Lack of antioxidant adaptation to short-term aerobic training in human muscle.

The effects of 8 wk of 35 min of aerobic cycle training (3 times/wk) on indexes of male and female human vastus lateralis muscle antioxidant status were investigated. Training resulted in significant elevations in whole body maximal O2 consumption and muscle citrate synthase activity. Despite this, muscle superoxide dismutase, catalase, and glutathione peroxidase activities were not significantly altered by the training protocol. In addition, training did not affect muscle vitamin E (alpha- and gamma-tocopherol) concentrations. Glutathione status determined as the concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), total glutathione (GSH + 2 x GSSG), and GSH/GSSG ratio was unaffected by the training protocol. There were no significant differences between males and females in any indexes of muscle antioxidant status. These results indicate that the moderate aerobic training typically performed by regularly exercising humans did not positively alter endogenous antioxidant status. This suggests that short-term aerobic training increases capacity for flux through the citric acid cycle without necessarily increasing the ability to handle potential free radicals generated by the enhanced electron flux.