Sex-Specific Responses of Heat Acclimation on Endurance Performance under Cool Environmental Conditions in Highly Trained Runners
Year: 2026
Type: dissertation
Study design: Clinical Trial
Abstract: Environmental heat stress imposes significant physiological strain and impairs endurance performance, largely through disruptions in thermoregulatory and cardiovascular function. Heat acclimation (HA) is an established strategy to mitigate these effects, eliciting adaptations such as reduced heart rate, lower core temperature, plasma volume expansion, and enhanced sweating responses. While these adaptations are known to improve performance in hot environments, their potential to enhance endurance performance in cool conditions—and whether these responses differ between sexes—remains incompletely understood. Therefore, the purpose of this dissertation was to examine sex-specific physiological and performance adaptations to a medium-term HA protocol in highly trained endurance runners, with particular emphasis on performance outcomes in cool environmental conditions. Using a randomized, counterbalanced design, male and female runners completed a 7-day controlled-intensity HA intervention and a temperate training (TEMP) control condition. Measures of thermoregulatory and cardiovascular function were assessed alongside endurance performance outcomes, including aerobic capacity and 8-km time trial performance in cool conditions. The findings demonstrate that HA induced meaningful thermoregulatory and cardiovascular adaptations in both males and females, including reductions in exercising heart rate and core temperature, with largely similar responses between sexes. Despite these physiological adaptations, improvements in endurance performance in cool conditions following HA were modest and not consistently different from those observed following TEMP. Furthermore, the relationship between specific physiological adaptations and performance outcomes appeared variable, suggesting that not all HA-induced changes translate directly to performance benefits in cooler environments. In conclusion, medium-term HA elicits comparable physiological adaptations in male and female highly trained runners; however, the transfer of these adaptations to improved endurance performance in cool conditions is limited. These findings provide important insight into the role of HA as a training strategy and highlight the need for further research to elucidate the mechanisms linking heat-induced adaptations to performance across environmental contexts.
Author: Keefe, Marcos
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7171276540