We found five studies of moderate quality that offer some support for the use of chair interventions to improve musculo-skeletal pain or discomfort in workers who sit for prolonged periods. However there was a high degree of clinical heterogeneity meaning that more specific conclusions cannot be drawn. Because of the high occurrence of musculoskeletal problems among office workers, changes to their chairs are often recommended. The shortage of evidence involving office workers (only one study) is thus of concern, considering the investment in ergonomic chairs by corporations and companies. There is also a lack of evidence to assess the effect of chairs on children and adolescents in preventing or reducing musculoskeletal symptoms. Further research into this population with growing keyboard time is required - reinforced by the increasing trend of musculoskeletal symptoms among youths
The findings of this review indicate a consistent trend of support for the role of a chair intervention to reduce the severity, intensity and frequency of musculoskeletal pain among workers who are required to sit for prolonged periods. However because the studies reported different body areas it is not possible to be more specific about which kinds of musculoskeletal pain benefit the most. The most common parameter introduced in the chair intervention/s was to have an adjustable feature such as seat and back height. Electromyographic (EMG) studies have reported that a chair which is height adjustable and has adjustable backrest and armrests can reduce the muscle activity of the neck, shoulder and back, and also decreases the inter-vertebral disc pressure
[24–26]. Therefore there is some support that adjustability of the chair can be directly associated with the function of the musculoskeletal system. The second most common feature reported as a chair intervention, was that the participants received training in the use of their chair (how to adjust appropriately). This is intuitive and it is now valuable to have studies which support this as an essential feature of ergonomic interventions.
Other features of the interventions varied such as curved pan versus flat seating – two studies[17, 19]compared these with some suggestion that curved pan seating may be better in reducing upper body pain whilst flat seating may be superior for lower body pain. The authors postulated that the curved, 2-part seat pan supports the forward leaning posture by allowing a more open thigh-torso angle. These findings need confirmation in further studies. Saddle seating also seemed to have differential effects on back versus lower limb comfort – again this requires further careful investigation before recommendations can be made
The study by Gadge
 was the only eligible publication which included productivity as an outcome. The study sample was very small and the types of outcomes – i.e. typing speed and errors – were not relevant to all seated workers. It is an assumption that ergonomic intervention correlates with productivity
[9, 27]. However, this review found no supporting evidence for positive gains in productivity and this factor should be incorporated as an outcome in future research. No studies reported on cost aspects of the intervention.
Although all five studies conducted follow-up assessments of the symptoms, the longest follow-up period was only a year
. This indicates a gap in showing whether the effectiveness of a chair intervention has long-term benefits, particularly with respect to musculoskeletal symptoms, as well as the recurrence of symptoms and the consequent cost of care. Chronicity in work-related musculoskeletal pain is multifactorial, with risk profiles relating to psychosocial factors dominating the literature
. We believe future studies, addressing long-term effects, need to be designed to take these factors into account.
The effect of bias on the interpretation and trustworthiness of the evidence cautions against making conclusive recommendations pertaining to the effect of a chair intervention. The key methodological shortcomings which introduced bias were absent/unclear randomization procedures and concealed allocation. These may introduce selection bias which can result in a higher association (odds ratio) between the exposure and the subject. Because of the occurrence of selection bias, it is also not possible to relate the results to the general population. A further methodological issue arose in that two papers used the same overall population to report two different subgroups (based on two regions of pain). We therefore treated these sub-groups as two studies, assuming pain regions were independent events. Across the board the authors of the reviewed articles failed to mention whether confounding factors, such as female gender, were controlled for as the allocation procedures were not mentioned. Future research should address these methodological shortcomings to improve the validity of the findings and thereby increase the quality of the evidence to support a chair intervention.
Clinical implications - clinicians can cautiously support or advocate for the provision of adjustable chairs in the workplace and offer appropriate training in how to adjust and manage posture whilst seated. Monitoring of pain reduction/increased comfort ratings will confirm effectiveness in individual cases.
Research implications – further urgent research is required to clarify the relationship between environmental features (such as chairs), poor posture and symptoms as currently these relationships are inferred. Furthermore specific effectiveness research is required to confirm the reviewed studies using
Clearly defined interventions;
Outcome measures that include symptoms as well as performance;
Cost-effectiveness needs to be measured to allow interpretation of health benefits in light of intervention costs;
Longer term follow-up to monitor effects after the period of observation/attention;
Robust methodology (in particular concealed allocation and randomisation);
Other populations including occupational groups in the information technology and call centre industries, adolescents and children who are also required to sit for prolonged periods.