- Email: [email protected]
Ergonomics in the Workplace
Ergonomics in the Workplace E N CORLETT PhD DSc CEng FIProdE FIMechE ABPsS FErgS Fellow Human Factors Society (USA) Director. Instilute for Occupational Ergonomics
L McATAMNEY BSc GradDipPhty MAPA Member, Ergonomic Society of Australia Physiotherapist. studying in the Department of Production Engineering and Production Management University of Nottingham
Key Words:
Ergonomics, physiotherapy. work-place, work-related musculoskeletal factors.
Summary: This paper introduces ergonomics, its application to the work-
place and the potential involvement of physiotherapists in the area. Ergonomics is the matching of environments, tasks, products, and work organisations to people’s abilities and capacities. In the work-place, ergonomic knowledge can be applied to improve productivity and the well-being of the workers. The application of this knowledge is not always realised and a number of reasons and questions are offered for this. Physiotherapists possess a firm theoretical and practical base on which to develop ergonomic and occupational health skills, especially in the musculoskeletal areas. Physiotherapy as a profession has an important role in the application of ergonomics and the challenge before us is to broaden our sights and take our skills into the work-place.
ERGONOMICS should be a natural part of the work-place. It is the matching of environments, tasks, products, and so on, to people‘s abilities and capacities. For centuries there have been descriptions of the need and importance of matching the workers’ abilities, capacities and health with their craft, the raw materials they handle, their working postures and working environment. Even so, ergonomics is a relatively recent science developed out of the needs in World War II to design machinery and equipment for maximum function and control in war conditions and to design industrial jobs for the growing female workforce. How then can work-places be created without the influence of ergonomics being evident? The fact is that many work-places show little evidence of ergonomics, and we must admit that the reason this state of affairs continues is that it has always existed! ‘We‘ve never had to bother before and everything’s OK - why bother now?‘ or ’That‘s just part of the j o b or ‘It would cost too much to change’ are common comments. If these statements were true then the conclusion would be correct, yet every physiotherapist could probably quote instances where it is quite definitely wrong. Why it appears to be true is because the link between work conditions and diseases, performance, errors, accidents or other responses is not always immediate or self-evident. Furthermore there is a too-ready assumption by some management that any lack of performance or complaints indicates malingering, ie that people should get on with it and overcome the workplace circumstances. When today’s general standard of living
physiotherapy, September 1988, vd 74, no 9
Biography: Professor Nigel Corlett is currently head of the Department of Production Engineering and Production Management at the University of Nottingham, and also director of the University’s Institute for Occupatioiial Ergonomics. Prior to this appointment he was professor of industrial ergonomics at the department of engineering production at Birmingham University, joining that department in 1957. After industrial experience and war service in the Fleet Air Arm he graduated in engineering in 1948 and continued to work in industry. His posts have included factory management and head of design and development for a large domestic equipment company. Professor Corlett has a DSc in Ergonomics from London University and is a Fellow of the Ergonomics Society and of the Human Factors Society. He is also a Fellow of the Institute of Mechanical Engineering. Lynn McAtamney is currently studying ergonomics at the Department of Production Engineering and Production Management, University of Nottingham. In 1986 she was awarded a one-year National Occupational Health and Safety Commission scholarship to undertake postgraduate studies in ergonomics and has recently returned to continue studies towards a PhD. Lynn has a BSc in anatomy from the University of New South Wales, Australia, and a postgraduate diploma in physiotherapy from Cumberland College of Health Sciences, Sydney. Since her graduation in 1980 she has worked in general, orthopaedic and sports physiotherapy. Since 1984 she has worked in occupational ergonomics research, teaching and consultation with the Commonwealth Institute of Health and the newly formed National Institute of Occupational Health and Safety. Lynn has been actively involved in the National Special Group in Ergonomics and Occupational Health of the Australian Physiotherapy Association and in the Ergonomics Society of Australia.
