Neck-shoulder-arm pain is frequent among computer workers but there is a controversy with regard to the character of disorders responsible for these symptoms and their prevention remains a challenge. However, in heavily exposed symptomatic computer operators it is possible to identify neurological abnormalities including selective muscle weakness, deviation from normal of sensibility, and mechanical allodynia of nerve trunks. The occurrence of physical findings in distinct neurological patterns suggests the involvement of the brachial plexus at chord level (located infraclavicularly behind the pectoralis minor muscle), and of the posterior interosseous and median nerves at elbow level 1. These patterns were identified by a neurological examination which has been previously shown to be reproducible and reflecting symptoms 234.

Applied to a sample of computer operators with few and minor symptoms, a similar neurological examination has demonstrated the presence and relation to symptoms of specific patterns of abnormalities 5. While this study did not intend to determine the relation of upper limb symptoms to computer work, the findings are concurrent with hypotheses of external causation of work-related upper limb nerve-afflictions 67 including the relation to office work 8.

Researchers seem to share the view that computer use (hours per day or week) is related to upper limb morbidity 9. However, those involved in computer intensive work, e.g. computer aided design, are reluctant to accept half-time jobs and other preventive options likewise appear insufficient. A recent Cochrane review has concluded that there is limited evidence for the efficacy of exercises and breaks and that the benefit of ergonomic interventions has not been clearly demonstrated 10. While education in office ergonomics has resulted in less pain and discomfort in some studies 111213 others have failed to demonstrate this effect 14. The effect of work environment improvements seems to be superior when combined with changes in work techniques 15. One study has suggested the preventive role of forearm support 16 while others found no effect of postural interventions 17.

The failure of ergonomically designed workstations to satisfactorily prevent adverse musculoskeletal health effects has been attributed to their inability to correct for a major contribution of constrained posture. To address this factor computer operators have been recommended physical exercises many of which, however, have been regarded as conspicuous and potentially embarrassing to perform, as disruptive of work routines, as posing health hazards by exacerbating the biomechanical stress in computer work, or as contraindicated in subjects with certain health problems 18. The limited evidence for the effectiveness of exercises may be due to their content which constituted strengthening and endurance rather than stretching 10. One study has shown that frequent short breaks from computer work improve productivity and well-being when the breaks integrate with task demands – especially when combined with stretching exercises 19. In another study recovery from upper limb and neck complaints was promoted by regular breaks but there was no additional effects of physical exercises 20. In a review of the efficacy of stretching for prevention of injury related to exercise (sports) no conclusions could be drawn due to the paucity, heterogeneity and poor quality of studies 21. Isolated stretching exercises have not been studied in computer operators but were rated as beneficial by ultrasonography staff with musculoskeletal complaints 22. The static components in ultrasound examinations may be comparable to that of computer work but the forces involved are higher and the variability of upper limb posture probably greater.

A recent systematic review of the effect of interventions among computer users found that our ability to draw conclusions about ergonomic interventions including the effect of rest brakes and exercises was limited by the small number of good quality studies 23.

Our clinical observations have indicated that upper limb symptoms and physical findings may still develop in computer workers in spite of attempts to optimize ergonomics and work organization, e.g. by reducing computer workload through addressing deadlines and overtime. The current insufficiency of effective preventive measures suggests the need for a broader scope.

Physical findings in computer operators 5 suggest that at specific anatomic locations with narrow passages nerve trunks may be compressed, tethered or fixed by surrounding structures. Accordingly, a rational preventive approach would aim to maintain nerve-mobility at these locations. This may be accomplished by influencing gradients of tissue pressure in order to improve capillary blood flow and venous return in nerves 2425 and by re-establishing muscle balance (e.g., through strengthening of specific muscles and stretching of their antagonists) 7.

These considerations and prior encouraging experiences 1922 influenced our decision to study if stretching exercises aiming to mobilize the nerves at specific locations can reduce upper limb symptoms in computer operators. The demonstration of a beneficial effect of such targeted stretching would contribute to the prevention of upper limb pain in computer operators and also provide a further validation of the previously presented diagnostic approach 234.

We have aimed to test the value of such an intervention.

All the presented results refer to the right upper limb.

Compared to the intervention subjects the controls were slightly older (mean age 37 and 41, respectively) and the proportion of women higher (66% and 33%, respectively). The intervention subjects and the controls were comparable with regard to mean body mass index (25 and 24, respectively).

Compliance with the recommended intervention was generally good. Among the 66 subjects in the intervention group who answered the second questionnaire 60 affirmed that they had regularly completed the stretching exercises at the recommended rate and 53 that they included all exercises. Two subjects out of the 30 controls performed some sort of stretching (which would most likely differ from the recommended exercises). The content of the work, work hours and ergonomic features of work sites were unchanged and comparable in the two groups during the course of the intervention.

