Abstract: BACKGROUND: A heavy load exercise may lead to skeletal muscle damage and the mitochondrial dysfunction. As an important treatment measure, acupuncture should play a certain role in the repair of injury.
OBJECTIVE: To investigate the damage of skeletal muscle mitochondria in different phases after a heavy load exercise and acupuncture intervention, and further explore the role of acupuncture in preventing and treating exercise-induced skeletal muscle injury. 
METHODS: Male Sprague-Dawley rats were randomly divided into a control group, an acupuncture group, an exercise group and an exercise+acupuncture group. Among them, exercise and exercise+acupuncture groups performed a single bout heavy load exercise; and acupuncture and exercise+acupuncture groups performed acupuncture intervention. The acupuncture, exercise and exercise+acupuncture groups were further divided into 0, 2, 6, 12, 24, 48, and 72 hours groups according to the time points of sampling after the intervention. The ultrastructural changes of skeletal muscle mitochondria were observed by transmission electron microscopy. The fluorescence ratio of JC-1 was detected by fluorescent enzyme labeling technique. The content of cytoplasmic cytochrome C and mitochondrial function index, the activity of succinate ubiquinone oxidoreductase, were determined by ELISA.  
RESULTS AND CONCLUSION: After exercise, the mitochondrial ultrastructure was obviously damaged (severest at 12-24 hours), the cytoplasmic cytochrome C content was increased (P < 0.05), and the JC-1 ratio and succinate ubiquinone oxidoreductase activity were decreased (P < 0.05). The mitochondria were normal after acupuncture, and there was no significant changes in each test index (P > 0.05). Acupuncture intervention decreased the ultrastructural damage of skeletal muscle mitochondria, reduced the cytoplasmic cytochrome C content (P < 0.05), and increased the JC-1 ratio and succinate ubiquinone oxidoreductase activity (P < 0.05). To conclude, after a bout of eccentric exercise, the mitochondria have different degrees of damage and temporal changes, which peak from 12 to 24 hours. Acupuncture alone cannot cause obvious damage of skeletal muscle mitochondria. Acupuncture intervention can effectively improve mitochondrial damage caused by exercise and promote the recovery of mitochondrial function after exercise.

Key words: heavy load exercise, skeletal muscle, mitochondrial damage, acupuncture, rat