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.