Upper Limb Disorders – Time to relax?

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TREATMENT REPORT

Upper Limb Disorders - Time to relax? Alison Smith

Key Words Occupational overuse syndrome, repetitive strain injury, keyboard operators, ergonomics, Relax Arm rest.

Summary Experiments with a small number of people showed that keyboard operators tended to find working with an arm rest more comfortable than having no support, though the results were not conclusive and further research is required.

Introduction It has been recognised for many years that disorders of the musculoskeletal system are a major source of health-related absenteeism in industry. It has also been long recognised that poor design of machines, tools, jobs and furniture can compound such problems (Van Wely, 1970; Ardnt, 1983). Figure 1 shows a simplified model for the development of musculoskeletal disorders.

Individual capacity Physical work demands

Imbalance, Y m u s c u l o s k e l e t a l ~ ~ s y c~ological

stress stress

Musculoskeletal strain

J- Perceived pain, fatigue

/ Rest, job redesign

Recovery + \

No action I t

Chronic disorder

Fig 1: Simplified model for the development of musculoskeletal disorders (from Kilbom, 1988)

There are many causes of musculoskeletal disorders, one of which is the adoption of static or constrained postures. Any working position places a load on the musculoskeletal system and discomfort, pain, fatigue and disability will be influenced by the amount, duration and distribution of this load (Ardnt, 1983). Dynamic muscular activity will generally sustain loading by ensuring suffi- cient nutritive blood flow to active muscles, and facilitating removal of waste products causing ischaemic pain and localised fatigue (Grandjean, 1987; Chaffin, 1973). In practice, most tasks tend

to be a mixture of dynamic and static muscle activity, with static expenditure rarely greater than 20% of maximum. However, if the static loading is long lasting or repeated daily, patho- logical changes will occur, resulting in conditions such as arthritis, tendonitis, or peritendonitis (Grandjean, 1987). Grieve (1992), Grandjean and Hunting (1977) and Grandjean (1987) note that such damage has been observed in muscles, tendons, joint capsules, joints, ligaments, nerves and intervertebral discs.

Highly repetitive activities, ie those with repeated cycle times less than 30 seconds without rest, have been found to contribute to musculoskeletal disease by causing inflammation of body tissue (Grandjean and Hunting, 1977; Grieve, 1992; Hunting et al, 1981; Anderson, 1984; Ardnt, 1983; Moore et al, 1991). According to Grieve (1992) the detrimental effects of repeated movement are increased by: 1. Increased load or force. 2. Prolonged static loading. 3. Increased speed of movement. 4. Those movements requiring strain and preci- sion under conditions of proximal static loading, eg keyboard operation. 5. Adoption of extreme joint positions, eg combined extension, adduction and pronation of the wrist as seen when typing. Repetitive movement under these conditions will perpetuate trauma, prevent resolution of inflammation and lead to chronicity.

It is recognised that some people will be more predisposed to injury than others even when exposed to the same work conditions. Reasons for this are unclear. In addition, a correlation between psychological stress and musculoskeletal complaints has been observed (Ardnt, 1983; Bammer and Bignault, 1987; Waersted et al, 1991).

Occupational Overuse Syndrome What Is It? Occupational overuse syndrome (OOS), formerly termed repetitive strain injury (RSI) can occur in any part of the body, but is mainly observed in the upper limb. There is much disagreement as to its pathology. Indeed, each patient may present with different combinations of tissue involvement

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(Barrett, 1987). Boyling (1991) defines RSI as ‘A collective term for those conditions characterised by discomfort or persistent pain in the muscles, tendons, and other soft tissues. This can be a clearly-defined clinical condition or an ill-defined symptom complex.’ Others would say that it bears the hallmarks of a ‘sociopolitical phenomenon’ rather than a medical condition, and is used to bring attention to job dissatisfaction or an attempt at monetary gain (Barton, 1989; Spillane and Deves, 1987).

Size of the Problem 00s strikes at half a million people per year in the UK alone. One-third of all reported injuries a t work are disorders of the hands, fingers, wrist, elbow or shoulders (Business Life, 1992). Recently, professions undertaking prolonged keyboard work such as journalists and data inputters have been particularly hard hit, but in fact symptoms associated with 00s have been recognised for hundreds of years. The Times (1992) reported that some of the earliest cases were noted in the leather beaters of ancient Babylon! The cost to industry is now no longer just in terms of lost working hours. Litigation claims of $50,000 to $100,000 in Australia, and $60,000 to 52100,000 in the UK are not uncommon (The Times, 1992; Kroner, 1992).

