This study was conducted to assess the effects of chronic daily spinach supplementation on known markers of muscle damage following half-marathon in well-trained healthy young men. Twenty well-trained men volunteered for this study. Participants were randomized in an open study placebo-controlled fashion into two groups, Spinach (S) (n = 10) and placebo (P) (n = 10). The participants took supplementation or placebo daily for 14 days before running. Participants ran 21 km. The spinach supplementation was prepared at 1 mg/kg body weight. Total Antioxidant Capacity (TAC) was determined as marker of plasma antioxidant capacity. LDH and bilirubin were measured as markers of muscle damage. TAC significantly elevated after supplementation in S group (P<0.05). The plasma level of LDH and bilirubin were significantly higher in P group after exercise (P<0.05). These results suggest that chronic daily oral supplementation of spinach has alleviating effects on known markers of muscle damage following a half-marathon in well-trained healthy young men.