Overview: potential role of segmental motor circuitry in muscle fatigue.

This chapter reviews several mechanisms that the CNS may use to mitigate muscle fatigue, including intrinsic motoneuron properties and feedback systems. The emphasis is on the effects of sensory inputs on spinal cord interneurons including: Renshaw cells; Ib inhibitory interneurons; interneurons mediating presynaptic inhibition; Ia inhibitory interneurons; and interneuronal networks constituting central pattern generators for locomotion. This exercise brings out how little is known about the operation of these circuits in dealing with muscle fatigue.