and advances in technology are considered then the existence of such unchanged industrial conditions and the non-ergonomic use of new technology must be seriously questioned. We have today on the one hand a greater‘understanding of the matching of people and work, together with more sophisticated, adaptable technology, and on the other hand a shortfall in the application of this knowledge t o many work-places. Where does the physiotherapist’s role lie in this? If we look at what people are trying t o achieve by their work it is clear that they are fighting against difficulties. They may have to stand on one leg to operate a pedal, maintain a flexed posture to reach the operating surfaces, maintain a twisted posture to see over something or achieve good vision of the task. The activities may be repeated at frequent intervals with no chance of respite or choice of time, or there may be a need for instant alertness to things of little intrinsic interest. Such situations are widespread, stressful and damaging to people and inefficient in performance terms, yet assumed t o be of no importance. Using Ergonomics in Hand Tool Design When observing people at work it is not unusual to see the person adapting to accommodate the equipment or tool they are using. One example is the use of hand tools, both industrial and domestic. In Sweden, Japan, the United States and to an extent in the United Kingdom, work has been done to redesign hand tools for better fit and function (Fraser,
475
1980: Greenberg and Chaffin, 1977; Miller and Freivalds, 1987; Lindstrom in Fraser, 1980). However, we recently reviewed the use of pliers and found a number of possibilities for changing the design to suit the user's comfort and functional capacity better. Interestingly, although the design fails in a number of ways, one may wonder w h y manufacturers have not considered improving their product. Is it that pliers are not commonly used for long periods of time (except perhaps in manufacturing industry) so people put up with discomfort knowing they will soon be finished? Even so one study (Monod in Fraser, 19801, showed that even with short holding times (10% of the task time) exhaustion can be experienced after 30 minutes of working if the person is using a force which is approaching their maximal strength. If we look at pliers there are three main factors to consider. They are: .The endurance and working position of the hand. @The hand size and hand strength. .The force-bearing area of the handles. The working position of the hand will affect the development of muscle fatigue, discomfort and reduced performance. If the width between the handles is too large or small for the span of the hand, the person is contracting forcibly from a position of reduced muscle efficiency. The relationship of the handle and jaw axes will influence the wrist and arm position, especially important when twisting and/or forceful actions are required. One frequent posture adopted t o use pliers is w i t h the wrist in extreme ulnar deviation, eg when using the ends of the jaws. If the handles are too narrow or have ridges then the forcebearing area is reduced and a greater pressure is exerted on t o the soft tissue structures of the fingers (including the flexor tendons, vascular tissue and so on). Physical Well-being and Work If we talk t o people about their jobs they will tell us, directly or indirectly, about the effects of their work, from which it is often possible t o derive the causes of these effects. Records of discomfort at intervals throughout the day, of changes in activity or in postures, are all indicative of problems. Studying the output, rest pauses or errors and how they are distributed across the working hours are also fruitful ways of revealing possible problems. A study which is under way at present (McAtamney and Corlett) is investigating the effect of high task loading on some aspects of the person's physical well-being. This developed out of a large study by McPhee in Australia (1988) which included an investigation of work-related musculoskeletal discomfort (then called repetition strain injury) in data entry operators using video display units (VDUs). This present study assessed the electromyographic (EMG) activity in the trapezius muscle, the stress and arousal mood levels, perceived physical discomfort. and the performance of 20 female secretaries when asked t o perform t w o %-hour VDU tasks. Both were data entry tasks similar t o those done in a financial institution, but one task was presented so that the secretary was constantly pushed t o the limit of her capabilities, while the other was done at the secretary's preferred work capacity. Preliminary results have shown an almost double error rate in the loaded task while there was a small drop in the amounl of work completed compared t o the non-loaded task. There was a greater increase in the stress rating and decrease in the arousal rating (indicating the tendency t o boredom and
476
lack of stimulation) when performing the loaded task, as compared t o the non-loaded task. The EMG patterns varied among the subjects with an overall significant trend towards greater EMG activity in the loaded task despite the fact that the same movements and postures were required for each task. The level of physical discomfort increased with time over the t w o trials regardless of which trial was performed first, although if the loaded task was performed first the physical discomfort trend was greater. In ergonomics it is always important to keep research close t o the work-place needs. For example a number of studies have designed predictive models or measured the forces required for pushing and pulling. This is a very important area in manual handling and back pain research; however the application of the knowledge has been limited because it has often been in either the frontal or saggital planes. Obviously this is difficult t o apply t o a mechanic working in a pit on an engine above him or someone working in a confined space. A recent study by Haslegrave, Tracy and Corlett (1987) ,has assessed the strength and reach capabilities of workers in the laboratory t o provide information on industrial maintenance ,tasks involving overhead working. They found that subjects could exert much greater forces when lifting upwards or pressing downwards than they were able t o exert in the horizontal plane. Also they found that the amount of force t