly used for this purpose. This has resulted in several analyses concerning spinal motion (Buchalter et al., 1989; Pearcy and Hindle, 1989; Rusell et al., 1992; ; Pearcy, 1993; Rusell et al., 1993; Mulvein et al., 1995; Trott et al, 1996; Walmsley et al., 1996 and Willems et al., 1996) With an electromagnetic tracking device, kinematics are recorded within a restricted volume of space in front of the transmitter (source). This source provides a low intensity electromagnetic field, which remains sufficiently homogeneous within-the considered space (Fig.l). Positioned on (one ore more) body segments, the sensors (receivers) detect the 3-D changes in orientation and position of their own reference frames in regard to the (general) reference frame of the source. The real time readings and relatively low costs of this equipment are substantial advantages. A drawback is that the presence of ferromagnetic material may disturb appropriate recording. It is also important to avoid interface artefacts between equipment and subject (Capozzo et al., 1996) with an adequate control of the relationship between the anatomical reference frames of the body segments and the technical reference frames of the equipment. R5422/485

transmitter

Figure 1. Configuration of an electromagnetic tracking system with 1 transmitter (source) and 2 sensors (receivers).

To facilitate the measurement of joint motion with an electromagnetic tracker [Flock of Birds (FOB)] in a clinical context, new software has been implemented to control, to treat and to organise the output stream of kinematic results. A set up with two receivers was used, operating in the so-called "master-slave configuration".

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Concrete aims were: 1. To guide the registrations of discrete motion sequences by a restricted number of interface instructions. 2. To obtain relative kinematic data between the receivers (instead of separate kinematic recordings of both sensors with respect to the general reference frame). 3. To start the measurements from zero values, comparable to the neutral-zero method in clinical goniometry (American Academy of Orthopaedic Surgeons, 1965). 4. To present the Euler angles together in one graph as well as to present a graph with the translation components. 5. To store the data in formats which can be exported to current spreadsheets.

2. The implementation of the additional software The creation of the new software (Lanssiers, 1997 and Van Roy et al., 1998) was primarily based on the following strategies: 1. The creation of a number of user friendly menus The creation of a number of user friendly menus yields an easy file management. Starting from the main menu, discrete recordings of a motion sequence are realised through the "start" and "stop" commands. Names of the subjects and some comments about the investigated joint or movement can be added. 2. The calculation of relative 3-D angles From the absolute kinematic data of each sensor, relative kinematic data between the sensors are deduced to estimate joint kinematics, with the FOB in "stream mode". Mounting the sensors on a clinical goniometer, 3-D angles were checked in a transversal, a frontal and a sagittal plane. The results demonstrated good reliability (Vermoesen, 1997). However, when the elevation angle approximated 90°, a "gimbal lock" effect occurred, which resulted in faulty roll and azimuth angles. These artefacts were removed by a posteriori manipulation of the general reference frame (see also 3).

3. Software based adaptation of the technical reference frames of the sensors Software based adaptations of the reference frames of the sensors were realised in order to start from zero values and to obtain meaningful results in a functional anatomical context. Technically, zeroing was reached through the implementation of a time independent correction matrix and a time independent correction vector, mathematically adjusting the reference system of the first (master) sensor to that of the second (slave) sensor at the moment of the "start" instruction. Further control of the technical reference frames was done through the function "recalculate", manipulating a posteriori the reference frame of the master sensor. Originally, it was created to clean the data from gimbal lock artefacts. It also demonstrated

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useful to align the reference frames of the transmitter and the master sensor, to adapt the general reference frame of the equipment to changes of the anatomical reference frame of the subject and to orient reference frames according to the standardisation proposal of the International Society of Biomechanics (I.S.B). 4. Graphical display of 3-D angles and translations With the "graph" menu, a simultaneous graph of the three Euler angles of the investigated motion sequence is obtained. Opening a second window, the three translation components may be observed. 5. Data storage With the "file" menu, the data can be saved in a format which can be exported to current spreadsheets allowing for further statistical analysis. 3. Patterns of coupled motion in axial rotation of the cervical spine In the present report, six cases are commented upon from a larger study (Vermoesen, 1997), performed on 40 male and 43 female healthy volunteers between 19 and 69 years of age. Coupled motion in axial rotation of the cervical spine was recorded with the new software. The source of the magnetic device was placed in front of the subject at the level of the cervical spine and properly oriented in the midsagittal anatomical plane. According to Walmsley et al. (1996), the master sensor was connected to the skin over the manubrium sterni and the slave sensor was fixed on the forehead using a Velcro strap. Thus, the recordings included motion of the entire cervical region and the cervicothoracic transition zone. With the cervical spine initially held in the neutral position, the subjects proceeded in axial rotation of the head to the left and to the right side. (This was repeated with the cervical spine in flexion and in extension; the results of these recordings will be discussed elsewhere). Using the function 'recalculate', reference frames were converted into the standardisation proposal of the I.S.B. LEFT (-) / RIGHT (+) LATERAL BENDING FU6XION (-) / EXTENSION (+) ;— LEFT (-)/RIGHT (+) AXIAL ROTATION

Figure 2. Subject AK (female - 24 years of age) - Patterns of coupled motion in axial rotation of the cervical spine.

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Subject AK (Figure 2), a young lady of 24 years of age, showed three subsequent readings of symmetric curves of axial rotation. In a consistent manner, the peak value of the ipsilateral coupled lateral bending accompanying the axial rotation to the right was reached approximately at the same moment of the maximum value of axial rotation. However, the lateral bending accompanying the axial rotation to the left appeared soon and displayed an irregular curve. Its maximum value was maintained during back rotation to the neutral position and only decreased at the onset of axial rotation to the opposite side. In axial rotation to the right side, coupled lateral bending started later and disappeared sooner than the main motion. The axial rotations were accompanied by a flexion component, which was slightly higher in axial rotation to the left. LEFT (-) / RIGHT (+) LATERAL BENDING FLEXION (-) / EXTENSION (+) LEFT (-) / RIGHT (+) AXIAL ROTATION

Figure 3. Subject BY (male - 25 years of age) - Patterns of coupled motion in axial rotation of the cervical spine.

In the 25 years old male subject BY, only poor and asynchronous lateral bending components were recorded during each of the subsequent axial rotation movements. Axial rotation to the left side was accompanied by a reduced heterolateral lateral bending component. In axial rotation to the right side, some ipsilateral lateral bending followed a few degrees of heterolateral lateral bending. Axial rotations were accompanied by an extension component, which was more pronounced in axial rotation to the right side. In the 37 years old male subject BU (Figure 4), slightly larger amplitudes of right axial rotation were registered. However, a slightly larger ipsilateral lateral bending component was noticed on the left side. Although the maximal values of coupled lateral bending were reached at the instant of maximal axial rotation, the lateral bending curves started with a certain delay. Every axial rotation started with a small extension component, which disappeared in maximal axial rotation and subsequently reappeared at the end of every axial rotation.

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— :

LEFT (-) / RIGHT <+) LATERAL BENDING' FLEXION <-)/ EXTENSION (*) LEFT (-); RIGHT (*) AXIAL ROTATION

Figure 4. Subject BU (male - 37 years of age) - Patterns of coupled motion in axial rotation of the cervical spine.

LEFT (-) / RIGHT (+) LATERAL BENDING FLEXION H I EXTENSION (+> LEFT HIRK3HT (+) AXIAL ROTATION

Figure 5. Subject DB (male - 26 years of age) - Patterns of coupled motion in axial rotation of the cervical spine.

In the 26 years old male subject DB (Figure 5), substantial amounts of coupled ipsilateral bending were recorded. Although the axial rotation to the left showed smaller amplitudes than on the other side, this left axial rotation was accompanied by a larger coupled ipsilateral lateral bending. A clear extension component of the cervical spine was present during the entire motion sequence. Every peak value of left axial rotation was associated by a plateau of maximal extension. On the other hand, minimum values of coupled extension appeared simultaneous with the peak values of right axial rotation.

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— LEFTH/RIOHT(»> LATERAL BENDING nJOOOH H/ EXTENSION (*) LEFT (-) IRKJHT <+) AXIAL ROTATION

Figure 6. Subject DH (female - 39 years of age) - Patterns of coupled motion in axial rotation of the cervical spine.

In comparison to the foregoing examples, subject DH, a 39 years old woman, demonstrated a higher amount of axial rotation to the left side, accompanied by a higher amount of ipsilateral coupled lateral bending (Figure 6). The curves indicate that the maximal amplitudes of axial rotation were achieved rather prudently. In other words, the last degrees of axial rotation were reached at a lower velocity than the main course of the movement. A comparable pattern is found in the lateral bending component on the left side. During axial rotation to the right the maximum value of coupled lateral bending slightly precedes the maximal values of the main motion. Every axial rotation to the left side was accompanied by a slight extension component, slightly diminishing at the peak values of left axial rotation. Coupled extension components disappeared or changed into small flexion components during axial rotation to the right side. — LEFT <-)/RX3HT(«-) LATERAL BENDING; • - FUMOtH-)'EXTENSION <*) I LEFT <-) IMOHT <*> AXIAL ROTATION i

Figure 7. Subject DL (male - 34 years of age) - Patterns of coupled motion in axial rotation of the cervical spine.

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Although the amplitudes of left and right axial rotation are comparable in the 34 years old male subject DL, right axial rotation was substantially accompanied by more ipsilateral lateral bending (Figure 7). Once again, the last degrees of axial rotation were reached at a lower velocity. This pattern is also recognised in the shape of the lateral bending curves. In this example, small flexion and extension components oscillated around the base line.

4. Discussion 4.1 Methodological aspects The additional software resulted in a number of technical measures, which facilitate the use of the electromagnetic tracking device for 3-D kinematic analysis in a rehabilitation context. Real time outcomes are depicted in a format which allows interpretation in functional anatomical or arthro-kinematic terms. Software based manipulation of the reference frames of the sensors provided recordings, starting from zero values. With the implementation of a function "recalculate", a posteriori manipulation of the reference frames provided useful applications to avoid gimbal lock artefacts, to align technical reference frames and to adopt the reference frames to the standardisation proposal of the I.S.B. This function allows for a correction of the general reference system, if a particular motion takes place following a well-known tilt of the anatomical reference system, for instance starting head rotation from a flexed posture. The impact of the change in posture on the angular expression of coupled motion has already been discussed in an electrogoniometric study of cervical spine motion (Feipel et al., 1999). Considerable differences within and between the different methods and set-ups for measuring range of motion were reported in a meta-analysis of normative cervical motion (Chen et al., 1999). Such differences can be expected between angular results, obtained with planar goniometry and with an Euler approach. Comparisons between different measuring techniques are required to progress towards a better standardisation of clinical measurements of range of motion. 4.2 Patterns of coupled motion The simultaneous graphical display of the basic movement and the associated components of lateral bending and/or flexion/extension allowed good insight into the time characteristics of coupled motion. Most of the graphs showed the traditionally described ipsilateral coupled lateral bending. However, amplitude and shape of the curves revealed substantial inter-individual differences in amplitude and timing of coupled motion. Leftright differences were obvious in many graphs. One has to consider that the recorded patterns of coupled motion by the electromagnetic device counts for the entire region of the cervical spine, which is the global reflection of the different adding and sometimes counteracting components of coupling motion in each of the individual motion segments of the cervical spine. Consequently, the absence of global coupled motion does not necessarily mean a lack of coupled motion at

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the segmental levels. Coupled lateral bending is more pronounced in the middle than in the lower cervical spine (Onan et al., 1998 and Penning et al., 1999) and may partially be counteracted in the upper cervical spine, where the amount and direction of coupled motion highly depend on posture (Panjabi et al., 1993). Also the amplitude of main motion is revealed to be posture dependent. From foregoing anatomical studies, it can be hypothesised that asymmetric patterns of coupled motion probably result from morphological asymmetries of zygapophyseal joint facets, in a number of cases in combination with asymmetrical lever arms for muscles (Machiels, 1996; Wullepit, 1996; Van Roy et al., 1997; Kevelaers, 1999 and De Vis, 1999). Inter-individual differences were previously reported in the study of regional coupled motion in lateral bending of the thoracic spine (Mulvein and lull, 1995) and in the study of segmental coupled motion in the lumbar spine (Pearcy, 1985). The relationship between anatomical asymmetries and asymmetric motion components will be verified in further research comparing the kinematic data with anatomical information obtained from medical imaging. Current research deals with the study of coupled motion in elderly and patients with rheumatoid arthritis. The substantial functional variation in coupled motion that was presented in young volunteers without complaints must warn us not to jump to conclusions. Acknowledgements: * The Research Council of the Vrije Universiteit Brussel provides funding of the project on coupled motion in the lumbar and cervical spine. Matching funds are provided by the European Community, taking part in the Biomed-4 programme: "Investigation of musculoskeletal disorders in health-related occupations". * We acknowledge the Department of Biometry and Biomechanics of the "Vrije Universiteit Brussel" for providing the magnetic tracking device. References American Academy of Orthopaedic Surgeons. (1965). Joint Motion, Method of Measuring and Recording. Edinburgh, London and New York: Churchill Livingstone. Buchalter, D., Parnianpour, M, Viola, K., Nordin, M. and Kahanovitz, N. (1989). Three-dimensional spinal motion measurements. Part 1: A technique for examining posture and functional spinal motion. Journal of Spinal Disorders, I , 279-283. Capozzo, A., Catani, F., Leardini, A., Benedetti, M.G. and Delia Groce, U. (1996). Position and orientation in space of bones during movement: experimental artefacts. Clinical Biomechanics, 11, 90-100 Chen, J., Solinger, A.B., Poncet, J.F. and Lantz, C.A. (1999). Meta-analysis of normative cervical motion. Spine,24, 1571-1578. De Vis, J-P. (1999). Lumbaal tropisme, een literatuurstudie en experimented studie, non published Masters degree thesis in manual therapy (written in Dutch). Department of Experimental Anatomy, Vrije Universiteit Brussel, p. 102. Feipel, V., Rondelet, B., Le Pallec, J.P. and Rooze, M. (1999). Normal global motion of the cervical spine: an electrogoniometric study. Clinical Biomechanics, 14, 462-470. Kevelaers, I. (1999). Morphometrisch onderzoek van de foramina transversaria van de axis, (Morphometric study of foramina transversaria in C2-vertebrae, non published licentiate thesis in Motor Rehabilitation

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and Physiotherapy (written in Dutch). Department of Experimental Anatomy, Vrije Universiteit Brussel, p. 89. Lanssiers, R. (1997). The Flock of Birds™, Software for 3-D motion analysis, technical report (written in Dutch). Department of Experimental Anatomy, Vrije Universiteit Brussel, p. 14. Machiels, B. (1996). Links-rechts asymmetrieln van de cervicale wervels C3 tot C7. (Left-right asymmetries of the vertebrae C3-C7), non-published Masters degree thesis in manual therapy (written in Dutch). Department of Experimental Anatomy, Vrije Universiteit Brussel, p. 98. Mulvein, K. and Jull, G. (1995). Kinematic analysis of the lumbar lateral flexion and lumbar lateral shift movement techniques. The Journal of Manual & Manipulative Therapy, 3, 104-109. Onan, O.A., Heggeness, M.H. and Hipp, J.A. (1998). A motion analysis of the cervical facet joint. Spine, 23, 430-439. Panjabi, M. M., Oda, T., Crisco III, J. J., Dvorak, J. and Grob, D. (1993). Posture affects motion coupling patterns of the upper cervical spine. Journal of Orthopaedic Research, 11, 525-53. Pearcy, M. J. (1985). Stereo radiography of lumbar spine motion. Acta Orthopaedica Scandinavica, 56, Suppl. 212, 1-41. Pearcy, M. J. (1993). Twisting mobility of the human back in flexed postures, Spine, 18, 114-119. Pearcy, M. J. and Hindle, R. J. (1989). New method for the non-invasive three-dimensional measurement of human back movement. Clinical Biomechanics, 4, 73-79. Penning, L. and Wilmink, J. T. (1987). Rotation of the cervical spine, a CT study in normal subjects. Spine, 12, 732-738. Rusell, P., Pearcy, M. J., Unsworth, A. (1993). Measurement of the range and coupled movements observed in the lumbar spine. British Journal of Rheumatology, 32, 490-497 Rusell, P., Weld, A., Pearcy, M. J., Hogg, R. and Unsworth, A. (1992). Variation in lumbar spine mobility measured over a 24-hour period. British Journal of Rheumatology, 31, 329-332. Trott, P. H., Pearcy, M. J., Ruston, S. A., Fulton, I. and Brien, C. (1996). Three-dimensional analysis of active cervical motion: the effect of age and gender. Clinical Biomechanics, 11, 201-206. Van Roy, P., Caboor, D., De Boelpaep, S., Barbaix, E. and Clarijs, J. P. (1997). Left-right asymmetries and other common anatomical variants of the first cervical vertebra, Part I: Left-right asymmetries in Cl vertebrae. Manual Therapy, 2, 24-36 Van Roy, P., Lanssiers, R., Vermoesen, A. and Clarijs, J. P. (1998). Implementation of software adaptation for 3-D cervical kinematics by means of a magnetic tracking device. In: Proceedings of the Twelfth Congress of the International Society of Electrophysiology and Kinesiology (edited by A. Arsenault, P. McKinley and B. McFadyen), Montreal, Quebec, Canada, June 27-30, pp. 10-11. Vermoesen, A. (1997). Coupled motion in axial rotation of the cervical spine, measured with a magnetic tracking device, non published licentiate thesis in Motor Rehabilitation and Physiotherapy (written in Dutch). Department of Experimental Anatomy, Universiteit Brussel, Brussels, 101 p + appendices. Walmsley, R. P., Kimber, P. and Culham, E. (1996). The effect of initial head position on active cervical axial rotation range of motion in two age populations. Spine, 21, 2435-2442. Willems, J. M., Jull, G. A. and Ng, J. K-F. (1996). An in vivo study of the primary and coupled rotations of the thoracic spine. Clinical Biomechanics, 11,311-316. Wullepit, C. (1996). Links-rechts asymmetric van de 2e halswervel (Left-right asymmetries of C2vertebrae), non published licentiate thesis in Motor Rehabilitation and Physiotherapy (written in Dutch). Department of Experimental Anatomy, Vrije Universiteit Brussel.

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A METHOD FOR JOB EVALUATION USING A MODIFIED DELPHI-SURVEY Dirck Caboor Vrije Universiteit Brussel Belgium

Abstract: The delphi technique is a method which can be applied to job evaluation to identify particular stresses in occupational tasks. In the current study the technique was used to examine workload in the nursing profession. Handling and transferring patients were identified as highly stressful. The method enables a comparison to be made of the kinds of tasks demanded by the job. Frequency of load was an important factor along with perceived stress.

1. Introduction Information about safety problems concerning the daily job is necessary for the public at large, for policy making, and last but not least as feedback for the occupational group involved, because such information is crucial for good job design and job re-design. Many manual handling jobs expose the worker to heavy peak loadings and to smaller but repetitive loadings; still the subjective description of this workload mostly needs more specifications. Job evaluation can be approached in different ways, of which the questionnaire, the interview and various ergonomic approaches are widely used allowing for a great variety of feedback elements. Different criteria for physical loading and for the duration within a task (e.g. the observer can have a different perception from the worker) can result in a discrepant quantitative and qualitative assessment of the influencial factors within a job (Burdorf et al., 1991). The choice of a modified Delphi-survey represents the concept that the workers are experts concerning their job, that they are the best qualified persons to make statements about the load of the tasks they are involved in, and that only they can provide the details needed to have a complete set of information about musculoskeletal loading during manual handling jobs. The impact of low-back problems (LBP) upon the present society has become phenomenal, when considering the consequences for the current society (Nachemson,1971; Videman et al., 1984; Biering-Sorensen, 1985). Nursing personnel shows a relative high prevalence of LBP (Magora, 1970; Stubbs et al., 1983; Klein et al., 1984; Videman et al., 1984; Biering-Sorensen, 1985). The nursing profession has been the subject of studies worldwide to establish the prevalence and incidence of back problems, to determine the economic and social impact associated with its morbidity and to identify risk factors associated with the occupational duties (Harber et al., 1988; Stobbe et al., 1988; Garg and Owen, 1992).

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Nurses are frequently required to perform dynamic tasks and manouevres with a considerable isometric component. The adult human form is an awkward burden to lift or carry, it has no handles, it is not rigid, and it is liable to severe damage if mishandled or dropped (Anonymous, 1965). Nurses perceive patient handling and transferring as the most demanding tasks and manouevres and they perceive those also as important factors influencing the incidence of LBP (Dehlin et al., 1976; Gagnon et al., 1986; Garg et al., 1992). There is a lack of a simple, cheap and fast method to specify how workers evaluate the severity and difficulty of the many tasks they manage to carry out in their job, and a method to fulfill the need for more specifications about the exposure to physical loading during manual handling. In this case the focus is on the nursing profession. This study, therefore, evaluates the problem-defining approach of a simple, inexpensive and 'low tech' method for the correct evaluation of physical loading during the performance of a manual handling job, nursing in particular. 2. Methods The approach can be divided into four phases using a modified Delphi-survey method (Figure 1). For this study the experts were selected by the senior nurses of four different hospitals in Belgium. The selected nurses participated independently of each other, and they were asked not to discuss the study with other colleagues.

The modified Delphi-Survey for job evaluation

Base list with "all" possible tasks/manoeuvres

Classification of the tasks/manoeuvres ranged by stress

Final classification of the tasks/manoeuvres ranged by stress and frequency algorithm S1 - S5 = 5 nurses from 4 different hospitals V1 - V15 = 15 nurses of different departments in 4 different hospitals

Figure 1. Diagram of the modified Delphi-survey methodology.

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First, five nurses out of one hospital drew up a list of all the possible tasks and/or manouev'res ranging from low to high stress. Amongst them, 70 items were recognised. The 70 items were randomised into one single list. Second, the randomised 70-item list was presented to 15 other nurses, from 3 other hospitals different from the first one. For the perception of the latent attitude towards the stress we used a 7-point Likert scale (Garg et al., 1992) (1 = absolutely not stressful, and 7 extremely stressful) and independently of each other, they rated the stress. The absolute mean of all stress-ratings per item was normalised to a relative score of 10. On the basis of the respective scores of the 15 nurses, the 70 tasks/manouevres items were ranked in descending order of stressfulness. Later the ranked 70-item list was presented to the same 15 nurses again so that they could indicate, independently from each other, the frequency of each task, using a 6-pomt Likert scale (Garg et al., 1992) (1-never, and 6=continuous) for the perception of time-consumption of the tasks. The' absolute mean of all frequency-ratings per item was converted to a relative score of 10 (see Figure 2).

Frequency

Figure 2. Stress/Frequency plotting of the task/manouevres (normalised zone).

The level of stress and the time factor were combined. The relative scores were plotted as variables in an X-Y co-ordinate system, to allow for a final and overall load classification of the tasks and/or manouevres. All tasks with a normalised score of 5 and more for both stress and frequency are indicated as stressful. Subsequently, in order to evaluate the tasks correctly, this first classification is polished using an algorithm (Figure 3). For the final ranking of the most stressful tasks and/or manouevres, the outcome of the algorithm (A) has to be 6 or more.

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A = 2(X)(Y)/(X+Y) X>5 Y>5 A>6

A = the final ranking-score X = the frequency-score of the task Y = the physical stress-score of the task Figure 3. The algorithm for the final ranking for stressfulness of the tasks and /or manouevres.

