Effect of pre-acclimatization training under hypoxic environment for one week on work capacity and physiological responses under hypoxic environment

We examined the effect of pre-acclimatization training under hypoxia for competition or training at high altitude on work capacity and physiological responses in hypoxia. Eight healthy male university students performed pre-acclimatization training under normobaric hypoxia (equivalent to about 2500 m; 15.4% inspired oxygen) for a week. Each student was exposed for a total of 90 minutes. During the exposure, each student rested for 60 minutes and pedaled at a workload of lactate threshold (LT) under normobaric hypoxia (equivalent to about 2500 m) for 30 minutes. In the result, workload of LT under normobaric hypoxia significantly increased after pre-acclimatization training (+15%). In physiological responses, arterial oxygen saturation at rest and exercise and peak ventilatory volume significantly increased after pre-acclimatization training. Arterial oxygen saturation at rest during pre-acclimatization training significantly increased. In addition, the ratio of low- and high-frequency power in heart rate variability significantly decreased after pre-acclimatization training. These results suggest that pre-acclimatization training is able to bring in acclimatization to high altitude on cardiopulmonary function and prevent decline of work capacity in high altitude. The ratio of low- and high-frequency power in heart rate variability as well as arterial oxygen saturation may reflect degree of acclimatization to high altitude.