Passive exercise and reinnervation of the rat denervated extensor digitorum longus muscle after nerve crush.

Denervated extensor digitorum longus muscles of Wistar rats were passively exercised for 4 days (2 h/day) after peroneal nerve crush 1 cm from the muscle. Isometric contractile properties and endplate ultrastructure were measured 11 days postcrush. No significant differences were observed in tension characteristics between the exercised and nonexercised muscles on day 11. However, the postsynaptic area of endplates for exercised muscles were closer in size to controls than those for the nonexercised ones. In addition, the endplates from the exercised muscles exhibited increased numbers of axonal sprouts and terminals than nonexercised muscles. These results demonstrate that denervated muscles exercised 4 days before reinnervation can preserve the structure of the endplate as well as enhance reinnervation and sprouting at these endplates after 11 days of denervation.