What is the real problem?

Repetitive Strain Injury (RSI) or Carpal Tunnel Syndrome (CTS), are names that are commonly associated with computer-related injuries. However, the problems are actually far wider that these names suggest. Table 1 lists the range of medically defined injuries/conditions that are known to be associated with musculoskeletal injuries (otherwise known as work-related musculoskeletal disorders (WMSD)) [1].

Table 1 shows there are a considerable range of conditions - we are not talking about just one injury type (e.g. carpal tunnel syndrome). This range of conditions applies to injuries caused in many work situations. However, when it comes to VDU¹ use it is the pain syndromes and eyestrain that are the most common. This is an interesting finding because it is actually the opposite of what many people commonly believe. True tendinitis and carpal tunnel syndrome are relatively uncommon amongst computer users.

What are the true underlying causes?

There are a number of causes of the conditions shown in Table 1. Localised inflammations like tendinitis result from a combination of forceful and repetitive movement. The compression syndromes can be caused by postural extremes or pressure on nerves as a result of inflammation. The pain syndromes have multiple contributing causes, but an important one is constrained posture and static muscle tension. Use of a computer keyboard and mouse does require some repetitive action, however very little force, meaning that the first two groups of conditions are less likely. In practice, computer use is primarily characterised by a static constrained posture, fixed focal distance, and sustained muscle tension (e.g. gripping the mouse). These factors contribute to making eyestrain and the pain syndromes very common.

How common are the problems?

Many studies have shown a high prevalence of complaints amongst computer users. One report "Investigation into the Factors Associated with Symptoms of ULDs² in Keyboard Users" [2] published in 1996 by the UK Institute of Occupational Medicine surveyed 3,500 keyboard users and found that

"... 55% of the subjects had at some time suffered from some discomfort in the upper limbs. Fourteen percent of all subjects were currently suffering, or had suffered within the last three months, from ULDs symptoms which were severe enough for them to seek professional medical advice...".

Other studies have found similar results for eyestrain, and neck and shoulder pains. For example, a review paper published in 1992 [3] looked at the issues of visual fatigue, musculoskeletal problems and stress with respect to VDU use. It found a prevalence rate of up to 50% in some studies. Rates for visual symptoms in particular were reported between 40% and 92% for occasional problems, and from 10% to 40% for daily complaints.

How important are breaks?

The importance of breaks has been somewhat overlooked by a preoccupation with the physical ergonomics of the work area/workstation. The need for a shift in focus to recognise the importance of breaks is illustrated by discussion in the Ergonomics Journal paper entitled "A Field Study of Supplementary Rest Breaks for Data-entry Operators" published in 2000 [4].

"... workstation redesign does not appear to be sufficient for completely eliminating work induced discomfort, and in some cases, discomfort has been virtually unaffected by ergonomics interventions. For example, compared to discomfort in the upper and lower extremities, discomfort in the neck and shoulders has been shown to be particularly impervious to ergonomic/workstation improvements (Oxenburgh 1984, Winkel and Oxenburgh 1990, Sauter et al 1991). Neck and shoulder discomfort associated with VDT³ work has been attributed to prolonged muscle tension from static contractions of the neck and shoulder muscles (Waris 1979, Hagberg 1983). Winkel and Oxenburgh (1990) noted that since constrained shoulder/neck postures are inherently characteristic of VDT work, prolonged stated contractions in these muscles are probably not preventable through workstation design changes. They suggested the possibility that neck and shoulder discomfort in VDT work might be relieved only by changes in work organisation, such as task rotation or increased rest breaks, which allow for periodic interruptions of the VDT task (Winkel and Oxenburgh 1990)."

This paper was written by authors at the Taft Laboratories of the National Institute for Occupational Safety & Health (NIOSH), USA.

The 1996 UK Institute of Occupational Medicine Report, previously referred to, looked at 450 computer users and undertook a detailed ergonomic evaluation of each workstation. It examined a number of factors such as:

"... keyboard work, furniture and equipment, postures adopted when keying; physical work environment; psychosocial aspects of work, activities outside work, and personal factors".

Interestingly it found that:

"After adjusting for age and gender, the most significant factor associated with symptoms of ULDs was the length of time the subjects spent at the keyboard during the week (highly correlated with the length of time spent keying without a break)...".

In other words, the most important risk factor was using a computer for a long period of time without taking breaks.

How effective can breaks be?

In the NIOSH study described above [4] the authors looked at the effect of introducing supplementary breaks to a working regime which normally included only a couple of breaks each day. The conclusions were that:

"In addition to their positive effects on ratings of musculoskeletal discomfort supplementary rest breaks also led to decreased levels of eye soreness and visual blurring".

The authors found:

"... increases in discomfort of the right forearm, wrist and hand over the course of the work week under the conventional schedule were eliminated under the supplementary schedule".

An important finding was that:

"These beneficial effects were obtained without reductions in data-entry performance".

In fact, it was found that there was actually a slight increase in work rate after the rest breaks which more than compensated for any time lost taking the break.

