Protection of Heat Pre-treat Adaptability against Skeletal Muscle Injury Induced by Eccentric Exercise and its Effects on Free Radical Metabolism

Objective: to investigate the effects of heat adaptation of 16 days on skeletal muscle injury induced by an eccentric exercise. Methods: 80 male Sprague-Dawley (SD) rats were randomly divided into non-heat adaptive groups and heat adaptive groups, each of which was further divided into quiet group, immediately after exercise group, 24 hours after exercise group, 48 hours after exercise group, and 6days after exercise group. Rats in heat groups were subjected to whole-body hyperthermia for 16 days (30-35 min /d of heat stimulation) and were allowed to recover from the last whole-body hyperthermia for 24 hours. Following all the exercise groups performed exhaustive exercise on a treadmill with the gradient of -16 degrees and the speed of 20m/min. The rats were killed on 0,1,2,6 days after exercise and isolated gastrocnemius, which were sampled to be observed by light microscopy and analyze SOD activity and MDA content. Results: 1) Skeletal muscle injury degrees of heat stress-exercise groups were largely lower than that of simple exercise groups. 2) SOD activity in heat stress-exercise groups was higher than simple exercise groups at any time points. Its activity of 24 hours after heat stress-exercise group was significantly higher than that of 24 hours after simple exercise group (P<0.01); while the tendency of MDA content was opposite and its content of 24 hours and 48 hours after heat stress-exercise group were markedly lower than that of 24 hours and 48 hours after simple exercise group (P<0.0 land P<0.05, respectively). Conclusion: The 16-day heat adaptation can protect against eccentric exercise induced muscle injury, and correct free radical metabolism disorder in skeletal muscles.