Exercise and restricted activity effects on reinnervated and cross-innervated skeletal muscles.

The effects of relative degrees of post-operative muscle activity and inactivity were compared in animals having undergone peripheral nerve section and repair (i.e. cross-innervation and self-innervation). The muscles involved were the fast twitch flexor hallucis longus and the slow twitch soleus muscles of the guinea pig. Reinnervation of the muscle was complete with either the original nerve or with a foreign nerve after 6 months in all groups of animals regardless of whether the animals were exercised or confined to small individual cages so as to restrict their activity. It can be stated that: (a) the duration (1 week-1 month) of hind-limb immobilization did not alter the extent and efficiency of reinnervation; (b) muscle protein concentration fell in animals whose hind-limbs were immobilized 1 month post-operatively; (c) by using the cross-innervation procedure, histochemical fiber populations correlated closely with the physiologically determined contraction time of the muscle.