Oxidative Stress in Young Football (Soccer) Players in Intermittent High Intensity Exercise Protocol. JEPonline 2009;12(5):1-10. Exercise can be associated with various benefits for health, but excessive physical activity may be stressful, for example high performance football, leading to oxidative cellular damage. Football training can produce an imbalance between RNOS and antioxidants, which is referred as oxidative stress. In the present work we performed the quantification of carbonylation levels, and antioxidants enzyme activities SOD and CAT in intermittent high intensity exercise protocol. Eighteen trained football players performed an intermittent high intensity exercise protocol. Blood samples were obtained before and immediately after exercise and centrifugation was used to separate plasma and cell fraction. SOD and CAT enzyme(s) activities had been determined by spectrophotometer. Lipid oxidative damage was analyzed by TBARS and protein damage by carbonyl groups. This study showed that this type of specific repeated-sprints exercise protocol for football players, produced oxidative stress, illustrated by significant differences in lipid peroxidation and protein carbonyls after exercise. Moreover, an increased (activity of) SOD and CAT enzyme activities, suggests an antioxidant adaptation of these athletes to this protocol.