Antioxidants (beta carotene, vitamin C, vitamin E) have been promoted to enhance performance and to reduce the muscle damage that routinely occurs from exercise.
The work on the effect of antioxidants on performance has been mixed.
In general, supplements do not seem to provide additional benefits for athletic performance in well-nourished individuals. In vitamin C-deficient individuals, physical performance was improved with vitamin C supplementation. Some studies have shown that vitamin E supplementation improves performance at altitudes of 5000 and 15,000 feet.
Muscle Damage Studies:
Only small studies on antioxidants and muscle damage have been reported, and they have not been well-controlled. Some studies suggested that vitamin E reduced certain byproducts that are "markers" for muscle damage. Others found that vitamin C alleviated muscle soreness. More research is needed to confirm the role of antioxidants in exercise-induced muscle damage.