Mitochondrial adaptations from heat acclimation - A narrative review

In recent decades, global temperature and humidity levels have surged. These increases in temperature and humidity are associated with higher risk of heat-related illnesses and impaired exercise performance, thereby prompting investigation into physiological responses to heat stress. Preconditioning strategies, including heat acclimation/acclimatization (HA), elicit physiological adaptations to enhance response to future heat exposures. Within HA research, an area of growing interest is examination of subcellular adaptations that contribute to whole-body acclimation, such as changes to/within mitochondria. External heat stress alters molecular pathways involved in mitochondrial biogenesis and bioenergetic function, but the relationship between these alterations and whole-body HA adaptations remains relatively unknown. Therefore, this review provides a detailed examination of the impact of HA on mitochondria across cell models, rodent models, and humans, linking these changes to exercise performance. Based on the current evidence, we propose a HA protocol aimed at promoting mitochondrial adaptations while maximizing traditional HA benefits. Lastly, we identify key areas for future research to further explore and enhance our understanding of mitochondrial responses to HA.