We investigated the effect of antioxidant supplementation on markers of muscle damage, antioxidant status, and delayed onset of muscle soreness (DOMS) after repeated downhill runs. Moderately-trained males (n=22) were randomly assigned to a supplement (S) or placebo (P) group. Capsules (vitamin C:1?000?mg/d; vitamin E: 400 IU/d) were ingested daily for 2 weeks. before the first (1D) and second (2D) downhill runs, and for 2 additional days following each run. Creatine kinase (CK) activity and oxygen radical absorbance capacity (ORAC) were measured pre-exercise and at 0 (immediately), 6, 24 and 48?h post-exercise (POST). DOMS was rated for quadriceps, hamstring, gluteus, gastrocnemius, and tibialis anterior at 0, 24, 48 and 72?h POST. CK at 48?h following 1D remained elevated above pre-exercise only in P (P<0.01). Overall, DOMS of the quadriceps was lower in S (1.1?0.3) than P (2.2?0.5) (P<0.05). At 24?h POST in S, CK was lower (P<0.01) and ORAC was higher (P<0.05) following 2D than 1D. CK and ORAC following 2D were blunted and augmented, respectively, in response to 1D and antioxidant supplementation enhanced this protective effect as indicated by an attenuation of biomarkers of muscle damage and a greater antioxidant capacity observed 24?h POST 2D.

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