The aim of this study was to clarify the effects of intermittent hypoxia on endurance running performance and cardiorespiratory adaptation in trained endurance athletes. Ten trained male endurance runners volunteered to participate in this study. The subjects in the hypoxic group (n=5) were exposed to a simulated altitude of 4,500 m for 90 min, three times a week for 3 weeks. The measurements of 3,000-m running time, cardiorespiratory parameters during maximal exercise test, and hematological status at rest were performed before (Pre) and after intermittent hypoxia for 3 weeks (Post). These measurements were repeated after the cessation of intermittent hypoxia for 3 weeks (3wk). The same parameters were measured in the control group (n=5), which was not exposed to intermittent hypoxia, at Pre, Post, and 3wk. The 3,000-m running time in the hypoxic group improved significantly (p<0.05) following intermittent hypoxia, but not in the control group. There were no changes cardiorespiratory parameters to maximal exercise in either group at Post, while oxygen uptake (VO₂) during submaximal exercise in the hypoxic group decreased significantly (p<0.05) after intermittent hypoxia. No changes in resting hematological parameters were found after intermittent hypoxia. The improved 3,000-m running time and the decreased VO₂ during submaximal exercise returned to Pre level after the cessation of intermittent hypoxia for 3 weeks. These results suggest that intermittent hypoxia could improve submaxial exercise efficiency and endurance running performance, but these improvements do not continue after the cessation of intermittent hypoxia for 3 weeks.

DESCENTE SPORTS SCIENCE Vol.24/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE