Acute exercise markedly increases blood oxidative stress in boys and girls.

This study investigated the effect of an acute swimming protocol on selected blood redox status indices in trained children. Eleven boys and 11 girls (aged 9-11 y) swam 12 bouts of 50 m at a pace corresponding to 70%-75% of the participant's 50 m maximum velocity, with each bout separated by 1 min rest periods. At rest, no differences in any redox status marker between boys and girls were observed. As compared with the pre-exercise values, significant increases in thiobarbituric acid-reactive substances (TBARS), protein carbonyls, catalase activity, total antioxidant capacity (TAC), and oxidized glutathione (GSSG) concentration, as well as significant decreases in reduced glutathione (GSH) concentration and GSH:GSSG, were found post-exercise in both boys and girls. The magnitude of the exercise-induced alterations in the blood redox status based on the calculated effect sizes could be considered large for all parameters in both sexes (median effect size in absolute values was equal to 1.38). The main finding of the present study is that an acute swimming bout at 70%-75% maximum velocity resulted in blood oxidative stress in a similar manner in both trained young boys and girls.