Antioxidants, like vitamin C, are commonly taken by athletes to reduce free radical production. Free radicals increase after exercise and may play a role in the development of muscle soreness and damage. Scientists have shown that taking moderate doses of vitamin C (100 to 500mg a day) for two weeks can help improve muscular recovery from intense eccentric exercise (like downhill running). However, vitamin C does not always reduce muscle soreness despite the fact that it can decrease the formation of free radicals. Some researchers have demonstrated that 400mg of vitamin C given for two weeks prior to an intermittent shuttle run can moderately reduce muscle soreness, while other researchers have found that 1g of vitamin C given for two weeks did not reduce muscle soreness two days after downhill running. The reduction of soreness may depend on the type of exercise and the time at which soreness is evaluated. The latest investigation on vitamin C supplementation showed that a high dose of vitamin C (3g per day) given for two weeks, reduced arm muscle soreness for up to 24 hours following intense eccentric elbow extensions. However, after 1 day, muscle soreness did not differ from placebo. The mechanism of reduced soreness was speculated to be a result of decreased oxidized muscle glutathione levels in the blood, which were lower at 4 and 24 hours post-exercise. This study also evaluated recovery rates and muscular force development after the exercise, and saw no improvement with vitamin C. Therefore, vitamin C may confer benefits for reducing muscle soreness after damaging exercise.

Goldfarb AH, Patrick SW, Bryer S, You T. Effect of High Dose Vitamin C Supplementation on Muscle Soreness, Damage, Function, and Oxidative Stress to Eccentric Exercise. Int J Sport Nutr Exerc Metab. 2005 Jun;15(3):279-90.