While it’s normal to experience a little muscle soreness every now and then, normal muscle soreness generally goes away after a couple of days. Therefore, training of the back muscles and a varied organisation of work might have a preventive effect with respect to musculoskeletal complaints in VDU workers.Living with chronic pain can bring anyone to their wit’s end. Another part of the EMG activity increase has to be attributed to fatigue, to attention-related activity or to the combination of both. The increase in trapezius muscle activity was partly related to a lifting of the shoulders to compensate a slight slumping of the back. C7 became lower on average by 5.5 mm within an hour, whereas the acromions became lower by only 1.7 mm (left) and 3.3 mm (right).
On average, the distance between C7 and the left and right acromion decreased within each working an hour. The increase of the normalised RMS was significantly lower when the linear influence of posture was excluded. The normalised RMS of the left and right trapezius muscle increased, while the median frequency did not change. The position of the seventh cervical spinous process and the left and the right acromion were analysed synchronously with the EMG characteristics using regression analysis. Sitting posture was assessed using an eight-channel movement analysis system with ultrasound markers. Root mean square (RMS) and power spectrum median frequency of the EMG were calculated. Sixteen-channel surface EMG was bipolarly recorded from the erector spinae, trapezius, deltoid and sternocleidomastoid muscles. After the first and again after the second hour there was a break of 15 min. Nine healthy female office workers typed texts spoken from tape during three 1-h-long sessions.
Moreover, postural parameters were recorded to distinguish fatigue-related from posture-related changes of the myoelectrical activity. A study was carried out to investigate temporal changes of activation of shoulder and back muscles in workers at visual display units by means of surface EMG.
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