The purpose of this study was to investigate the effects of heat-stress on skeletal muscles. In vivo experiments by using mice and rats, the wet weights and protein contents in soleus muscles were significantly increased by heat-stress (p<0.05). Histochemical analyses showed the increase in the cross-sectional area of soleus muscle fibers also were observed following heat-stress. The application of heat-stress facilitated the regrowth of atrophied soleus muscles induced by unloading. In the experiments by using cultured mouse skeletal muscles (C2C12), heat-stress stimulated the insulin-related intracellular signals involving Akt and glycogen synthase kinase 3β. These results strongly suggested that heat-stress could cause to increase in not only the basal metabolic rate via muscular hypertrophy but also the stimulation of intracellular glucose metabolism via the activation of insulin-related intracellular signals. Application of heat-stress on skeletal muscles would be a useful tool for the prevention and the improvement of metabolic syndrome.

DESCENTE SPORTS SCIENCE Vol.30/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE