Strenuous physical exercise generates intracellular free radicals which may impair the pro-oxidant to antioxidant balance thus resulting in an oxidative stress which led to cell biomolecules damage. In this paper a survey of the main antioxidant enzyme systems involved in the sport activity is presented. We will focus on the molecular and functional properties of the major antioxidant enzymes and on their involvement in physical sport activity and muscle contraction, In particular, superoxide dismutase, catalase, as well as the enzymes involved in glutathione level homeostasis and the thioredoxin system will be approached.