At baseline/follow-up 120/66 computer operators in the division in Esbjerg and 44/30 in Aarhus, respectively, answered questionnaires about upper limb symptoms and 80/70 computer operators in Esbjerg and 37/28 in Aarhus, respectively, were subjected to physical examinations by the same examiner (JRJ) (Figures 1, 2).

Any preventive intervention should preferably be based on an understanding of the phenomena underlying the disorder or at least a theory founded on evidence with regard to this issue. In the absence of such understanding, any intervention may target irrelevant issues and would most likely be ineffective. The intervention in this study was based on indications from a former study of the relation of symptoms to upper limb nerve afflictions at three locations (brachial plexus at chord level, posterior interosseous nerve and median nerve at elbow level) 5. Accordingly, a six month course of stretching was designed with the aim to mobilize the nerve segments at these locations.

The ability of the intervention to reduce symptoms in the studied sample of computer operators is encouraging. The decrease after the intervention of physical findings in the entire sample could not be related to the stretching exercises, however. This is not necessarily contrary to the favourable subjective improvement, but may be explained by statistical weaknesses and other potential sources of error.

First of all, the physical work environment of this small sample of computer operators was already optimized prior to the study. They also had fewer symptoms than reported in other studies on upper limb complaints in computer workers. These favourable circumstances in terms of health would tend to make it more difficult to demonstrate an effect of the intervention.

Secondly, 20 computer workers did not answer the questionnaire at start and 88 did not participate at the follow-up (Figures 1, 2). For the physical examinations the corresponding figures were 67 and 31 subjects, respectively. In fact only 62 subjects in the intervention group and 16 controls participated in all parts of the study. This small number especially of controls is a clear weakness, which together with the high number of limbs without symptoms and findings reduces the statistical power of the study.

The composition of the intervention group and the control group was comparable with respect to gender and age. We did not analyse for prior disorders and psychosocial factors but the two groups were of similar composition with respect to age, sex, and educational and social background. We consider bias due to differences in exposure or vulnerability in the two groups unlikely because of the almost identical content and organization of work, workstation ergonomics and psychosocial work environment. We did not analyse for other covariates such as prior disorders and psychosocial factors but the two groups were comparable with respect to these factors.

Complete blinding of the physical examination could not be achieved. This would demand randomization to the intervention which, however, was deliberately offered to staff in one division of an engineering company with controls in a geographically separated division in order to avoid mutual contacts between intervention and control subjects and thus to prevent the controls to also engage in the stretching exercises if the intervention subjects would perceive them as beneficial. Apart from this, subjectivity was reduced by performing all physical assessments blinded to any other information about the studied computer operators.

Findings were entered into patterns according to predefined algorithms. Still, it cannot be excluded that one finding, e.g. of weakness in a specific muscle, can bias other findings such as sensory deviations because all physical examinations were made by the same examiner. The execution of the examination may have changed slightly from baseline to follow-up. However, the intra-examiner reliability of the applied examination is likely to be good because the inter-examiner reliability has previously been found satisfactory 23. It may also be argued that a tendency of the study subjects towards more familiarity with the physical examination at the second examination could result in muscle function for example improving over time or nerve trunk soreness being perceived as less uncomfortable than previously. These potential sources of bias cannot be overcome.

A certain fluctuation of findings was noted in the intervention group as well as among controls. However, persistence for some time of physical neurological findings which appear to be characteristic for peripheral nerve afflictions would result in a reduced influence on physical findings of the intervention. Our clinical experiences with assumed neuropathic upper limb conditions suggest that patients reporting fewer symptoms at control visits after successful treatment may still present unchanged levels of pareses and sensory dysfunction. It therefore seems possible that a significant reduction of physical findings would require a follow-up of longer duration.

There is no indication that effective prevention can be accomplished by the isolated use of stretching exercises. However, as a supplement to ergonomic and organizational change stretching may well contribute to reduce the burden of computer-related upper limb disorders.

The outcome of this intervention may serve to further illustrate the character of computer-related upper limb disorder by indicating the relation of incident symptoms to neurological patterns suggesting nerve-afflictions with specific locations. Consequently, it contributes to a further validation of the employed physical examination 234.

When performed three times a day stretching designed to improve the available space and mobility of nerves at the infraclavicular brachial plexus and the posterior interosseous and median nerves at elbow level can reduce computer-related upper limb pain. However, no firm conclusions can be drawn with regard to an influence on physical findings except for the observation that incident symptoms were related to findings suggesting pathology at the three levels. The results of this study may contribute to the prevention of computer-related upper limb disorders and also provide support to hypotheses on the role of peripheral nerve-afflictions in these conditions.

The author(s) declare that they have no competing interests.

G Thomsen and J R Jepsen have designed the study. J R Jepsen collected the data relating to the physical examination. G Thomsen was responsible for the electronic questionnaire, data-management and the statistical calculations. J R Jepsen prepared the manuscript which has been approved by G Thomsen.