Objective To determine whether antioxidant supplements and antioxidant-enriched foods can prevent or reduce delayed-onset muscle soreness after exercise.

Methods We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, SPORTDiscus, trial registers, reference lists of articles and conference proceedings up to February 2017.

Results In total, 50 studies were included in this review which included a total of 1089 participants (961 were male and 128 were female) with an age range of 16–55 years. All studies used an antioxidant dosage higher than the recommended daily amount. The majority of trials (47) had design features that carried a high risk of bias due to selective reporting and poorly described allocation concealment, potentially limiting the reliability of their findings. We rescaled to a 0–10 cm scale in order to quantify the actual difference between groups and we found that the 95% CIs for all five follow-up times were all well below the minimal important difference of 1.4 cm: up to 6 hours (MD −0.52, 95% CI −0.95 to −0.08); at 24 hours (MD −0.17, 95% CI −0.42 to 0.07); at 48 hours (mean difference (MD) −0.41, 95% CI −0.69 to −0.12); at 72 hours (MD −0.29, 95% CI −0.59 to 0.02); and at 96 hours (MD −0.03, 95% CI −0.43 to 0.37). Thus, the effect sizes suggesting less muscle soreness with antioxidant supplementation were very unlikely to equate to meaningful or important differences in practice.

Conclusions There is moderate to low-quality evidence that high-dose antioxidant supplementation does not result in a clinically relevant reduction of muscle soreness after exercise of up to 6 hours or at 24, 48, 72 and 96 hours after exercise. There is no evidence available on subjective recovery and only limited evidence on the adverse effects of taking antioxidant supplements.