Shifting focus: Time to look beyond the classic physiological adaptations associated with human heat acclimation

Abstract

New Findings What is the topic of this review?This review summarizes studies that advance our understanding of the mechanisms mediating improved thermoeffector output following heat acclimation and investigate adaptations that go beyond those classically associated with heat acclimation. What advances does it highlight?Most studies that investigated possible mechanisms mediating greater thermoeffector output following heat acclimation have focused on end‐organ responses. Some evidence suggests that heat acclimation improves cardiac function, body fluid regulatory functions, and preserves cognitive performance under heat stress. However, these conclusions are based on limited and conflicting data. AbstractPlanet Earth is warming at an unprecedented rate and our future is now assured to be shaped by the consequences of more frequent hot days and extreme heat. Humans will need to adapt both behaviorally and physiologically to thrive in a hotter climate. From a physiological perspective, countless studies have shown that human heat acclimation increases thermoeffector output (i.e., sweating and skin blood flow) and lowers cardiovascular strain (i.e., heart rate) during heat stress. However, the mechanisms mediating these adaptations remain understudied. Furthermore, several possible benefits of heat acclimation for other systems and functions involved in maintaining health and performance during heat stress remain to be elucidated. This review summarizes recent advances in human heat acclimation, with emphasis on recent studies that (1) advanced our understanding of the mechanisms mediating improved thermoeffector output and (2) investigated adaptations that go beyond those classically associated with heat acclimation. We highlight that these studies have contributed to a better understanding of the integrated physiological responses underlying human heat acclimation while leaving key unanswered questions that will need to be addressed in the future.