Objective To explore whether a single bout of exhaustive exercise can activate autophagy in mice skeletal muscles and to investigate the effect and possible mechanisms of exercise-induced autophagy on antioxidant defense function in vivo.Methods Thirty healthy 4-week-old male C57BL/6 mice were randomly divided into a control group(n=6) and an exercise group(n=24).The latter was subjected to a single bout of exhaustive treadmill exercise.Gastrocnemius muscles of 6 mice on both sides were then isolated right after,as well as 6h,12h and 24h after the running.The manganese super oxide dismutase(MnSOD),total superoxide dismutase(T-SOD) and Copper-Zinc superoxide dismutase (CuznSOD) activities were determined using the xanthine oxidase method and the content of the total anti-oxygen capability(T-AOC) using the colorimetric method.The expression of Beclin1,P62 and Bcl2 mRNAs,as well as their proteins were determined using the fluorescent quantitative PCR and Western blotting.Results The expression of Beclin1 mRNA in gastrocnemius muscles of the exercise group increased more significantly than that of the control group right after the exercise,as well as 6 hours later(P＜0.01).P62 mRNA expression also increased significantly(P＜0.01) 24h after the exercise.In contrast,the expression of P62 protein at 0h,12h and 24h after the exercise decreased more significantly(P＜0.05 or P＜0.01) than that of the control group.Similarly,the expression of Bcl2 protein at 0h,6h and 12h increased significantly(P＜0.05 or P＜0.01).The MnSOD and CuznSOD activity increased significantly right after the exercise(P＜0.05).The T-SOD activity decreased significantly(P＜ 0.01) 6h after the exercise.T-AOC content increased significantly 6h,12h and 24h after the exercise (P＜0.05 or P＜0.01).The P62 protein expression was negatively correlated with T-AOC content.Conclusion The single bout of exhaustive treadmill exercise can activate the expression of such autophagyrelated factors as Beclin1 mRNA and P62 protein and increase the autophagy to a certain extent to maintain antioxidant defensive function of the skeletal muscle.