3. Results The results show (Table 1) a top ranking often tasks and/or manouevres with a final score A > 6 (Table 2). This evaluation gives the ranking of the most demanding tasks of the nursing profession and the nurses indicate that handling and transferring patients are very stressful as well as the work pressure. In our evaluation of the nursing job, 6 groups can be found. In the first group, we find the situation with transfer of the patient in and/or out of bed (Table 1) with a mean algorithmscore of A=5.81 (SD=0.75). Table 1. Top ranking of the tasks/manouevres (normalised score). Tasks/Manouevres score /1 0

1° 2° 3° 4° 5° 6° 7° 8° 9« 10°

Positioning corpulent patients onto the bed-pan Helping non-collaborating patients in and out of bed Helping hemiplegic patients: out of bed / into bed / sitting up Bed-washing in elderly patients with a poor physical condition Helping to transfer heavy patients carrying a plaster cast, out of bed into a chair Patient helping in and out of bed (hemiplegic patients) Presenting a bed-pan in bed-ridden patients Changing patients' posture as prevention of decubitus Installing a water mattress in bed-ridden patients Hurrying and getting stressed during work (work-pressure)

stress

time

algorithm

7.04 6.83

7.95 7.31

7.46 7.06

6.83

6.54

6.68

5.71

8.08

6.68

7.50 6.53 5.20 5.20 6.26 5.00

5.77 6.28 8.33 8.08 6.28 7.82

6.52 6.40 6.40 6.33 6.26 6.10

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Table 2. The group of tasks with transfer of the patient in and/or out of bed, and the mean score for the whole group.

Tasks/Manouevres score/10

stress

time

algorithm

Helping non-collaborating patients in and out of bed Helping hemiplegic patients: out bed / in bed / sitting up Helping heavy patients carrying a plaster cast, out of bed into a chair Helping a patient in and out of bed (hemiplegic patients) Positioning patients in a chair Installing a patient in the bed or in the chair Helping a patient in and out of bed Installing a patient in a chair or vice versa Positioning patients onto a toilet chair Installation in normal position of fallen-down-patient Lifting patient from one bed to another Positioning a patient into the bath Lifting patients from stretcher to bed and vice versa Lifting and transferring patients for clinical examinations Helping a patient to the lavatory

6.83 6.83

7.31 6.54

7.06 6.68

7.50 6.53 4.80 4.69 4.59 4.69 4.80 7.04 5.92 6.12 5.82 5.20 3.27

5.77 6.28 8.33 8.21 8.46 8.08 7.69 4.87 5.51 4.62 4.10 4.10 7.31

6.52 6.40 6.09 5.97 5.95 5.94 5.91 5.75 5.70 5.27 4.81 4.58 4.52

Mean Score ±SD

5.64 ±1.18

6.47 ±1-57

5.81 ±0.75

Table 3 shows the handling of the patient in bed with a mean score A=5.78 (SD=0.65). Table 3. The group of handling with the patient in bed, and the mean score for the whole group. Tasks/Manouevres score/ 10 Positioning corpulent patients onto the bed-pan Bed-washing in elderly patients with a poor physical condition Presenting a bed-pan in bed-ridden patients Changing patients' posture as prevention of decubitus Installing a water mattress in bed-ridden patients Installing a water mattress onto the bed Presenting a bed-pan by one nurse Positioning patients, subject to traction, onto the bedpan Daily bed-washing and nursing Nursing decubitus-wounds in patient with a poor physical condition Immobilization of a disturbed patient Up right positioning patient for meals Bed-washing Dressing and undressing the patient, both in and out of bed Upright positioning a patient in bed for meals Giving a bath in bed Presenting and removing bed-pan Positioning patient in bed Mean Score

±SD

stress

time

algorithm

7.04 5.71 5.20 5.20 6.26 5.93 4.59 6.53 4.08

7.95 8.08 8.33 8.08 6.28 5.90 8.08 5.13 9.23

7.46 6.69 6.40 6.33 6.27 5.91 5.85 5.74 5.66

4.80 5.20 4.08 3.88 4.59 3.88 3.78 3.67 3.16

6.54 5.90 8.59 8.89 6.41 8.59 8.97 8.33 8.59

5.54 5.53 5.53 5.40 5.35 5.35 5.32 5.10 4.62

4.87 ±1.10

7.70 ±1.26

5.78 ±0.65

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D. Caboor /A Method for Job Evaluation Using a Modified Delphi-Survey Administration and work-pressure show a mean score A=4.81 (SD=1.40) (Table 4).

Table 4. The group of administration and work-pressure, and the mean score for the whole group. Tasks/Manouevres score/ 10

stress

time

algorithm

Hurrying and get stressed during work (work-pressure) To much (unnecessary) administration Sometimes being subjected to high responsibility Communication and briefing, administration Running back and forth between laboratories

5.00 4.49 4.59 2.04 2.14

7.82 7.82 7.31 8.97 6.92

6.10 5.70 5.64 3.32 3.27

Mean Score ±SD

3.65 ±1.44

7.77 ±0.77

4.81 ±1.40

The group of tasks around the bed without the patient yielded a mean score A=4.48 (SD=0.96) (Table 5). Table 5. The group of tasks around the bed without patient, and the mean score for the whole group. Tasks/Manouevres score/ 10

stress

time

algorithm

Making up the beds (not the height adjustable beds) Making up a bed covered with a water mattress Upmaking the beds Making up the bed Maintaining patients' household

4.90 4.95 2.55 2.35 2.42

6.41 6.15 9.87 9.87 6.54

5.55 5.49 4.05 3.80 3.53

Mean Score ±SD

3.43 ±1.36

7.77 ±1.92

4.48 ±0.96

Table 6 shows the group of transferring all kind of loads except patients, and that group gives a mean score A=3.09 (SD=1.04). Table 6. The group of transferring loads, and the mean score for the whole group. Tasks/Manouevres score/ 10 Transferring a bed carrying a patient Serving a full tray into the room Transporting patients between care-units Serving meals Handling the meals cart Serving and clearing the meals Distributing meals Serving the meals and clearing the things Carrying the bed-pan after defecation Mean Score ± SD

stress 4. 1 8 2.24 2.45 .73 .63 .55 .53 .33 .12 1 .97 ±0.93

time

algorithm

8.08 8.72 6.41 9.23 7.78 8.97 9.31 8.97 8.85

5.51 3.56 3.55 2.91 2.70 2.64 2.63 2.32 2.00

8.48 ±0.93

3.09 ±1.04

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The technical and medical acts in Table 7 have a score A=2.80 (SD=1.01). Table 7. The group of technical and medical acts, and the mean score for the whole group. stress

Tasks/Manouevres score/ 10

time

algorithm

Taking blood samples in erect position (bended back) Reanimation and massage of the heart Caring of wounds and bandages Taking samples (blood - urine) Catheterizing (drip, bladder tube, stomach tube, etc.) Standing up straight while preparing and administering medicine Assisting the doctor during medical interventions Preparing medication Applying a perfusion Taking blood samples Maintenance and cleaning of material and appliance Application of intramuscular injections Registering ECG Examining parameters (blood pressure, count the pulses, etc.) Cleansing the mouth and cleaning the set of false teeth in elderly patients Monitoring and following telemetries Cleaning nursing material Supplying material

i

1.29 (5.53 \1.55 -1.24 '*1.24

7.18 3.59 8.72 7.82 7.82

5.37 4.63 3.95 3.48 3.48

I1.04 '*109 .63 .63 .53 .43 .33 .22 .12

8.89 4.23 7.82 7.36 6.67 8.21 7.95 5.51 9.23

3.32 2.80 2.70 2.67 2.49 2.43 2.28 2.00 2.00

.12 .31 .12 .02

7.69 3.85 7.18 8.46

1.96 1.95 1.94 1.82

Mean Score ±SD

2.02 =bl.37

7.12 ±1.71

2.85 ±1.01

Table 8, where we find an overview of the classification of the grouped tasks and/or manouevres, shows another possibility of the method we used. Table 8. Classification of the grouped tasks and manouevres with the normalized scores for the algorithm, the stress and the frequency (± standard deviation). patient in/out bed (n=15)

patient in bed (n=18)

administration/ work-pressure (n=5)

bed without patient (n=5)

transfer of load (n=9)

technical/ medical (n=18)

Algorithm

5.81 ±0.75

5.78 ±0.65

4.81 ±1.40

4.48 ±0.96

3.09 ±1.04

2.85 ±1.01

Stress

5.64 ±1.18

4.87 ±1.10

3.65 ±1.44

3.43 ±1.36

1.97 ±0.93

2.02 ±1.37

Frequency

6.47 ±1.57

7.70 ±1.26

7.77 ±0.77

7.77 ±1.92

8.48 ±0.93

7.12 ±1.71

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4. Discussion This type of problem defining approach - using a modified Delphi-survey - can be helpful in identifying the physical load and the frequency of the tasks during the performance of the job, and may also allow the overall evaluation of workers' perceptions concerning their occupational tasks. It is not only the emerging technology of occuational biomechanics which can be applied to evaluate the demands of a job (Chaffin et al., 1977). For this specific occupational group the "experts" approach identified the tasks and/or manouevres corresponding with other approaches. Harber et al. (1987) performed an observational study of work shifts, and their study demonstrated a high incidence of static activities which may also require the adoption of awkward postures for the duration of the isometric action. Patient handling tasks perceived to be most stressful by nursing assistants were identified by Owen and Garg (1989), and the tasks ranked as the most stressful were those that involved the lifting and transferring of patients from one destination to another. These findings corroborate the results of Stobbe et al. (1988) whereby nursing personnel believed back stress to occur as a result of the lifting of patients, and static tasks were not included within the patient handling tasks suggested as being the most stressful to perform. Therefore, although Harber et al. (1987) observed that static activities were regularly performed they may not be perceived as stressful. Despite differences in methodology, it is apparent that nurses attribute back pain symptoms to the patient handling activities routinely performed. Our approach gives the possibility to compare all kinds of tasks in the observed profession. In the nursing profession we find that transferring loads, other than patients, and the medical and technical acts are not very stressful, although the nurses take more time to complete those tasks. Frequency is an important factor in combination with perceived stress, and it becomes a very accurate instrument by using the algorithm outlined. The results of our study support the findings of other researchers (Harber et al., 1987; Stobbe et al., 1988; Owen and Garg, 1989; Garg et al., 1992) using another methodology, but they only studied the patient handling manouevres in relation to LBP, and they did not make a combination of stress and frequency in a co-ordinate system. In the present study we evaluated all kinds of nursing tasks and/or manouevres without information about the LBP character of the study, and we plotted the normalised scores in a Stress-Frequency co-ordinate system. This algorithm using the combination of stress and frequency is of great value. 5. Conclusions Complementary to the technology of occupational biomechanics, this inexpensive and 'lowtech' approach can be applied to identifying occupational health and safety problems. This simple and cheap method gives a correct evaluation of the perception of physical load during the performance of the job, and can be useful in any work-place. The workers - in this case nursing personnel - are deemed the experts. The simplicity, relevance and lack of expense of the Delphy-survey approach potentially makes it an excellent screening tool for the medical clinic and the work-place, though more sophisticated assessment using isolated strength measures and tests may be required under certain circumstances. The usefulness of the test in nursing personnel is documented, but its usefulness in other work-places awaits further investigation.

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References Anonymous. (1965). The nurse's load (leading articles). The Lancet, 422-423. Biering-Sorensen, F. (1985). National statistics in Denmark - back trouble versus occupation. Ergonomics, 28, 25-29. Burdorf, L., Laan, J. and van Kiel, M. (1991). Het meten van belastende factoren voor de rug in arbeidssituaties. T. Soc. Gezondheidsz, 69, 439-445. Chaffin, D. B., Herrin, G. D., Keyserling, W.M. and Garg, A. (1977). A method for evaluating the biomechanical stresses resulting from manual materials handling jobs. American Industrial Hygiene Association, 38, 662-675. Dehlin, O., Hedenrud, B. and Moral, J. (1976). Back symptoms in nursing aides in geriatric hospital. Scandinavian Journal of Rehabilitation Medicine, 8, 47-53. Gagnon, M., Sicard, C. and Sirois, J. P. (1986). Evaluation offerees on the lumbo-sacral joint and assessment of work and energy transfers in nursing aides lifting patients. Ergonomics, 29,407-421. Garg, A., Owen, B. D. and Carlson B. (1992). An ergonomic evaluation of nursing assistants' job in a nursing home. Ergonomics, 35, 979-995. Garg, A. and Owen, B. D. (1992). Reducing back stress to nursing personnel: an ergonomic intervention in a nursing home. Ergonomics, 35, 1353-1375. Harber, P., Shimozaki, S., Gardner, G., Billet, E., Voitecky, M. and Kanim, L. (1987). Importance of nonpatient transfer activities in nursing-related back pain: II Observational study and implications. Journal of Occupational Medicine, 29, 971-974. Harber, P., Billet, E., Shimozaki, S. and Vojtecky, M. (1988). Occupational back pain of nurses: special problems and prevention. Applied Ergonomics, 19, 219-224. Klein, B. P., Jensen, R. C. and Sanderson, L. M. (1984). Assessment of workers' compensation claims for back strains/sprains. Journal of Occupational Medicine, 26,443-448. Magora, A. (1970). Investigation of the relation between low back pain and occupation. 1. Age, sex community, education and other factors. Industrial Medicine, 39,465-471. Nachemson, A. L. (1971). Low back pain. Its aetiology and treatment. Clinical Medicine, January, 18-24. Owen, B. D. and Garg, A. (1989). Patient handling tasks perceived to be most stressful by nursing assistants. In: Advances in Industrial Ergonomics and Safety I (ed. A. Mital), pp. 775-781. London: Taylor and Francis. Stobbe, T. J., Plummer, R. W., Jensen, R. C. and Attfield, M. D. (1988). Incidence of low back pain injuries among nursing personnel as a function of patient lifting frequency. Journal of Safety Research, 19, 21-28. Stubbs, D. A., Buckle, P. W., Hudson, M. P. and Rivers, P. M. (1983). Back pain in the nursing profession II. The effectiveness of training. Ergonomics, 26, 767-779. Videman, T., Nurminnen, T., Tola, S., Kuorinka, I., Vanharanta, H. and Troup, J. D. G. (1984). Low back pain in nurses and some loading factors of work. Spine, 9,400-404.

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Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

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PHYSIOLOGICAL ASSESSMENTS OF OCCUPATIONAL ACTIVITIES T. Reilly, J. Burke, S. D. M. Bot* and A. P. Hollander* Research Institute for Sport and Exercise Sciences Liverpool John Moores University Henry Cotton Campus, 15-21 Webster Street Liverpool, L3 2ET, U. K. *Faculty of Human Movement Sciences Vrije Universiteit, Van der Boechorstraat 9, 1081 BT Amsterdam, The Netherlands.

Abstract. The conventional criteria for estimating energy expenditure during occupational work may be distorted when the activity is intermittent. The heart rate has been extensively employed as an index of physiological strain. A series of methodological studies were completed to establish the measurement error associated with using heart rate to estimate energy expenditure in non-steady state activity. Heart rate and oxygen uptake were then measured in a simulation of the activity-rest schedules of hospital-based porters. The responses were compared with those of a novel work-rate schedule designed on ergonomic grounds. There were no discernible differences between the two regimens, likely because of the overall low severity of the tasks. In such instances postural and transient factors rather than metabolic loading may need attention in the analysis of musculoskeletal strain.

1. Introduction The physiological strain of occupational work can be indicated by determining the average response over a complete working shift. Such variables might include oxygen uptake or energy expenditure. In view of the relationship between heart rate and oxygen uptake, which is assumed to be linear throughout the most relevant part of its range, the heart rate is often used as an index of occupational strain. The relationship may in fact be disturbed by the existence of non-steady state activity, isometric or overhead work, heat stress or emotional factors. Of particular present concern is the influence of intermittent as opposed to continuous work and the combination of actions that engage arm muscles, leg or trunk muscles or whole-body activities. The total energy expenditure of a typical male office worker is approximately 2500 kcal (10465 kJ). In industry a relatively light job might require daily energy

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expenditure of 3000 kcal (12558 kJ) whilst heavy work such as coal mining (3500 kcal) and forestry work (up to 6000 kcal or 25116 kJ) are more exacting (Pheasant, 1991). In sport daily energy expenditure values have been reported to range from 14.5 MJ for professional soccer players (Reilly and Thomas, 1979) to 32-35 MJ per day for Tour de France cyclists. The cyclists are obliged to operate over 3 weeks at this level which is 3.5-5.5 times the normal basal metabolic rate (Westerterp and Saris, 1991). The energy expenditure in the Tour de France cycle race was measured using the doubly-labelled water method combined with recorded activities and dietary intake. The values in the footballers were estimated from records of habitual activities of each player over a full week, heart rates measured during training and work-rate assessments during competitive games. There are some guidelines in the ergonomics literature with respect to the upper limit of work over an 8-hour shift sustained for many months. Christensen (1962) suggested 2000 kcal (8.372 MJ) was an acceptable guideline for heavy work over 8 hours in an industrial context. If an allowance of 1.5 kcal.min"1 (6.3 kJ.min"1) is made for the remaining 8 h awake and 1.1 kcal (4.6 kJ) min"1 for an 8-hour sleep, a value of 3248 kcal (13.6 MJ) is obtained for the estimated daily energy expenditure. This figure is just over twice the basal metabolic rate (BMR). A subject who is minimally active during the day would expend energy comparable to 1.4 BMR whereas the lumberjacks studied by Dill (1936), in an age where there was little mechanical support for forestry work, operated at four times BMR values. 2. Work-rest ratios Interspersed with the activities that constitute a typical work shift are periodic bouts of peak activity and also postural loading. Unless the individual has opportunities to recover at these points the likelihood is that fatigue will follow. Alternating rest periods or periods of lighter work with the more intense physical activities may actually increase the total quality of physical work the individual is able to do compared to steady work at a lower level for the course of the working day. A key challenge, therefore, for the ergonomist is the design of work schedules, averaged over the working day and accounting for both work periods and rest breaks, that remain within acceptable limits. Various formulae have been published for calculating the rest allowances which are required for physical work (Murrell, 1969), for example:r = E - A t E - B where r = resting time (min) t = total working day (min) E = energy expenditure during working task B = energy expenditure during rest A = average level of energy expenditure considered acceptable The average level of energy expenditure deemed acceptable should be related to the individual's aerobic power (VOi max)- A value of 33% maximum aerobic power has been recommended by NIOSH (1981). Nevertheless, building workers left to work spontaneously, pace themselves at about 40% VOamax (Pheasant, 1991). Furniture removal workers tend to have more frequent but shorter breaks in view of the high periodic loading on their musculoskeletal systems, and the associated local

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muscular fatigue due to the lifting and carrying which their jobs entail. Petrofsky and Lind (1978) reported that fatigue was clearly evident during a 4-hour lifting study at a work rate of about 50% VC^max, so clearly this level is too high for safety. These authors indicated that a figure of 23% VC>2max would be an appropriate limit for manual handling tasks with predominantly arm muscle work. For the employer the ideal work-rest schedule would be one that permits a complete recovery from the fatiguing bouts of activity but does not allow excessive rest breaks. Physical activity at a low to moderate intensity is fuelled mainly by the aerobic system. In very brief intense efforts the muscle's internal phosphagen system is utilised. Where the high-intensity activity is sustained for longer (10-40 s), fuel for muscle contraction is provided mainly by means of anaerobic glycolysis. The consequences are that there is an 'oxygen deficit' incurred which must be paid back when the activity ceases and lactate accumulates first within the muscle before a build-up appears in the blood. The 'oxygen deficit' explains the elevated VO2 postactivity whilst the accumulated lactate must be removed or oxidised. The 'anaerobic threshold' represents the work-rate at which lactate begins to accumulate in the blood and is generally recognised as the upper limit for sustaining endurance exercise. Christensen et al. (1960) investigated how design of a task, which normally exhausted the subject within 4 min when working continuously, could be improved by altering it to intermittent work. With a 5-s rest alternating between 10-s activity bouts, the total exercise plus rest period could be extended to 30 min. In this instance the work-rate for 10 s was the same as that which had induced exhaustion by 4 min. Wood (1997) required subjects to perform a manual task that is similar to the repetitive jobs that exist in industry. Three different work-rest schedules were used in this study, a low, medium and high-force schedule. Results showed that the fatigue that developed in the medium-force schedule was significantly lower than that developed in the low or high-force schedule. Another study investigating the effects of 6 different work-rest schedules (no rest, 4 min work-1 min rest, 9-1, 18-2, 27-3 and 12-3 minutes work-rest), yielded no significant differences in heart rate, oxygen consumption, rectal temperature, respiratory exchange ratio or endurance time. There was, however, a slight trend toward the longer endurance times when rest periods were more frequent and subjectively the subjects felt much better with more rests. Workers involved in loading and unloading operations in a railway yard were studied by Ganguly et al. (1981) to identify the extent of physiological strain experienced and the need for re-organising the work-rest schedule for promoting efficiency. It was found that although the workload remained constant, the corresponding physiological strain increased towards the end of the work shift. This suggested that cumulative fatigue occurred, due to the rest breaks being insufficient in length to allow full recovery to take place. This finding was supported by heart rate values which remained above 125 beats.min"1 for long periods of work and did not reach resting levels during any of the recuperation periods. Rest breaks are provided to allow recovery from reduced levels of performance, so it is essential that they are long enough to do so. Women who carry out manual materials handling (MMH) activities need more frequent and longer rest breaks than men and that high frequency tasks require more frequent rest allowances (Genaidy and Al-Rayes, 1993). A recommendation was made with regards to the best method used to attain the maximum physiological efficiency for arm lifting tasks. It was suggested that when handling a 20-kg load, a frequency of 9 lifts.min"1 for a 4-1 minute work-rest schedule should be used (Genaidy, 1990). It must be noted, that

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although valuable information can be obtained from these studies, there are limitations to their applicability to the actual work situation. 3. Heart rate as a criterion of physiological strain The heart rate has been employed as a measure of physiological strain, in view of its concomitant increase with VC>2 as the severity of work increases. Nowadays shortrange radio telemetry has made the measurement of heart rate easy and socially acceptable. The heart rate response can be recorded over an entire work-shift and the data later down-loaded. Nevertheless there remains a question about how to interpret the heart rates, especially if the work schedule is complete. In several studies a linear relationship between HR and VO2 during non-steady state activities was found, but all tests were limited to progressive incremental exercise (Gilbert and Auchincloss, 1971; Fardy and Hellerstein, 1978; Fairshter et al., 1987; Matthys et al., 1996; Bernard et al., 1997). Statements about the presence or absence of a relationship between HR and VC>2 have not been tested statistically (Edwards et al., 1973; Bailor and Volovsek, 1992), or the specific nature of activities like weight-lifting (Shaw and Deutch, 1982) and karate (Collins et al., 1991) may impede generalisations. The indirect assessment of VC>2 by measuring HR has mainly been limited to steady-state exercise. Although not yet proven, a linear relationship between HR and VO2 during intermittent and non-steady state exercise is plausible. Bunc et al. (1988) concluded that the regulation of the HR at the onset of exercise might be similar to the regulation of VC>2. Several studies have indicated the time constant or mean response time for VC>2 to be similar to that for HR in the transition from rest or from unloaded cycling to a certain workload (Hughson and Morrisey, 1983; Sietsema et al., 1989; Casaburi et al., 1997), which suggests a close relationship. Furthermore, heart rate gave a close estimate of VO2 during intermittent exercise in the study of Lothian and Farrally (1995). The first aim therefore was to investigate the validity of the use of HR-response in estimating the VC>2 during non-steady state exercise. The intention was that the applicability of HR measurement to predict V02 would be extended if the relationship between HR and VC>2 during non-steady state activities can be demonstrated. 4. Summary of methodological studies for estimating VOj Dynamic and static exercise engaging large and small muscle masses were studied in four different experiments. In a first experiment, 16 subjects performed an interval test on a cycle ergometer, and 12 subjects performed a field test consisting of various dynamic leg exercises. Simultaneous HR and VC>2 measurements were made. Linear regression analyses revealed high correlations between HR and VC>2 during both the interval test (r = 0.90 + 0.07) and the field test (r - 0.94 + 0.04). In the second experiment, 14 non-wheelchair-bound subjects performed both an interval wheelchair test on a motor driven treadmill, and a wheelchair field test consisting of dynamic and static arm exercise. Statistically significant relationships were found for all subjects during both the interval test (r = 0.91 ± 0.06) and the field test (r = 0.86 + 0.09). During non-steady state exercise using both arms and legs in a third experiment, contradictory results were found. For 11 of the 15 subjects who performed a field test

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consisting of various nursing tasks, no significant relationship between HR and VO2 was found (r = 0.42 + 0.16). All tasks required almost the same physiological strain, which induced a small range in data points. In a fourth experiment, the influence of a small data range on the HR-VO2 relationship was investigated: five subjects performed a field test that involved both low and high physiological strain, non-steady state arm and leg exercise. Statistically significant relationships were found for all subjects (r = 0.86 ± 0.04). Although the rvalues found in this study were less than under steady-state conditions (see Table 1), it can be concluded that VC>2 may be estimated from individual HR-VOi regression lines during non-steady state exercise. Table 1. Comparison of the group correlation coefficients (r) between HR and VC<2, and standard error of estimate (SEE), during steady state exercise testing.

