Study aim: To assess the effects of training on the activities of antioxidant enzymes in erythrocytes and on the total plasma antioxidant status in competitive pentathletes.

Material and methods: A group of 10 senior male pentathletes (P) and of 10 sedentary male subjects (S) participated in the study. Blood was withdrawn from the antecubital vein in the morning, in the preprandial state. The activities of superoxide dismutase (SOD), glutathione reductase (GR) and catalase (CAT) were determined in erythrocyte haemolisates, that of glutathione peroxidase (GPX) in whole blood haemolysate, and the total antioxidant status (TAS) in plasma.

Results: The activities of all enzymes were significantly (p<0.05 - 0.001) higher in P than in S group while no significant between-group difference was found for TAS.

Conclusions: The pronounced enzymatic antioxidative potential and oxidative stress defence observed in athletes practicing modern pentathlon may be attributed to their extensive training.