Although the benefits of heat acclimation are the same for males and females, males may achieve these adaptations at a faster rate than females.

August 11, 2021

Author: Kate Wickham

Ph.D. Candidate, Environmental Ergonomics Lab, Brock University


  • The 2020 Olympic Games were the hottest in Olympic history. The weather threatened the health, safety, and performance of athletes, as average daily temperatures in Tokyo exceeded 30°C and were paired with extreme humidity of 66 to 84% (making some events ‘feel’ hotter than 40°C!).
  • Heat acclimation, typically involving daily exercise in the heat over 7 to 14 days, is an effective tool used by athletes to minimize physiological stress (e.g. elevated heart rate and body temperature) and improve performance in hot environments.
  • Females comprised ~49% of athletes competing in the hot and humid 2020 Olympic Games. However, the majority of heat acclimation data is based on males. This review addressed the potential sex-related differences in adaptations to heat acclimation.

How the study was done

  • All relevant heat acclimation studies in males and females were obtained from reputable, peer-reviewed journals.
  • The methods and findings of these studies were organized, synthesized, and compared.
  • Conclusions were drawn regarding the existing literature and a narrative review was composed.

What researchers found

  • Although the benefits of heat acclimation (e.g. lower heart rate and body temperature, higher sweat rate, improved performance) are the same between males and females, males may achieve these adaptations with fewer heat acclimation sessions (< 7 days) than females (10 to 14 days).
  • Why? Due to sex differences in body composition (e.g., muscle mass and body fat), females may store less heat during each heat acclimation session compared to men. This may cause slower heat adaptations for females following the same heat acclimation programs as males.
  • What can be done? Females can increase the amount of heat stored during a heat acclimation session by wearing additional clothing (e.g., a sweatsuit) during exercise or increasing the humidity of the environment.


  • Heat acclimation is an effective strategy for improving an athlete’s health, safety, and performance in hot environments. However, males and females may not adapt at the same rate for a given heat acclimation program.
  • The scientific community is strongly encouraged to strive to increase the representation of females in heat acclimation research. This will help develop sex-specific heat acclimation programs.

Take home message

  • Heat acclimation can prevent fatigue and improve athletic performance in the heat by increasing sweat loss (i.e. removing heat from the body), which can help keep heart rate and body temperature lower.
  • Although the benefits of heat acclimation are the same for males and females, males may achieve these adaptations at a faster rate than females.
  • More research is needed to explore differences between the sexes on responses to heat acclimation programs to optimize the safety and performance of female athletes in hot environments, such as the Tokyo Olympic Games.

Original Article: Wickham, K.A., Wallace, P.J., and Cheung, S.S. [Sex differences in the physiological adaptations to heat acclimation: a state-of-the-art review] European Journal of Applied Physiology. 2021; 121: 353 – 367.

If you cite any information from this, please consult the original article and cite that source. This summary was written for the Canadian Society for Exercise Physiology and it has been reviewed by the CSEP Knowledge Translation Committee.