QOS and Visual Display Unit Operators Within the past 20 years there has been a significant change in work conditions and practices. It is thought that the rapid introduction of new tech- nology without adequate understanding of its implications has contributed to the epidemic numbers of 00s cases reported (Horin, 1984). For

180 rnrn M --..

R - over the edge of the seat

I I I

H The polyurethane arm pad cushion rotates 360~. I Total length 450 mm Minimum length 300 mm Full length 150 rnrn

example, the trend towards more simplified and repetitive tasks has resulted in greater postural constraints. Relatively fixed positions of the operator’s head and arms are required t o provide proximal stability while operating a keyboard or viewing a screen. This results in static loading throughout the body, but mainly in the neck, shoulder, arm and hand area (Grandjean et a l , 1983; Laville, 1980). Increased work pace and high productivity obligations in conjunction with electric keyboards have led to a vast increase in repetitive motion, as keying rates may exceed 12,000 strokes per hour (Ardnt, 1983).

The increased incidence of RSI has led to involvement of physiotherapists in treatment of symptoms and provision of ergonomic advice. The importance of correct posture and seating has long been recognised (Chaffin and Andersson, 1984; Grandjean et al, 1977, 1983), but the value of arm supports has been less widely explored.

Arm Supports and Wrist Rests There is some controversy as to the value of arm supports and wrist rests for visual display unit (VDU) operators and light assembly workers. Many field studies have been undertaken to determine muscular loading (particularly in the trapezius), during the work cycle. About half of the published studies report decreased loading with use of supports (Schuldt et al, 1987; Weber et al, 1984; Granstrom et al, 1985); the others report increased muscle loading (Bendix and Jessen, 1986; Hagberg). Despite this fact almost all studies agree that, given the choice, the majority of operators will choose to use an arm support if it

U I

Fig 2: Diagram of Relax Arm (from suppliers’ literature, 1992) and photograph of the apparatus in use

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is made available. If a support is not available operators will rest their arms on the desk or table instead. Most studies have been conducted on height adjustable arm and wrist supports, but little work has been done on supports that are also horizontally movable. One such support is the Relax Arm.

Supplier literature 1992 states that the Relax Arm ‘is a new concept in arm support which elim- inates static pressure and follows the natural movements of the arm ... .It is for use while typing at a keyboard. I t makes finger work easier and alleviates both neck and shoulder pain.’ Figure 2 demonstrates its use.

The Relax Arm consists of a relatively large flex- ible forearm support, mounted on a freely movable arm rest. The large forearm support avoids compression at the wrist and elbow and is fairly well padded. The Relax Arm is manufac- turered by the Rh Seating Company and can be fitted to its standard range of fully adjustable office chairs. The Relax Arm is easily inter- changeable with the standard arm rests normally fitted to the chairs.

As the majority of operators will choose to use an arm support if it is available, it appeared relevant to compare and contrast the use of freely-moving height-adjustable arm rests (Relax Arms) with standard height adjusting arm rests produced by the same company.

Methodology Seating evaluation may be undertaken in many ways, both in the field or laboratory. A laboratory study was chosen to provide effective objective measures with which t o compare the arm rests under standardised conditions. However, the novel design of the Relax Arm, and the subjects’ lack of experience with such a support, necessitated a longer trial period. It was therefore decided to conduct a field trial in addition to the laboratory study.

After a review of appropriate literature the following techniques were selected: Laboratory study Field trial Postural analysis Comfort ratings Comfort ratings Design features evaluation Electromyography Design features evaluation

Postural Analysis Postural analysis provides an objective and analytical assessment of working postures, with a view to injury prevention. VDU operation involves fairly static posture, so the method chosen was the calculation of body angles from a series of

photographs and goniometry. Angles calculated were adapted from Grandjean et a1 (19831, Porter e t a1 (1991) and Bridger (1988) and included head angle, neck inclination, trunk inclination, shoulder flexion, shoulder abduction, elbow angle, wrist angle, ulnar deviation, and thigh angle. Reflective markers were applied to bony points, and three photographs taken at a right angle to the subject. These were enlarged and body angles were calculated using a goniometer.

