Hypoxic preacclimatization combining intermittent hypoxia exposure and physical exercise significantly improves hypoxic tolerance

Background: Hypoxic preacclimatization has been an effective strategy to enhance the tolerance to high altitude hypoxia. We aimed to determine whether preacclimatization combining intermittent hypoxia exposure (IHE) and physical exercise can further promote hypoxia acclimatization and select the optimal protocol. Methods 120 Han Chinese young men were enrolled and randomly assigned into the control group and 3 experimental groups with 5-day rest, 5-day exercise, and 3-day exercise in a hypobaric chamber. Main parameters for hypoxia acclimatization, AMS incidence, physical capacity, and cognitive function were measured in the hypobaric chamber 2 days after training. The effect was compared between different protocols. Results SpO 2 and HR of the 5-day rest group were significantly higher than those of the controls ( p  = 0.000, p  = 0.000, respectively). The proportion of moderate and severe headache of 3-day exercise group was significantly lower than that of the controls ( p  = 0.002). The 5-day exercise group had significantly higher SpO 2 , VO 2 max, digital symbol and pursuit aiming test scores ( p  = 0.005, p  = 0.002, p  = 0.005, and p  = 0.005, respectively), while shorter color selection reaction time ( p  = 0.004), as compared with the control group. Participants with 5-day exercise achieved better performance on digital symbol and color selection reaction test than those of 5-day rest group did ( p  = 0.004 and p  = 0.007, respectively). Conclusions Hypoxic preacclimatization combining IHE with physical exercise of moderate intensity appears to be efficient in promoting hypoxia acclimatization, especially for improvement of mental and physical capacity in hypoxia.