Four-month operational heat acclimatization positively affects the level of heat tolerance 6?months later

摘要

Benefits obtained after heat acclimation/acclimatization should be completely lost after an estimated period of 6?weeks. However, this estimate is still hypothetical. We evaluate the long-term effects of heat acclimatization on the level of heat tolerance. Physiological and subjective markers of heat tolerance were assessed during a heat stress test (HST: 3?×?8-min runs outdoors [~?40?°C and 20% RH] at 50% of their estimated speed at VO2max) performed on the 2nd day upon arrival to the desert military base in the United Arab Emirates after a first day of mostly passive exposure to heat. Among the 50 male French soldiers, 25 partook in a 4-month military mission in countries characterized by a hot environment?~?6?months prior to the study (HA). The other 25 participants were never heat acclimatized (CT). Rectal temperature (p?=?0.023), heart rate (p?=?0.033), and perceived exertion (p?=?0.043) were lower in the HA than CT group at the end of HST. Soldiers who experienced a former 4-month period of natural heat acclimatization very likely had a higher level of heat tolerance during exercise in the heat, even 6?months after returning from the previous desert mission, than that of their non-acclimatized counterparts.