Comfort Ratings Feelings of discomfort or pain may indicate neuro- musculoskeletal damage or be the precursors of disease (Corlett and Bishop, 1976). Users’ assessment of seating remains valid and important, as Shackel e t a1 (1969) found that neither British Standards nor expert opinion could predict seating comfort of a lay person.

The selected format for the body chart and comfort rating for both the laboratory and field trial were derived from Corlett and Bishop (19761, Sauter et a1 (1991) and Porter et a1 (19911, and was used to assess local and general body comfort. This involved rating each body area on a scale from 1 (very comfortable) to 5 (very uncomfortable). The field trial also used a baseline questionnaire in a similar format t o determine frequency and type of discomfort experienced by subjects on a regular basis.

Self Reported Stress and Arousal Lueder (1983) points out that comfort also depends on task requirements and psychological state. The Self Reported Stress and Arousal Inventory of Mackay et a1 (1978) can therefore be used in conjunction with comfort ratings, as a measure of self-reported activation. The inventory is a method of gathering data about an individual’s awareness of body processes and provides an indication of ‘mood’, which can affect other experimental results.

Design Features Evaluation A questionnaire based on the chair feature checklist by Shackel e t al (1969) was developed t o evaluate the design features of the Relax Arm. Modifications to the original checklist were necessary t o match chair features common to 1990s designs, as the original list was developed in the 1960s. Ratings of features such as ease of adjustability, freedom of movement, and hardness/ softness of arm rest material were obtained and graded on a scale of 1-5. For example, 1 = very easy to adjust chair features, 5 = very difficult to adjust.


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Electromyography Electromyography (EMG) can be used to assess the level of muscle activity over time or predict the presence of fatigue. Integrated EMG (IEMG)

gives a measure of the power of the signals produced, so a set of values representative of the quantity of muscle activity over time is calculated.

The Laboratory Study The Workstation All aspects of the Rh chair were fully adjustable. I t was decided to use a fixed-height desk (within BS 7179 recommendations), as adjustable desks are rarely seen in the office environment. A limit- ation in available VDU equipment meant that only a personal computer that was not height or tilt adjustable was available for use, although this is again often the case in the office environment. Screen distance was controlled within recom- mended guidelines. Height-adjustable document holders and foot rests were made available for those who wanted them.

Table 1: Dimensions of the work station (mm and degrees)

Desk height 71 0 Keyboard height 25 or 33 Screen height 1, 065 Keyboard tilt 5" or 10" Screen distance

(from desk edge) 565 Foot rest height 60 to 90

Seat adjustment was left to individual preference to try to achieve optimum comfort.

Two pilot studies were conducted to determine the ease of use and effectiveness of the IEMG system in collecting the required data, and to determine which muscle areas would be most appropriate to study. Results showed that when typing with an arm support the majority of muscle activity was observed in the descending fibres of the trapezius, and that measurable activity was apparent in the extensor carpi ulnaris (ECU).

Aims To evaluate the use of Relax Arms against standard arm rests using EMG, postural analysis, comfort ratings, and design feature evaluation.

Subjects Twelve healthy subjects participated in the study (six men and six women aged between 25 and 35 years). All had regularly used keyboards for a minimum of nine months, and four were touch typists. I t was decided to use a mixture of ability because not all VDU operators are touch typists.

Method and Procedure A balanced presentation order was used for the two arm rests under investigation. Subjects undertook two half-hour typing sessions, one with

each type of arm rest. During the session EMG sampling was taken once per minute over the half-hour typing period. Photographs and goniometry were undertaken at eight-minute intervals for the purpose of postural analysis. Comfort ratings and stress/arousal inventories were completed at the beginning and end of the session. A design feature questionnaire was completed at the end of the experiment.

Results and Discussion Self-reported Stress and Arousal No significant difference in stress or arousal was observed between tests 1 and 2 using the Wilcoxon signed rank test.

Electromyography The trend was for slightly less overall activity for both muscle groups with the use of the Relax Arms. However, a related t-test for same subject design was conducted on the total EMG activity for the different arm rests, but no significant difference in muscle activity was determined for either the trapezius or ECU. The lack of significant results may be explained by the fact that the Relax Arm 'takes some getting used to', and the body must learn to relax on to the arm rest rather than 'fight it'. This may indicate the need for a longer adaptation period t o enable subjects to become accustomed to and skilled with the Relax Arm prior to EMG testing. In addition, while using the standard rests many subjects supported their elbows on the arm rest and their forearms on the desk, effectively providing support for the whole of the lower arm and reducing muscle activity. Adoption of this position did however result in an extreme wrist posture.

