The present study was performed to clarify the effects of intermittent exposure to altitude at 4,500m with endurance training on physical performance at sea level and ventilatory chemosensitivity. Seven subjects (AL group) performed endurance training during hypoxic situation for 30 min･d⁻¹, 5 d･wk⁻¹ for 2 wk, while other seven subjects (SL group) trained at sea level for the same period. Before and after the training period, maximum oxygen uptake (VO₂max) and endurance time were measured for each subject using a bicycle ergometer with incremental loading. Hypoxic ventilatory response (HVR) was measured using an isocapnic progressive hypoxic method. Resting hypercapnic ventilatory response was measured by two methods, i.e., hypercapnic ventilatory response as an index of central hypercapnic chemosensitivity (HCVR) using CO₂ rebreathing method and hypercapnic ventilatory response as an index of peripheral hypercapnic chemosensitivity (HCVRSB) using single breath CO₂ method. After 2 weeks of endurance training, significant increases were noted in VO₂max and endurance time in both groups, but there were not significant differences between the groups. HVR tended to increase in the AL group but not statistically significant, while there was significantly decreased in the SL group. On the other hand, endurance training did not alter HCVR and HCVRSB in both groups. These results suggest that ventilatory chemosensitivity to hypoxia is more variable by endurance training than that ventilatory chemosensitivity to hypercapnia. It also suggests that changes of these chemosensitivity have little or no effect on VO₂max and time to fatigue at sea level.

DESCENTE SPORTS SCIENCE Vol.20/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE