The purpose of this study was to investigate the effect of exercise trainings. 12 weeks Resistance training on the changes of MDA and SOD, GPX concentrations which were known to be markers of antioxidant defense system. To accomplish this purpose, nineteen high school students was selected and chosen as the subjects and also were divided into 2 groups Resistance training (RT) and control groups (CG). Resistance training group practiced resistance training 3 times a week for 3 months at 70-80% of 1 RM. The results were as follows. (1) In RT group, MDA concentration in all-out stage was found to have a significant increased. (2) In RT group, SOD concentration was found to have a significant difference in resting and all-out respectively before and after training. (3) In RT groups. GPX concentration in all-out stage was found to have a significant increased. As a result, it was found that Resistance training increased not only MDA but also antioxidant enzyme concentrations.