Comfort Ratings Values for each body part in turn were compared for differences in comfort after each experimental condition. Very little difference was observed between the use of the Relax Arm or standard rests, and the Wilcoxon signed ranks test revealed no significant differences in comfort ratings after half an hour of typing.

Postural Analysis Mean postural angles were calculated from the three photographs and goniometry readings. Use of the Relax Arm resulted in significant reduc-


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tions in wrist extension and ulnar deviation. The adoption of a more neutral wrist position reduces pressure of the median nerve in the carpal tunnel, thus decreasing the risk of injury (Ardnt, 1983; Sauter et al, 1987; Duncan and Ferguson, 1974). Grieve (1992) suggested that office workers resting the weight of the arm on the bony front of the extended wrist on the table edge (as is commonly seen in VDU operators), alters the joint mechanics of the wrist and leads to secondary dysfunctions in the tendons and nerves. This action is prevented by use of the Relax Arm.

Relax Arm Design Features Adjustability, freedom of movement, arm rest size and material were all found to be satisfactory. Of the 12 subjects, six felt that the Relax Arm made them more comfortable while typing, one said he felt no different from usual, and five felt they were more uncomfortable. Giving the choice, seven subjects would choose to type with the Relax Arm, four would choose to type with the standard rest, and one would choose to type with no arm rest at all.

The Field Study Introduction There is disagreement as to the length of testing required for comfort assessment so it was felt that a medium to long-term field trial would be a valu- able addition to the arm rest assessment. As the Relax Arm design was such an unfamiliar addition to the keyboard operation it was decided to conduct the field trial over a two-week period - one week with standard arm rests and one week with the Relax Arms.

Aims To evaluate the medium term comfort and usability of the Relax Arms compared t o the standard arm rests.

Subjects It was initially hoped to conduct the field trial with 00s sufferers, because the Relax Arms are marketed for this group. Unfortunately communication with doctors, physiotherapists, medical journals and trade unions revealed only a very limited number of subjects. Many people explained that the political sensitivity of the 00s issue following the recent large litigation claims prevented them from disclosing subjects’ details or permitting staff to take part in trials. In addition, many people in contact with the medical profession or the RSI Association were no longer working because of their condition. It was therefore decided to conduct the trial with a mixture of four ‘normal’ and five 00s subjects. All were regular VDU operators (spending at least 50% of their day keying or typing), and all were in full- time employment. Subjects had a mean age of 35, two were male and seven female. Professions included journalists, secretaries and data inputters.

Methods and Procedures Subjects completed a baseline questionnaire and body chart modified from Sauter et aZ(1991) and

Slovak and Trevers (1988). This obtained information about location, type and frequency of any existing musculoskeletal pain, and details of any ongoing medication or rehabilitation treatment that might affect the daily comfort ratings. A balanced presentation order was used to allocate either a chair fitted with the Relax Arm or the standard arm rest. The subjects were instructed in the adjustable features of the chair and arms, and told to adjust any features as often as they liked over the week to provide optimum comfort.

A daily comfort chart measuring local and general comfort ratings, and a self-reported stress arousal inventory (as used in the laboratory study), were completed on arrival at work, and a t the end of the day just before leaving work. This was to demonstrate any discomfort or change in mood caused during the working day.

At the end of the first week the arm rests were changed and the process continued. A final questionnaire evaluating the design features of the Relax Arm was given at the end of week two.

Results and Discussion Baseline Questionnaire Of the RSI sufferers, length of time since diagnosis varied between four months t o five years, although four of the five patients had been diag- nosed for less than one year. Only two subjects had previously taken time off work because of their condition and only one was receiving physiotherapy at the time of the study.

None of the ‘normal’ subjects had received advice on sitting or keying posture or on work station adjustment. All of the 00s suffers had received such advice.

Stress and Arousal Scores The Wilcoxon signed ranks test was conducted using the total daily stress or arousal scores for each subject. Few significant results were observed and these were not found to be related to


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changes in comfort, arm rest or hours worked. Results are therefore felt t o be due to personal factors.