Authors

mode*

slope

intercept

r

SEE

Franklin et al. (1980) Katchefa/. (1978) Londeree & Ames (1976) Londeree et al. (1994) Londeree at al. (1994)

TM CE TM TM CE

1.33 1.39 1.37 1.30 1.41

-24.5 -44.8 -41.0 -34.5 -45.1

0.94 0.97 0.97 0.96 0.93

6.9 7.9 5.7 -

Londeree et al. (1994) Hooker et al. (1993) Vanderefa/. (1984)

R ACE ACE

1.18 1.41 1.43

-21.0 -46.2 -48.8

0.94 0.95 -

To.3

TM

1.42 1.49 1.16 1.31

-51.6 -57.8 -27.9 -43.0

0.88 0.89 0.79 0.74

8.7 10.6 10.8 12.9

Present study - interval test exp. I - exercise test exp. I - interval test exp. II - exercise test exp. II

we

5. Study of hospital porters 5.1 Introduction The problem of manual handling should not be confined to heavy 'industrial' work. In the health service manual handling is the cause of over 55% of reported injuries. Between 1992 and 1995, of all the manual handling accidents reported to the HSE, over 60% of them involved patient handling. No literature exists regarding the physiological responses of hospital-based porters. Such an occupation incorporates various activities like walking, pushing, and pulling, with varying degrees of intensity. Extensive research has been carried out on nurses and physiotherapists, who work in a similar health environment and investigations have shown that they suffer from physical stress and musculoskeletal disorders. Clearly, in an environment where workload and strain can affect work efficiency and an individual's health, it is important to consider all occupations involved, in this case, hospital porters. The present study is an attempt to identify the physiological responses to a simulated 4-hour work shift of a hospital porter and to examine the possibility of

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developing an optimum work-rest schedule for promoting physical health and work efficiency. 5.2 Methodology 5.2.1 Subjects Ten healthy male subjects were recruited as subjects to participate in this study. The mean (± SD) age of the subjects was 23 (+ 2.9) years, the mean height was 180 (+5.4) cm and the mean (+ SD) body mass was 81.3 (+ 12.71) kg. Each subject was required to attend the laboratory on three separate occasions and voluntary written consent was obtained prior to testing. 5.2.2 Experimental design The testing was divided into three main stages. Prior to testing, activity profiles (percentage of time spent standing, walking, sitting and so on) of eight hospital porters were determined by one of the researchers and the most physically demanding profile was used as the experimental protocol throughout this study. The existing work-rest schedule of the porters was also ascertained. This was an 8-hour shift that incorporated one 10-min break in the morning and afternoon and a 30-min break for lunch. A 4-hour period of testing was used as representative of the actual work-rest schedule. An alternative work-rest schedule was developed and these formed the two test protocols. The initial stage involved the familiarisation session. During this stage, subjects were familiarised with a portable radio telemetry system for respiratory gas analysis (Cortex Biophysik GmbH, Borsdorf). Subjects were connected to the equipment, ensuring maximum comfort and then undertook 15 minutes of activity (3 minutes of pushing, pulling, standing, walking and sitting). For the second stage, subjects performed a 4-hour, laboratory simulated work-rest schedule of a hospital-based porter. The work-rest schedule used in this stage of the experiment was the existing schedule and was as follows (trial 1): 53.45-min work -» 5-min break ->• 53.45-min work -» 15-minute break -» 53.45-min work —> 5-minute break —> 53.45-min work —> finish. An alternate four-hour activity-rest schedule was proposed and constituted the second test session (trial 2): 71.40-min work -> 12.30-min break -» 71.40-min work -> 12.30-minute break —> 71.40-min work —> finish. The two trials are graphically illustrated in Figure 1. It is evident that the experimental trial had two rest breaks compared with the three rests in the normal trial.

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Experimental trial

Normal trial

100

150

200

250

Time (min)

Figure 1. The activity - rest schedules used in the study.

The relative percentage of time that each action was performed was identical for each of the two test sessions. Rest breaks were differently distributed but the total time spent at rest was constant (25 min for both trials). During the rest breaks, the subjects remained seated. A random order of design was assigned to the subjects and each subject acted as their own control. Each subject was tested at the same time of day to control for natural diurnal variation. A four-hour simulation was used due to the difficulty in obtaining subjects able to participate for a normal eight-hour shift. Porters could not be used due to financial restrictions so university students were used to simulate their actions.

Figure 2. Portable telemetry system for measurement of oxygen uptake.

In both test sessions, heart rate and oxygen consumption (VO2) were measured continuously throughout each test using short range radio telemetry for heart rate (Polar Kempele, Finland) and a gas analysis Metamax telemetry system (Cortex Biophysik GmbH, Borsdorf), respectively. Minute ventilation ( VE) was also recorded using the Metamax system and at the end of each test, subjects gave a rating of perceived exertion on a 6 to 20 Borg scale (Borg, 1970).

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5.2.3 Analysis of data Energy expenditure was calculated using the energy equivalents of oxygen for the nonprotein respiratory quotient (McArdle, Katch and Katch, 1996). Differences in energy expenditure and RPE between the two trials were analysed using t-tests in Minitab (version 5). A median value for heart rate, VO2, and minute ventilation was obtained from each four-hour session. Due to evidence of skewness in the physiological data, the median value was used for a more accurate statistical analysis as opposed to the mean. A one-sample Wilcoxen test was performed. In the results section, median values are quoted for these variables. 5.3 Results No significant differences were found in any of the physiological variables measured (p>0.05). The median Vc>2 for Tl (normal trial) and T2 (experimental trial) were 0.75 (range, 0.65 to 0.94) and 0.81 (range, 0.65 to 0.98) l.min"1 respectively. Median heart rate (HR) values were very low for both test sessions; 78 (range 71 to 93) and 82 (range 71 to 90) beats.min'1 for Tl and T2 respectively. No significant differences were found in average energy expenditure between the two test sessions (p>0.05). Subjects expended an average of 948.1 and 979.5 kJ.h"1 for Tl and T2 respectively. There were no differences in \E between the two trials (p>0.05); median values being 18.41 (range 15.5 to 22.8) l.min'1 and 19.2 (range 15.0 to 24.0) l.min"1. See Table 2 for results. Table 2. Recorded variables (mean ± SD or the median and the range) and the level of probability.

Heart rate (beats.min" ) VO2 (l.min-1) Energy expenditure (kJ.h"') VE (l.min-1) Perceived exertion

Normal Trial

Experimental Trial

p Value

78 (range 7 1-93) 0.75 (range 0.65-0.94) 948.1 18.41 (range 15.5-22.8) 7.6 (±1.4)

82 (range 7 1-90) 0.81 (range 0.65-0.98) 979.5 19.2 (range 15-24) 7.8 (±1.5)

0.353 0.155 0.185 0.308 0.34

5.4 Discussion The results of these methodological studies indicated a linear relationship between HR and VO2 during both non-steady state leg exercise and non-steady state arm exercise. Although the r-values were less strong than under steady state conditions, it can be concluded that the estimation of VO2 by measuring the HR is not limited to steady state exercise. The VC>2 could be estimated from individual HR-VO2 regression lines during varying non-steady state activities. The mean heart rates of the subjects in the present study of hospital porters were in the range 71-93 beats.min"1. The narrowness of the range indicated that there were relatively little disturbances from periodic bouts of high intensity activity. Even if there had been, it seems the pace of work dictated by the experimental and normal protocols allowed the subjects to maintain the physiological stress at a low to moderate severity. The simulated work schedule was modelled on observations of

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hospital-based porters going about their routine duties. It is not known if the urgency of contingent events in a realistic work setting would always allow them to do so. The energy expenditure values would amount to 7.584 MJ over an 8-hour shift for the normal condition. This corresponds to roughly three times the basal metabolic rate, even though the perception of effort was still very light. Allowing for the typical energy expenditure over the remainder of the day, the overall daily expenditure can be estimated at 12.826 MJ (3064 kcal). The manipulation of the rest breaks failed to influence the physiological responses to the simulated work-cycle. It may be that at relatively low levels of physical activity when 'fatigue' does not occur, minor alterations in work-rest schedules are not important for physiological criteria. Nevertheless, in any intermittent work schedule, the rest breaks are a relevant consideration since postural or attentional factors may lead to discomfort and boredom in the absence of breaks from duty. References Bailor, D. L. and Volovsek, A. J. (1992). Effect of exercise to rest ratio on plasma lactate concentration at work rates above and below maximum oxygen uptake. European Journal of Applied Physiology, 65, 365-369. Bernard, T., Gavarry, O., Bermon, S, Giacomoni, M, Marconnet, P. and Falgairette, G. (1997). Relationship between oxygen consumption and heart rate in transitory and steady states of exercise and during recovery: influence of type of exercise. European Journal of Applied Physiology, 75, 170-176. Borg, G. (1970). Perceived exertion as an indicator of somatic stress. Scandinavian Journal of Rehabilitation Medicine, 2, 92-98. Bunc, V., Heller, J. and Leso, J. (1988). Kinetics of heart rate responses to exercise. Journal of Sports Sciences, 6, 39-48. Casaburi, R., Whipp, B. J., Wasserman, K., Beaver, W. L. and Koyal, S. N. (1977). Ventilatory and gas exchange dynamics in response to sinusoidal work. Journal of Applied Physiology, 42, 300311. Christensen, E. H. (1962). Speed of work and its relation to physiological stress and systems of payment. Ergonomics, 5,7-13. Christensen, E. H., Hedman, R. and Saltin, B. (1960). Intermittent and continuous running. Acta Physiologica Scandinavica, 50, 269. Collins, M. A., Cureton, K. J., Hill, D. W. and Ray, C. A. (1991). Relationship of heart-rate to oxygen uptake during weight lifting exercises. Medicine and Science in Sports and Exercise, 23, 636-640. Dill, D. B. (1936). The economy of muscular exercise. Physiological Reviews, 16, 263-291. Edwards, R. H. T., Ekelund, L-G, Harris, R. C., Hesser, C. M., Hultman, E., Melcher, A. and Wigertz, O. (1973). Cardiorespiratory and metabolic costs of continuous and intermittent exercise in man. Journal of Physiology, 234, 481-497. Fardy, P. S. and Hellerstein, H. K. (1978). A comparison of continuous and intermittent progressive multistage exercise testing. Medicine and Science in Sports, 10, 7-12. Fairshter, R. D., Salness, K., Walter, J., Minh, V-D. and Wilson, A. (1987). Relationships between minute ventilation, oxygen uptake, and time during incremental exercise. Respiration, 51,223-231. Ganguly, T., Ramachandra Rao, H. P. and Raja, S. (1981). Application of physiological parameters for evolving optimum work-rest rhythm in actual place of work. Indian Journal of Medical Research, 74, 721-728. Genaidy, A. M. (1990). The physiological effects of work-rest schedules on manual lifting tasks. In: Contemporary Ergonomics 1990 (edited by E. J. Lovesey), pp. 198-208. London: Taylor and Francis. Genaidy, A. M. and Al-Rayes, S. (1993). A psychophysical approach to determine the frequency and duration of work-rest schedules for manual handling operations. Ergonomics, 36, 509-518. Gilbert, R. and Auchincloss, J. H. (1971). Comparison of cardiovascular responses to steady- and unsteady-state exercise. Journal of Applied Physiology, 30, 388-393.

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Hughson, R. L. and Morrisey, M. A. (1983). Delayed kinetics in the transition from prior exercise. Evidence for O2 transport limitation of VO: kinetics: a review. International Journal of Sports Medicine, 4, 31-39. Lothian, F. and Farrally, M. R. (1995). A comparison of methods for estimating oxygen uptake during intermittent exercise. Journal of Sports Sciences, 13,491-497. Matthys, D., Pannier, J. L., Taeymans, Y. and Verhaaren, H. (1996). Cardiorespiratory variables during a continuous ramp exercise protocol in normal young adults. Acta Cardiologica, 51, 451459. McArdle, W. D., Katch, F. I. and Katch, V. L. (1996). Exercise Physiology: Energy, Nutrition and Human Performance. Baltimore: Williams and Wilkins. Murrell, K. F. H. (1969). Ergonomics- Man and his Working Environment. London: Chapman and Hall. NIOSH (1981). Work Practices Guide for Manual Lifting. Cincinnati: National Institute for Occupational Safety and Health. Petrofsky, J. S. and Lind, A. R. (1978). Metabolic, cardiovascular and respiratory factors in the development of fatigue in lifting tasks. Journal of Applied Physiology, 45,64-68. Pheasant, S. (1991). Ergonomics, Work and Health. London: MacMillan Press. Reilly, T. and Thomas, V. (1979). Estimated daily energy expenditure of professional association footballers. Ergonomics, 22, 541-548. Sietsema, K. E., Daly, J. A. and Wasserman, K. (1989). Early dynamics of O2 uptake and heart rate as affected by exercise work rate. Journal of Applied Physiology, 67, 2535-2541. Shaw, D. K. and Deutsch, D. T. (1982). Heart rate and oxygen uptake response to performance of Karate Kata. Journal of Sports Medicine and Physical Fitness, 22,461-468. Westerterp, K. R. and Saris, W. H. M. (1991). Limits of energy turnover in relation to physical performance, achievement of energy balance on a daily basis. Journal of Sports Sciences, 9, 1-15. Wood, D. D. (1997). Minimising fatigue during repetitive jobs: optimal work-rest schedules. Human Factors, 39, 83-101.

Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

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SPINAL SHRINKAGE DURING SIMULATED NURSING AND PORTERS' TASKS Caryl Beynon Research Institute for Sport and Exercise Sciences Liverpool John Moores University Henry Cotton Campus 15-21 Webster Street, Liverpool, L3 2ET United Kingdom

Abstract: Musculoskeletal disorders constitute the major occupational diseases reported in the European Union. Treatment of low-back pain costs more than any other disease in the working population and despite interventions the problem is still in evidence. People working in certain occupations, for example nursing, experience a particularly high prevalence of low-back pain. Long term loading of the spine is one factor associated with back pain, leading to trauma to intervertebral discs, damage to end-plates and underlying bone and nerve impingement. Spinal loading can be assessed by measuring small changes in stature with changes being directly related to the magnitude and duration of the load. Such changes are measured using precision stadiometry, an accurate assessment tool once subjects have been familiarised. The following two studies aimed to assess the effect of alterations in working practices on spinal shrinkage during nursing and porters' tasks. The aim of the study of the nurses was to compare the effect on spinal shrinkage during the course of 4 hours of simulated work when subjects had a 20min seated break or a 20-min standing break. The aim in the porters' study was to assess the effects of altered work-rest schedules on spinal shrinkage during a 4-hour simulation of porters' tasks. Shrinkage was significantly less at the end of 4 hours when the nursing subjects sat for the 20-min break than when they were required to stand. It is suggested that a period of sitting during and average shift would reduce the number of back problems experienced by nursing as a result of spinal loading due to prolonged standing. The modified work-rest schedule employed in the porters' study failed to have any effect in reducing spinal shrinkage. It is suggested that differences in the positioning and length of the breaks between the two trials were insufficient to demonstrate significant findings because 4 hours had been adopted as the trial period. Over this period the positioning and length of the breaks employed failed to show an overall effect of altering rest breaks.

1. Introduction It is estimated that 70-80% of all people living in the industrial world will suffer from back pain at some time during their lives (Biering-S0rensen, 1984; Waddell, 1987; Friedrich, 1994) with the annual incidence being around 5% (Friedrich, 1994). Treatment of low-back pain in the working aged population costs more than any other

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disease category (Peat, 1994). Hildebrandt (1995) reported that male construction workers and female nurses showed the highest back pain prevalence rates of Dutch men and women within the working population. It can be assumed that nurses in other Western countries have similar working practices and are at a similarly high risk. Buckle (1987) estimated the cost of the problem at 764,000 lost days per year. Harber et al. (1985) and Stubbs et al. (1983) quoted similar figures. Back pain therefore constitutes a huge financial burden to organisations, not to mention considerable worry to those afflicted. Most back pain is idiopathic. It is difficult to identify risk factors when the etiologic process underlying the non-specific health outcomes are not clearly understood. Identifying the factors associated with back pain is also difficult because of its multi-factorial aetiology (Lundberg, 1995). Despite this, numerous studies have attempted to identify possible risk factors with a range of causes being cited. Long term loading of the spine is one possible factor associated with back pain. Human stature varies throughout the course of a day, being greatest on rising and least prior to going to bed. This is because compressive loads on the spine during the day cause fluid to be expelled from the nucleus pulposus and bulging of the annulus (Van Dieen and Toussaint, 1993). This process leads to loss of stature. Once the compressive load on the spine has been removed, fluid is reabsorbed by the discs and stature is regained as a consequence (Helander and Quance, 1990). Long term loading and insufficient recovery may result in damage to the underlying bone and end plates and irreversible loss of disc height (Van Dieen and Toussaint, 1993). The disc loses its capability to respond to further compressive loading (Eklund and Corlett, 1984). Bulging of the annulus impinges on the nerve roots and increases the probability of pain (Eklund and Corlett, 1984). Changes in stature can be measured using a precision stadiometer, with stature being directly related to the load and exposure time (Leivseth and Drerup, 1997). Once a period of familiarisation has been undertaken by subjects, this piece of equipment has been shown to give precise, reliable measures (Eklund and Corlett, 1984; Leatt et al., 1985; Eklund, 1988). Spinal shrinkage has been measured in numerous conditions. Some work has considered differences in spinal shrinkage when varying the load acting on the spine. Eklund and Corlett (1984) reported significantly more shrinkage when subjects performed one hour of sedentary work with a 14-kg shoulder load than when the corresponding activities were repeated on a separate day without loading. Althoff et al. (1992) reported that decreases in stature were directly related to the load on the spine. Tyrrell et al. (1985) demonstrated that stature was related to the weights lifted over a large range of loads deployed in weight lifting. Others have compared differences in spinal shrinkage during sitting and standing and the beneficial effects of sitting on shrinkage are not conclusive. Magnusson et al. (1990) observed a decreased stature in a sitting position. In this study by Magnusson et al. (1990) the subjects lay down prior to testing and the shrinkage observed whilst sitting was probably due to the shrinkage naturally observed when subjects move from a supine to a sitting posture (Leivseth and Drerup, 1997). Stature loss has been measured when subjects sat for 1.5 hours in three different chairs, a stool, office chair with a lumbar support and an easy chair with a full-size backrest inclined at 110° and with a 4-cm deep lumbar support. Shrinkage was greatest in the stool, followed by the office chair but stature increased when subjects sat in the easy chair (Eklund and Corlett, 1984). A trial incorporating standing was not included in the research design

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so a comparison between shrinkage whilst sitting and standing could not be made. Only three subjects were used in this study so it is unclear what generalisations can be made. Spinal shrinkage in subjects sitting in a variety of different chairs was studied by Althoff et al. (1992) with a correction made for heel compression (Foreman and Linge, 1989). Sitting always resulted in an increased stature regardless of the chair used and it was concluded that sitting reduced spinal stress compared to standing. Static postures, heavy physical work demands, frequent bending and stooping, twisting, sudden unexpected movements, exposure to vibration and tasks involving lifting, pushing, and pulling have all been described as having the potential to cause back problems (Kaplansky et al., 1998). With the exception of vibration, nursing involves all the above components at some time. Such actions increase the compressive load on the spine and facilitate spinal shrinkage. Hospital based porters have to perform similar occupational activities. Both nurses and porters also have to spend extensive periods of time on their feet, a factor reported to be associated with low-back pain in nurses (Beynon et al., 1998). The aim in these studies was to assess the effect on spinal shrinkage of a 20-min 'sit down' break compared to a 20-min 'standing break' during a 4-hour trial of simulated nursing activities. The second aim was to assess the magnitude of spinal shrinkage of porters working under the existing hospital work-rest schedule. A modified work-rest schedule was then developed to ascertain whether spinal shrinkage could be lessened. The overall aim of the two studies was to establish whether spinal loading could be reduced using simple modifications to working practices. 2. Methods 2.1 Work profiles Work profiles were obtained for 8 nurses and 8 porters working in a District General Hospital. Each individual was 'shadowed' for 2 hours and the actions they performed were recorded every 5 seconds. The activities were standing, sitting, walking, pushing, pulling, lifting, bending and crouching. For each individual, the total duration each activity was established. Heart rate was recorded every 15 seconds over the 2-hour period using a short range telemetry system (Polar, Kempele, Finland). Mean heart rates were recorded from the work profiles. The mean heart rates of the porters varied greatly because the work they performed was totally dependent on the varying demands of different shifts on different days. The profile with the highest mean heart rate indicated the percentage of time each activity was performed in a 2-hour period and was used to form the basis of the laboratory protocol. Upon considering the nurses' profiles, one subject was eliminated from the study because the occupational demands of this subject were uncharacteristically low. The average duration for which each activity was undertaken within a 2-hour period was calculated from the remaining seven profiles. This value was used in the laboratory testing.

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2.2 Laboratory protocols Two different laboratory procedures were developed for the nursing study. In each of the 2 trials, subjects worked for 2 hours, had a break of 20-min and worked for a further 100 minutes. This regimen constituted 4 hours in total for each test as follows: 120-min work -> 20-min break -» 100-min work -> finish Both trials were identical except subjects sat during the break in trial 1 and stood during the break in trial 2. The order of testing was randomly assigned. The work-rest schedule of porters was ascertained. Porters worked an 8-hour shift with one 10-min break in the morning and afternoon and a 30-min break for lunch. A 4-hour test protocol was used to represent this with the breaks being halved accordingly. The existing work-rest schedule to be tested was as follows: 53.75-min work -> 5-min break -> 53.75-min work -» 15-min break -> 53.75-min work —> 5-min break —» finish An alternative 4-hour work-rest schedule was proposed as the second testing protocol and is as follows: 71.66-min work -» 12.50-min break -> 71.66-min work -» 12.50-min break -> 71.66min work —> finish During the rest periods of the porters' study the subjects were required to sit in the same chair each time. During both the nurses' and porters' study each subject worked for the same percentage of time in each of the two trials. The percentage of time in which subjects were resting was identical for both trials and the relative percentage of time for each activity performed was identical for both trials. Therefore, if a subject walked for 30 minutes in trial 1, the same length of time was used in trial 2. 2.3 Laboratory procedure 2.3.1 Subjects Ten female subjects participated in the nursing laboratory study. The mean age was 25 (± 3.9) years, their mean height was 166 (± 9.2) cm and their mean body mass was 63.5 (± 6.3) kg. Ten male subjects were recruited to participate as porters. The mean age was 23 (± 2.9) years, their mean height was 180 (± 5.4) cm and their mean body mass was 81.3 (± 12.7) kg. Each subject attended the laboratory on three separate occasions. On the first occasion, subjects were familiarised with the stadiometer. 2.3.2 Familiarisation Subjects required familiarisation with the stadiometer to ensure that changes in stature were due to shrinkage and not because the subject was adopting a different posture each time. The equipment and procedure were described by Althoff et al. (1992). A cross was drawn on the verbetra prominens. A camera was mounted behind the subject and connected to a linear transducer. The camera was moved up and down

C. Beynon / Spinal Shrinkage during Simulated Nursing and Porters' Tasks

until the horizontal line in the viewer was focused on the cross on the subject's neck. Changes in the height of the camera relative to its starting height gave a measure of spinal shrinkage. When the subjects were trained in use of the stadiometer, they were required to move away from and back onto the stadiometer in quick succession and asked to resume their previous posture. If the cross on the subject's neck returned to the horizontal line in the camera viewer each time, the familiarisation was considered complete. Exactly the same procedure was used for all subjects. 2.3.3 Test sessions On the two test sessions, subjects were required to attend the laboratory having participated in no physical activity 24 hours prior to testing. Subjects were required to lie in the Fowler's position (supine with knees and hips flexed and ankles supported) for 20 min. This allowed for a period of controlled spinal unloading so fluid would be reabsorbed into the nucleus pulposus and subjects would be near their maximum height. Subjects performed both trials at the same time of the day to control for any diurnal variation. The order of testing was randomly assigned to the subjects. Because of large inter-subject variation in spinal shrinkage, subjects effectively acted as their own controls. Shadowing the nurses had shown that their activities required a greater range of actions than did those of the porters. Whilst the nurses were standing they could still be performing certain actions with their upper limbs. During the standing periods of the nurses' trials, the subjects were required to undertake one of two activities with their arms. Firstly, they were required to lay out a sheet over a table at approximately bed height, smooth the sheet over the table before folding the sheet back up. This was to simulate a nurse performing activities involving the care of a patient in a bed. Secondly subjects were required to stack books from a table at approximately waist height to a shelve approximately head height. This replicated overhead activities such as changing drips, obtaining and replacing equipment from shelving or tidying the patients' lockers. There was no lifting component included in the testing sessions because the nurses shadowed never lifted. During care of the patient in the bed, nurses usually worked in pairs so that no single nurse was bearing all the patient's weight at any one time. The usual procedure as to 'roll' the patient. A low flat box weighing 20 kg was used in this study and was either 'rolled' away from or to the side of the subject and held for a number of seconds. This manoeuvre was similar to a nurse 'rolling' a patient to attend dressings or bed bathing and so on. 2.3.4 Variables measured Pre-test data points were obtained every 2 min to elicit the individuals' natural shrinkage. These data points were extrapolated to determine the predicted shrinkage over 4 hours. Spinal shrinkage was recorded at set intervals throughout the trials and at the end of each test session. The difference between the observed and expected measure was the final value for spinal shrinkage. Heart rate was recorded every 15 seconds using a short range telemetry system (Polar, Kempele, Finland). 2.4 Analysis of data Paired t-tests were used to analyse differences in spinal shrinkage and heart rate using Minitab (version 5). A p value of 0.05 was taken to indicate statistical significance.