o be applied vertically was greatest at the maximum reach distance while the ability t o apply force horizontally was greater at close reach distances. Physiotherapy in the Work-place Those physiotherapists who have worked with people in their work-place will know how well suited physiotherapy skills and techniques are t o the assessment and evaluation of ergonomic factors and t o prevention of work-related musculoskeletal disorders. M e t h o d s f o r assessing t h e work-place include questionnaires, direct observation, observation using tools, measurement of anthropometric, physiological, psychological and productivity factors (Wilson eta/, 1987). With some training the physiotherapist has a highly suitable background knowledge for this work. It widens the application of physiotherapy t o the preventive aspect of health and well-being and augments the existing treatment and rehabilitation role of the profession. Ergonomics is a wide scope multidisciplinary science where solutions are reached with input from a number of different skills. When working in the area of ergonomics, attention must be given not only t o the details of the workplace and the tasks but also t o the person as a whole. Those working in the area will recognise that more can be done if the psychological and social factors are considered along with the physical aspects. Job satisfaction, isolation, communication channels in the organisation, language barriers, environmental conditions and so on may be important factors in ergonomic assessments of the workplace. This requires an understanding of other areas in ergonomics and the recognition of problems which may require the skills of other professionals. Depending upon the problem or the working environment, input may come from the ergonomist, occupational physician, hygienist, unions, Health and Safety Executive, designer, architect, occupational therapist, occupational psychologist, manager, supervisor, safety officer, economist, equipment specialists and the occupational physiotherapist. Most importantly, input must come from the workers themselves. The areas of ergonomics t o which physiotherapists are
physiotherapy, September 1988, vol74, no 9
directly suited are the assessment of and intervention in musculoskeletal problems and fatigue. Our understanding of functional anatomy, posture and biomechanics is used in relation t o work physiology, spinal and other joint loadings and muscle fatigue. Much confusion, scepticism and unnecessary anxiety have occurred because of the difficulty in diagnosing work-related musculoskeletal disorders. This may be due t o a number of factors, but whatever the cause, what is important is getting the person back t o full-time gainful employment. Here the physiotherapist working in the work-place may help in avoiding unnecessary suffering and costs by early diagnosis, a thorough ergonomic assessment of the situation, and appropriate intervention. The most effective time t o incorporate ergonomics into the work-place is when new work-places are being set up. It is rare that we know exactly who will use them, so they must be arranged t o suit as wide a segment of the population as possible. Most ergonomists try t o cover 9 5 % of the adult population; design for 95% of adult males would permit only about 60% of adult females t o be suited. However, the use of anthropometric tables is not enough t o ensure a good design, although it can help t o prevent a bad one. People are different in so many ways that it is advisable t o run 'fitting trials' of one sort or another. Physiotherapists provide an important input, for anthropometry is a static study of people and work-station dimensions, and what is required is the understanding of movement and functional capacity t o be applied if the investigation is to be of maximum benefit. Where the question is one of deciding o n dimensions t o suit people of different sizes and builds, a sequential procedure ot adjustment of each important work-place dimension from 'too small' t o 'too large' is followed, crossing the 'acceptable' boundaries. Using a sample embracing the population extremes, it is possible t o decide on the fixed dimensions as a whole as well as identifying the range of adjustment needed on those dimensions which should not be fixed. Where a number of activities have t o be pursued, mockups of the work-places can be prepared and the working
day's activities simulated. Many forgotten points come to light by such simple means, but it is particularly important t o use the people who will be doing the jobs for this - their knowledge is essential for success. Static models are a useful guide t o the physical factors of a work-station layout. A number of models, anthropometric measuring devices and software packages are available t o assist in assessing the 'best-fit' dimensions of the work-place. One such example is the Sammie package which originated in the University of Nottingham. With Sammie the work-place, furniture, equipment and so on can be constructed in a 3-D computer model and viewed from any direction. A human model can be changed t o represent specific percentile dimensions and also to represent different body types (mesomorph, ectomorph, endomorph). Below is an example of'two Sammie models (a 10th and 90th percentile female) seated at a VDU workstation where the height of chair and table are the same. The physical limitations for the 10th percentile female are that: 1. The forearms are resting on the hard edge of the table causing pressure on the soft tissues. 2. The elbows are flexed at an angle of less than 90 degrees causing an increase in the static loading of the elbow flexors and the wrists t o be maintained in a flexed posture. If the person was typing in this posture the flexor muscles would fatigue more quickly than if the wrist was in a neutral or slightly extended posture. 3. The seat of the chair is too high, causing pressure on the underside of the thigh muscles and indicating the need for a footstool t o give support to the feet. 4. The backrest is too high and therefore not supporting the lumbar region t o maximum benefit. The 90th percentile female at this workstation would experience the limitations of: 1. Not being able t o sit at a comfortable distance from the keyboard without her legs being caught by the lower surface of the table. 2. Having t o increase neck flexion t o maintain her line of vision t o the screen.