Comfort Ratings Out of the total of nine subjects, seven completed the full two-week trial. Two of the 00s subjects (normally working without any arm rests at all), experienced an exacerbation of their symptoms and declined to finish the study. One subject experienced increased discomfort after four days using the Relax Arm, and after only one morning of using the standard rest. The other subject experienced an adverse reaction after two days’ use of the Relax Arm. The nature of his symptoms precluded him from attempting to use the standard rests. For the purpose of evaluation it was necessary to include information from those subjects who were unable t o complete the trial, to avoid biasing the results by using only subjects who did not experience an increase in discomfort when using the Relax Arm. A compromise was decided upon to provide data for the uncompleted days of the study. For the purpose of analysis, any body areas said by the two subjects to have been aggravated by the arm rests, or any areas marked as frequently or constantly suffering symptoms on the baseline body chart, were allocated a score of 5 (very uncomfortable). All other body areas were allocated a score of 3 (neutral). These results were then included with the data of the other participants.

The Wilcoxon signed ranks test was then applied to the scores for each body area over days one to five for each week, to determine any changes in comfort over time as the participants became used to the arm rests. Significant results were found almost exclusively on day five and are shown in table 2.

Table 2: Significant results and effects of the Relax Arms on comfort ratings in morning and afternoon periods over days 1 to 5 (at p < 0.05). All results indicate less discomfort with the Relax Arms

Body area Median score Significance

Morning Left upper arm 2 3 p < 0.05 Left fingers 2 3 p < 0.05 Right fingers 2 3 p < 0.05 Low back 2 3 p < 0.025

Afternoon Right lower arm 4 3 p < 0.05 Right thumb 2 3 p < 0.05 Mid back 2 3 p < 0.025* Low back 2 3 p < 0.025t

*Mid back also significant day 4 at p < 0.05 tLow back nonsignificant day 4 but significant days 2 and 3 at p < 0.05

Relax Standard (day 5)

Neck Upper back

Mid back Low back

Buttocks Right leg

Left leg Left foot

Right foot Stomach

Chest Left shoulder

Right shoulder Right upper arm

Left upper arm Right lower arm

Left lower arm Right wrist

Left wrist Left hand

Right hand Left thumb

Right thumb Left fingers

Right fingers Overall

0 5 10 15 20 25 30 Percentage expressing discomfort

Relax Arm 0 Standard

Fig 3: Percentage of ‘reports of discomfort’ in the mornings (all subjects combined)

Neck Upper back

Mid back Low back Buttocks Right leg

Left leg Left foot

Right foot Stomach

Chest Left shoulder

Right shoulder Right upper arm Left Upper arm Right lower arm




Right thumb Left fingers


0 10 20 30 40 50 60 Percentage expressing discomfort


Fig 4: Percentage of ‘reports of discomfort’ in the afternoons (all subjects combined)


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Neck Upper back

Mid back Low back Buttocks Right leg

Left leg Left foot

Right foot Stomach

Chest Left shoulder

Right shoulder flight upper arm

Left upper arm Right lower arm




flight thumb Left fingers


0 5 10 15 20 25 30 35 40 Percentage expressing discomfort


Fig 5: Percentage of ‘reports of discomfort’ over total study period (all subjects combined)

Percentage of reports of discomfort with use of the Relax Arm and standard arm were calculated and results are shown in figures 3 , 4 and 5.

The trend was for a greater percentage of reported discomfort in both mornings and afternoons when using the standard rests. The greatest differences were noted in the afternoons and further analysis revealed that results were most marked with the RSI subjects.

Relax Arm Design Features Adjustability, freedom of movement, size and material of the Relax Arm were all found to be satisfactory. Of the nine subjects, six felt the Relax Arm made them more comfortable at work and three felt the Relax Arm made them more uncomfortable. Given the choice six subjects would choose to typekey with the Relax Arm, one with the standard arm rest, and two with no arm rest at all.

Discussion Despite the problems mentioned, the field study revealed significant differences in comfort ratings that were not apparent in the laboratory study. The Relax Arm was associated with significantly less discomfort than the standard rest, most noti- ceably in spinal and upper limb areas. Improved comfort demonstrated in the low and mid back

may be an indication of reduced spinal loading (Andersson, 1983; Grandjean, 1987; Occipinti et al, 1985).

A lower incidence of discomfort in various areas of the upper limbs may indicate a reduction in muscle and joint loading and adoption of more neutral joint positions. Indeed a more neutral wrist posture was observed during use of the Relax Arm in the laboratory study although no significant differences in muscle activity were recorded.

