Differences in muscle load between computer and non-computer work among office workers

Abstract

Introduction of more non-computer tasks has been suggested to increase exposure variation and thus reduce musculoskeletal complaints (MSC) in computer-intensive office work. This study investigated whether muscle activity did, indeed, differ between computer and non-computer activities. Whole-day logs of input device use in 30 office workers were used to identify computer and non-computer work, using a range of classification thresholds (non-computer thresholds (NCTs)). Exposure during these activities was assessed by bilateral electromyography recordings from the upper trapezius and lower arm. Contrasts in muscle activity between computer and non-computer work were distinct but small, even at the individualised, optimal NCT. Using an average group-based NCT resulted in less contrast, even in smaller subgroups defined by job function or MSC. Thus, computer activity logs should be used cautiously as proxies of biomechanical exposure. Conventional non-computer tasks may have a limited potential to increase variation in muscle activity during computer-intensive office work.

Keywords:

• office ergonomics
• computer use
• exposure assessment
• EMG

Acknowledgements

The writers would like to thank Hans Bussmann, Fabiënne Schasfoort, Dorinde Keijzer-Oster and Jorn Fierstra for their help and cooperation during the workplace measurements. The study was possible with the financial support from the Dutch Science Foundation (NWO-Vidi, MF) and the Erasmus University (EUR-Fellowship, HS).