Abstract: Objective:To investigate the effects of heat pretreat adaptability of 16 days on skeletal muscle injury induced by an eccentric exercise.Methods:80 male Sprague-Dawley(SD) rats were randomly divided into non-preheat adapted groups and preheat adapted 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 6 days 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.All the exercise groups performed an exhaustive exercise on a treadmill.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 measured HSP70 expression.Results:1) The degrees of skeletal muscle injury in pre-heat adapted-exercise groups were markedly lower than that of simple exercise groups at corresponding time points.2) HSP70 expression of rats immediately and 48 hours after exercise in preheat adapted-exercise groups increased significantly comparing with the simple exercise groups at corresponding time points respectively(P<0.05).Conclusion:Heat pretreat adaptability can protect against eccentric exercise-induced muscle injury,and the mechanism may be related to heat pretreat adaptability of 16 days which can up-regulate the expression of HSP70.