I t is a matter for concern that two 00s subjects experienced an exacerbation of their symptoms while using the Relax Arm, because the rest is targeted at this group. However, the standard rest was perceived as even worse. I t was wondered if the degree of chronicity of the condition bore any relation to the comfort/discomfort experienced, but from the limited number of subjects in the study it is not possible t o draw conclusions about this factor.

Suggestion for Further Study Further long-term evaluation of all the differing arm and wrist supports on the market would help determine which, if any, would be preferable for RSI sufferers. This would be of benefit to those in the medical profession called upon to offer advice on this difficult condition.

On analysing the results of the ‘normal’ subjects in the field study, it was found that all four would choose to type with arm support (three with Relax Arm, one with the standard rest). Although subject numbers are small, it raises the question as to why most typist/VDU operator chairs lack small height-adjustable arm supports. A long term study to evaluate whether arm supports can prevent 00s or musculoskeletal disorders from occurring in normal subjects would be of consid- erable interest.

Conclusions It was felt that the laboratory and field trial complemented each other, and so conclusions are considered jointly.

1. Of 12 laboratory and nine field subjects, 11 and seven respectively prefer to typekey using an arm rest rather than no arm support at all. Of these, seven laboratory and six field subjects would choose to use the Relax Arm.

2. Compared with the standard height adjusting arm rest, the Relax Arm significantly reduced wrist extension and ulnar deviation, this being expected to help prevent joint and soft tissue dysfunction and their ensuing musculoskeletal disorders.


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3. A medium-term study revealed changes in comfort which the short-term study did not. The trend was for less discomfort while using the Relax Arm rather than the standard arm. Body areas revealing significant differences after five days' use were: the mid and low back, left upper arm, right lower arm, right and left fingers, and right thumb.

4. The Relax Arm may offer benefits t o many 00s sufferers, but should not be distributed to sufferers without careful consideration of their individual condition.

Author Alison Smith MSc MCSP is a consultant physiotherapist and ergonomist in Melbourne, Australia.

This article was received on December 8, 1992, and accepted on March 3, 1995.

Address for Correspondence Ms A Smith, c/o Work Solutions Group, 145-163 Smith Street, Fitzroy, Victoria 3065, Australia.

References Advance Seating Designs (1 992). Rh Products, Distributers Liter- ature, London.

Anderson, J (1984). 'Shoulder pain and tension neck and their relation to work', Scandinavian Journal of Work Environmental Health, 10, 435-442.

Anderson, G (1983). 'Loads on the lumbar spine: In vivo measurements and biomechanical analyses' in: Winter, D, Norman, R, Hayes, K and Patla, A (eds) lnternational Series on Biomechanics, 5b.

Ardnt, A (1 983). 'Working posture and musculoskeletal problems of VDU operators: Review and reappraisal', American lndustrial Hygiene Association Journal, 44, 6, 437-446.

Bammer, B and Blignault, I (1987). 'A review of research on repetitive strain injuries' in: Buckle, P (ed) Musculoskeletal Disorders at Work, Taylor and Francis, London, pages 1 18-1 23.

Barton, N (1 989). 'Repetitive strain disorder', British Medical Journal, 299, 405-406.

Barrett, P (1 987)., 'Repetition strain injury', unpublished paper.

Bendix, T and Jessen, F (1986). 'Wrist support during typing: A controlled electromyographic study', Applied Ergonomics, 17,

Boyling, J (1991). 'Upper limb disorders in the workplace', OCPPP In Touch, 61.

Bridger, R (1988). 'Postural adaptations to a sloping chart and work surface', Human Factors, 30, 2, 237-247.

British Standards Institution (1 990). Ergonomics of Design and Use of Visual Display Terminals (VDUs) in Offices, Part 5 , BSI, Milton Keynes.

Business Life Magazine (1992). 'Taking the sprain', April.

Chaffin, D (1 973). 'Localised muscle fatigue: Definition and measurement', Journal of Occupational Medicine, 15, 346-354.

Chaffin, D and Anderson, G (1984). Occupational Biomech- anics, Wiley, New York.

Corlett, N and Bishop, R (1976). 'A technique for assessing postural discomfort', Ergonomics, 19, 175-1 82.

Duncan, J and Ferguson, D (1974). 'Keyboard operating posture and symptoms in operating', Ergonomics, 17, 5, 651-662.

