Muscle activity during computer-based office work in relation to self-reported job demands and gender.

The aim was to investigate whether quantitative job demands influence muscle activity among women, and whether there are gender differences in duration of computer, mouse, and keyboard use and muscle activity of shoulder and forearm muscles during work. The study was carried out in an occupational setting, and 24 women and 11 men from a municipal administration participated. The duration of computer, mouse, and keyboard use was measured by a commercial software package. Quantitative job demands were registered by questionnaire. Electromyography (EMG) was measured bilaterally from the upper trapezius and the extensor digitorum communis muscles. No association was found between self-reported quantitative job demands and muscle activity among the women ( n=24). The women used the keyboard more frequently ( p=0.020) and tended to perform fewer mouse clicks compared to men ( p=0.057), but no difference was seen in EMG activity between men ( n=11) and women ( n=11) from the same department. However, office assistants (six women) showed significantly higher static EMG activity levels ( p=0.042) and almost significantly shorter EMG gap times ( p=0.060) than the rest of the subjects (5 women and 11 men). This indicated that shorter muscular resting periods among female office assistants as compared to the other subjects were due to differences in job content rather than gender differences.