Effects of Unilateral Muscle Fatigue on Performance and Force Coordination in Bimanual Manipulation Tasks.

We examined the effects of unilateral muscle fatigue on the performance and coordination of grip (GF; normal component acting between the hand and object) and load force (LF; tangential component) in bimanual manipulation tasks, as well as the associated lateral differences. Eleven participants performed various symmetric bimanual tasks either without fatigue, or after fatiguing the GF producing muscles of either the nondominant or dominant hand. The GF/LF ratio of the fatigued and nonfatigued hand decreased and increased, respectively, while the neither the effects of fatigue on the task performance and GF-LF coordination, nor the lateral differences were revealed. The lack of the fatigue associated effects on most of the tested variables typically observed from unimanual tasks could be explained by bimanual assimilation. The findings also suggest that in daily life switching to bimanual tasks when one hand becomes fatigued could be beneficial regarding preserving the high level of both the manipulation performance and force coordination.