Acute response to precision, time pressure and mental demand during simulated computer work

Objectives The electromyographic (EMG) activity of shoulder and forearm mus cles was recorded during a standardized computer task with different combin ations of time pressure, precision demands, and mental demands to study the interaction of these factors and their effect on muscular response during simulated computer work. Methods The computer task lasted 5 minutes, and it was performed by 14 fema le computer-aided design (CAD) operators during 8 exposure combinations tha t differed with respect to time pressure, precision demand, and mental dema nd. Performance (number of produced drawings, mouse clicks, and errors) wer e recorded. The EMG activity was recorded from the trapezius, infraspinatus , deltoid, and extensor digitorum muscles. An electrogoniometer was used to measure wrist postures and movements. Results High time pressure (combined with low precision and low mental dema nds) resulted in higher EMG activity for all the muscles and in a small inc rease in the number of produced drawings. High precision demands caused a l arge reduction in the number of produced drawings, but not always a change in EMG activity. High precision demands and high mental demands led to no c hange or a reduction in muscle activity because the number of drawings was greatly reduced. Conclusions The interaction between work pace and other exposure factors mu st be taken into account when the effects of changes in exposure demands on muscular response are predicted. Only then can it be predicted whether cha nging demands will constitute a risk of developing musculoskeletal disorder s.