131

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3. Results The mean, standard deviance and level of probability for heart rates and spinal shrinkage for the nurses' seated trial and standing trial are given in Table 1. Significant results are highlighted. Mean heart rates for the first 2 hours and the last 100 min did not differ significantly between the two trials (p>0.05). The mean heart rate during the seated break was significantly less than the mean heart rate during the standing break (p<0.05). Spinal shrinkage was significantly less after the seated trial than the standing trial (p<0.05). Table 1. Heart rate and spinal shrinkage during the nurses seated and standing trials (significant results are in bold).

Standing break

Sitting break

p value

Heart rate for the first 2 hours (beats.min"1)

88 (± 11)

87 (1 9)

0.80

Heart rate during the break (beats.min"1)

87 (± 1 1)

77 (1 8)

0.003

Heart rate for the last 100 min (beats.min"1)

89 (± 9)

88 (± 8)

0.60

Spinal shrinkage (mm)

3.80 (1 2.26)

2.77(11.61)

0.021

Considering the porters' study, there was no significant difference between the spinal shrinkage observed in trial 1 and the shrinkage observed in trial 2 (p>0.05). There was also no difference in the mean heart rates for the two trials (p>0.05). The results are given in Table 2. Table 2. Results for shrinkage and heart rates in response to simulated porters' tasks.

Trial 1

Trial 2

p value

Spinal shrinkage (mm)

2.1(13.16)

2.9 (1 2.92)

0.47

Mean heat rate (beats.min"1)

79 (1 6)

81(16)

0.35

4. Discussion Despite increased mechanisation the prevalence of musculoskeletal disorders, and in particular back problems, remains high (Van Diee'n and Oude Vrielink, 1998). It is well recognised that nurses constitute a group of healthcare professionals at a high risk from suffering some back trouble during the course of their working life (Hildebrandt, 1995) but the back pain problems experienced by other healthcare professionals are largely ignored.

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Logistic regression analysis of a questionnaire survey comprising of 813 nurses reported that the risk of suffering low-back pain increased when the percentage of time the individuals spent on their feet during the course of a shift increased. This was not a significant risk factor when musculoskeletal disorders in general were considered so it was suggested that prolonged standing primarily affected the back region (Beynon et al., 1998). Consultation with hospital-based nursing staff indicated that a 20-min break was scheduled during the course of their shift but was sometimes not taken due to the demands on the ward. Nurses were often required to be on their feet for the duration of the shift. The work performed by the subjects in the nurses' study was identical but the work was self-paced. It was important to establish that the differences observed in shrinkage for the two trials could not be attributed to differences in work-load. The average heart rates for the first two hours were not significantly different between the two trials. The average heart rates for the last 100 minutes were also similar. It was therefore assumed that the physiological strain did not vary for the two trials. Mean heart rates during the break did vary significantly, being greater during the standing trial (77 ± 11 beats.min"1) than the seated trial (87 ± 8 beats.min'1). This difference may be due to decreased venous return due to pooling in the extremities when standing, a situation which would result in increased heart rate to compensate for a reduced stroke volume. The higher heart rate whilst standing may also be due to the recruitment of additional muscles to maintain a standing posture. The additional muscular activity when standing may also contribute to the load on the spine. The results of this study of nursing activity showed that shrinkage was reduced when subjects had a 20-min seated break during 4 hours of simulated nursing tasks when compared to shrinkage observed when subjects stood for the 20-min break. This indicates that fluid loss from the nucleus pulposus was reduced and the rate of shrinkage was slowed when seated compared to standing. A seated break may therefore have the potential to reduce back problems linked with continued compressive loading of the spine. Establishing the optimal positioning of the work break may be beneficial in reducing back pain further. The optimum work-rest schedule, in terms of duration, frequency and time of both rest and recovery periods, must be established for each individual occupation depending on the different occupational demands (Genaidy and Al-Rayes, 1993; Kopardekar and Mital, 1994). This idea was developed in the study of porters by attempting to ascertain whether shorter, but frequent breaks resulted in less spinal shrinkage than one long break and two very small breaks. It was anticipated that the two 5-min breaks in trial 1 might be insufficient to allow for a change from fluid loss to fluid re-absorption in the nucleus pulposus because the period of unloading was too short. The rates of shrinkage and recovery are exponential. Recovery initially occurs rapidly but then slows. Small breaks yield the greatest relative recovery but breaks of an insufficient duration do not allow recovery to occur at all (Konz, 1998). Helander and Quance (1990) considered spinal shrinkage in sedentary workers required to sit and type for a 4-hour period. Forty minutes of rest were dispersed throughout this 4-hour period. These rest breaks constituted 8 breaks of 5 min, 4 breaks of 10 min, 2 breaks of 20 min or a single break of 40 min. During the breaks the subjects were required to stand or walk. There was significantly less shrinkage when rest breaks were 20 min or 40 min than when the 5-min or 10-min breaks were used and it was suggested that the 5-min or 10-min breaks were insufficient to allow a

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change from compression to expansion of the vertebral discs. The present study was slightly different in that it considered a period of sitting as rest and the work was performed standing or moving. No significant difference was found between the shrinkage observed in trial 1 and the shrinkage of trial 2 in the porters' study. The positioning and length of the rest breaks had no effect on spinal shrinkage. Due to difficulties in obtaining subjects able to participate for 8 hours on 2 separate occasions, a 4-hour testing protocol had been used. This allowed for only 25 min of break to replicate the real porters' work-rest schedule. It is suggested that an 8-hour testing protocol could have increased the likelihood of showing differences between the 2 trials because the breaks would have been extended. It is possible that all breaks in this study on porters were insufficient to allow for a change from fluid loss to fluid re-absorption. There was no significant difference between the mean heart rates in trial 1 and trial 2. This indicated that the work-load was identical for both trials. Mean heart rates were 79 (± 6) and 81 (±6) beats.min"1 for trial 1 and trial 2 respectively, which indicated that the work was not of a high intensity. The positioning and length of rest breaks are likely to become more important during work of a higher intensity. Mean heart rates for the porters' study were lower than mean heart rates for the nurses' study, despite all work being self-paced. 5. Conclusions A seated break of 20 min resulted in less spinal shrinkage than a standing break of the same duration during a 4-hour simulation of nursing activities. Ensuring that nurses take a 20-min break and stay seated during this time has the potential to reduce the consequences of spinal loading amongst nursing personnel. Altering the positioning and length of rest breaks during a 4-hour simulation of porters' tasks did not affect spinal shrinkage. The prevalence of back pain in porters would not necessarily be reduced by instigating the alternative work-rest schedule investigated in this study. References Althoff, I., Brinckmann, P., Frobin, W., Sandover, J. and Burton, K. (1992). An improved method of stature measurement for quantitative determination of spinal loading: application to sitting postures and whole body vibration. Spine, 17, 682-693. Benyon, C., Leighton, D., Reilly, T. and Nevill, A. (1998). A multi-disciplinary investigation into musculoskeletal disorders in healthcare professionals. In: Global Ergonomics (eds. P.A. Scott, R.S. Bridger and J. Charteris), pp. 81-91. Amsterdam: Elsevier. Biering-Sorensen, F. (1984). A one-year prospective study of low back trouble in a general population. Danish Medical Bulletin, 31, 362-375. Buckle, P. (1987). Epidemiological aspects of back pain within the nursing profession. International Journal of Nursing Studies, 24, 319-324. Eklund, J. A. E. (1988). Body height changes as a measure of spinal loads and properties of the spine. In: Rehabilitation Ergonomics (eds. A. Mital and W. Karwowski), pp. 199-210. London: Taylor and Francis. Eklund, J. A. E. and Corlett, E. N. (1984). Shrinkage as a measure of the effect of load on the spine. Spine, 9, 189-194. Foreman, T. K. and Linge, K. (1989). The importance of heel compression in the measurement of diurnal stature variation. Applied Ergonomics, 20, 299-300.

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Friedrich, M. (1994). Exact assessment of low-back pain and its management: is there a way to solve this problem? European Journal of Physical Medicine and Rehabilitation, 4, 100-111. Genaidy, A. M. and Al-Rayes, S. (1993). A psychophysical approach to determine the frequency and duration of work-rest schedules for manual handling operation. Ergonomics, 36, 509-518. Harber, P., Billet, E., Gutowski, M., SooHoo, K., Lew, M. and Roamn, P. (1985). Occupational lowback pain in hospital nurses. Journal of Occupation Medicine, 27, 518-524. Helander, M. G. and Quance, L. A. (1990). Effect of work-rest schedules on spinal shrinkage in the sedentary worker. Applied Ergonomics, 21, 279-284. Hildebrandt, V. T. (1995). Back pain in the working population: prevalence rates in Dutch trades and professions. Ergonomics, 38, 1283-1298. Kaplansky, B. D., Wei, F. Y. and Reecer, M. V. (1998). Prevention strategies for occupational low back pain. Occupational Medicine: State of the Art Reviews, 13, 33-45. Konz, S. (1998). Work/rest: Part I - Guidelines for practitioner. International Journal of Industrial Ergonomics, 22, 67-71. Kopardekar, P. and Mital, A. (1994). The effect of different work-rest schedules on fatigue and performance of a simulated directory assistance operator's task. Ergonomics, 37, 1697-1707. Leatt, P., Reilly, T. and Troup, J. D. G. (1985). Spinal loading during circuit weight training and running. British Journal of Sports Medicine, 20, 119-124. Leivseth, G. and Drerup, B. (1997). Spinal shrinkage during work in a sitting posture compared to work in a standing posture. Clinical Biomechanics, 12, 409-418. Lundberg, U. (1995). Methods and applications of stress research. Technology and Health Care, 3, 3-9. Magnusson, M. L., Almquist, M. and Lindstom, I. (1990). Measurement of time dependent height loss during sitting. Clinical Biomechanics, 5, 137-142. Peat, W. F. (1994). Occupational musculoskeletal disorders. Occupational Health, 21, 313-327. Stubbs, D. A., Buckle, P. W., Hudson, M. P., Rivers, P. M. and Worringham, C. J. (1983). Back pain in the nursing profession 1. Epidemiology and pilot methodology. Ergonomics, 26,755-765. Tyrrell, A. R., Reilly, T. and Troup, J. D. G. (1985). Circadian variation in stature and the effects of spinal loading. Spine, 10, 161-164. Van Diee'n, J. H. and Oude Vrielink, H. H. E. (1998). Evaluation of work-rest schedules with repsect to the effects of postural workload in standing work. Ergonomics, 41, 1832-1844. Van Diee'n, J. H. and Toussaint, H. (1993). Spinal shrinkage as a parameter of functional load. Spine, 18,1504-1514. Waddell, G. (1987). A new clinical model for the treatment of low back pain. Spine, 12,632-644.

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EFFECTS OF THE NURSE'S JOB ON THE DIURNAL VARIATION OF THE SEGMENTS OF THE SPINE - AN ANTHROPOMETRIC APPROACH Dirck Caboor Vrije Universiteit Brussel Belgium

Abstract: The compressive loading of the spine is reflected in shrinkage of total body length. In this study the effect of nursing tasks on spinal shrinkage was apportioned to different regions of the vertebral column. The diurnal variation in total shrinkage was 10.3 mm, of which 4.56 mm was attributable to the cervical spine and 3.71 mm to the thoraco-lumbar spine. There was no significant relation between shrinkage and low-back problems.

1. Introduction De Puky (1935) recognised that throughout the day the vertebral column is subjected to various loads as the result of a combination of gravity, muscle activity, position changes at different speeds and other compression forces due to external loads. The viscoelastic data of the spine are characterised by time dependent phenomena e.g. creep, relaxation, hysteresis and strain-stress rate sensivity (Panjabi, 1977), mostly influenced by the water-imbibing capacity of the discus intervertebralis. The cumulation of different activities during daily work can produce a decrease of the vertebral column height. Reilly et al. (1984) found that the difference between the body height in the morning and the evening is 1% of the total body height, and Krag et al. (1990) found a 0.9% difference, with a mean value of 16.39 mm. Tyrrell et al. (1985) reported a mean of 19 mm. The shrinkage mainly is achieved during the first hours of activity, and the study of Tyrrell et al. (1985) indicated that 54% of the loss of height occurred within 1 hour, whereas the results of Leatt et al. (1986) led to the conclusion that 38.4% of the total diurnal shrinkage had occurred by 90 min. Nursing activities involve tasks and postures which induce greater loss of stature than could occur during a non-working day (Foreman and Troup, 1987). Nurses are frequently required to perform dynamic tasks and manouevres with a considerable isometric component. The nursing profession has been the subject of studies worldwide to establish the prevalence and incidence of back problems, to determine the economical and social impact associated with its morbidity and to identify risk factors associated with the occupational duties (Harber et al., 1988; Stobbe et al., 1988; Garg and Owen, 1992). The shrinkage and the possible degeneration of the discus intervertebralis depend on the frequency and intensity of the load during frequent dynamic and persistent static actions (Videman et al., 1990). Nursing

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personnel shows a high prevalence and a high incidence of low-back problems (LBP), the nurses perceive patient handling and transferring as the most demanding tasks and manoeuvres they perform (Garg et al., 1992; Caboor et al., 1996) and the nurses perceive the performance of those tasks and manoeuvres also as an important factor influencing the incidence of LBP (Dehlin et al., 1976; Garg et al., 1992). The total body (and the spine) can be subdivided into different body regions and different height aspects. There is an abundance of literature describing the effects of compressive loading on the lumbar discus intervertebralis during different static postures, lifting techniques and dynamic activities (Nachemson, 1981; Adams et al., 1983; Tyrrell et al., 1985; White and Malone, 1990 and others). However, the effects on the cervical spine have not been as extensively investigated. It seems of interest to verify to what extent and at what level the different height aspects and the different regions of the spine are separately influenced by a very variable daily activity such as nursing tasks in the hospital or patientcare work. The first purpose of this study is to implement an anthropometric approach to study the effects of nursing tasks and manoeuvres on the diurnal variation in body height and length of the spine. A second aim deals with the localisation of significant changes of body height and significant spinal shrinkage. The third goal is to investigate if LBP and gender in nursing personnel are related to spinal shrinkage following a working day. 2. Methods The total body variation and the variation of several landmarks within the body were measured before and after a morning shift in two different Belgian hospitals. Seventeen nurses, 4 male and 13 female subjects, volunteered for this study. Two male nurses and 4 female nurses had a history of LBP, and 2 male and 9 female nurses had a history without LBP. The history of LBP was based on a life-time prevalence. With the head in the Frankfurt position, the stature, the C7 height, sitting height, and the height of the spina iliaca anterior superior (SIAS) and the spina iliaca posterior superior (SIPS) both on the left and right side, were measured twice at 06:00 hours before starting their job, and twice at the end of the normal daily work. Measurements were performed with an anthropometer (GPM) and a sitting height table (Holtain Limited, UK), both accurate to within 1 mm. The measurements in the morning took place at about 1 hour 15 min (SD 30 min) after getting up and in the afternoon after an average of 9 hours (SD 30 min) work. The results were checked for normal distribution. Using an ANOVA for repeated measures, differences between the data of the morning and the afternoon were checked. Differences in relation to LBP and gender were calculated using a 2-way ANOVA and a 1way ANOVA with the Scheffe-F post-hoc test. 3. Results The results are shown in Tables 1 and 2. The measured diurnal variation of the total body was 10.3 (SE 0.64) mm, the mean difference in sitting height was 8.09 (SE 0.66) mm and the mean difference of C7 height measured 5.82 (SE 1.43) mm. Calculations indicated an average shrinkage of 4.56 (SE 1.54) mm of the cervical spine and 3.71 (SE 1.84) mm of the thoraco-lumbar spine.

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Table 1. Results (mean ± standard deviation) of the measurements and calculations in the morning and in the afternoon. HEIGHT (mm)

MORNING

AFTERNOON

Total height C7 height Sitting height Cervical region Thoraco-lumbar region SIAS left SIAS right SIPS left SIPS right

1694.36 1438.00 904.72 255.97 645.97 936.36 932.80 965.84 964.88

1684.06 1432.18 896.63 251.41 642.26 935.84 931.62 965.28 964.52

±74.83 ± 58.62 ±36.80 ± 12.95 ± 28.95 ±60.31 ±59.10 ± 57.94 ±57.31

±73.97 ±57.91 ±35.50 ±11.65 ±28.89 ± 59.76 ±58.81 ± 57.86 ±56.92

SIAS = Spina iliaca anterior superior SIPS = Spina iliaca posterior superior

Stature, sitting height, C7 height and the cervical spine showed a significant shrinkage during the daily work (Table 2 and Figure 1). The thoraco-lumbar spine as well as the SIPS and SIAS measurements did not indicate significant differences . Table 2. Absolute (mean ± standard error) and relative shrinkage of the body-segments. Absolute Shrinkage (mm) Total height C7 height Sitting height Cervical region Thoraco-lumbar region SIAS left SIAS right SIPS left SIPS right a = significant (p< 0.05) SIAS = Spina iliaca anterior superior SIPS = Spina iliaca posterior superior

10.30 5.82 8.09 4.56 3.71 0.52 1.18 0.56 0.36

±0.64 ±1.43 ±0.66 ±1.54 ± 1.84 ±0.8 ±0.93 ± 0.85 ± 0.95

Relative Shrinkage (%)

0.6 0.4 0.9 1.8 0.5 0.05 0.1 0.06 0.04

a a a a

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Measurements Height C7- Height Sitting Height SIAS Height left SIAS Height right SIPS Height left SIPS Height right Cervical spine length lumbar spine length

Wake up (4h45'AM SD=30')

Figure 1. The schedule of the measurements and the shrinkage of the body regions

For the relation between the shrinkage of the total body and the shrinkage of the several body regions on one hand, and LBP and gender on the other hand, no significant differences (p>0.05) were found (Figure 2). -LBP(N=16)

+ LBP (N=9) Thoraco-lumbar spine length Cervical Spine length SIPS height right SIPS height left SIAS height right SIAS height left Sitting Height C7-height

-

Height -

Changes in posture (mm) Figure 2. Relation between LBP and the shrinkage for the several regions.

4. Discussion In our experiment the relative shrinkage, measured as a function of the total height, was 0.6%, as a function of the sitting height 0.9%, as a function of C7-height 0.4%, and as a function of the cervical spine 1.8%. Taking into consideration the shrinkage during the first hour after getting up, our results confirm those of Reilly et al. (1984), Tyrrell et al. (1985), Leatt et al. (1987) and Kragetal. (1990).

