Heat acclimation training combined with hypoxia training enhances heat-tolerance ability

Abstract

Objective To explore an effective method to improve the heat resistance of the body by combining classic heat acclimation and hypoxia training. Methods In 2018, a total of 60 healthy male volunteers who were strictly screened from a troop were recruited in this study. They were equally divided into control group, heat acclimation group, and hypoxia training combined heat acclimation group. Then they were trained for 12 d under a damp heat condition (temperature >33 ℃ and humidity >70%). Their ear temperature, heart rate, sweating amount, cardiopulmonary function, comprehensive feeling scores, physiological strain index (PSI), maximal oxygen uptake (VO2max), and physical work capacity at heart rate of 170 beats per minute (PWC170) were tested and evaluated before and after heat acclimation. Results Compared with the control group, the heat acclimation group and the combination group had significantly lower basic ear temperature and the ear temperature after heat test (P < 0.05), decreased basic and post-test heart rate (P < 0.05), and reduced PSI and respiratory rate (P < 0.05), but increased sweating amount, VO2max, PWC170, maximum cardiac output, oxygen consumption/maximal heart rate, maximum CO2 emission, and maximum lung ventilation (P < 0.05). What's more, the heart rate and ear temperature after heat test were obviously lower in the combination group than the heat acclimation group (P < 0.05), so were PSI and respiratory rate (P < 0.05). But the former group had notably higher sweating amount, VO2max, PWC170, maximum cardiac output, oxygen consumption/maximal heart rate, maximum CO2 emission, and maximum lung ventilation than the latter group (P < 0.05). Conclusion Based on the classic heat acclimation, combination of hypoxia training can promote heat acclimation more effectively.

Keywords

• heat acclimation
• hypoxia training
• cardiopulmonary function
• heat tolerance