Effects of Three Different Distance/Elevation-Gain Ultra-Trail Races on Red Blood Cell Oxidative Stress and Senescence, and Blood Rheology.

Purpose: Red blood cells (RBCs) senescence and blood rheology during ultra-endurance running events appear to be impacted differently depending on the race distance. The physiological mechanisms underlying these differences are poorly understood.

Methods: We investigated the effects of three different ultra-trail running races performed in La Reunion Island (Mascareignes, "the 70 km", 70 km/4,000 m D+; Trail Du Bourbon, "the 100 km", 100 km/6,090 m D+; Diagonale des Fous, "the 170 km", 170 km/10,500 m D+) on RBC oxidative stress, RBC senescence and blood rheology in 66 finishers (18 "70 km", 24 "100 km", 24 "170 km").

Results: We observed a decrease in RBC antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase and catalase) positively related to the race distance, and an increase in RBC H2O2 and isoprostane levels after the three races. However, RBC H2O2 and isoprostane levels were found to be higher after the 70 km compared to the 170 km and the 100 km races. RBC phosphatidylserine externalization increased over baseline value after the 70 km only. Chymotrypsin-like and trypsin-like activities of the RBC proteasome were decreased after all races compared to before. RBC-derived microparticles (RBC-MPs) were increased after the 170 km and the 70 km races. Despite increased RBC senescence markers, RBC deformability increased after the three races. Blood viscosity was differently impacted by the three races with a decrease at low shear rate after the two longest races (the 170 km and the 100 km), and an increase at high shear rate after the shortest one (the 70 km).

Conclusions: Our results confirm that ultra endurance running events differently impact on RBC senescence markers and blood viscosity depending on the race distance, and suggest that RBC oxidative stress could play a key role in the observed alterations.