Task dependence of muscle synchronization in human hand muscles.

We put forward the hypothesis that synchronous muscle activation would be less frequent with increasingly more complex grip tasks. Six subjects performed a visuo-motor step-tracking task using the precision and the power grip. During the experiment transcranial magnetic stimuli were applied. Electromyographic activity was recorded from the hand muscles active in both tasks. Muscle synchronization was found to be enhanced during the power grip as compared to the precision grip. Magnetic stimulation had a stronger effect during the precision grip than during the power grip. Our findings are in favour of a variable organization of muscle activation in hand muscles during various tasks and support the stronger contribution of the corticomotoneuronal system in the precision than the power grip.