Even more recently in June 2001 a paper titled "Computer Terminal Work and the Benefit of Micro-breaks" was published in the Applied Ergonomics Journal [18]. This paper reported on a detailed study of the effects of micro-breaks on computer users. They too found significant positive effects.

"It was found that by complying with regularly scheduled breaks "micro-breaks", subjects had less discomfort. In terms of reduced discomfort ... scheduled breaks were found to be generally more effective than allowing the worker to take breaks on their own."

The authors concluded that:

"The major contribution of this work is the determination of the beneficial effect of regularly scheduled "micro-breaks" on subjective discomfort ratings at the neck, low back, the shoulder, and the forearm/wrist areas."

These studies are amongst a large and growing body of evidence showing the effectiveness of breaks in reducing musculoskeletal discomfort and eyestrain amongst computer users. A document by research physiotherapist Nicola Green "Breaks and Micropauses - A Survey of the Literature" [5, 16] gives a comprehensive overview of the scientific papers that have been published on this topic.

Some examples are a 1986 paper by Hagberg & Sundelin [6] looking at micropauses (15 seconds every 6 mins). They found a reduction in discomfort ratings. Henning et al (1989) [7] also investigated "micro-breaks" and found that they were "instrumental in reducing fatigue and associated performance decrements...".

How often should breaks be?

Some of the best early research on muscular fatigue was conducted by Rohmert. In some discussion papers (1973) [8, 9] he found an exponential relationship between fatigue and recovery. In other words, a doubling of the fatigue level required a quadrupling of recovery time. Based on these results Rohmert's recommendations for rest breaks were "little and often". This research and that of many others has culminated in the general recommendation that breaks should be taken "before the onset of fatigue not in order to recover" (from UK Guidance on VDU Regulations). Out of this has arisen the concept of the 'micropause' or 'micro-break'. These are short breaks of perhaps only 5-10 seconds taken every 5-10 minutes of continuous use. The effectiveness of these micro-breaks has been studied in detail [6, 7, 10, 11, 12, 18]. In the Applied Ergonomics Journal paper [18] the authors looked at several intervals between micro-breaks and found that more frequent micro-breaks produced the greatest reduction in discomfort.

Should breaks be prompted or left to discretion?

Unfortunately, computer users are not good at regulating their own breaks. If not reminded a VDU user is unlikely to take a break at the optimum time physiologically speaking i.e. they will only take breaks after significant fatigue has accumulated and once discomfort has arisen. Anecdotally speaking this is a well-known problem with computer use. Studies illustrating this problem include:

1. Henning et al [7] who found that rest breaks were not regulated effectively by users if left entirely to their discretion.

2. McLean L. et al [18] who found that: "scheduled breaks were found to be generally more effective than allowing the worker to take breaks on their own."

What is the impact of breaks on productivity?

An interesting result from the numerous studies undertaken is that additional introduced breaks do not seem to impact negatively on productivity, and in fact the reverse can be the case. As mentioned earlier this was a finding of the NIOSH study [4]

"... beneficial effects were obtained without reductions in data-entry performance".

In a 1989 review paper "The Design of Rest Breaks for Video Terminal Work: A Review of Literature" [13] the authors concluded that the evidence suggests frequent rest breaks benefit production and comfort in VDU work.

The paper "The Effect of Different Work Rest Schedules on Fatigue and Performance of a Simulated Directory Assistant Operators Task" [14] found a performance deterioration after 120 minutes of continuous VDU work with error rates increasing by almost 80% towards the end of the period. The introduction of rest breaks prevented this performance deterioration from occurring.

The Applied Ergonomics Journal paper "Computer Terminal Work and the Benefit of Micro-breaks" [18] found:

"...that the addition of 30s micro-breaks showed no detrimental effect on worker productivity"

Further their overall conclusion was:

"The major contribution of this work is the determination of the beneficial effect of regularly scheduled "micro-breaks" ... . In addition, this work contributes evidence that the implementation of such a strategy has no detrimental effect on worker productivity."

Overall there appears to be no evidence of any negative impact on productivity from introduced breaks.

How important is prevention?

Recent evidence suggests that some of the musculoskeletal disorders arising from VDU use may be the result of the cumulative effect of "micro-trauma" over a period of time.

A recent paper from the University College of London, "Vibration Sense in the Upper Limb of Patients with Repetitive Strain Injury and a Group of at Risk Office Workers" [15] caused a stir in international medical circles by finding evidence of actual nerve damage in people suffering from pain syndromes as a result of VDU use. Perhaps even more concerning was the finding of similar indications of nerve damages in otherwise symptom-free intensive VDU workers. The implication of this finding was that a VDU user may begin to accumulate damage before symptoms become evident - providing an even greater impetus for prevention. Once significant symptoms become apparent it may be too late for effective action to be taken.

This issue was also discussed in the NIOSH paper:

"Theories of cumulative trauma propose that chronic disorders result from the cumulative effects of repeated 'microtraumas' manifested as small to moderate increments in discomfort during work".

