Antioxidants for preventing and reducing muscle soreness after exercise: a Cochrane systematic review

Cochrane systematic review of 50 randomized trials, including parallel-group and crossover designs, in 1089 adults engaged in exercise. Participants were generally healthy, mostly male (961 male, 128 female), aged 16 to 55 years; elite athletes were not represented in the analyzed data.

Oral antioxidant supplements or antioxidant-enriched foods were given at doses higher than the recommended daily amount, typically once daily to up to three times per day. Regimens were started before exercise, continued on the day of exercise and afterward for several days; three studies used postexercise-only supplementation. Interventions were heterogeneous and included vitamin C, vitamin E, mixed antioxidant preparations, antioxidant extracts, whole food sources, and a few specific products such as N-acetylcysteine and tart cherry juice.

High-dose antioxidant supplementation did not provide a clinically relevant reduction in delayed-onset muscle soreness after exercise. Small effects were seen early, including up to 6 hours (SMD -0.30, 95% CI -0.56 to -0.04; MD -0.52 on a 0-10 scale), 24 hours (SMD -0.13, 95% CI -0.27 to 0.00; MD -0.17), 48 hours (SMD -0.24, 95% CI -0.42 to -0.07; MD -0.41), and 72 hours (SMD -0.19, 95% CI -0.38 to -0.00; MD -0.29), but these were below the minimal important difference for pain reduction of 1.4 cm. There was no clear benefit at 96 to 168 hours, and the authors concluded that antioxidant supplements or antioxidant-enriched foods are not an effective strategy to reduce DOMS after exercise. Adverse effects were poorly reported; 9 studies (216 participants) reported harms, with diarrhea and indigestion in one NAC study and mild gastrointestinal distress in one tart cherry juice study.

Evidence quality was moderate to low, and the review pooled a highly heterogeneous set of antioxidant products, doses, and exercise protocols. Most participants were young to middle-aged men, limiting generalizability, and elite athletes were not represented. Adverse effects were sparsely reported, and subjective recovery outcomes were unavailable.