An example of the Sammie package assessing the optimal height of a VDU table in relation to 10th and 90th percentile females (courtesy of Sammie CAD Limited, Loughborough)
10th percentile female
PhVsiotherapn September 1988, vd 74,
9
90th percentile female
477
The solution to these limitations is the modification of the chair, screen height and table height to best fit the worker, or the use of adjustable furniture. In the past too much emphasis has been placed upon adjustable and 'ergonomic' furniture as providing the solution t o problems experienced by those using VDUs. There are a number of other very important factors to consider such as the type, duration and variety of the tasks and postures maintained, the work organisation, job satisfaction and environmental factors (Grandjean, 1981; Singleton, 1982; Chaffin and Andersson, 1984). Unfortunately it is not often we have the opportunity to incorporate ergonomics into the work-place at a developmental stage, most often we must adapt existing work-places to fit the worker better. For example, the depth of a pit from which a mechanic may work on an engine above him will dictate his neck position, his shoulder position and the amount of force he is able t o exert. If the mechanic is too tall t o fit, the neck must be held for prolonged periods in side-flexion and slight rotation. If the operator is too short then he will be at risk of shoulder and arm discomfort from having t o work from a reaching posture. The quick way out may be to employ mechanics of a certain height only and of course this sort of thinking occurred in the olden days when children worked in the mines because they were small enough t o fit. However, solutions t o this problem are relatively simple with stepped working heights, removal of objects which reduce the pit floor working surface and, importantly, a change in the design of the job so a mechanic is not working i n that position for long periods.
Broadening our Sights We reflected earlier on the shortfall of ergonomic knowledge being applied in the work-place. Not only is it necessary to incorporate ergonomics into the design of workplaces but also to educate people as to their responsibility in caring for their health and awareness of how they can manage work-place factors which may put them a t risk. Awareness and education programmes require careful introduction and review to ensure the correct knowledge is being gained and used by the workers. The physiotherapist
has proved a highly appropriate person in the awareness and education process of musculoskeletal, postural, exercise and manual material handling aspects of work. The special perspective on physical inquiries available to physiotherapists, particularly those working in occupational health, gives them considerable opportunities t o recognise many 'inadequacies in the work-place. Those experienced in the business will recognise that more can be done if they expand their understanding into other areas of ergonomics. Our own expertise tells us that our jobs are more than the physical efforts involved, important though these are. Personally expanding our own expertise, or linking with ergonomists in a joint attack, could make very many improvements to the experience, and effects, of work with widespread and all-round benefits. We hope that this special issue of Physiotherapywill encourage many in the profession to increase their interests in the subject.
REFERENCES Chaffin, D B and Andersson. G (1984). OccupationalBiomechanics, John Wiley and Sons, New York. Fraser, T M (1980). Ergonomic Principles in tht?Design of Hand Tools, International Labour Office, Geneva. Grandjean, E (1981). Fitting the Task to the Man - An ergonomic approach, Taylor and Francis, London. Greenberg, L and Chaffin, D (1977). Workers and their Tools. A guide to the ergonomic design of hand tools and small presses, Pendell Publishing Company, Michigan, USA. Haslegrave, C M, Tracy, M and Corlett, E N (1987). 'Industrial maintenance tasks involving overhead working', in: Megaw, E (ed) Contemporary Ergonomics 1987, Taylor and Francis, London. McPhee, B J (1988). 'Work-related symptoms in the neck and upper extremities of keyboard and clerical workers', thesis submitted for Master of Public Health (Occupational health), University of Sydney, Australia. Miller, G D and Freivalds, A (19871. 'Gender and handedness in grip strength - a double whammy for females', Proceedings of the Human Factors Society 31st Annual Meeting, pp 906-910. Pheasant, S (1986). Bodyspace Anthropometry, Ergonomics and Design, Taylor and Francis, London. Singleton, W T led) 11982). The Body at Work, Cambridge University Press. Wilson, J R, Corlett, E N and Manenica, I (eds) (1987). New Methods in Applied Ergonomics, Taylor and Francis, London.
The Assodation of Chartered Physiotherapists In Occupational Health Honorary aecres~ly:Mrs B M Blair, 2 Spencer Road, Strawberry Hill, Twickmharn, Middlesax TW2 6TH Membership: 106
Annual subscription: €10
Aim8: 1. To provide links between our members in occupational health. 2. To arrange courses on topics of particular interest to our members. 3. To arrange meetings at which mutual problems and interests can be discussed. 4. To negotiate terms and conditions of employment including salaries through The Chartered Society of Physiotherapy. 5. To increase the understanding of physiotherapy in occupational health.
478
physiotherapy, September 1988, vd 74, no 9
L McATAMNEY BSc GradDipPhty MAPA Member, Ergonomic Society of Australia Physiotherapist. studying in the Department of Production Engineering and Production Management University of Nottingham
Key Words:
Ergonomics, physiotherapy. work-place, work-related musculoskeletal factors.
Summary: This paper introduces ergonomics, its application to the work-
place and the potential involvement of physiotherapists in the area. Ergonomics is the matching of environments, tasks, products, and work organisations to people’s abilities and capacities. In the work-place, ergonomic knowledge can be applied to improve productivity and the well-being of the workers. The application of this knowledge is not always realised and a number of reasons and questions are offered for this. Physiotherapists possess a firm theoretical and practical base on which to develop ergonomic and occupational health skills, especially in the musculoskeletal areas. Physiotherapy as a profession has an important role in the application of ergonomics and the challenge before us is to broaden our sights and take our skills into the work-place.
ERGONOMICS should be a natural part of the work-place. It is the matching of environments, tasks, products, and so on, to people‘s abilities and capacities. For centuries there have been descriptions of the need and importance of matching the workers’ abilities, capacities and health with their craft, the raw materials they handle, their working postures and working environment. Even so, ergonomics is a relatively recent science developed out of the needs in World War II to design machinery and equipment for maximum function and control in war conditions and to design industrial jobs for the growing female workforce. How then can work-places be created without the influence of ergonomics being evident? The fact is that many work-places show little evidence of ergonomics, and we must admit that the reason this state of affairs continues is that it has always existed! ‘We‘ve never had to bother before and everything’s OK - why bother now?‘ or ’That‘s just part of the j o b or ‘It would cost too much to change’ are common comments. If these statements were true then the conclusion would be correct, yet every physiotherapist could probably quote instances where it is quite definitely wrong. Why it appears to be true is because the link between work conditions and diseases, performance, errors, accidents or other responses is not always immediate or self-evident. Furthermore there is a too-ready assumption by some management that any lack of performance or complaints indicates malingering, ie that people should get on with it and overcome the workplace circumstances. When today’s general standard of living
physiotherapy, September 1988, vd 74, no 9
Biography: Professor Nigel Corlett is currently head of the Department of Production Engineering and Production Management at the University of Nottingham, and also director of the University’s Institute for Occupatioiial Ergonomics. Prior to this appointment he was professor of industrial ergonomics at the department of engineering production at Birmingham University, joining that department in 1957. After industrial experience and war service in the Fleet Air Arm he graduated in engineering in 1948 and continued to work in industry. His posts have included factory management and head of design and development for a large domestic equipment company. Professor Corlett has a DSc in Ergonomics from London University and is a Fellow of the Ergonomics Society and of the Human Factors Society. He is also a Fellow of the Institute of Mechanical Engineering. Lynn McAtamney is currently studying ergonomics at the Department of Production Engineering and Production Management, University of Nottingham. In 1986 she was awarded a one-year National Occupational Health and Safety Commission scholarship to undertake postgraduate studies in ergonomics and has recently returned to continue studies towards a PhD. Lynn has a BSc in anatomy from the University of New South Wales, Australia, and a postgraduate diploma in physiotherapy from Cumberland College of Health Sciences, Sydney. Since her graduation in 1980 she has worked in general, orthopaedic and sports physiotherapy. Since 1984 she has worked in occupational ergonomics research, teaching and consultation with the Commonwealth Institute of Health and the newly formed National Institute of Occupational Health and Safety. Lynn has been actively involved in the National Special Group in Ergonomics and Occupational Health of the Australian Physiotherapy Association and in the Ergonomics Society of Australia.
