EFFECTS OF INTERMITTENT HYPOXIA ON CARDIORESPIRATORY AND HEMATOLOGICAL ADAPTATIONS IN COLLEGIATE ENDURANCE ATHLETES

Abstract

A number of studies have reported that intermittent hypoxia during endurance exercise training, i.e., living low-training high, induces several physiological adaptations in athletes. However, the effects of short-term intermittent hypoxia at rest while simultaneously endurance training at sea level on cardiorespiratory and hematological adaptations in trained athletes are unclear. PURPOSE The aim of the present study was to clarify the influences of intermittent normobaric hypoxia at rest on cardiorespiratory and hematological adaptations in trained athletes. METHODS Fifteen collegiate male endurance athletes were assigned to either a hypoxic group (n=8) or a control group (n=7). The subjects in the hypoxic group were exposed to normobaric hypoxia (12.3% oxygen) at rest for 2 weeks (3 hours/day). The measurements of cardiorespiratory parameters during maximal and submaximal treadmill exercise tests and resting hematological parameters were performed before (Pre) and after (Post) intermittent hypoxia. In the control group, the same parameters were determined at Pre and Post without intermittent hypoxia. The athletes in both groups continued their normal training together at sea level throughout the experiment. RESULTS Neither cardiorespiratory parameters, e.g., maximum oxygen uptake (VO2max), at exhaustion during maximal treadmill exercise test nor resting hematological parameters were changed in either group at Post. In contrast, oxygen uptake (VO2) and heart rate (HR) during submaximal treadmill running (268m/min) in the hypoxic group decreased significantly (p < 0.05) after intermittent hypoxia (VO2, 54.3 ±3.6 to 52.5 ±3.5 ml/kg/min; HR, 166.5 ±16.7 to 160.8 ±12.9 beats/min, respectively), but not in the control group. CONCLUSION These results suggest that intermittent hypoxia at rest could improve submaximal exercise efficiency at sea level in endurance athletes.