Effects of hyperoxic training on red blood cell deformability and mechanical properties in elite male endurance athletes: A randomized crossover study

Background: The effects of hyperoxic environments on red blood cell (RBC) deformability and mechanical properties in athletes during high-intensity exercise remain poorly understood. This study aimed to investigate these effects and their potential implications for athletic performance. Methods: Forty elite male endurance athletes participated in a randomized, double-blind, crossover study. Participants completed high-intensity interval training sessions under normoxic (21% O2) and hyperoxic (40% O2) conditions. RBC deformability, whole blood viscosity, and physiological parameters were measured pre-exercise, immediately post-exercise, 1-hour post-exercise, and 24 h post-exercise. Results: Hyperoxic exposure resulted in significantly enhanced RBC deformability, particularly at higher shear stresses (p < 0.001). Whole blood viscosity was reduced across all shear rates in the hyperoxic condition (p < 0.05). Oxygen saturation (SpO2) levels were consistently higher (p < 0.001), while blood lactate concentrations were lower (p < 0.001) in the hyperoxic condition. Individual responses to hyperoxia varied considerably, with some athletes showing markedly greater improvements in RBC deformability than others. Conclusions: Acute hyperoxic exposure during high-intensity exercise enhances RBC deformability and reduces blood viscosity in elite endurance athletes, potentially improving microcirculatory function and oxygen delivery to tissues. These findings suggest that hyperoxic training may offer performance benefits, but the observed individual variability highlights the need for personalized approaches in its application.