Does Endurance Exercise Training Increase the Need for Dietary Antioxidants?

1 KEY POINTS • Prolonged exercise at 65-80% VO 2 max increases the production of radicals in the contracting skeletal muscles. This exercise-induced radical production often results in oxidative damage to skeletal muscle fibers and contributes to muscle fatigue. • Antioxidant supplements are widely available and are commonly consumed by endurance athletes. Arguments exist both for and against the use of antioxidant supplementation. • The strongest argument supporting antioxidant supplementation exists in endurance athletes who do not consume a well-balanced diet. Specifically, if a nutritional evaluation reveals that the athlete is deficient in antioxidant intake (e.g., consumption below the recommended daily allowance [RDA] for antioxidant vitamins), dietary supplementation designed to achieve the RDA standard for antioxidant vitamins appears warranted. • The major argument against antioxidant supplementation is the possibility that megadoses of antioxidants (e.g., vitamin E and C) can diminish the training response to endurance exercise. • Although exercise-induced radical production can contribute to muscle fatigue during endurance exercise, studies demonstrate that supplementation with common antioxidants (e.g., vitamin E and C) do not improve exercise performance. Nonetheless, there are some suggestions that treatment with N-acetylcysteine can delay fatigue at work rates between 65-80% VO 2 max.