Background: Intensive physical activity is known to induce oxidative stress. that could endanger the health of athletes. Also Quercetin is a flavonoid with antioxidant and anti-inflammatory properties. Therefore, the aim of this study was to investigate the effect of quercetin on time to exhaustion and oxidative stress in male soccer players.

Methods: This placebo‑controlled, double‑blind clinical trial was conducted on 22 football players for Six weeks. The subjects were randomly assigned to one of two groups to receive quercetin (1000 mg) or placebo (1000 mg dextrose). Anthropometric measurements, time to exhaustion and blood biochemical parameters including SOD, CAT, GPx  and MDA were measured at the beginning and end of the study. and the data were analyzed using paired t-test.

Results: At the end of the study in Quercetin group time to exhaustion, Enzyme activity of SOD, CAT and GPx  were significantly increased (p<0.05) and mean serum malondialdehyde (MDA) were significantly decreased (p<0.05). Also mean of these parameters between the two groups were significantly different from each other (p <0.5).

Conclusion: In this study, supplementation with 1000 mg of Quercetin per day for 6 weeks, increased time to exhaustion and SOD, CAT and GPx  enzyme activity and decreased serum malondialdehyde significantly.