Strenuous endurance training in humans reduces oxidative stress following exhausting exercise

The aim of this study was to evaluate whether high-intensity endurance trai ning would alleviate exercise-induced oxidative stress. Nine untrained male subjects (aged 19-21 years) participated in a 12-week training programme, and performed an acute period of exhausting exercise on a cycle ergometer b efore and after training. The training programme consisted of running at 80 % maximal exercise heart rate for 60 min . day(-1), 5 days . week(-1) for 1 2 weeks. Blood samples were collected at rest and immediately after exhaust ing exercise for measurements of indices of oxidative stress, and antioxida nt enzyme activities [superoxide dismutase (SOD), glutathione peroxidase (G PX), and catalase (CAT)] in the erythrocytes. Maximal oxygen uptake ((V) ov er dot O-2max) increased significantly (P < 0.001) after training, indicati ng an improvement in aerobic capacity. A period of exhausting exercise caus ed an increase (P < 0.01) in the ability to produce neutrophil superoxide a nion (O-2(.-)) both before and after endurance training, but the magnitude of the increase was smaller after training (P < 0.05). There was a signific ant increase in lipid peroxidation in the erythrocyte membrane, but not in oxidative protein, after exhausting exercise, however training attenuated t his effect. At rest, SOD and GPX activities were increased after training. However, there was no evidence that exhausting exercise enhanced the levels of any antioxidant enzyme activity. The CAT activity was unchanged either by training or by exhausting exercise. These results indicate that high-int ensity endurance training call elevate antioxidant enzyme activities in ery throcytes, and decrease neutrophil O-2(.-) production in response to exhaus ting exercise. Furthermore, this up-regulation in antioxidant defences was accompanied by a reduction in exercise-induced lipid peroxidation in erythr ocyte membrane.