Grandjean, E (1 987). Ergonomics in Computerised Offices, Taylor and Francis, London, pages 96-1 56.

3, 162-168.

Grandjean, E and Hunting, W (1977). 'Ergonomics of posture: A review of various problems of standing and sitting posture', Applied Ergonomics, 8, 3, 135-1 40.

Grandjean, E, Hunting, W and Piderman, M (1983). 'VDU workstation design: Preferred settings and their effects', Human Factors, 25,2, 161-175.

Granstrom, B, Kvarnstrom, S and Tiefenbacher, F (1985). 'Electromyography as an aid in the prevention of excessive shoulder strain', Applied Ergonomics, 16, 1 I 49-54.

Grieve, E (1 992). 'A study of chronic arm pain in industry', PhD thesis, University of Birmingham.

Hagberg, M (year unknown). Optimising Occupational Muscular Stress of the Neck and Shoulder, National Board of Occupational Health and Safety, Medical Division, Sweden.

Horin, A (1984). 'RSI: What it is, What to do about it', The Times, October 12-18.

Hunting, W, Laubli, T and Grandjean, E (1981). 'Postural and visual loads at VDU workplaces: 1. Constrained postures', Ergonomics, 24, 12, 917-931.

Kilbom, A (1988). 'Intervention programmes for work related neck and upper limb disorders: Strategies and evaluation', Ergonomics, 31,5,735-747.

Kroner Company Administration Briefing (1992). 'Latest RSI damages award', issue 7, May.

Laville, A (1980). 'Postural reactions related to activities on VDU' in: Grandjean, E and Vigliani, E (eds) Ergonomic Aspects of Visual Display Terminals, Taylor and Francis, London.

Lueder, R (1983). 'Seat comfort: A review of the construct in the office environment', Human Factors, 25, 6, 701-71 1.

Mackay, C, Cox, T, Burrows, G and Lazzerini, T (1978). 'An inventory for the measurement of self-reported stress and arousal', British Journal of Social and Clinical Psychology, 17,

Moore, A, Wells, R and Ranney, D (1991). 'Quantifying exposure in occupational manual tasks with cumulative trauma disorder potential', Ergonomics, 34, 12, 1433-53.

Occipinti, E, Columbini, D, Grieco, A, Frigo, C and Pedotti, A (1985). 'Sitting posture: Analysis of lumbar stresses with upper limbs supported', Ergonomics, 28, 9, 1333-46. Porter, J M, Gyi, D and Robertson, J (1991). 'An evaluation of a tilting computer desk' (personal communication).

Sauter, S, Schleifer, L and Knutson, S (1991). 'Work posture, workstation design, and musculoskeletal discomfort in a VDU data entry task', Human Factors, 33, 2, 151-167. Sauter, S, Chapman, L, Knutson, S and Anderson, H (1987). 'Case example of wrist trauma in keyboard use', Applied Ergonomics, 18, 3, 183-1 86.

Schuldt, K, Ekholm, J, Harms-Ringdahi, K, Arborelius, U and Nemeth, G (1987). 'Neck and shoulder muscular activity during arm movements at work in various sitting postures, with and without ergonomic aids' in: Jonsson, B (ed) lnternational Series on Biomechanics, 6a.

Shackel, B, Chidsey, K and Shipley, P (1969). 'The assessment of chair comfort', Ergonomics, 12, 269-306.

Slovak, A and Trevers, C (1 988). 'Solving workplace problems associated with VDUs', Applied Ergonomics, 19, 2, 99-1 02.

Spillane, R and Deves, L (1987). 'RSI: Pain, pretence or patient- hood?' Journal of industrial Relations, 29, 41-48.

The Times (1992). 'Strain that's a pain', March 5.

Van Wely, P (1 970). 'Design and disease', Applied Ergonomics,

Waersted, M, Bjorklund, R and Westgaard, R (1991). 'Shoulder muscle tension induced by two VDU-based tasks of different complexity', Ergonomics, 34, 137-1 50.

Weber, A, Sancin, E and Grandjean, E (1984). 'The effects of various keyboard heights on EMG and physical discomfort', in: Grandjean, E (eds) Ergonomics and Health in Modern Offices, Taylor and Francis, London, pages 477-483.

283-284.

1, 5, 262-269.


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Upper Limb Disorders – Time to relax?