Effects of Normobaric Hypoxia on Aerobic Performance and Hematological Adaptations

초록

This study examined the physiological and hematological effects of a four-week aerobic training program conducted under normobaric hypoxic (NH, FiO₂ = 15.5%) versus normobaric normoxic (NN, FiO₂ = 20.9%) conditions in healthy young men. Twenty participants were randomly assigned to either group and completed identical endurance training protocols consisting of 60-minute sessions at 75% of HRmax (maximal heart rate), five times per week. VO2max (maximal oxygen uptake) significantly increased in both groups, indicating comparable improvements in aerobic capacity. However, time to exhaustion (TTE) and blood lactate levels remained unchanged. Hematological responses varied between groups: the NN group showed significant decreases in red blood cell (RBC) count and hemoglobin (Hb) concentration, while these parameters remained stable in the NH group. Reticulocyte percentage decreased in both groups, and erythropoietin (EPO) levels did not change significantly. Additionally, HRmax decreased significantly in the NN group but not in the NH group. These results suggest that while both training conditions are effective in enhancing aerobic capacity, training under moderate normobaric hypoxia may help maintain hematological stability. This indicates that normobaric hypoxic training could be a practical strategy for supporting oxygen transport capacity during endurance training, particularly in situations involving increased training load or frequent exposure to cardiovascular stress.

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