Antagonistic effects of endurance training and testosterone on alkaline proteolytic activity in rat skeletal muscles.

Endurance swimming training for 8 weeks led to an increase by about 50% of alkaline proteinase activity in musculus extensor digitorum longus and about 10% in musculus soleus of normal male rats as compared to sedentary control rats. This exercise-mediated increase of proteolytic activity was prevented by the simultaneous administration of 10 mg testosterone propionate/kg body weight twice a week. The data suggest that testosterone has a regulatory effect on the alteration of the protein-degradative mechanism during endurance training.