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The changes in the height of SIAS and SIPS were very small, floating on the zero-line. According to the findings of Althoff et al. (1992) we can assume that there is a negligible contribution of the lower limb. The data of the SIPS and the SIAS confirm the reliability of the postures of the subjects for the anthropometric measurements. In addition, we noted that the changes of stature before and after the daily work were mostly influenced by the shrinkage of the cervical spine. Tondury (1974) and Penning (1978) suggested that morphology and function of the cervical discus intervertebralis change during life-time, characterised by a pseudo-degeneration of the fibres of the annulus fibrosus beginning at the age of nine. We wonder if, complementary to the hydration and dehydration process of the discs, this morphological aspect could be a reason why we found the highest shrinkage at the cervical level. The cervical intervertebral disc is not similar to the lumbar intervertebral disc with regards to morphology, biomechanics and the nature of physiological processes (Mercer and Ml, 1996). Part of the reason that these assumptions have been made, lies in the scarcity of studies which have specifically examined the structure and the function of the cervical intervertebral disc. There is evidence that the cervical intervertebral disc has a distinct morphology which reflects the biomechanics of this region. Lifting and transferring patients are essential parts of the nursing profession, and the associated loading that goes with them is perceived as very demanding and severe (Garg et al., 1992; Caboor et al., 1996). An important part of work during these tasks and manoeuvres is performed by the upper limbs , and that assumes a high level of axial compression within the cervical region caused by a considerable activity of the muscles of the shoulder and the neck. It is assumed that this functional aspect explains in part why we found the highest shrinkage at the cervical level. The nature of these data suggests that this conclusion can be extrapolated to several manual handling jobs with heavy loading. The influence of the cervical part of the vertebral column on the spinal shrinkage might also explain why we did not found a relation with LBP. The results of this study support the observations of Garbutt et al. (1990) who found no differences in shrinkage between subjects with and without low-back pain, following both running and repetitive lifting. On the other hand the clinical study of Kindle et al. (1987) in patients with ankylosing spondylitis showed a significantly reduced diurnal variation in stature for the symptomatic group, 0.34% of total body height vs. 0.68% in the control group. The ossification of the outer collagen fibres of the annulus fibrosus reduces the mobility of the intervertebral disc and reduces also the response of the vertebral column to the compressive loads associated with gravity, habitual activity and professional activity. The diurnal body oscillation observed in the asymptomatic individuals was lower than the values previously reported (Reilly et al., 1984; Tyrrell et al., 1985; Krag et al., 1990). Differences in time schedule would account for this discrepancy. Such findings highlight the complex nature of the relationship between spinal shrinkage, disc function, disc degenaration and low-back problems. Shrinkage is a time dependent phenomenon. Taking into consideration the shrinkage over the first hour after getting up and the cervical shrinkage during the job, and looking at the specific properties of the lumbar and cervical discs, this phenomenon can be influenced mostly by the lumbar spine during the first hours of the day and during the rest of the day by the cervical region. 5. Conclusions The results of this study suggest that the change in stature during the daily nursing job primarily is located in the vertebral column, and in particular due to the shrinkage of the cervical spine. This is assumed to be a primary reason why no relation between spinal shrinkage and LBP could be found, either in the male or in the female nurses. The nature of these data suggests that this conclusion can be extrapolated to several manual handling jobs

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with heavy loading. The shrinkage of the cervical spine under these loading conditions needs to be reviewed in relation to the mechanism and occurrence of neck problems. Further research can be done in terms of electromyographic studies of the shoulder and neck muscles during the performance of manual handling tasks, with respect to time-control of the shrinkage in the lumbar and cervical region of the spine. References Adams, M. A. and Hutton, W. C. (1983). The effect of posture on the fluid content of the lumbar intervertebral discs. Spine, 7, 665-671. Althoff, I., Brinckmann, P., Frobin, W., Sandover, J. and Burton, K. (1992). An improved method of stature measurement for quantitative determination of spinal loading - Application to sitting postures and whole body vibration. Spine, 17, 682-693. Caboor, D., Zinzen, E., Van Roy, P. and Clarys, J. P. (1996). Job evaluation in nursing personnel using a modified Delphi-survey. Communication to The Second International Conference on Health in the Workplace, Liverpool, UK, 2-4 April. Dehlin, O., Hedenrud, B. and Moral, J. (1976). Back symptoms in nursing aides in a geriatric hospital. An interview study with special reference to the incidence of low back symptoms. Scandinavian Journal of Rehabilitation Medicine, 8,47-53. De Puky, P. (1935). The physiological oscillation of the length of the body. Acta Orthop, Scand., 6, 338-347. Foreman, T. K. and Troup, J. D. G. (1987). Diurnal variations in spinal loading and the effects on stature: a preliminary study of nursing activities. Clinical Biomechanics, 2,48-54. Garbutt, G., Boocock, M. G., Reilly, T. and Troup, J. D. G. (1990). Running speed and spinal shrinkage in runners with and without low back pain. Medicine and Science in Sports and Exercise, 22, 769-772. Garg, A. and Owen, B. (1992). Reducing back stress to nursing personnel: an ergonomic intervention in a nursing home. Ergonomics, 35, 1353-1375. Garg, A., Owen, B. D. and Carlson, B. (1992). An ergonomic evaluation of nursing assistants'job in a nursing home. Ergonomics, 35, 979-995. Harber, P., Billet, E., Shimozaki, S. and Vojtecky, M. (1988). Occupational back pain of nurses: special problems and prevention. Applied Ergonomics, 19,219-224. Hindle, R. J., Murray-Leslie, C. and Atha, J. (1987). Diurnal stature variation in ankylosis spondilitis. Clinical Biomechanics, 2, 152-157. Krag, M. H., Cohen, M. D., Haugh, L. D. and Pope, M. H. (1990). Body height changes during upright and recumbent postures. Spine, 15, 202-207. Leatt, P., Reilly, T. and Troup, J. D. C. (1986). Spinal loading during circuit weight-training and running. British Journal of Sports Medicine, 20, 116-124. Mercer, S. R. and Jull, G. A. (1996). Morphology of the cervical intervertebral disc: implications for McKenzie's model of the disc derangement syndrome. Manual Therapy, 2, 76-81. Nachemson, A. (1981). Disc pressure measurements. Spine, 6, 314-318. Panjabi, M. M. (1977). Experimental determination of spinal motion behavior. Orthopedic Clinics of North America, 8, 169-180. Penning, L. (1978). Normal movements of the cervical spine. AmerJ.Roentgenol., 130, 317-326. Reilly, T., Tyrrell, A. R. and Troup, J. D. G. (1984). Circadian variation in human stature. Chronobiology International, 1, 121-126. Stobbe, T. J., Plummer, R. W., Jensen, R. C. and Attfield, M. D. (1988). Incidence of low back injuries among nursing personnel as a function of patient lifting frequency. Journal of Safety Research, 19, 21-28. Tondury, G. (1974). The Cervical Spine. Bern: Huber. Tyrrell, A. R., Reilly, T. and Troup, J. D. G. (1985). Circadian variation in stature and the effects of spinal loading. Spine, 10, 161-164. Videman, T., Nurminnen, M. and Troup, J. D. G. (1990). Lumbar spinal pathology in cadaveric material in relation to history of back pain, occupation and physical loadings. Spine, 15, 728-737. White, T. L. and Malone, T. R. (1990). Effects of running on intervertebral disc height. JOSPT, 139-146.

Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

BODY COMPOSITION: PART I Physical and structural distribution of human skin J. P. Clarys and M. Marfell-Jones Department of Experimental Anatomy Vrije Universiteit Brussel Belgium Abstract: Few research groups take into account the complex and variable distribution of human skin. Twenty five cadavers were studied to update the assessment of skin dimensions: this work provided background fundamental research prior to applying findings to the body composition assessment of nursing personnel. Comparisons were made between different segments and between males and females. Systematic differences, i.e. skin thickness, weight, volume and density, between segments and between the sexes were found.

1. Introduction In medicine, variations in physical and structural dimensions of the human skin are associated with endocrinological diseases and congenital syndromes. In physiotherapy the knowledge of skin characteristics is important for electrotherapy and decubitus treatment, while in anthropology it is an essential part of anthropometric and body composition studies. Bischoff (1863) presented a study of skin weights of two adults and later von Liebig (1874) added similar information, again based on a limited number of cadaver subjects. For over a century, many studies have been conducted on skin tension and elasticity, both on the living and on cadavers, and in different age groups (Schmidt, 1891; Reizenstein, 1894; Lindholm, 1931; Ejiri, 1938; Sodeman and Buch, 1938; Hill and Montgomery, 1940; Dick, 1947; Strobel, 1948; Kirk and Kvorning, 1949; Ma and Cowdry, 1950; Lee, 1957, 1967; Ragnell, 1957). Despite these studies, the overall physical dimensions of the skin have received scant mention in textbooks and periodical literature (Leider and Buncke, 1954; Lee, 1957; Baker et al., 1958; Booth et al., 1966; Doyle, 1969; Billznak et al., 1975). Data on absolute and comparative thickness, regional topography, volume, density, total body and segmental weights of the skin do not seem to have loomed important enough to have excited much interest or comment among dermatologists, physiotherapists, endocrinologists or anatomists. In a joint venture undertaken at the Vrije Universiteit Brussel, with Simon Fraser University Canada, 25 cadavers were completely dissected into their major tissues for the purpose of making up to date human body composition analyses

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(Clarys et al., 1984; Clarys and Marfell-Jones, 1986a, 1986b). Another joint venture was undertaken with the University of Gotenborg, resulting in another 9 whole-body cadaver dissections with tissue data acquisition. For a state of the art of adult dissection processing, we refer to the review of Clarys et al. (1999). Data of 17 cadavers have been used in subsequent skin analyses and calculations. 2. Material and methods Prior to the dissection, the cadavers were marked and measured anthropometrically including skinfolds. The marks of the skinfold were used after dissection to measure skin thickness. The cadavers were dissected into six segments: head, trunk, upper and lower limbs according to a slightly modified segmentation technique as described by Clauser et al. (1969) and Dempster (1955). As pieces of skin were dissected, they were placed immediately into airtight plastic containers, one for each of the six body segments. Eventual excess of adipose tissue adhering to the skin was scraped off prior to the physical measurements. It was observed that skin shape could be distorted by stretching, but it appeared that dimensions were little affected. This was investigated by marking 10-cm squares on the segmental skin pieces before dissection and remeasuring these after dissection. There was no indication of substantial changes in dimensions. The areas of the skin tracings were determined by planimetry in order to validate human body surface area formulae. These results are presented in Martin et al. (1984). Subsequently, skin thickness was measured (on double layer) at the marked (external) skinfold locations using a Harpenden caliper, while total and segmental skin was weighed in air and water for volume and density determination. 3. Results and discussion The mean skin thickness values per region (corresponding to the classical skinfold locations) and for both left and right sites are listed in Tables 1 and 2, respectively. Values are included for males and females. The mean weight of the skin per segment, and the contribution as a % of total segmental weight, as a % of skin weight of the whole body and as a % of total body weight are shown in Table 3 for each sex separately. Corresponding skin volumes are indicated in Table 4 while mean values of segmental densities are shown in Table 5. From Tables 1 and 2 we can see that, on the average, the skin thickness is greater in males than in females. The findings of Billznak et al. (1975), and Leider and Buncke (1954) are thereby confirmed. If we consider skin thickness per region and at the locations where the classical cutis-subcutis "skin fold" measurements are taken, the same tendencies are found between male-female and left-right, except for the pectoral chest thickness. Probably because of an important increase of connective tissue, we see an average of +2.65 mm in females and +2.45 mm in males at the chest region. The greatest skin thickness for both sexes is to be found in the subscapular region while the smallest is situated in the upper limb.

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In contrast to the variability of "classical skin folds", the skin thickness shows a relative constant distribution left and right both in males and females. In terms of skin contribution to the cutis-subcutis skinfold, we found that in men +19.5% of a skinfold is skin. For women this is +11% (average for all measured sites). Reflecting the skin thickness findings, the total and segmental skin weights are higher in males than females (Table 3 and Fig. 1), although the data are, on average, lower than those presented by Leider and Buncke (1954). Skin weight contributed relatively little to total segmental weight (TSW) and total body weight (BW). Table 1.

Mean skin thickness per region, left and right in males (mm).

Male

Left

Region Subscapular Triceps Biceps Forearm Pectoral chest Axillary chest Mid-axillary line Supra-spinae Ventral thigh Medial thigh Dorsal thigh Supra-patellae Medial calf Total mean

Table 2.

Mean 4.06 2.42 1.55 1,50 2.47 2.70 2.87 2.04 2.22 1.81 2.41 2.25 1.71 2.30

SD 0.78 0.63 0.22 0.40 0.44 0.58 0.59 0.47 0.58 0.51 0.56 0.65 0.38 0.67

Max 5.00 3.10 1.90 2.20 3.20 4.50 3.90 2.70 3.10 2.60 2.80 3.20 2.20 4.06

Right Min 2.90 1.60 1.20 1.10 1.90 2.00 2.10 1.20 1.50 1.20 1.30 1.40 1.20 1.50

Mean 4.11 2.61 1.60 1.52 2.45 2.82 3.11 2.54 2.42 1.75 2.44 2.35 1.78 2.42

SD 0.68 0.79 0.40 0.41 0.51 0.46 0.53 0.63 0.60 0.42 0.55 0.71 0.45 0.70

Max 5.10 3.90 2.00 2.10 3.30 3.30 3.70 3.50 3.30 2.50 3.10 3.40 2.50 4.11

Min 3.10 1.30 1.00 0.90 1.60 2.10 2.50 1.40 1.40 1.40 1.40 1.50 1.00 1.51

Mean skin thickness per region, left and right in females (mm).

Female Region Subscapular Triceps Biceps Forearm Pectoral chest Axillary chest Mid-axillary line Supra-spinae Ventral thigh Medial thigh Dorsal thigh Supra-patellae Medial calf Total mean

Right

Left Mean 3.47 2.02 0.98 1.20 2.68 1.95 2.72 1.87 1.86 1.63 2.18 1.82 1.57 1.99

SD 0.64 0.45 0.21 0.21 0.58 0.76 0.65 0.37 0.28 0.29 0.36 0.41 0.23 0.66

Max 4.20 2.60 1.30 1.50 2.30 3.60 3.70 2.20 2.20 2.10 2.70 2.50 1.80 3.47

Min 0.22 1.00 0.80 0.90 1.80 1.30 .70 .10 .50 .20 .60 .40 .20 0.98

Mean 3.41 2.25 1.00 1.20 2.64 1.80 2.72 1.95 2.02 1.56 2.12 1.97 1.57 0.98

SD 0.62 0.63 0.22 0.16 0.69 0.57 0.49 0.15 0.17 0.26 0.53 0.38 0.19 0.64

Max 4.40 2.90 1.30 1.50 3.80 2.80 3.30 2.20 2.20 1.90 2.90 2.50 1.90 3.41

Min 2.50 0.90 0.70 1.00 1.60 1.20 2.00 1.80 1.70 1.10 1.20 1.30 1.40 1.00

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Table 3.

Male Head L. arm R. arm L.leg R.leg Trunk Total Female Head L. arm R. arm L.leg R.leg Trunk Total

Average skin weight (SW) per segment and as a % of total body skin weight (TBW), total segmental weight (TSW) and total body weight (BW), in male and female cadavers.

SW(g)

% of TSW

%ofBW

7.5 7.8

8.5 8.3 8.3

0.6 0.4 0.4

738 715 1310 3757

19.6 19.0 34.9

5.7 5.8 4.3

1.1 1.0 1.9

100

5.5

5.5

299 213 214

9.4 6.7 6.8

7.3 7.3 6.9

0.5 0.3 0.3

642 627 1148 3167

20.3 19.8 36.2

5.4 5.4 4.1

1.0 1.0 1.8

100

5.1

5.1

405 281 292

% of TBW 10.8

An identical situation is found for skin volumes (Table 4 and Fig. 1). However, the contribution of skin volume to total segmental volume (SeV) and total body volume (T.B.V.) was not significantly different between the sexes, confirming the constancy of the skin tissue. Higher skin density averages were found for men in all segments (see Table 5). It can be concluded that there are systematic differences in skin dimensions between males and females. These differences, however, were small in comparison to the differences of the other body components (Fig. 2). In this situation, only bone approaches the body composition constancy of skin.

Figure 1. Weight, volume and density per segment of human skin.

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% IBM

DMale H Female

40 30 20 10 -

Skin

Adipose

Muscle

Bone

Residual

Figure 2. Masses of skin, adipose tissue, muscle, bone and residual as percentages to total body mass (% TBM).

Finally, if masses of skin, muscle, bone and viscera are presented as percentage of adipose-tissue-free mass (ATFM), the previous absolute value interpretation is reversed for skin, bone and residual masses (Fig. 3). This finding highlights the significance of the adipose tissue mass within the body, both male and female.

50 -

% ATFM DMale 0 Female

40 30 20 10 -

0

Skin

Muscle

Bone

Residual

Figure 3. Masses of skin, muscle, bone and residual, as percentages of adipose - tissue - free mass (% ATFM).

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Table 4. Mean skin volume (SV) per segment and as % of total skin volume (TSV), total segmental volume (SeV) and total body volume (TBV) in male and female cadavers. Male Head L. arm R. arm L.leg R.leg Trunk Total Female Head L. arm R. arm L.leg R.leg Trunk Total

SV (ml) 402 274 283 720 702 1268 3650

% of TSV 11.0 7.5 7.8 19.7 19.2 34.7 100

% of SeV 8.7 7.7 9.1 5.6 5.7 4.0 5.4

%ofBV 0.6 0.4 0.4 1.1 1.0 1.9 5.4

301 211 212 643 631 1133 3133

9.6 6.7 6.8 20.3 20.1 36.2 100

7.7 7.1 6.7 5.2 5.2 3.8 4.9

0.5 0.3 0.3 1.0 1.0 1.8 3.9

Table 5. Mean skin densities (Sd) per segment (g.mr1). Sex Segment Head Left arm Right arm Left leg Right leg Trunk

Female

Male Sd .046 .056 .061 .052 .052 .064

SD 0.011 0.011 0.010 0.010 0.011 0.010

Sd 1.026 .040 .047 .036 .039 .047

SD 0.010 0.014 0.011 0.016 0.013 0.013

Male + Female SD Sd .035 0.014 .047 0.015 .054 0.012 .043 0.016 0.014 .045 .055 0.014

References Baker, P. T., Hunt, E. E. and Sen, T. (1958). The growth and interrelations of skinfolds and brachial tissues in man. American Journal of Physical Anthropology, 16, 39-58. Billznak, J. M. D., Tom, W. and Staple, M. D. (1975). Roentgenographic measurements of skin thickness in normal individuals. Radiology, 118, 55-60. Bischoff, E. (1863). Einige Gewichts und Trockenbestimmungen de Organe des menschlichen Korpers. Zeitsch.fir rationelle Medizin , 3, 75. Booth, R. A. D., Goodard, B. A. and Paton, A. (1966). Measurements of fat thickness in man; a comparison of ultra-sound, Harpenden calipers and electrical conductivity. British Journal of Nutrition, 20, 719-725. Clarys, J. P., Martin, A. D. and Drinkwater, D. T. (1984). Gross tissues weights in the human body by cadaver dissection. Human Biology, 56, 459-473. Clarys, J. P. and Marfell-Jones, M. J. (1986a). Anthropometric prediction of component tissue masses in the minor limb segments of the human body. Human Biology, 58, 761-769. Clarys, J. P. and Marfell-Jones, M. J. (1986b). Anatomical segmentation in humans and the prediction of segmental masses from intra-segmental anthropometry. Human Biology, 58, 771782. Clarys, J. P., Martin, A. D., Marfell-Jones, M. J., Janssens V., Caboor D. and Drinkwater, D. T. (1999). Human body composition: A review of adult dissection data. American Journal of Human Biology, 11, 167-174. Clauser, C. E., McConville, J. T. and Young, J. W. (1969). Weight, volume, and center of mass of segments of the human body. Wright-Patterson Air Force Base, Ohio.

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Dempster, W. T. (1955). Space requirements of the seated operator, Wright-Patterson Air Force Base, Ohio. Wright Air Development Center TR 55-159, AD 87892. Dick, J. C. (1947). Observations on the elastic tissue of the skin with a note on the reticular layer at the function of the dermis and the epidermis. Journal of Anatomy, 81, 201-211. Doyle, F. M. (1969). Radiological measurements of skin thickness and bone mineral. Scientific Basis of Medicine. Annual Reviews, 139-145. Ejirl, I. (1938). Histology of the human skin : II. On differences in the elastic fibers of the skin according to sex and age. Abs. in Arch. Dermat. and Syph., 37, 664. Hill, R. and Montgomery, H. (1940). Regional changes and changes caused by age in the normal skin. J. Invest. Dermat. 3, 231-245. Kirk, E. and Kvoming, S. A. (1949). Quantitative measurements of the elastic properties of the skin and subcutaneous tissue in young age and old individuals. J. Geront., 4, 273-284. Lee, M. M. C. (1957). Physical and structural age changes in human skin. Anat. Rec. 129, 473494. Lee, M. M. C. and Ng, C. K. (1965). Postmortem studies of skin fold caliper measurement and actual thickness of skin and subcutaneous tissue. Human Biology, 37, 91-103. Liebig von, G. (1874). Gewichtsbestimmungen der Organe des menschliches Korpers. Archiv. F. Anat. Physiol. u. Wissensch. Medizin, 96-117. Leider, M. and Buncke, C. M. (1954). Physical dimensions of the skin. Arch. ff. Dermat. and Syph. 69, 563-569. Lindholm, E. (1931). Uber die Schwankungen in de verteilung de elastichen Fasern in de menschlichen Haul, als Beitrag zur Konstitutionspathologie. Frankfurt Zeitschrift 42; 394-414 cit. in Lee, M.M.C. (1957) Physical and structural age changes in human skin. Anat. Rec. 129; 473-494. Ma, C. K. and Cowdry, E. V. (1950). Ageing of the elastic tissue in human skin. J. Geront., 5, 203-210. Martin, A. D., Drinkwater, D. T. and Clarys, J. P. (1984). Human body surface area: validation of formulae based on a cadaver study. Human Biology, 20,475-488. Ragnell, A. (1957). The tensibility of the skin: An experimental investigation. Plastic and Reconstructive Surg. 14; 317-323 - cit. in Lee, M.M.C. Physical and structural age changes in human skin. Anat. Rec. 129, 373-394. Reizenstein, A. (1894). Uber die Altersveranderungen der elastichen Fasern in de Haul. Monath. F. prakt. Dermat. 18, 1-7. Schmidt, M. B. (1891) Uber die Altersveranderungen der elastichen Fasern in de Haut. Virehows Arch.f. Path. Anat. 125, 239-251. Sodeman, W. A. and Buch, G. E. (1938). A direct method for the estimation of skin distensibility with its application to the study of vascular states. Journal of Clinical Investigation, 17, 785793. Strobel, H. (1948) Die Gewebsveranderungen de Haut im Verlaufe des Lebens. Arch. ff. Dermat. and Syph. 186,636-668.

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Musculoskeletal Disorders in Health-Related Occupations T. Reilly (Ed.) IOS Press, 2002

BODY COMPOSITION: PART II "Whole-Body Adiposity5' prediction: Males versus Females J. P. Clarys, A. Martin and D. Drinkwater Department of Experimental Anatomy Vrije Universiteit Brussel Belgium

Abstract: The skinfold is a central factor in adipose tissue patterning and for monitoring adiposity in males and females. The interest in skinfolds, given the easy accessibility of the subcutaneous layer and its non-invasive nature, has led to a proliferation of "skinfold formulae" again both for men and women separately. To obtain data to investigate human body composition, particularly the determination of whole-body adiposity, an extensive cadaver dissection study was undertaken on 34 subjects (17 females, 17 males). In addition, 40 elderly "living" subjects of the same age range were compared with the cadaver population and no significant macro-morphological differences were found, particularly in females. The available data have clearly demonstrated that skinfold compressibility is by no means constant. Adipose tissue patterning by assessment of skinfold thickness using calipers and incision confirms significant sex differences but emphasises the neglected importance of skin thickness. It appears that the best adipose tissue predictors are different from those used in general. Also the problem of estimating body fat content by skinfold is compounded by the fact that two identical thicknesses of adipose tissue may contain significantly different concentrations of fat. Skinfolds are significantly related to external (subcutaneous) adipose tissue. However, the relation to internal adipose tissue is less evident for men than for women. The sample specificity of skinfold formulae to predict whole-body adiposity is in part a result of the wide variations in compressibility, internal to subcutaneous adiposity ratios and adipose tissue composition. The data of this study clearly suggest that it is unreasonable to introduce further error by transforming anthropometric values into % of body adipose tissue in males. On the other hand, this study has demonstrated that skinfold predictions of whole-body adipose tissue in women allow for a more confident application.

1. Introduction Body composition and the assessment or prediction of whole-body adiposity - mostly referred to as "total body fat" - in particular, is a common, popular and at the same time an important ingredient of physical anthropology, medicine, sport science (Fig. 1) and more specifically of kinanthropometry, biomechanics and auxology. The most

151

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Figure 1. Application areas for body composition.

common methods for estimating total body fat are densitometry, whole-body potassium counting, body water measurement, anthropometry (e.g. skinfolds) and more recently, computerised tomography and magnetic resonance imaging (MRI). Anthropometry, however, relies for its validation on one or more of the other techniques and is therefore a doubly-indirect method. Skinfold measurements and quantities derived from them are used in physiology, anatomy, endocrinology, nutrition, health and fitness, growth, sport and exercise sciences. They have specific applications in occupational biomechanics, human hydrodynamics, drug quantification, diabetes, coronary heart disease, hypertension, anorexia nervosa and in many epidemiological and human body biological studies. The skinfold is a central factor in adipose tissue patterning (Edwards, 1951; Garn, 1955, 1971; Mueller and Stallones, 1981; Mueller, 1985), in "fat" distribution studies, in somatotyping (Heath and Carter, 1967 and others) and in the commercialised O-scale system (Ross and Ward, 1984) for monitoring adiposity and proportional weight. The skinfold is an essential measure to identify male-female gender and ageing differences. The interest in skinfolds, given the easy accessibility of the subcutaneous layer and its non-invasive nature, has led to a proliferation of "skinfold" applications and formulae. In the literature, over 1000 articles can be found dealing directly or indirectly with skinfold measurements, both in applied and fundamental research. Altogether more than 100 equations to predict "body fat" from skinfolds have been produced (Lohman, 1981; Martin et al., 1985; Clarys et al., 1987; Clarys et al., 1999). In spite of this proliferation of techniques for the in vivo determination of body composition, the fact remains that none of the approaches for estimating body fat has been validated against cadaver dissection. Even beyond the issue of validation, data on directly weighed body compartments are sparse. These limited data have been reported over a period of 150 years, some in obscure periodicals and in languages other than English. Results of 25 dissections of older Belgians, along with a brief summary of previously published data have been previously reported (Clarys et al., 1984). Subsequently, two further projects included nine more whole-body dissections (Clarys and Marfell-Jones, 1986; Janssens et al., 1994). In addition,

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further 19th century data have been located, thus giving a total of 51 adults for whom body weight and the major tissue weights are known (Clarys et al., 1999). These studies, known as the Brussels Cadaver Study (CAS), were a joint venture between Simon Fraser University, Burnaby (Canada), Goteborg University (Sweden) and the Free University of Brussels, Belgium. Although body composition analysis has become increasingly popular, dissection data are sometimes difficult to access. Published data that include the weights of skin, adipose tissue, muscle and bone, along with body weight, have been reviewed (Clarys et al, 1999). The 31 men and 20 women included 34 cadavers from three separate dissection studies in Brussels, 12 from 19th century reports, and 5 from the United States. Men differed from women in that they had less adipose tissue and more muscle. The body mass index (BMI) did not differ between the sexes, because lower weights of muscle and bone compensated for the greater adiposity in women (Fig. 2).

,r

Women

Women

Figure 2. Major human body tissue weights in kg and expressed as a percentage of total body weight in men (N=17) and women (N=17).

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Men

Skin

Muscle

Women

Bone

Skin

Muscle

Bone

Figure 3. Normalised tissue weights expressed as a percentage of adipose tissue free weight (ATFW).

The composition of the fat-free weight (FFW) and adipose tissue free weight (ATFW) (Fig. 3), though less variable than body weight, showed enough variability that the assumption of constancy of the fat-free body, required for densitometry and other indirect methods of fat estimation, could not be supported. It is the purpose of this present study to analyse the pooled data of CAS to allow a review of hazards and steps in the transformation from caliper readings to whole-body adipose tissue mass.

2. The Brussels Cadaver Analysis studies 1979-1999 - Methods The data are from three separate whole-body dissection projects, details of which have been published elsewhere. In the original Brussels Cadaver Analysis study, 13 female and 12 male cadavers, age range 55-94 years, 12 embalmed and 13 unembalmed, were selected from about 75 cadavers on the basis of least emaciation and most normal appearance (Clarys et al., 1984). After comprehensive anthropometry, each cadaver was dissected into skin, adipose tissue, muscle, bones, organs and viscera. Tissues were separated by six body segments: arms, legs, head and trunk. The weight of any fluid separating from the tissue was added back to the tissue weight. All tissues were stored in airtight humidified containers until weighing. The evaporative weight loss occurring through the dissection process, taken to be the difference between predissection body weight and the sum of all tissues after the dissection, was added back to each component in proportion to its weight. Volumes and densities of all tissues were determined by weighing the tissues underwater. One complete dissection lasted about 10-15 hours and required a team of about 12 people. The second study was undertaken to measure the composition of body limb segments and to derive prediction equations for segment weights of skin, adipose tissue, muscle and bone (Clarys and Marfell-Jones, 1986). For these purposes incomplete dissections were sufficient. However, for three subjects full dissections were completed, with a similar protocol to that of the initial study. The three subjects were two 16 year-old males and an 80 year-old female. The third study investigated the relationship between body composition estimated by computed tomography and values obtained by dissection and weighing of tissues

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of three male and three female cadavers, age range 72-88 years (Janssens et al., 1994). The cadavers were dissected into the same components as previously. For all of the subjects, body height was estimated from the supine length measurement according to a previously-derived equation (Martin et a/., 1984). Pooling all Brussels data yielded a data set of 34 cadavers. These consisted of 17 males and 17 females, with an age range of 16 to 94 years. An immediate question that can be raised concerns the validity of applying the relationship found in such a sample to the living. If there are changes in circumferences and segment composition, these changes should be detectable by anthropometry. The relationships should not change to any marked extent, only the absolute values. It is a major assumption of this study, therefore, that the relationship between anthropometric variables and segment composition in cadavers is similar to their relationship in the living. We have therefore measured in vivo 18 elderly male and 22 elderly female subjects ranging in age from 55 to 92 years (age match selection). Using a selection of anthropometric measurements employed also in the cadaver sample and determining the somatotype of both the cadaver group and the "living" subjects according to the Heath and Carter (1967) technique as adapted by Duquet (1980), an overall comparison of the physique of post-mortem and living Belgian subjects of a similar age group was attempted (Fig. 4). Apart from a few single measurements it appears that both embalmed and unembalmed cadavers can be used to approximate these relations in the living; in other words, the use of embalmed cadavers, as opposed to fresh cadavers, will not affect the predictive ability and validity of the models and conclusions generated from the cadaver data.

CIRCUMFERENCES

FEMUR HAUEOLUS ACBOHIAL THORAX (Frontal) THORAX'(Sa?iUl) IL1ACAL SUPINE SUSPENDED

Figure 4. Normalised anthropometric comparison between age matched in vivo (zero axis) and post mortem subjects (^Vembalmed women; D unembalmed women; & embalmed men; O unembalmed men).

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3. Results and discussion Based on the pooled data from CAS, we have been able to review step by step the combined facts, assumption and hazards to be taken into account in the transformation of skinfolds to whole-body adipose tissue mass. This approach will allow also a discrimination between men and women. The measurement of subcutaneous "fat" with skinfold calipers has become a routine laboratory and field method of assessing body composition and nutritional status. Hagar (1981) stated that "... two important assumptions must be made in the calculation of body fat from skinfold measurements: (1) subcutaneous fat constitutes a constant proportion of total body fat over all ranges of body weight, and (2) the sites of measurement are representative of all subcutaneous fat". This is at least doubtful. What is really being measured is the thickness of a double fold of skin and compressed subcutaneous adipose tissue. To infer from this the mass of fat in the body requires another series of assumptions whose validity has never been seriously challenged (Clarys et al., 1987). The evidence is available to test the validity of the transformation. In order to review the (old and new) assumptions associated with the caliper adiposity transformations, we refer to our previous "step by step" model (Martin et al, 1985; Clarys et al., 1987) as shown in Fig. 5.

Figure 5. The CAS step-by-step model of the transformation from caliper measurement to whole-body adipose tissue. (*AT = Adipose Tissue).

J.P. Clarys et al. /Body Composition: Part II

The transformation from caliper reading to total body fat can be divided into a number of steps. The thickness of a compressed double layer of skin and subcutaneous adipose tissue should be representative of the uncompressed double layer of adipose tissue. This should indicate total subcutaneous adiposity. This adiposity must be converted into a whole-body value and thus include fat and the internal fat. Assumption I-constant compressibility The decline in caliper reading after the initial application of the caliper to the skinfold is familiar to all users of skinfold calipers. This dynamic aspect of caliper use has been documented but given little investigative attention but it is general knowledge that the compressibility of the calipers shows an exponential decrease in reading over the first minute. Most workers adopt some strategy to standardise the reading in spite of its dynamic characteristics. Some wait "for all needle movements to cease before taking the reading" while others record after "an initial rapid phase of the movement" or read the dial after 2 or 4 s of applied pressure. In addition to the dynamic compressibility, there is also a static component to compressibility (Fig. 6). Even after standardising the timing of the caliper reading, similar thicknesses of adipose tissue may yield different caliper values due to different degrees of tissue compressibility. Since the Brussels CAS data include both skinfold thickness and the direct measurement, after incision, of the thickness of the subcutaneous adipose tissue layer, skinfold compressibility could be calculated directly at each site. Compressibility is defined as: (incised depth - 1/2 caliper reading) 100 x

Incised depth

Figure 6. Skinfold compressibility... double skin... double subcutaneous adipose layer (Courtesy of Int. J. Obesity).

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Skinfold site Figure 7. Compressibility means for a series of commonly used skinfolds.

Means for all subjects are shown graphically in Fig. 7. The available data clearly demonstrate that skinfold compressibility is by no means constant. This has important implications and the Brussels study included several examples, including two male cadavers with almost identical dissected adiposities of 27.1 and 27.8%, whose skinfold caliper readings at the seven commonly used sites show wide differences in compressibility, in turn resulting in very different predicted (anthropometrical) adiposities. Assumption II - skin thickness in negligible or a constant fraction All skinfold measurements contain a double layer of skin of unknown thickness. If this is very small in comparison to the skinfold measurement then its influence may be negligible. Data on skin thickness are sparse. A comprehensive review of skin thickness and surface data was completed by Clarys et al. (1988). The effect of the variability of skin thickness on skinfold values has never been seriously assessed. Since the doubled skin thickness is generally of the order of a few millimetres, it would appear that the effect of skin would be most marked at those sites and in subjects with little adipose tissue. The site where the effect of skin thickness was most marked is the subscapular, where skin thickness accounted for 28.1% of the skinfold reading (34.0% for males, 23.9% for females). Two of the most commonly used sites for predicting body fat, the subscapular and triceps, were found to have quite different proportions of skin (Clarys et al., 1987). While the contribution of skin to total skinfold thickness is generally not large, it may lead to significant error, especially in lean males. Normalised as a percentage of total adipose tissue free mass (ATFM), it can be noted that skin may have an important contribution (Fig. 3). Sites where skin thickness is small relative to skinfold might prove better predictors of adiposity. Consequently, on the basis of skin thickness, the subscapular skinfold should be a poorer predictor than the skinfold at arm and leg sites. Assumption III-Fixed adipose tissue patterning "Fat patterning" refers to differences in the anatomical placement of adipose tissue (Mueller, 1985). For reasons mentioned hereafter, the term "fat" should be replaced

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by "adipose tissue". The patterning of subcutaneous adipose tissue is known to exhibit very large variations between individuals (Mueller and Stallones, 1981). To assess the value of various sites as predictors of subcutaneous adiposity, correlations between the caliper and incision thickness with the dissected subcutaneous adipose tissue mass have been determined (Clarys et al., 1987). An unexpected finding is the high correlation for lower limb sites. Of the six best sites, all but one were on the lower limb. The triceps, a highly favoured site for "fat" prediction and considered to be the best single indicator of adipose tissue (e.g. in digitised commercial devices), ranked a poor eleventh. As would be expected, correction for skin thickness for both caliper and incision values improved the correlations in 17 out of the 28 values, but it must be noted that most of the improvements were marginal. The best predictors were front thigh, medial calf, rear thigh and supra-spinale confirming in part the calculated findings of Martin (1984). This finding suggests that the common-sense approach of selecting sites from all important storage levels - e.g. segments, and especially the legs - is well founded. Assumption IV- the fat in adipose tissue Even if the mass of subcutaneous adipose tissue was known exactly, the prediction of subcutaneous fat mass requires some assumption concerning the fat content of adipose tissue. Reported values range from 5.2 to 94.1% (Martin, 1984), but they are generally in the range 60-85%. Besides, the fat content of adipose tissue increases with increasing adiposity. In view of considerations such as this, compounded by the fact that "fat" is ether-extractable, while "adipose tissue" is an "anatomical-morphological" entity, we should not use "fat" terminology in the anthropometric prediction of adiposity or not mix chemical fat in the anatomical adipose tissue studies as is too often the case still. Assumption V - the linear relation between internal and external adipose tissue From evidence based on cadaver studies it is assumed that, both in male and female subjects, the excess of adipose tissue is piled up subcutaneously, inter-muscular and internally, mostly in the trunk. The amount of intra-muscular fat in the obese should not be underestimated and should therefore be considered as a third compartment. However, in our cadaver analysis and for this purpose, the intramuscular amount has been allocated to the internal adipose tissue. Skinfold calipers are only able to estimate subcutaneous adiposity. In order to estimate total body adiposity some assumption must be made about the relation between internal and subcutaneous adipose tissue. If internal adiposity stores are proportional to subcutaneous fat, this relationship provides a rationale for use of skinfold calipers. An alternative is that internal adipose tissue may be negligible compared with subcutaneous fat, again providing some justification for the use of calipers. If, however, it is not negligible and if there is not a significant relation between internal and subcutaneous adipose tissue masses, then there cannot be an evidence based prediction of total or whole-body adiposity, nor is there a justification to use caliper measurements. Assumption VI - Internal versus external (subcutaneous) adipose tissue equality. In the continuation of reasoning as in assumption V, the Brussels CAS project provides comprehensive data on the relation of internal or visceral to external or

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subcutaneous adipose tissue masses. Fig. 8 shows the mass of dissected adipose tissue for both men and women. These data clearly indicate a high correlation between internal and external masses in women and no correlation in men. Many studies have already indicated that skinfold formulae are sample specific, but here we show that there is no justification for applying skinfold formulae for the prediction of adiposity in men.

36

Figure 8. The relation between internal (visceral + intra muscular) and external (subcutaneous) adipose tissue in men and women.

4. Closing remarks These data suggest clearly that all assumptions in the step-by-step transformation from skinfold measurement to whole-body adiposity are non-existent or highly variable. The assumptions have become very questionable. These problems will result in a serious increase of error with an increasing number of skinfolds within a prediction equation. It is unreasonable to continue to introduce further error into the prediction or determination of total body adiposity by transforming and combining anthropometric (skinfold) values, especially within formulae. On the positive side, it was possible to indicate a few skinfold sites as rather good "indicators" of adiposity. Eventually a summation of subcutaneous adipose tissue sites selected from all storage levels will allow for the prediction of the wholebody adipose tissue status in women (but certainly not in men). These findings have implications for measurements of body composition in health-care workers (see Part III).

References Clarys, J. P., Martin, A. D. and Drinkwater, D. T. (1987). The skinfold: myth and reality. Journal of Sports Sciences, 5, 3-33. Clarys, J. P., Martin, A. D., Marfell-Jones, M. J., Janssens, V., Caboor, D. and Drinkwater, D. T. (1999). Human body composition: a review of adult dissection data. American Journal of Human Biology, 11, 167-174.

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Clarys, J. P. and Marfell-Jones, M. J. (1986). Anthropometric prediction of component tissue masses in the minor limb segments of the human body. Human Biology, 58, 761-769. Clarys, J. P., Martin, A. D. and Drinkwater, D. T. (1984). Gross tissue masses in adult humans: data from 25 dissections. Human Biology, 56, 459-73. Clarys, J. P., Martin A. D. and Drinkwater, D. T. (1988). Physical and structural distribution of human skin. Humanbiologia Budapestinensis, 18, 55-63. Duquet, W. (1980). Studie van de toepasbaarheid van de Heath-Carter somatotype methode op kinderen van 6 tot J3jaar. PhD thesis, Vrije Universiteit Brussel. Edwards, D. A. W. (1951). Differences in the distribution of subcutaneous fat with sex and maturity. Clinical Science, 10, 305-15. Garn, S. M. (1955). Relative fat patterning: an individual characteristic. Human Biology, 27, 75-89. Garn, S. M. (1971). Measurement and interpretation of subcutaneous fat, with norms for children and young adult males. British Journal of Preventive Social Medicine, 9, 201-11. Hagar, A. (1981). Estimation of body fat in infants, children and adolescents. In: Adipose Tissue in Childhood (ed. by P. Bonnet), pp. 49-56. Boca Raton, FL: CRC Press. Heath, B. H. and Carter, J. E. L. (1967). A modified somatotype method. American Journal of Physical Anthropology, 27, 57-74. Janssens, V., Thys, P., Clarys, J.P., Kvist, H., Chowdhury, B. and Zinzen, E. (1994). Post-mortem limitations of body composition analysis by computed tomography. Ergonomics, 37, 207-216 Lohman, T. G. (1981). Skinfolds and body density and their relationship to body fatness: a review. Human Biology, 53, 181-225 Martin, A. D. (1984). An anatomical basis for assessing human body composition: evidence from 25 dissections. PhD thesis, Simon Fraser University, Burnaby, Canada (and Vrije Universiteit Brussel). Martin, A. D., Ross, W. D., Drinkwater, D. T. and Clarys, J. P. (1985). Prediction of body fat by skinfold caliper: assumptions and cadaver evidence. International Journal of Obesity, 9, Suppl. 1, 31-9 Mueller, W. H. (1985). Biology of human fat patterning. Communication at the Euro-Nut Conference. London: Ciba Foundation. Mueller, W. H. and Stallones, L. (1981). Anatomical distribution of subcutaneous fat: skinfold site choice and construction of indices. Human Biology, 53, 321-35. Ross, W. D. and Ward, R. (1984). The O-scale System. Vancouver, Canada: Rosscraft.

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BODY COMPOSITION: PART III In vivo application of a selection of formulae for predicting whole-body adipose tissue in male and female nurses J. P. Clarys, K. Alewaeters and E. Zinzen Department of Experimental Anatomy Vrije Universiteit Brussel Belgium

Abstract: The body's distribution of its adipose tissue is an indication of health among professionals. The aim in this study was to examine the existing equations for predicting body composition from skinfold measurements. Fifty one formulae were investigated. Except for one formula, there was a high correlation between the formulae examined. The simplest method of discriminating adipose tissue difference between subjects is by means of summed skinfolds.

1. Introduction The distribution of the body's adipose tissue mass is an important indicator of health risk. The relationship of its distribution with mortality and disease is well known. Central adipose predominance is a strong risk factor for cardiovascular disease, hypertension, stroke and diabetes. Knowledge of these phenomena is important for the health of the population at large, but in particular for professions known or recognised as "at risk". The nursing profession is one of these, especially in relation to low-back problems (LBP) and musculoskeletal inconveniences. However, against expectations in a study of 784 nurses, no relation was found between skinfold predictions of the whole-body adiposity and LBP associated phenomena (Zinzen, 1998; Zinzen et a/., 2000); assuming the data collection and the corresponding calculations are correct the no-relation status remains. Nevertheless, the calculated predictions confirm what is suggested from cadaver studies (see the two preceeding chapters). The purpose of this part of the study was to select amongst 98 known, anmropometric "whole-body adipose tissue" prediction equations, those formulae that are composed of skinfolds only (=51). Out of these 51 formulae, those equations were chosen that used one or more of the eight (8) skinfolds that were part of the Amsterdam, Brussels, Liverpool "LBP and nurses project" (Fig. 1). This joint venture was

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registered in Belgian and European contracts (BmH4-CT96-1057, PBO98/24-65/85, ST/03/029, HH/03/004).

2. Methods The subscapular skinfold was measured in parallel with the M. latissimus dorsi, 2 cm below the angulus caudalis scapulae; the triceps skinfold was measured at the proximal one third of the upper arm; the biceps skinfold on top of the most visual part of the muscle belly; the abdominal skinfold to the right of the umbilicus; the supra-cliacal (or waist) skinfold was taken 5 cm above SIAS; the thigh skinfold in the frontal mid and the calf skinfold at the medial site of the greatest calf circumference. The thoracic skinfold was measured halfway between the nipple and the umbilicus.

Figure 1. Skinfold distribution in various body segments used in the LBP-nurses project (Zinzen 1998).

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This final selection resulted in four (4) suitable formulae for the female nurses and nine (9) equations for the male nursing personnel (Table 1 and 2). Table 1. A selection of formulae for the in vivo estimation of the whole-body adipose tissue in female subjects, using selected skinfolds solely.

Parizkova

1961

1.079-0.043 log X,

Nagamine & Suzuki

1964

1.0869-0.00268 X,

Katch & McArdle

1973

1.08347 + 0.0006 X2 - 0.00151 X, - 0.00097 X6

Parizkova & Roth

1971

40.249 log (X2 + X,)- 32.413

Table 2. A selection of formulae for the in vivo estimation of the whole-body adipose tissue in male subjects, using selected skinfolds solely.

Sloan

1967

1.1043 - 0.00133 X6 - 0.00131 X,

Sloan

1967

1 .0967 - 0.00 1 2 1 X4 - 0.00 1 28 X2

Wilmore & Behnke

1969

1.081 1-0.00195X 2

Wilmore & Behnke

1969

1 .0854 - 0.00086 X4 - 0.0004 X6

Forsyth & Sinning

1973

1.10647 - 0.00162 X, - 0.00144 X4- 0.00077 X2 + 0.0007 1 X8

Katch & McArdle

1973

1.0967 - 0.00103 X2 - 0.00056 X, - 0.00054 X,

Pollock et al.

1976

1.0936 -0.001 86X 2

Lohman

1981

1.0982 - 0.000815 (X2 + X4 + X,) + 0.0000084 (X2 + X4 + X,)2

Parizkova & Roth

1971

33.852 log (X2 + XO- 23.876

These formulae were calculated with the data from 176 males and 608 females (total N - 784). A few of these equations produce a density (D) value in g.cc"1. In those cases the conversion formula of Brozek et al. (1963) - Adipose Tissue = 4.570/D-4.142 - was used in completion. In addition the sums of respectively 3, 6 and 8 skinfolds were added for comparison. This grouping was based on the predictive value for adipose tissue according to the cadaver study (see part II) e.g. the best 3, the best 6, and so on. Table 3 and 4 include their mean, SD, minimum and maximum values.

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Table 3. Sum of skinfolds (in mm) of male subjects.

3 skinfolds (X) 6 skinfolds (Y) all 8 skinfolds (Z)

Mean 33.69 72.78 86.44

SD 15.13 31.87 36.28

Minimum 10.20 22.60 29.80

Maximum 87.80 188.80 199.50

Skinfolds used: subscapulary'z; tricepsy'z; biceps7; abdominaly>z; supra iliacax'z; thigh x>y>z ; medial calf1*3 thoracicy'z

Table 4. Sum of skinfolds (in mm) of female subjects.

3 skinfolds (X) 6 skinfolds (Y) all 8 skinfolds (Z)

Mean 62.96 112.63 125.98

SD 22.87 42.64 45.15

Minimum 14.20 33.80 41.10

Maximum 177.50 334.20 352.20

Skinfolds used: subscapulary> z; tricepsy'z; bicepsz; abdominal*z; supra iliacax'z; thigh"'y'z; medial calf0 thoracicy'z

3. Results and discussion All formulae are predictors of the "whole-body adipose tissue" both in women and in men. The formulae use the same populations of nursing personnel with their respective skinfolds but the amount of skinfolds used per equation varies. All calculated results correlated almost perfectly, with r between 0.71 and 0.99 (p<0.05) including a majority of r >0.90 in females. The correlation matrix of the males showed a minimum r of 0.76 against a maximum r of = 0.98. One formula showed no correlation at all, namely the Lohman (1981) equation. On this basis, it is acceptable to assume almost equal calculations of the wholebody adipose tissue for all formulae abstracted. This statement is true irrespective of whether it is an overrated, a correct or an underrated value. The female nurses showed a minor variation of maximal value 4% (min. 25% and max. 29% of adipose tissue) between the respectively calculated equations (Fig. 2) while the male nurses had 13% adipose tissue calculated with the equation of Katch and McArdle (1973) against 22% adipose tissue using the formulae of Pariskova and Roth (1971) (Fig. 3). All other calculated values lie in between the previous ones (the data obtained from Lohman are no longer included).

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% adipose tissue 35 T

30

25

20 -

15

10

5

Katch & McArdle (73)

Nagamine & Suzuki ('64)

Parizkova ('61)

Parizkova & Roth (71)

Figure 2. The whole-body adipose tissue predictions for female nurses (N=608).

% adipose tissue 35,00 30,00 25,00 20,00 15,00 10,00

5,00 0,00

Forsyth & Sinning

Katch & McArdle

('73)

('73)

Lohman ('81)

Parizkova & Pollock et al. Sloan ('67) Sloan ('67) Roth ('71) ('76)

Wilmore & Behnke

Wilmore & Behnke

('69)

('69)

Figure 3. The whole-body adipose tissue predictions for male nurses (N=176).

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We clearly observed greater differences and a higher variation in the male predictions. These data confirm in a sense the findings of the step-by-step cadaver analyses (Part II) and they are enforced by the fact that we measure significantly less skin in the skinfold (see Part I). Observing the male adipose tissue percentages, one might as well visually determine the amount of adipose tissue without really making a greater error than with the prediction equations. This assumption may be bold, but is not unrealistic. The simplest and probably best method to discriminate adipose tissue between subjects e.g. nurses in this case, may be the sum of skinfolds. Realising we used the better predictors first, it clearly makes no difference if one uses the sum of 3, 6 or 8 skinfolds. The discrimination value is close to being equal. Finally, Fig. 4 indicates also that female nurses had a significantly (p<0.005) higher amount of adipose tissue than males. This observation confirmed the findings in other professional groups.

Figure 4. Adipose tissue between males and females using the sum of skinfolds.