Does awareness increase reporting?

A paper published in the Journal of Environmental Medicine (JOEM) [17] in 1999 studied whether educating employees about musculoskeletal disorders contributed to any increase in reported injuries and compensation. It concluded that it did not, counteracting some employer fears that educating employees and making an issue of Cumulative Trauma Disorders (CTDs) might result in increased problems and costs for the employer.

The abstract stated:

"...there was no increase in the number of OSHA 200 events and no increase in the incidence of workers' compensation claims after completion of an individual risk screening program that included education and employee awareness about work-related musculoskeletal pain. ..."

References

[1] "Prevention of Work Related Musculoskeletal Disorders (WMSD) - An Evidence Based Approach", UK Journal of Physiotherapy (1999), by Occupational Specialist Dr WED Turner.

[2] "Investigation into the Factors Associated with Symptoms of ULDs in Keyboard Users", UK Institute of Occupational Medicine (1996), Hanson, M., Graveling, R., Donnan, P.

[3] "Musculoskeletal Disorder, Visual Fatigue and Psychological Stress of Working with Display Units: current issues and research needs", Work with Display Units 92: Proceedings of the third International Scientific Conference on work with Display Units (1992), Technische Universitat Berlin, H.Luczak, A.Cakir and G. Cakir (eds), p288-289.

[4] "A Field Study of Supplementary Rest Breaks for Data-entry Operators", Journal of Ergonomics (2000), Vol 43, No. 5, p622-638, T. L. Galinsky, N. G. Swanson, S. L. Sauter, J. J. Hurrel, L. M. Schleifer.

[5] "Breaks and micropauses - a survey of the literature", Internal Research Document for Niche Software Ltd (1999), Nicola Green.

[6] "Discomfort and Load on the Upper Trapezius Muscle when Operating a Wordprocessor." Ergonomics (1986), Vol 29, No. 12, p1637-1645, Hagberg, M. and Sundelin, G.

[7] "Microbreak Length, Performance, and Stress in a Data Entry Task", Ergonomics (1989), Vol 32, No. 7, p855-864, Henning, R.A; Sauter, S. L; Salvendy, G and Krieg, E. F.

[8] "Problems of Determination of Rest Allowances. Part 1: Use of Modern Methods to Evaluate Stress and Strain in Static Muscular Work", Applied Ergonomics (1973), 4, 2, p91-95, Rohmert,W.

[9] "Problems of Determination of Rest Allowances. Part 2: Determining Rest Allowances in Different Human Tasks" Applied Ergonomics (1973), 4, 3, p158-162, Rohmert, W.

[10] "Physiological Effects of Micropauses in Isometric Hand Grip Exercises" European Journal of Applied Physiology (1991), 63,405-411, Byström, S. E. G; Mathiassen, S. E. and Fransson-Hall, C.

[11] "The Effects of Exercise on the Health and Performance of Data Entry Operators", Work with Display Units 92: Proceedings of the Third International Scientific Conference on work with Display Units (1992), p288-289, H. Luczak, A. Cakir and G. Cakir (eds), Technische Universitat Berlin.

[12] "Active Microbreak Effects on Musculoskeletal Comfort Ratings in Meatpacking Plants", Ergonomics (1995), 38, 2, p326-336, Genaidy, A. M; Delgado, E. and Bustos, T.

[13] "The Design of Rest Breaks for Video Terminal Work: A Review of the Literature", Advances in Industrial Ergonomics and Safety I: Proceedings of the Industrial Ergonomics and Safety Conference (1989), In A. Mital (Ed), Taylor and Francis, London, pp 895-899, Swanson, N. G., Sauter, S.L., and Chapman, L.J.

[14] "The Effect of Different Work-rest Schedules on Fatigue and Performance of a Simulated Directory Assistance Operator's Task", Ergonomics (1994), 37, 10, p1697-1707, Koparadekar, P. and Mital, A.

[15] "Vibration Sense in the Upper Limb in Patients with Repetitive Strain Injury and a Group of At-risk Workers", International Archives of Occupational and Environmental Health (1998), 71, 1, p29-34, Greening, J. and Lynn, B.

[16] "Work-Related Musculoskeletal Disorders (WMSD) and Breaks", Internal Research Document for Niche Software Ltd (1999), Nicola Green.

[17] "The Impact of Workplace Screening on the Occurrence of Cumulative Trauma Disorders and Workers Compensation Claims", Journal of Environmental Medicine (1999), Vol 41, No. 2, pp84-92, Melhorn, J. M.

[18] "Computer Terminal Work and the Benefit of Micro-breaks", Applied Ergonomics (2001), Vol 32, No 3, pp225-37, Mclean, L., Tingley, M., Scott, RN., Rickards, J.

1) VDU = Visual Display Unit

2) ULD = Upper Limb Disorder - the technical name for RSI in the United Kingdom

3) VDT = Visual Display Terminal