Fifteen male Wistar strain rats were used to study the effect of endurance and sprint exercises on the volume and number of skeletal muscle mitochondria. In soleus muscle (SOL), the fraction of the mitochondrial volume, revealed by a point counting method, was significantly increased in SO and FOG fibers from the endurance-trained rats (p<0.05) and in FOG fiber from the sprint-trained rats (p<0.01). A significant increase (p<0.05) in the mitochondrial volume was observed in FOG, but not in SO and FG, of extensor digitorum longus muscle (EDL) from sprint-trained rat. Oxidative adaptation has been found in SO as well as FOG after the training program of endurance exercise. There was no change in concentration of elemental composition, except for decrease of potassium concentration, determined with rapid freezing, electron microscopy, and electron probe analysis, in the whole muscle cells of SOL and EDL after the training program. The mechanism of the swelling of mitochondria was also discussed.

DESCENTE SPORTS SCIENCE Vol.9/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE