Discharge properties of group III and IV muscle afferents.

Stimulation of group III and IV muscle afferents has been shown to have important reflex effects on both the somatic and autonomic nervous systems. These include an inhibitory effect on alpha motoneurones, an excitatory effect on gamma motoneurones and an excitatory effect on the sympathetic nervous system. The purpose of this review is to describe the mechanical and metabolic stimuli that discharge group III and IV muscle afferents. Particular attention will be paid to the responses of these afferents to dynamic exercise induced by electrical stimulation of the mesencephalic locomotor region.