and advances in technology are considered then the existence of such unchanged industrial conditions and the non-ergonomic use of new technology must be seriously questioned. We have today on the one hand a greater‘understanding of the matching of people and work, together with more sophisticated, adaptable technology, and on the other hand a shortfall in the application of this knowledge t o many work-places. Where does the physiotherapist’s role lie in this? If we look at what people are trying t o achieve by their work it is clear that they are fighting against difficulties. They may have to stand on one leg to operate a pedal, maintain a flexed posture to reach the operating surfaces, maintain a twisted posture to see over something or achieve good vision of the task. The activities may be repeated at frequent intervals with no chance of respite or choice of time, or there may be a need for instant alertness to things of little intrinsic interest. Such situations are widespread, stressful and damaging to people and inefficient in performance terms, yet assumed t o be of no importance. Using Ergonomics in Hand Tool Design When observing people at work it is not unusual to see the person adapting to accommodate the equipment or tool they are using. One example is the use of hand tools, both industrial and domestic. In Sweden, Japan, the United States and to an extent in the United Kingdom, work has been done to redesign hand tools for better fit and function (Fraser,
475
1980: Greenberg and Chaffin, 1977; Miller and Freivalds, 1987; Lindstrom in Fraser, 1980). However, we recently reviewed the use of pliers and found a number of possibilities for changing the design to suit the user's comfort and functional capacity better. Interestingly, although the design fails in a number of ways, one may wonder w h y manufacturers have not considered improving their product. Is it that pliers are not commonly used for long periods of time (except perhaps in manufacturing industry) so people put up with discomfort knowing they will soon be finished? Even so one study (Monod in Fraser, 19801, showed that even with short holding times (10% of the task time) exhaustion can be experienced after 30 minutes of working if the person is using a force which is approaching their maximal strength. If we look at pliers there are three main factors to consider. They are: .The endurance and working position of the hand. @The hand size and hand strength. .The force-bearing area of the handles. The working position of the hand will affect the development of muscle fatigue, discomfort and reduced performance. If the width between the handles is too large or small for the span of the hand, the person is contracting forcibly from a position of reduced muscle efficiency. The relationship of the handle and jaw axes will influence the wrist and arm position, especially important when twisting and/or forceful actions are required. One frequent posture adopted t o use pliers is w i t h the wrist in extreme ulnar deviation, eg when using the ends of the jaws. If the handles are too narrow or have ridges then the forcebearing area is reduced and a greater pressure is exerted on t o the soft tissue structures of the fingers (including the flexor tendons, vascular tissue and so on). Physical Well-being and Work If we talk t o people about their jobs they will tell us, directly or indirectly, about the effects of their work, from which it is often possible t o derive the causes of these effects. Records of discomfort at intervals throughout the day, of changes in activity or in postures, are all indicative of problems. Studying the output, rest pauses or errors and how they are distributed across the working hours are also fruitful ways of revealing possible problems. A study which is under way at present (McAtamney and Corlett) is investigating the effect of high task loading on some aspects of the person's physical well-being. This developed out of a large study by McPhee in Australia (1988) which included an investigation of work-related musculoskeletal discomfort (then called repetition strain injury) in data entry operators using video display units (VDUs). This present study assessed the electromyographic (EMG) activity in the trapezius muscle, the stress and arousal mood levels, perceived physical discomfort. and the performance of 20 female secretaries when asked t o perform t w o %-hour VDU tasks. Both were data entry tasks similar t o those done in a financial institution, but one task was presented so that the secretary was constantly pushed t o the limit of her capabilities, while the other was done at the secretary's preferred work capacity. Preliminary results have shown an almost double error rate in the loaded task while there was a small drop in the amounl of work completed compared t o the non-loaded task. There was a greater increase in the stress rating and decrease in the arousal rating (indicating the tendency t o boredom and
476
lack of stimulation) when performing the loaded task, as compared t o the non-loaded task. The EMG patterns varied among the subjects with an overall significant trend towards greater EMG activity in the loaded task despite the fact that the same movements and postures were required for each task. The level of physical discomfort increased with time over the t w o trials regardless of which trial was performed first, although if the loaded task was performed first the physical discomfort trend was greater. In ergonomics it is always important to keep research close t o the work-place needs. For example a number of studies have designed predictive models or measured the forces required for pushing and pulling. This is a very important area in manual handling and back pain research; however the application of the knowledge has been limited because it has often been in either the frontal or saggital planes. Obviously this is difficult t o apply t o a mechanic working in a pit on an engine above him or someone working in a confined space. A recent study by Haslegrave, Tracy and Corlett (1987) ,has assessed the strength and reach capabilities of workers in the laboratory t o provide information on industrial maintenance ,tasks involving overhead working. They found that subjects could exert much greater forces when lifting upwards or pressing downwards than they were able t o exert in the horizontal plane. Also they found that the amount of force t