Antioxidants and exercise.

Muscular exercise results in an increased production of radicals and other forms of reactive oxygen species. Further more, growing evidence implicates cytotoxic ROS as an underlying cause in exercise-induced disturbances in muscle redox status that could result in muscle fatigue or injury. Muscle cells contain complex cellular defense mechanisms to minimize the risk for oxidative injury. Two major classes of endogenous protective mechanisms work together to reduce the harmful effects of oxidants in the cell: (1) enzymatic and (2) nonenzymatic antioxidants. Key antioxidant enzymes include superoxide dismutase, glutathione peroxidase, and catalase. These enzymes are responsible for removing superoxide radicals, hydrogen peroxide or organic hydroperoxides, and hydrogen peroxide, respectively. Important nonenzymatic antioxidants include vitamins E and C, beta-carotene, GSH, uric acid, ubiquinone, and bilirubin. Vitamin E, beta-carotene, and ubiquinone are located in lipid regions of the cell, whereas uric acid, GSH, and bilirubin are in aqueous compartments of the cell. Although numerous animal experiments have demonstrated that the addition of antioxidants can improve muscular performance, to date, limited evidence shows that dietary supplementation with antioxidants improves human performance. This is an important area for future research.