References Brozek, J., Grande, F., Anderson, J. T. and Keys, A. (1963). Densitometric analysis of body composition; Revision of some quantitative assumptions. Annals of the New York Academy of Science, UO, 113-140. Forsyth, H. L. and Sinning, E. W. (1973). The anthropometric estimation of body density and lean body weight of male athletes. Medicine and Science in Sports, 5, 174-180. Katch, F. I. and McArdle, W. D. (1973). Prediction of body density from simple anthropometric measurements in college-age men and women. Human Biology, 45,445-454.

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Lohman, T. G. (1975). Prediction of lean body mass in young boys from skinfold thickness and body weight. Human Biology, 47, 245-262. Nagamine, S. and Suzuki, S. (1964). Anthropometric and body composition of Japanese young men and women. Human Biology, 36, 8-15. Parizkova, J. and Roth, Z. (1972). The assessment of depot fat in children from skinfold thickness measurements by Holtain (Tanner/Whitehouse) caliper. Human Biology, 44, 613-620. Pollock, M. L. (1975). Prediction of body density in young and middle-aged men. Journal of Applied Physiology, 38, 745-749. Sloan, A. W. (1967). Estimation of body fat in young men. Journal of Applied Physiology, 23, 311-315. Wilmore, J. H. and Behnke, A. R. (1969). An anthropometric estimation of body density and lean body weight in young men. Journal of Applied Physiology, 27, 25-31. Zinzen, E. (1998). Epidemiologisch, anthropometrisch en lichaamssamenstellings-onderzoek naar de prevalence van musculo skeletale ongemakken van cervicale en de lumbale wervelkolom bij ziekenhuisverpleegkundigen. Doctoral thesis. Published by Experimental Anatomy - EXAN - VUB. Zinzen, E., Caboor, D., Verlinden, M., Catrysse, E., Duquet, W., Van Roy, P. and Clarys, J.P. (2000). Will the use of different prevalence rates influence the development of a primary prevention programme for low back problems? Ergonomics, 43, 1789-1803.

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Musculoskeletal Disorders in Health-Related Occupations T. Re illy (Ed.) IOS Press, 2002

MUSCULOSKELETAL DISORDERS IN HEALTH-RELATED OCCUPATIONS: PROJECT OVERVIEW AND OUTCOMES T, Reilly*, D. Leighton**, C. Beynon**, J. Burke*, J. P. Clarys***, P. Van Roy***, E. Zinzen***, D. Caboor***, M. Verlinden*** and A. P. Hollander**** * Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Henry Cotton Campus, 15-21 Webster Street, Liverpool, L3 2ET, UK. ** Public Health Sector, School of Health and Human Sciences, LiverpoolJohn Moores University, 70 Great Crosshall Street, Liverpool, L3 2AB, UK. *** Department of Experimental Anatomy, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussels, Belgium. **** Faculty of Human Movement Studies, Vrije Universiteit Amsterdam, Van der Boechorststraat 9, 1001 BT Amsterdam, The Netherlands. Abstract: Musculoskeletal disorders are the most commonly reported occupational diseases within workforces of the European Union. This project (Biomed IV) was focused on health-related occupations to compare the prevalence of musculoskeletal disorders in different specialisms, identify causes of occupational strain, establish physiological indices of strain, evaluate effects of altering typical work-rest cycles and develop a multidisciplinary preventive model. Lifetime prevalence of musculoskeletal disorders for nurses and physiotherapists was 49%, point prevalence being 20.7%. Lower back/hip area accounted for 46% of complaints. Prevalence of symptoms was greatest in the agerange 50-59 years. Handling and lifting patients were causal in 67% of cases. The working environment was deemed unsuitable by 40% of respondents. Lifting aids were not consistently used and disorders increased with perceived work pressure. High-risk and low-risk specialisms were identified; lifting patients or equipment emerged as the main source of injury in both cross-sectional and prospective studies. Static holding carried equal risk when formal risk assessments were made. The activity-rest schedule observed in hospital porters provided a model for investigating the efficacy of short breaks from work. The heart rate response was found to be a valid index of physiological strain in intermittent activity in both laboratory and field-based protocols, the standard error in predicting oxygen uptake being 7%. Altering the work-rest schedule whilst keeping overall rest constant did not reduce the metabolic load or the compressive spinal loading (shrinkage). Epidemiological investigations in Brussels replicated the important observations from both surveys and risk assessments in Liverpool whilst extending the database to identify links between personal, social, environmental and workrelated variables. The project culminated in the design of a multidisciplinary preventative model for implementation in back-care education and decreasing musculoskeletal loading.

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1. Background/rationale Lower back pain affects a large part of the adult population, over 60% of whom have a cumulative lifetime prevalence of the syndrome. Back pain is a very common cause or morbidity, disability and threat to health and well-being. The lower back is more commonly affected by occupational over-exertion than are other parts of the body, and accounts for about two-thirds of total occupationally related injuries. The major part of the remainder is attributable to other musculoskeletal disorders (MSD) associated with poor working postures or working practices. Such postures and manual handling practices are evident in occupations within healthcare professionals and the hospital environment. Data from the U.K. and Belgium emphasise the huge economic consequences to industry of certified sickness due to working days lost as a consequence of musculoskeletal disorders. Since their causes are multifactorial, it is important that an ergonomics appraisal should take an interdisciplinary approach towards identifying critical epidemiological factors. Identification of the interactions between factors would help form a strategy for reducing the incidence of musculoskeletal disorders. A decrease in prevalence would have huge economic benefits to the employers. Since these disorders adversely influence participation in leisure and recreational activities in those people affected, any improvement in the preventative practices would help preserve the health and well-being of workers, especially among the European communities. It was envisaged that the work would have potential also for the education and training of personnel at risk of musculoskeletal disorders in the work-place. The ergonomics check-list incorporated into the preventive model (which represented the culmination of the current project) could form a basis for reducing occupationally related biological problems and thereby benefit the employer in healthcare professions. 2. Objectives and primary approaches i)

ii) iii)

iv)

v)

Establish prevalence of MSDs among nurses and physiotherapists by means of an extensive questionnaire and information gained from hospital Occupational Health Department records, Identify possible causes of occupational strain using questionnaire and extensive ergonomic risk assessments within the hospital environment, Establish the interaction between risk factors in the work-place environment and the incidence and prevalence of occupational MSDs, employing a multivariate approach to data collection, Examine the physiological and biomechanical effects of alterations in work-rest schedules among hospital porters using physiological and physical indices of occupational strain, Develop a model to be used in the prevention of back problems in nursing personnel based on synthesis of data collected from a variety of different tests.

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3. Methods, statistics, ethical aspects a) Liverpool and Amsterdam: Epidemiology of Musculoskeletal Disorders: A Cross-Sectiona Survey of Nurses and Physiotherapists; Two questionnaire were designed for the purpose of the study. The questionnaires for nurses and physiotherapists were fundamentally identical to allow valid comparisons to be made between the two occupations. Altogether 5029 questionnaires were distributed, 4235 to nurses and 794 to physiotherapists. Staff of all grades and specialities were requested to complete the form, irrespective of whether or not they were suffering, or had previously experienced, any musculoskeletal symptoms. Data were analysed using the statistical software SPSS (version 6.01). To establish the relationship between two or more categorical variables, chi-squared analyses were used. Logistic regression analysis was used to identify risk factors associated with MSDs (i.e. presence or absence). Epidemiology Of Musculoskeletal Disorders:A Prosepctive Study Within An Occupational Health Department', The Broadgreen Hospital N.H.S. Trust's Occupational Health Department assisted with this study, which consisted of two parts. Case studies of individuals suffering severe musculoskeletal symptoms were recorded and their progress followed over a 12-month period (1st October 1996 - 31st September 1997). Information included a clinical diagnosis and the treatment initiated, the severity of the problem and sickness absence, and the perceived cause of the injury. Information from patient records was transferred onto a data collection sheet through consultation between researcher and physician to avoid any compromise of confidentiality. Secondly, the number of individuals consulting the Occupational Health Department was recorded over a one-month period (August 1997) to ascertain the number of people using this practitioner as the mode of treatment. Some details relating to the location of the disorder and the perceived cause were also recorded. An ergonomic evaluation of hospital based nursing and physiotherapy tasks; The risk assessment pro-forma was developed based upon guidelines provided by the Health and Safety Executive (U.K.), but the results of the epidemiological study were also incorporated. Pilot work was undertaken at Southport and Formby District General Hospital to ensure all occupational actions could be recorded. The risk assessment pro-forma included six sub-sections. A cumulative scoring system was devised, the total score indicating the overall risk of performing a specific activity. A short description of the task was included at the time of recording so that the composite score was associated with specific activities. By separating the pro-forma into sub-sections, it was possible to identify which of the sub-sections were responsible for the overall high task score. High and low risk specialities were identified by the logistic regression analysis of the questionnaire data. This information was used to select specialities for this study, with a combination of high and low risk specialities being chosen. The assessor 'shadowed' one member of staff for a one-hour period during the course of an individual's working day and an instantaneous assessment was carried out every 10 minutes. By remaining with the member of staff continuously for the one-hour period, the assessor was also able to assess the psychological characteristics of the individual, a factor which was shown to be important in the questionnaire analysis. Altogether, 276 risk assessments were completed, comprising data collected for 46

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hours in total. Assessment was performed on both physiotherapists and nurses, at different times of the day, on both sexes and on different grades to ensure a crosssection of information was obtained. In total, 197 nurse assessments and 97 physiotherapist assessments were performed. By collecting large amounts of data on numerous individuals, any individual differences in the way personnel perform tasks were smoothed out. A mean score for performing each specific task was therefore obtained. The information was analysed using Minitab (version 9.2). Analysis of variance was used to examine differences in tasks and between subjects. When the residuals were extracted from the above analysis, the residuals failed to show a normal distribution using the Anderson-Darling test of normality as implemented in Minitab. A Kruskal-Wallis non-parametric test was used to establish which of the six subsectional scores were responsible for the increased overall score of the high risk tasks and to indicate whether other factors such as age, nursing grade and specialty, and time of day had any significant effect on the overall task scores. Occupational Strain In Hospital Based Porters; Eight porters from Southport and Formby District General Hospital were 'shadowed' by an observer for a two-hour period in which time their activities and the amount of time each action took were recorded (this protocol replicated that of similar occupations from observations in Amsterdam). The actions included walking, standing, sitting and pushing or pulling whilst walking. The percentage of time each action occupied within the two-hour period was then obtained. The work-rest schedule of the hospital porters was ascertained for subsequent experimental investigation and formed the first 4-hour test protocol as follows (trial 1); Work: 5 minute break: work: 15 minute break: work: 5 minute break: work: finish. An alternative 4-hour work-rest schedule was proposed and constituted the second test session (trial 2); Work: 12.5 minute break: work: 12.5 minute break: work: finish. The relative percentage of time the subjects were walking, standing, pushing and so on was identical for each of the two tests. The rest breaks were differently distributed but the total time spent at rest was constant. Each subject performed the existing work-rest schedule and the modified work-rest schedule on two separate occasions: the prediction was that two longer breaks as opposed to one long and two very short breaks would facilitate spinal recovery. The order of testing was randomly assigned to the subjects. A stadiometer was used to measure spinal shrinkage and the subjects were familiarised with the equipment prior to testing. Rating of perceived exertion (RPE) was also recorded. Heart rate, oxygen uptake (VCh) and minute ventilation (VE) were recorded using a portable telemetry device (Metamax, Birmingham). Preliminary experimental and field-based work in Amsterdam concluded that heart rate could be used during intermittent activity to indicate metabolic loading, the SEE being 7%. The research design adopted meant that the subjects effectively acted as their own control. Data were analysed using t-tests in Minitab. b) Brussels: Abbreviations: LBP = low-back problem(s), MSD = musculoskeletal disorder(s), SBHC = standard bed-height condition(s), ABHC = adjusted bed-height condition(s), CMR = continuous movement registration, ROM = range of motion, EMG = electromyography.

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The multidisciplinary approach to the research commenced (and still goes on) with a comprehensive literature review, continuously upgrading a "LBP" database from which a large group of neck problems and LBP-related variables were extracted and introduced into an epidemiological study. Nurses (n=1216) from four Flemish hospitals volunteered for the study (68.2% return). Internationally validated questionnaires were used covering professional activities, habitual work, general health, smoking and drinking habits, gynaecological problems, degree of depression (Modified Zung Depression Index), musculoskeletal problems (other than neck and back problems), pain coping strategies (Pain Locus of Control Questionnaire), the Fear and Avoidance Beliefs Quest, work satisfaction (Work Apgar), working environment, the use of manual handling techniques, work clothing, sleeping habits, leisure time and time spent in housework. Altogether 699 nurses (540 female, 159 male) volunteered for an anthropometric investigation measuring body lengths, skinfolds, circumferences and breadths, somatotype classification (Heath-Carter method) and body composition. On the basis of lifetime, year and point prevalence, six different experimental groups were derived and compared to their control group, using ANOVA, Kruskall-Wallis and Chi-square tests (all p < 0.05). All variables determined as significantly different from the control group were exposed to a factor analysis in order to reduce the number of variables. Finally, a discriminant analysis provided determinants that were considered for the development of a preventative model. In order to produce additional information needed for formulating the model a psychomotor task analysis, using an adapted Delphi Survey-project (Med'tox questionnaire), established the top 10 most 'heavy' nursing duties as a means to steer the in-depth multidisciplinary research with the accent upon the analysis of bedpatient related tasks. The 'heaviness' of a task was determined by combining a taskloading score and a task-frequency score. VICON®-analyses: two-dimensional opto-electronic kinematic data and calculated vertebral positions and ground-force parameters (Kistler®)) in combination with anthropometric data led to the calculation and determination of compression and shear forces at the level of L5/S1 vertebrae. Kinesiological surface EMG of the M. biceps femoris, M. obliquus externis abdominis and the M. erector spinae on both sides of the body, was carried out using active bipolar Ag-Cl surface electrodes and a data recorder (Teac-MR30) in an online set-up. Analogue to digital conversion took place at a sample frequency of 1000 Hz. The ESPAS system was used to effect a quantitative (integrated EMG) and a qualitative analysis to determine muscular co-activation patterns. All analyses were based upon full-wave rectified signals and linear envelope presentations of the EMG signals. Normalisation to highest peak was part of the criteria in order to compare the nursing tasks at different bed-heights. Student t-tests (two-tailed) were used to identify possible differences between the conditions as well as left to right body comparisons in terms of muscular activity (iEMG). Female (n^H) and male nurses (n=8) were considered both separately and as a total population. Part of the analysis was carried out in two different methodological ways for reasons of reliability and validity. Spinal movement was determined continuously by means of an adapted 3Dregistrational electrogoniometer attached to the nurses (n=18) without limiting any of their movements during the conduct of standard nursing tasks. The registrations describe spinal movement in terms of sagittal inclination, axial rotation, latero-flexion of the trunk and sagittal bending of the lower back. These nursing tasks consisted of handling a hemi- or quadriplegic patient in both SBHC (51.5 cm) and ABHC.

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Furthermore an 8-hour registration (full working day) was part of the experiment. All the recordings were at a sampling frequency of 32 Hz. Attitude changes (inclination divided in 5° boundaries) and changes of shape [axial rotation using 2° boundaries, side and sagittal bending using 5-mm boundaries (spring system enlargement measurements)] as well as 6 combinations were analysed using the number of entries, hence the time spent within a movement zone. The results obtained were then compared, using Student-t statistics, to the SBHC. Identification of a 'danger zone', a 'potentially dangerous zone' and a 'neutral zone' was based upon the combination of NIOSH lifting limits (National Technical Information Service, US Department of Commerce; scientific support documentation for the revised 1991 NIOSH lifting equation) and the modified OWAS analysis (Lee and Chiou, 1995). The research on segmental (cervical, thoracic and lumbar) spinal shrinkage (n=37), determining the anatomical segmental region where the highest loading took place, was carried out both during specific standardised handling techniques (laboratory conditions) and a full working day (working environment). With the head in the Frankfurt position, measurements such as stature, C7 height, sitting height, height of SIAS and SIPS left and right were taken twice (before the full day's job and at the end of the daily work, 9 hours ± 30 min). The GPM anthropometer and sitting height table (Holtain Limited, UK), both with a 1 -mm accuracy, were used. Isokinetic (KIN/COM, Chatanooga) and isoinertial (IsoStation B200 dynamometer) force registrations (n=14 experimental group, n=23 control group) were induced as a means of determining a relation (unpaired 2-sample t-tests) between prevalence of LBP/Neck problems and concentric/eccentric muscular (extremities on both body sides and trunk) torque/force development (flexion and extension) at different angular velocities (1.04 rad.s"1, 2.09 rad.s"1, 3.12 rad.s"1). Also different isoinertial trunk speeds during performance to fatigue of 25 maximal (speed/force) flexion-extension repetitions (flexion/extension, rotation and lateroflexion) were evaluated. The degree of general fitness in the nursing population (n=37) as opposed to an age-matched group of civil servants was determined by using the EUROFIT TestBattery (Council of Europe, 1988) without the cardio-respiratory part. ANOVA-tests were used to detect relations with LBP/Neck problems. As the literature prescribes the use of correct handling and lifting techniques to prevent the development of LBP, the ongoing research tried to determine educational aspects (time spent in instruction of the techniques) in the different curricula (n=26) of the paramedical professions, using a questionnaire and comparing the findings. Furthermore, a selection of accurate methods and an ergonomic evaluation of the effects after a 3-month back school intervention (factory workers) were carried out (n=23) using a psychological and a health-related questionnaire. Student t-tests were used to determine pre-post differences. At this stage the whole of the multidisciplinary research together with the epidemiologial study formed the back-bone for proposing a theoretical model geared towards prevention.

T. Reilly et at. / Musculoskeletal Disorders in Health-Related Occupations

4. Results, discussion, conclusion a) Liverpool and Amsterdam Epidemiology of Musculoskeletal Disorders: A Cross-sectional survey of nurses and physiotherapists; Lifetime prevalence of MSDs of various anatomical locations for nurses and physiotherapists combined was 49%. The point prevalence was 20.7%. The location of MSDs and percentages of sufferers were as follows:- low back/buttocks/pelvis/hips/upper legs (46.3%), neck/shoulder/upper and midback/upper arm/chest (21%), wrist/hand/forearm/elbow/fmgers (6.1%), knee/lower limb (2.4%), torso; whole-body area (11.7%) and other/not stated (13.2%). There was no significant difference in the relative percentages of nurses and physiotherapists who had suffered MSDs during their working life indicating that physiotherapists should, as nurses, be considered a high risk group (p>0.05). Physiotherapists experienced significantly more symptoms relating to the wrist, fingers, hand and forearm, knee and lower limb (p<0.05). Absence from work due to their complaints was indicated by 25% of respondents. In total, musculoskeletal disorders accounted for 19% of all absences from all respondents within the previous years. Symptoms had forced 4% of sufferers to change job/specialities and over half (56%) had modified the way they performed their tasks to alleviate any discomfort. Nurses and physiotherapists showed a significantly higher percentage of MSDs between the ages of 30 and 59 years than above or below this range (seven subjects reporting ages of over 60, despite this being the recognised retirement age). The prevalence of musculoskeletal symptoms was proportionately the greatest for those staff aged between 50 and 59 (p<0.05). The percentage of time within the profession was not significantly related to the presence/absence of musculoskeletal symptoms, so the peak in symptoms of those between 50 and 59 years would appear to be due to the natural physiological ageing process. Regarding lifetime prevalence, 36.4% of respondents with musculoskeletal symptoms could recall a specific causal incident. For 66.7%, the cause indicated was patient handling and lifting. Of those personnel who attributed their symptoms to continued exposure to a stressor, patient handling and lifting were implicated by 51.3% of respondents. It was indicated by 92% of nurses that they were involved in the lifting and handling of patients. Three quarters (n=380) of those individuals carried out less than 10 manual transfers per shift without the use of any assistive devices, and one-quarter (n=127) carried out more than 10 transfers, with the maximum per shift indicated as 60. This was comparable to the number of lifts that physiotherapists performed without the use of assistive devices (77% less than 10 per shift and 23% more than 10 per shift). Nurses indicated that assistive aids were not always available/appropriate (49%) or not required (42%). Physiotherapists also rated these reasons highly, 21% and 31% respectively, but 28% of respondents felt the main reason for not using the lifting aids was that lifting and manually transferring patients were part of the rehabilitation process, with patients encouraged into normal functioning requiring manual assistance in movement. Carrying out manual lifts or the number of manual lifts performed by the nurses and physiotherapists was not a significant indicator for musculoskeletal symptoms when entered into the logistic regression equation. It is conceivable that all personnel have to participate in lifting/handling of patients and equipment and are exposed to this 'detrimental' aspect of the job. It is also possible that the attention manual

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handling has received partly means that individuals suffering MSD automatically attribute it to this cause. Specifically which manual handling tasks have the potential to cause MSD needs to be explored and pushing and pulling must also be considered. The working environment was deemed to be unsuitable by 40% of respondents. Personnel perceived the main problem to be a poorly designed work area or space constraints (61%). Those physiotherapists whose work required the regular adoption of stooped positions were 23% more likely to suffer musculoskeletal symptoms than those who answered no to this question. This adoption of stooped postures, confounded by space constraints, may be equally important in the onset of LBP as manual handling. Another factor significantly associated with MSDs was the speciality in which the nurse or physiotherapist worked. This is shown in Table 1 below. High risk specialities were not only those with highly dependant patients, again suggesting that it is not patient handling alone that predisposes to MSDs. The cumulative effects of previous work (i.e. in other specialities) must also not be ignored. Table 1. High and low risk specialities among nursing and physiotherapist personnel. High risk specialities (nurses and physiotherapists combined) General Medicine Orthopaedics Theatre/Recovery Care Of The Elderly Intensive Care Accident and Emergency Oncology Ear, Nose and Throat Plastics/Burns Rheumatology Spinal Injuries Respiratory Care Rehabilitation

Low risk specialities (nurses and physiotherapists combined) Surgery Paediatrics Psychiatry/Mental Health Out-Patients Dermatology Haematology Midwifery/Obstetrics/Gynaecology Renal/Urology Coronary Care

Psychosocial variables proved to be the most useful set of factors in predicting those individuals susceptible to both MSDs and LBP specifically. Work pressure was especially important, for the nursing population of the study. The risk of incurring a MSD or LBP increased by 7% and 9% respectively for nurses with every unit increase in perceived work pressure. Those nurses who stated that they had high job aspirations were also less likely to suffer LBP (p<0.05). Considering just LBP, the risk increased by 1% for every percentage increase in the time the staff members spent on their feet during the course of an average shift. Prolonged standing may increase the rate of natural spinal shrinkage resulting in damage to the end plates, disc degeneration and stiffness and the probability of nerve root pressure and pain. There was also a significant relation between LBP and increased work pressure (p<0.05). Epidemiology of Musculoskeletal Disorders: A Prospective Study Within an Occupational Health Department. In August 1998, all individuals visiting the department with MSDs were recorded for the study which totalled 9 nursing staff of different grades and specialties and 2 physiotherapists. Their MSDs were in a variety of different locations. Information was also collected on seven patients with severe problems and their treatment and progress were followed as case studies. The highest

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number of problems concerned the lower back (5 subjects), with patients usually suffering additional sciatic symptoms. The second most commonly injured area was the neck. All subjects who had visited the Occupational Health Department in August had experienced a period of time off work. Considering the 7 case studies, this time span ranged from 153 days to 335 days. Assuming that August was a typical month, it can be deduced that 120 new cases are presented at the Occupational Health Department each year. This figure may represent only part of the whole musculoskeletal problem, with other staff choosing other modes of treatment. Of the 7 case study individuals, 4 had to be retired from nursing and the remaining 3 continued to work, having had symptoms relieved. With the exception of one individual, all subjects attributed their diverse symptoms to lifting (of both patients and equipment). As suggested in the questionnaire survey, lifting may be so prominent in the minds of healthcare professionals that other possible factors are neglected and that lifting is still ubiquitous to most nursing and physiotherapy roles. It is essential to pin-point exactly which lifting/handling tasks have this potential to cause problems and this task can be achieved by means of risk assessment. An Ergonomic Evaluation of Hospital Based Nursing and Physiotherapy Tasks; There was a significant difference between the risk scores of the different tasks (p<0.05). The tasks identified as having the highest risk were those concerned with transferring and lifting patients and those involving a static hold component or standing patients in a static position as part of the rehabilitation process. The results of the risk assessment are shown in the Table 2 below. Table 2. Median risk score for various nursing and physiotherapy tasks according to risk assessments. Description of task Transferring/lifting patients Static hold/standing patients Physio manipulations Transfer/push/pull equipment Chest physiotherapy Assisting patient (feeding/washing, etc.) Treating patient (medical procedures) Rehabilitation exercises Bed making/tidying Writing/reading notes Preparing/checking equipment/treatment Patient assessment Other Walking patients Talking to patients Talking to staff/relatives Walking/standing