o be applied vertically was greatest at the maximum reach distance while the ability t o apply force horizontally was greater at close reach distances. Physiotherapy in the Work-place Those physiotherapists who have worked with people in their work-place will know how well suited physiotherapy skills and techniques are t o the assessment and evaluation of ergonomic factors and t o prevention of work-related musculoskeletal disorders. M e t h o d s f o r assessing t h e work-place include questionnaires, direct observation, observation using tools, measurement of anthropometric, physiological, psychological and productivity factors (Wilson eta/, 1987). With some training the physiotherapist has a highly suitable background knowledge for this work. It widens the application of physiotherapy t o the preventive aspect of health and well-being and augments the existing treatment and rehabilitation role of the profession. Ergonomics is a wide scope multidisciplinary science where solutions are reached with input from a number of different skills. When working in the area of ergonomics, attention must be given not only t o the details of the workplace and the tasks but also t o the person as a whole. Those working in the area will recognise that more can be done if the psychological and social factors are considered along with the physical aspects. Job satisfaction, isolation, communication channels in the organisation, language barriers, environmental conditions and so on may be important factors in ergonomic assessments of the workplace. This requires an understanding of other areas in ergonomics and the recognition of problems which may require the skills of other professionals. Depending upon the problem or the working environment, input may come from the ergonomist, occupational physician, hygienist, unions, Health and Safety Executive, designer, architect, occupational therapist, occupational psychologist, manager, supervisor, safety officer, economist, equipment specialists and the occupational physiotherapist. Most importantly, input must come from the workers themselves. The areas of ergonomics t o which physiotherapists are
physiotherapy, September 1988, vol74, no 9
directly suited are the assessment of and intervention in musculoskeletal problems and fatigue. Our understanding of functional anatomy, posture and biomechanics is used in relation t o work physiology, spinal and other joint loadings and muscle fatigue. Much confusion, scepticism and unnecessary anxiety have occurred because of the difficulty in diagnosing work-related musculoskeletal disorders. This may be due t o a number of factors, but whatever the cause, what is important is getting the person back t o full-time gainful employment. Here the physiotherapist working in the work-place may help in avoiding unnecessary suffering and costs by early diagnosis, a thorough ergonomic assessment of the situation, and appropriate intervention. The most effective time t o incorporate ergonomics into the work-place is when new work-places are being set up. It is rare that we know exactly who will use them, so they must be arranged t o suit as wide a segment of the population as possible. Most ergonomists try t o cover 9 5 % of the adult population; design for 95% of adult males would permit only about 60% of adult females t o be suited. However, the use of anthropometric tables is not enough t o ensure a good design, although it can help t o prevent a bad one. People are different in so many ways that it is advisable t o run 'fitting trials' of one sort or another. Physiotherapists provide an important input, for anthropometry is a static study of people and work-station dimensions, and what is required is the understanding of movement and functional capacity t o be applied if the investigation is to be of maximum benefit. Where the question is one of deciding o n dimensions t o suit people of different sizes and builds, a sequential procedure ot adjustment of each important work-place dimension from 'too small' t o 'too large' is followed, crossing the 'acceptable' boundaries. Using a sample embracing the population extremes, it is possible t o decide on the fixed dimensions as a whole as well as identifying the range of adjustment needed on those dimensions which should not be fixed. Where a number of activities have t o be pursued, mockups of the work-places can be prepared and the working
day's activities simulated. Many forgotten points come to light by such simple means, but it is particularly important t o use the people who will be doing the jobs for this - their knowledge is essential for success. Static models are a useful guide t o the physical factors of a work-station layout. A number of models, anthropometric measuring devices and software packages are available t o assist in assessing the 'best-fit' dimensions of the work-place. One such example is the Sammie package which originated in the University of Nottingham. With Sammie the work-place, furniture, equipment and so on can be constructed in a 3-D computer model and viewed from any direction. A human model can be changed t o represent specific percentile dimensions and also to represent different body types (mesomorph, ectomorph, endomorph). Below is an example of'two Sammie models (a 10th and 90th percentile female) seated at a VDU workstation where the height of chair and table are the same. The physical limitations for the 10th percentile female are that: 1. The forearms are resting on the hard edge of the table causing pressure on the soft tissues. 2. The elbows are flexed at an angle of less than 90 degrees causing an increase in the static loading of the elbow flexors and the wrists t o be maintained in a flexed posture. If the person was typing in this posture the flexor muscles would fatigue more quickly than if the wrist was in a neutral or slightly extended posture. 3. The seat of the chair is too high, causing pressure on the underside of the thigh muscles and indicating the need for a footstool t o give support to the feet. 4. The backrest is too high and therefore not supporting the lumbar region t o maximum benefit. The 90th percentile female at this workstation would experience the limitations of: 1. Not being able t o sit at a comfortable distance from the keyboard without her legs being caught by the lower surface of the table. 2. Having t o increase neck flexion t o maintain her line of vision t o the screen.
