Extreme running competition decreases blood antioxidant defense capacity

OBJECTIVE: We tested whether an extreme running competition ("Marathon of Sands") might alter the blood's enzymatic and non-enzymatic antioxidant status in 6 well-trained athletes. METHODS: The Marathon of Sands is a competition consisting of six long duration races in the desert in which the athletes carry their own food. Blood samples were collected from an antecubital vein while the athletes were at rest before the competition and then again 72 hours after. Erythrocyte antioxidant enzyme activity (glutathione peroxidase, superoxide dismutase), erythrocyte glutathione level, plasma non-enzymatic status (vitamin C, alpha-tocopherol, retinol, beta-carotene and carotenoids) and plasma lipid peroxidation marker (TBARS) were measured. RESULTS: The Marathon of Sands induced a significant alteration of the blood antioxidant defense capacity. Indeed, 72 hours after the race, significant decreases were recorded in erythrocyte superoxide dismutase activity and in plasma concentrations of retinol, beta-carotene and other carotenoids. These changes were associated with a concomitant increase in erythrocyte glutathione and in plasma TBARS levels. CONCLUSION: This study indicated that such extreme competition induced an imbalance between oxidant and antioxidant protection.