Effect of endurance exercise on fibre type composition and muscle weight of reinnervating rat plantaris muscle.

The purpose of this study was to evaluate the effect of endurance exercise on the histochemistry and wet weight of the reinnervating rat plantaris muscle. Two groups of young female Wistar rats (6 weeks old), 1 sedentary denervated control (n = 13) and 1 exercised denervated experimental (n = 17), were denervated unilaterally by cutting and resecting the sciatic nerve. To effect reinnervation a skin grafting operation was carried out on the nerve so that the gap caused by resection was bridged. The third group was the sedentary non-denervated normal control (n = 10). A progressive training program of 18 weeks of treadmill running was carried out by the experimental group. Approximately 5 months after denervation, the plantaris muscles were studied histochemically for reduced nicotinamide adenine dinucleotide diaphorase (NADH-D) and mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) activities. Fibres were classified as "red", "white", or "intermediate" with NADH-D. Alpha-GPD differentiates "intermediate" from "red" fibre types in case of difficulty in differentiating these fibre types from each other with NADH-D. The weight of the reinnervated plantaris muscle increased significantly after exercise. The exercise did not change the fibre type proportions--including "red" fibre type--in the deep region of the reinnervating plantaris. There were significant differences between normal control and denervated control or experimental groups in histochemical fibre populations in the deep region of the plantaris. The findings of this study suggest that: treadmill running did not increase the oxidative capacity of the deep region of the reinnervating rat plantaris muscle; treadmill training did not damage the reinnervating plantaris.(ABSTRACT TRUNCATED AT 250 WORDS)