Task-dependent nature of fatigue in single motor units

The loss of force production during sustained activity presents the CNS a unique control problem. Different tasks stress the neuromuscular system at different sites and times, and involve different cellular mechanisms. The functional organization of muscles and their motor units has evolved to avoid fatigue processes that impair motor performance. The purpose of this brief review is to examine the fatigue properties of type-identified motor units and to speculate what these properties reveal about the organization and control of muscle.