An example of the Sammie package assessing the optimal height of a VDU table in relation to 10th and 90th percentile females (courtesy of Sammie CAD Limited, Loughborough)
10th percentile female
PhVsiotherapn September 1988, vd 74,
9
90th percentile female
477
The solution to these limitations is the modification of the chair, screen height and table height to best fit the worker, or the use of adjustable furniture. In the past too much emphasis has been placed upon adjustable and 'ergonomic' furniture as providing the solution t o problems experienced by those using VDUs. There are a number of other very important factors to consider such as the type, duration and variety of the tasks and postures maintained, the work organisation, job satisfaction and environmental factors (Grandjean, 1981; Singleton, 1982; Chaffin and Andersson, 1984). Unfortunately it is not often we have the opportunity to incorporate ergonomics into the work-place at a developmental stage, most often we must adapt existing work-places to fit the worker better. For example, the depth of a pit from which a mechanic may work on an engine above him will dictate his neck position, his shoulder position and the amount of force he is able t o exert. If the mechanic is too tall t o fit, the neck must be held for prolonged periods in side-flexion and slight rotation. If the operator is too short then he will be at risk of shoulder and arm discomfort from having t o work from a reaching posture. The quick way out may be to employ mechanics of a certain height only and of course this sort of thinking occurred in the olden days when children worked in the mines because they were small enough t o fit. However, solutions t o this problem are relatively simple with stepped working heights, removal of objects which reduce the pit floor working surface and, importantly, a change in the design of the job so a mechanic is not working i n that position for long periods.
Broadening our Sights We reflected earlier on the shortfall of ergonomic knowledge being applied in the work-place. Not only is it necessary to incorporate ergonomics into the design of workplaces but also to educate people as to their responsibility in caring for their health and awareness of how they can manage work-place factors which may put them a t risk. Awareness and education programmes require careful introduction and review to ensure the correct knowledge is being gained and used by the workers. The physiotherapist
has proved a highly appropriate person in the awareness and education process of musculoskeletal, postural, exercise and manual material handling aspects of work. The special perspective on physical inquiries available to physiotherapists, particularly those working in occupational health, gives them considerable opportunities t o recognise many 'inadequacies in the work-place. Those experienced in the business will recognise that more can be done if they expand their understanding into other areas of ergonomics. Our own expertise tells us that our jobs are more than the physical efforts involved, important though these are. Personally expanding our own expertise, or linking with ergonomists in a joint attack, could make very many improvements to the experience, and effects, of work with widespread and all-round benefits. We hope that this special issue of Physiotherapywill encourage many in the profession to increase their interests in the subject.
REFERENCES Chaffin, D B and Andersson. G (1984). OccupationalBiomechanics, John Wiley and Sons, New York. Fraser, T M (1980). Ergonomic Principles in tht?Design of Hand Tools, International Labour Office, Geneva. Grandjean, E (1981). Fitting the Task to the Man - An ergonomic approach, Taylor and Francis, London. Greenberg, L and Chaffin, D (1977). Workers and their Tools. A guide to the ergonomic design of hand tools and small presses, Pendell Publishing Company, Michigan, USA. Haslegrave, C M, Tracy, M and Corlett, E N (1987). 'Industrial maintenance tasks involving overhead working', in: Megaw, E (ed) Contemporary Ergonomics 1987, Taylor and Francis, London. McPhee, B J (1988). 'Work-related symptoms in the neck and upper extremities of keyboard and clerical workers', thesis submitted for Master of Public Health (Occupational health), University of Sydney, Australia. Miller, G D and Freivalds, A (19871. 'Gender and handedness in grip strength - a double whammy for females', Proceedings of the Human Factors Society 31st Annual Meeting, pp 906-910. Pheasant, S (1986). Bodyspace Anthropometry, Ergonomics and Design, Taylor and Francis, London. Singleton, W T led) 11982). The Body at Work, Cambridge University Press. Wilson, J R, Corlett, E N and Manenica, I (eds) (1987). New Methods in Applied Ergonomics, Taylor and Francis, London.
The Assodation of Chartered Physiotherapists In Occupational Health Honorary aecres~ly:Mrs B M Blair, 2 Spencer Road, Strawberry Hill, Twickmharn, Middlesax TW2 6TH Membership: 106
Annual subscription: €10
Aim8: 1. To provide links between our members in occupational health. 2. To arrange courses on topics of particular interest to our members. 3. To arrange meetings at which mutual problems and interests can be discussed. 4. To negotiate terms and conditions of employment including salaries through The Chartered Society of Physiotherapy. 5. To increase the understanding of physiotherapy in occupational health.
478
physiotherapy, September 1988, vd 74, no 9