Median risk score 8.00 8.00 5.00 5.00 5.00 4.00 4.00 4.00 3.00 3.00 2.00 2.00 2.00 1.00 1.00 1.00 1.00

Number of observations

14 10 4 16 7 11 15 14 4 39 23 9 8 7 24 29 41

Manual handling did not score the highest of all tasks for the load handled, but scored more highly than any other task for the postures adopted to perform the lift. The questionnaire indicated that space constraints were a problem so it may not be the lifting per se that is fully responsible for MSDs but the awkward postures adopted due to problems with the working environment. Static postures had a risk score equal to

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lifting/transferring. Lifting/transferring scored highest for load because these tasks are performed alone without the use of aids. Differences between the risk of tasks performed in different specialties were significant (p<0.05), with the 'spinal injuries' unit associated with the highest risk. Second were care of the elderly and surgical specialties. The high risk specialties may reflect the degree of dependency of the patients within these wards. The specialties deemed to have the lowest risk were orthopaedics and casualty. Staff aged between 20 and 39 performed more tasks of higher risk than other staff (p<0.05). The questionnaire showed that older staff actually suffered more MSDs. This finding would appear to support the premise that the increased prevalence with age was due to the physiological ageing process and the overall wear and tear of the body but further study would be useful in this area. Occupational Strain in Hospital Based Porters; No significant difference was observed between the standard work-rest schedule and the experimental regimen on any of the physiological variables (p>0.05). The activities in this study were of lowintensity, with mean heart rates for test 1 and test 2 being 79 beats per minute and 81 beats per minute respectively. Average energy expenditure was 948.1 and 979.5 kJ.h"1 respectively which is also considered light work. It is evident that neither trial 1 nor trial 2 exerted any major physiological stress on the subjects. The alternative workrest schedule was designed to reduce physiological strain and prevent cumulative fatigue. Due to the low intensity of the work involved, cumulative fatigue was not evident, accounting for the lack of difference between the two trials. At higher workloads, the positioning and length of the rest breaks would be of more importance. There was no significant difference between the shrinkage of the subjects in trial 1 and trial 2 (p>0.05). There was also no difference in the rating of perceived exertion for the two trials (p>0.05). Short breaks (less than 10 minutes) are considered insufficient to allow time for recovery to occur (Helander and Quance, 1990). However, shrinkage and recovery occur at an exponential rate, with the speed of recovery being greatest at the onset of the break and slowing down as the break progresses so that very long breaks offer no additional benefit. The process of spinal recovery is greatest when the load is removed from the spine totally and the individual lies down with legs slightly elevated. In a work situation, a period of sitting facilitates recovery. In this study, manipulation of the work-rest schedule did not affect spinal shrinkage. The rest breaks would facilitate recovery but this was not affected by when the breaks occurred. Some sitting was incorporated into the work period of the task (as is the case when porters are awaiting their next specific task) and this may also have had a positive effect on recovery. The scores for the rating of perceived exertion ranged from 6 to 10 on a 6 to 20 Borg scale, showing that the work load was perceived by the subjects to be relatively light. This is also shown in the heart-rate and minute ventilation data. Shrinkage recorded during the test probably included the natural diurnal shrinkage of the subjects that was occurring whilst observations were being made. More physically demanding work would induce greater shrinkage and the length of recovery time then becomes more important. Finally, the manipulation of work-rest schedules must also be considered from a practical view-point. Discussion with the hospital based porters showed that they did not want fragmented work breaks during the course of the day, but preferred a single break of longer duration.

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b) Brussels The whole project was backed-up by a large relevant literature database currently containing up to 900 references. From the epidemiological study, lifetime prevalence for LBP was 53%, year prevalence was 41% and point prevalence was 28%, rather low values when compared to the literature. Prevalence values for neck problems were respectively 27%, 22% and 15%, similar to the international literature. Out of 237 variables analysed, 111 showed a significant difference between experimental and control groups. In summary, it is stated that groups with LBP or neck problems have had a poorer education, were less healthy, were older, had a longer nursing career, were pregnant more frequently, smoked more, scored higher on the depression scale, experienced more MSD and pain, showed a greater fear and avoidance behaviour towards physical activity and work, used more negative coping strategies and were less satisfied at work. The 'neck problem1 population produced very similar results. Further discussion includes both LBP and 'neck problem' populations. No differences were detected concerning sleeping habits, leisure time, working environment, the use of alcohol, the working environment, the type of tasks and the working schedule. The factor analysis of the 111 variables, failed to produce clusters of variables (Keizer Mayer Olkin value, 0.06). The discriminant analysis needed 47 steps to determine a significant function in which 43 variables were listed, hence producing a 83.2% classification coefficient grouping of an individual into an LBP or neck problems group. Despite the complexity of 43 deteminants, the first step produced an 80.8% correct prediction. This could be explained by the fact that the first variable (fear and avoidance behaviour in working conditions) was the only strong discriminating variable. Further stepwise discriminant analysis showed that coping strategies and pain experience had a discriminating power between 74 to 79.5%. A full analysis taking into account a failed factor analysis, high odds-ratios and multiple noncorrelating variables, produced a "drop-bucket" model explaining that every variable (drop) has the power to overfill the "bucket". However, it is impossible to predict which "drop" would do so. That is why the primary preventive programme deals with both the "large drops" and "small drops" in order to embrace as much variables as possible. It was decided that a primary prevention model consisting of the combination and integration of psychosocial, ergonomic, general health and management interventions (especially those that augment work satisfaction) may well reduce prevalence and incidence on LBP and neck problems (Figure 1). PSYCHOLOGICAL APPROACH - action against fear-avoidance behavior towards work and physical activity - learn how to cope with LBP/NP

ERGONOMICAL APPROACH - development of new nursing aids - improve lifting techniques and the use of lifting aids

PRIMARY AND MULTIDISCIPLINARY PREVENTION OF LOW BACK AND NECK PROBLEMS IN HOSPITAL NURSES

GENERAL HEALTH APPROACH - increase general health - increase physical fitness level

POLICY APPROACH - increase work satisfaction admission to apply other 3 approaches

Figure 1. Primary preventive programme approach.

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The anthropometric array produced a mean somatotype for the male nurses of 3.5 - 4.5 - 2.5, meaning that they had less fat, were more muscular and showed a less fragile body than the average population somatotype. For female nurses the values were 5 - 4 - 2 . There were no extreme deviations detected. The analysis of the total population indicated that the experimental group (LBP/Neck problems) a priori did not differ from the control group with the only exception being a difference between left and right trochanter height. This difference was considered coincidental. The classification of nursing tasks as a result of the job evaluation generated 70 identifiable nursing "jobs" out of which the top 10 most "heavy" ones (in terms of frequency and loading) were determined and categorised as follows: 1. giving bed-pan to corpulent or immobile patients - 2. rotation of the patient to prevent bed sores - 3. washing of older or bed-ridden patients - 4. moving patients from the bed to the toilet chair - 5. assisting helpless or para- or hemiplaegic patients in and out of bed - 6. positioning water mattresses on beds. Manual handling of patient-bed related tasks was experienced as a most "heavy" task due to a combination of a high loading factor and a high frequency factor. These tasks were subject to further research. When an adjustable bed-height was proposed for the performance of these standard nursing tasks, the observed mean changes in bed-height were 6.4 cm (± 4.4 cm, Range: +14 cm to -2 cm). There was no relation between the height adjustments and anthropometric variables (body length and hip height). However, male nurses preferred lower bed-heights as opposed to the higher bed-heights chosen by the female nurses. VICON®-analyses and Kistler® ground-force platform data showed the occurrence of both maximal peak compression and time-integrated shear forces during the straight-up positioning of a patient into bed. Adjusting the bed-height did not decrease significantly the peak compression forces. However, when integrated in time, significant differences were found. Summation of tasks as opposed to the analysis of a single task supports the importance of the time factor. Results of the EMG analyses did not show important significant differences between bed-height conditions (quantitative analysis) but did support the underlying assumption that adapting the bed-height reduces the muscular activity. According to task characteristics there was an increase or a decrease of muscular activity (iEMG) but even so, it was non-significant in all cases. As these EMG findings represented a very small moment in time (1 minute or less), they may not reveal the consequences for MSD of this adjustment as opposed to the importance within fatiguing situations, after a day's work for instance. A qualitative analysis showed that for both female and male nurses, after their bed-height adjustment, an adaptation in muscular co-activation in terms of a shift of the greatest muscular activity towards the opposite half of the body occurred as a means of adapting to the loading. A second aspect of adaptation to loading which provided an argument for adjusting bed-heights, is that the qualitative analysis showed that in carrying out specific asymmetrical tasks, the load evidently is taken unilaterally (body side) by the side which should or is supposed to take the load in an arbitrary SBHC. By definition this is a wrong height for everybody. This faulty placement may mean that the loading is forced to be taken by a non-comfortable coupled muscle pattern due to the height of the bed rather than the body position in relation to the load. Based upon the 8-hours spinal movement registration, the nursing profession required a change of attitude every 2 seconds. Female nurses tended to move the spine more than their male colleagues. Analyses of spinal movements in ABHC, during standard nursing tasks, showed a non-significant change in ROM when related

T. Reilly et al. /Musculoskeletal Disorders in Health-Related Occupations

to the SBHC. An economically beneficial shift towards time spent (exposure) in a less dangerous zone (closer to the erect position) was observed. Taking into account both NIOSH and OWAS guidelines (National Institute for Occupational Safety and Health, Work practice guide for manual lifting, 1981), the use of an adjustable bedheight during standard nursing tasks had significant ergonomic implications on the quality of spinal motion. The effects of nursing tasks on spinal shrinkage were evident mainly in the cervical spine. After a full day's work, a significant (p<0.05) cervical spinal shrinkage was observed (4.56 mm ± 1.54), although no significant difference could be detected between the experimental (LPB/Neck problems) and control groups. According to the literature the neck is, besides the lumbar region, the second most affected musculoskeletal area. The neck should be diagnosed for causal pathologies as a preventive measure for further complications and not only as a consequence of a reported current neck problem. A study on coupled motion in the cervical spine revealed the existence of anatomical and functional variations, in particular left-right asymmetric of cervical vertebrae, indicating that very often the spinal segments move in the conditions of articular tropism combined with asymmetric lever arms (Van Roy etal., 1997). Neither isokinetic or isoinertial force registrations showed a general relation with the prevalence of neck problems/low-back problems. However, the total flexionextension ROM and the maximal speed of the latero-flexion component during a flexion-extension movement showed a significant (p<0.05) difference between the experimental and control groups. A noteworthy result of the EUROFIT-test was that the nursing population, as opposed to their age-matched civil servants, scored significantly lower on the fitness items (Hand grip strength, Sit-up and Bent arm hang) except for the shuttle-run (10x5 m) on which they were significantly better. Nevertheless no correlation could be found with LBP life-time prevalence. Only 3.5 hours were spent in the first year of the nursing profession's curriculum on the educational aspects of handling and lifting techniques. Furthermore, when multiple educational institutes were considered, a maximum of 20% fulfilled the requirements of a 10 to 20 hours course in handling techniques. Directorates of schools stated that although it is desirable, it is practically impossible to realise such education. Back school intervention certainly would create a change in attitudes. Factory workers reported a lower relation between LBP and physical activities after the intervention as opposed to before. Interdisciplinary considerations based upon the perceived exertion, force, EMG and CMR results, suggested that the SBHC is already close to optimal for the majority of the nurses. Since the rating of perceived exertion did not show a significant difference when comparison was made between the two conditions, the influence of a height adjustment on the muscular activity probably depended on the capability of the nurses to adjust until sufficient reduction of muscular activity is reached, hence determining the optimal bed-height with respect to the specificity of the nursing task. Where EMG could not show the influence of the differences in body positions in space on the muscular activity, the CMR could demonstrate the attitude shift towards less dangerous zones. Additionally the VICON analyses indicated significant differences in shear and in compression forces at the level of L5/S I when integrated in time. Conclusively, bed-height adjustments are considered as very meaningful on a long term basis to prevent LBP.

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Experts' opinions on further factor and discriminant analyses of the multidisciplinary approach stated that extending this procedure would not be desirable because of small populations but most of all because it would not deliver an in-depth study of the ergonomic approach of the preventive programme. The addition of such a statistical approach would not increase the clustering of variables with respect to the prevalence of LBP/Neck problems and therefore was considered as not valuable for further model development. In conclusion, the overall research succeeded in building a glossary of ergonomic, general health and psycho-social factors that influenced the MSD in general and the low-back problems/neck problems in particular. As the model is multivariate so the prevention programme also has to be. With respect to its feasibility, after a dialogue with the academic hospital management and a multifaceted nursing school, and in accordance with staff of educational institutes, policy makers and hospital managers, there seems to be an enthusiasm developing for implementing the multidisciplinary preventive model as a preventive programme. Complete and detailed design of this preventive programme built on that which is theoretically derived will be part of future research. The translation and implementation of the theoretical model into a practical one, followed by a longitudinal evaluation, might well provide proof for its effectiveness in preventing lower back and neck problems. In early stages, however, fitness of nursing personnel can be tackled as well as the use of adjustable bed-heights and correct handling techniques. The use of ergonomically designed aids and devices may well be considered as very important for the health status of a nurse on a long term basis. The interdisciplinary analysis and the questionnaires support the need for adequate training of nursing personnel. Since an ergonomic intervention alone will be insufficient to limit MSD in nursing personnel. A psychosocial approach incorporating the improvement of the work satisfaction should be a cornerstone for unions, policy makers and occupational physicians. Finally, supported by the multidisciplinary study indicating the importance of the time factor, the implementation of a preventive programme has to be considered on a long-term basis. Moreover, the database gives insights on which interventions would be successful and which are likely not to be. c) Synthesis of work Lifetime prevalence of MSDs was 49% with the lower back area being the anatomical site most affected. In total, MSDs accounted for 19% of all sickness absences in the previous year. The prevalence of MSDs varied according to the specialty in which the individual worked. Most of those who perceived they could attribute their MSD to a specific cause implicated lifting as a significant risk factor, although a regression analysis failed to confirm lifting as the prime cause of MSD. The risk assessment indicated that manual handling scored highly but was equalled in score by static holding tasks, the detrimental importance of which is often neglected. Both epidemiological studies (Liverpool and Brussels) determined the importance of psychosocial, general health, ergonomic and management aspects with respect to prevalence of LBP and neck problems. The interdisciplinary approach revealed that the ergonomic impact of the use of bed-height adjustments was beneficial. Training of nursing personnel in handling and lifting techniques is currently inadequate both during their education and in the professional environment. Heart rate was deemed to be a valid indicator of occupational strain when locomotion and large muscle groups were engaged in intermittent activity.

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Physiological strain and spinal shrinkage were not influenced by alterations in the work-rest schedules primarily because of the moderate work load. The length and frequency of rest breaks would be more important should the intensity of the work be increased. Any manipulations of work-rest schedules must also comply with the wishes and personal preferences of the workers. The preventive model that was developed is distinguished by being multivariate in nature. The time factor dictates a long term consideration of implementing a multidisciplinary preventive programme and its evaluation with respect to the prevention of LBP and neck problems. d) Results relating to individual objectives and primary approaches i) ii) iii) iv) v)

Lower-back pain is the most commonly experienced MSD and point prevalence of all musculoskeletal disorders was 49%. Manual handling tasks and tasks involving a static component have the highest potential risk of resulting in MSD. The prevalence of LBP, neck problems and MSD is based on a multivariate interaction within the healthcare professions, Alterations to existing work-rest schedules by manipulating the length of intermissions have only marginal impact on load reduction, The primary preventive programme is to be considered on a longitudinal basis so that its impact in practice can be properly evaluated.

Acknowledgements i)

Dr. Glynne Thomas of the Occupational Health Department of The Broadgreen Hospital N.H.S. Trust. ii) Southport and Formby District General Hospital, iii) Dr. Kim Burton, Huddersfield University, iv) The staff and personnel of the Academisch ziekenhuis VUB, Brussel, Belgium; Maria-Middelares ziekenhuis, St.Niklaas, Belgium; Middeleheim ziekenhuis, Wilrijk, Belgium; Erasmus ziekenhuis, Borgerhout, Belgium, v) All hospitals in Belgium, vi) Prof. dr. W. Duquet, Dept. of Human Biometry and Biomechanics, Vrije Universiteit Brussels, Belgium, vii) All staff and subjects involved in any of the studies.

References Helander, M. G. and Quance, L. A. (1990). Effect of work-rest schedules on spinal shrinkage in the sedentary worker. Applied Ergonomics, 21, 279-284. Lee, Y. and Chiou, W. (1995). Ergonomic analysis of working posture in nursing personnel: example of modified Ovako Working Analysis System application. Research in Nursing & Health, 18, 6775. Van Roy, P., Caboor, D., De Boelpaep, S., Barbaix, E. and Clarijs, J. P. (1997). Left-right asymmetries and other common anatomical variants of the first cervical vertebra, Part 1: Leftright asymmetries in Cl vertebrae. Manual Therapy, 1, 24-36.

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INDEX Abdominal belt Abdominal muscles Absence from work Adipose tissue Alcohol Anatomy of the spine Anthropometry

Asymmetry Axial rotation

33 3,27 3, 55, 68-74 177 147, 151-161, 163-169 48, 54, 82 26, 137-142 137-142, 143149, 151-161, 163-169 36, 103-105 100-101

Health and safety Heart rate Hospital specialty Hospital porters Isokinetic assessment

176, 183

Job satisfaction Jumping

41-61 34-36

Kinematics Kinesiological EMG

93-98 89, 175

Lateral flexion Likert scale Locus of control

3,99 109 41-61

Menstrual cramps Metabolism Muscle actions Muscle fibres

48 1-6,117-126,172 91 91

Neck pain Nucleus pulposus

67, 97-105, 172185 26, 128, 137-142

Office chairs Osmotic pressure OWAS Oxygen deficit Oxygen uptake

31,93 25-27 42, 176 119 1-6,117-126

Personal factors Plyometrics Posture Prevention Psychological assessment Psychosocial factors

41-61 35 8,11,31,36-37, 172, 178 172-185 12 9,12,80-81

Rectus abdominis Repetitive strain injury Risk assessment

3 4 3, 7-24, 173

73-74 25-39, 127-135, 137-142, 172-185 3, 55, 74

Body density Body mass index Borg's scale

86,91,97-105, 141 143-149, 151161, 163-169 165 153 4, 117-126

Cadaver analysis Case studies Christensen's classification Coping strategies Coupled motion Cramp Creep Cross-talk

143-149, 151-161 100-104 4 41-61 97-105 42,54 30 87

Delphi method Depression index Diurnal variation

107-115 41-61 32, 123, 137-142

Eccentric actions Electromyography Energy expenditure Epidemiology Erector spinae

91 85-93, 142, 175 1-6, 117-126 7-24,41-61,6384, 171-185 3,26-27,91

Fitness Flock of Birds Fowler position

44, 176-183 97-105 28,35,80,131

Gender

137-142, 151160, 163-169

Sciatica Shrinkage

Handedness

19

Sick leave

Biomechanics Body composition

7 1-6,117-126, 129-134 18,70-73, 178-179 121-125, 127-135, 174

188

Skiing Skin Smoking Spondylosis Sports Stress

88 143-149,151-161 44,82 73 34-36,118 109-113

Task demands

Treatment Trunk rotation

85-94,109-113, 117-126,137-142 86,91,123,129, 171-184 63-84 3, 100-104

Vibration VICON

8, 25, 82 175

Weight training Work environment Working postures Work-rest ratios

32 55-56, 69, 178 1-6, 8-12, 129 117-126,127135,171-184

Telemetry

189

Appendix 1. Publications from the Biomed IV research project (Bm H4 - CT96 - 1057) i)

Research Reports Beynon, C. and Reilly, T. (2001). Spinal shrinkage during a seated break and standing break during simulated nursing tasks. Applied Ergonomics (in press). Beynon, C., Burke, J., Doran, D. and Nevill, A. (2000). Effects of activity-rest schedules on physiological strain and spinal load in hospital-based porters. Ergonomics, 18, 1763-1770. Beynon, C, Leighton, D., Nevill, A. and Reilly, T. (1998). Risk assessment design for musculoskeletal disorders in healthcare professionals. In: Contemporary Ergonomics 1998 (edited by M. A. Hanson), pp. 56-60. London: Taylor and Francis. Beynon, C., Leighton, D, Reilly, T. and Nevill, A. (1998). A multidisciplinary investigation into musculoskeletal disorders in healthcare professionals. In: Global Ergonomics (edited by P. A. Scott, R. S. Bridger and J. Charteris), pp. 81-89. Amsterdam: Elsevier. Bot, S. D. M. and Hollander, A. P. (2000). The relationship between heart rate and oxygen uptake during non-steady state exercise. Ergonomics, 18, 1578-1592. Caboor, D. E., Verlinden, M. O., Zinzen, E., Van Roy, P., van Riel, M. P. and Clarys, J. P. (2000). Implications of an adjustable bed height during standard nursing tasks on spinal motion, perceived exertion and muscular activity. Ergonomics, 18, 1771-1780. Van Roy, P., Caboor, D., De Boelpaep, S., Barbaix, E. and Clarijs, J. P. (1997). Left-right assymetries and other common anatomical variants of the first cervical vertebra, Part I: Leftright assymetries in CI vertebrae. Manual Therapy, 1, 24-36. Verlinden, M., Caboor, D., Zinzen, E, Van Roy, P. and Clarys, J. P. (1999). Ergonomic implications of an adjustable bed-height during standard nursing operations: muscular activity (EMG). Communications to the 4th International Conference in Sport, Leisure and Ergonomics. Journal of Sports Sciences, 17, 926. Zinzen, E., Caboor, D., Verlinden, M., Catrysse, E., Duquet, W., Van Roy, P. and Clarys J. P. (2000). Will the use of different prevalence rates influence the development of a primary prevention programme for low back problems? Ergonomics, 18, 1789-1803.

ii) Communications Caboor, D., Zinzen, E., Van Roy, P. and Clarys, J. P. (1996). Job evaluation in nursing personnel using a modified Delphi-survey. Communication to the Second International Conference on Health in the Workplace, Liverpool, 2-4 April. Caboor, D., Zinzen, E., Verlinden, M., Van Laere, I., Van Roy, P. and Clarijs, J. P. (1998). Ergonomical comparison between left and right back and legs muscle activity using kinesiological surface EMG, during a typical nursing task. XIIISEK Congress Abstract Book, Montreal, June 27-30. Verlinden, M., Caboor, D., Zinzen, E., Van Roy, P., Van Laere, I. and Clarijs, J. P. (1998). Ergonomic comparison between left and right back and legs' muscle activity, using kinesiological surface EMG, during a typical nursing task. XII ISEK Congress Abstract Book, Montreal, June 27-30.

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Author Index Alewaeters, K. Baeyens, J.P. Beynon, C. Bot, S.D.M. Burke, J. Caboor,D. Clarys,J.P. Drinkwater, D. Hollander, A.P. Lanssiers, R. Leighton, D.J. Marfell-Jones, M. Martin, A. Reilly,T. Van Roy, P. Verlinden, M. Vermoesen, A. Zinzen,E.

163 97 7,63,127,171 117 117,171 97,107,137,171 85,97,143,151,163,171 151 117,171 97 7,171 143 151 v, 1,25,63,85,117,171 97,171 97,171 97 41,97,163,171