and the dynamic muscle activity of the extensor. This was to be expected but it must be pointed out that the two subjects with the longest endurance time initially had a rather high EMG activity in the extensor that was constant during the whole registration time. It also was higher than the end EMG level of subjects that stopped tapping very soon and showed an increase of the EMG.
In the trapeze muscle the levels of both the phasic and dynamic activity strongly differed between subjects. In two subjects the static component surpassed five percents MVC, while two other subjects had a phasic activity that was below two percents MVC. In some subjects fast tapping provoked a high and constant tension in the trapeze muscle although we asked for a relaxed posture. In a prior experiment ( Schnoz et al., 1999) increased neck muscle activity also occurred at slow tapping speed.
We hypothesize that interactions between individual muscle activation patterns (here biornechanically not needed muscle contractions) and certain repetitive tasks (here fast tapping) may cause overloading of the involved muscles and may explain why tasks that involve repetitive finger movements constitute a high risk to develop tension neck pain.
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