These experiments were designed to investigate whether elevation of heat shock protein 70 (HSP70) in skeletal muscle prior to exercise contributes to protect from skeletal muscle damege induced by eccentric exercise In experiment 1, male ICR mice were exposed to 30 min of heyperthermia at 42℃. Soleus and extensor digitorum longus (EDL) were excised under the anaesthesia 24h after the exposure to heat. The amount of HSP70 in both skeletal muscles was determined by SDS-PAGE and western blot. Heat stress significantly increased the amount of HSP70 in both soleus and EDL muscle compared with the resting level. In experiment 2, male ICR mice were divided into two groups, exercise group and heat+exercise group. Heat+exercise group of mice was exposed to the same heat stress 24 h before exercise as experiment 1. Both groups of mice performed 60 min of downhill running (-20 degrees, 25 m/min). Skeletal muscles and plasma were removed under anesthezisis 12, 24 and 48 h after downhill running. Creatine kinase (CK) activity in plasma increased 12 h and 24 h after downhill running, while β-glucuronidase activity in soleus and EDL increased 48 h after downhill running. However, heat+exercise group of mice showed more suppressed level in both enzyme activities compared with exercise group. These finding suggest that heat stress prior to downhill running induces skeletal muscle HSP70 and leads to protective effect against skeletal muscle injury induced by downhill running.

DESCENTE SPORTS SCIENCE Vol.24/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE