Overstretch-Induced Reactive Oxygen Species Formation and Functional Decline in Skeletal Muscle: 2281 Board #117 June 1 9 30 AM - 11 00 AM

Lengthening of skeletal muscle in eccentric exercise is linked with reduced fatigue resistance and muscle injury. Previous study has shown that eccentrically-biased exercise (i.e., downhill run) induced muscle damage is associated with leukocyte apoptosis. However, molecular evidence of reactive oxygen species (ROS) in stretched or eccentric muscle activities induced muscle dysfunction and apoptosis is not clear. PURPOSE: To evaluate ROS formation and muscle function in overstretched skeletal muscle in mice and to determine the effects of antioxidant intake on peripheral leukocyte apoptosis following eccentrically-biased downhill running. METHODS: Diaphragm muscle strips were isolated from C57BL6 mice and mounted in a contractile chamber. The muscles were either kept at its optimal length (control) or stretched to 30% of the optimal length, followed by a 5-min tetanic contraction. Cytochrome c was used to monitor superoxide O •- release during contraction. Muscle force was recorded during the contractile protocol. In human eccentric exercise model, 22 subjects were randomly assigned into two groups taking: i) vitamin C (1000 mg/day) and vitamin E (400 IU/day); ii) maltodextrin (placebo) in a double-blinded fashion. Supplementation was administered for two weeks before downhill running exercise and two additional days after the training. At 0, 6, 24, 48h following the trial or prior to the trial, blood samples were collected for anti-apoptosis Bcl-2 assay via ELISA. Data were statistically analyzed as mean ± SE using one-way ANOVA. RESULTS: Overstretched diaphragm showed compromised muscle function compared to control (n = 10-13; p < 0.05). More ROS were induced in overstretched groups than control during contraction (n = 6-10; p < 0.05). In human model, we observed an increase in circulating leukocyte apoptosis and muscle soreness/damage 24-48 hours following exercise. Antioxidant attenuates the decrease in Bcl-2 at 24 hours following acute downhill running. CONCLUSION: Overstretched skeletal muscle is subjected to declined contractile function and exacerbated ROS formation. The combination of antioxidants supplementation appears to have a protective role via the attenuation of decrease in anti-apoptotic protein during eccentric exercise.