The effects of muscular fatigue on the coordination of a multijoint movement in human.

The purpose of the present experiment was to investigate the adaptation to fatigue in a multijoint movement. The subjects' task was to throw a ball towards one of three targets in two conditions of no fatigue and fatigue. Results showed that the number of successful trials decreased with fatigue. Analysis of these successful trials showed that, without fatigue, the final hand velocity resulted from a 'summation of speed' principle from the elbow to the hand joint. With fatigue, a new inter-segmental organization was necessary in order to maintain a good motor performance. This compensating strategy was characterized by the absence of a temporal delay between the elbow and hand peak velocity suggesting that, with fatigue, movement organization was similar to that of a rigid system. In other words, the 'summation of speeds' principle was no more respected.