PURPOSE: The unique physiology of females, which includes anatomical, physiological, and thermoregulatory factors, has rarely been considered within heat adaptation investigations. The purpose of this review was to examine: 1) the effects of heat adaptation (i.e., heat acclimation and heat acclimatisation) on physiological adaptations in females; 2) the impact of heat adaptation on performance test outcomes in the heat; and 3) the impact of moderators including duration (min and/or days), total heat dose (°C^.min), exercise intensity (kcal^.min^-1), total energy expended (kcal), frequency of heat exposures and training status on the physiological adaptations. 

METHODS: A systematic literature search of SPORTDiscus, MEDLINE Complete, and Embase databases was completed for articles published up to and including December 2022. Random effects meta-analyses (Hedges’ g effect size) were completed for resting and exercise core temperature (T_core), skin temperature (T_sk), heart rate (HR), sweat rate (SR), plasma volume (PV), and performance tests in the heat using Stata Statistical Software: Release 17. Sub-group meta-analyses were performed to explore the effect of duration, total heat dose, exercise intensity (EI), total energy expended (TEE), frequency of heat exposure and training status on resting and exercise T_core, T_sk, HR, and SR. An explorative meta-regression was conducted to determine the effects of physiological adaptations on performance test outcomes in the heat following heat adaptation.

RESULTS: Thirty studies were included in the systematic review; 22 studies were meta-analysed. After heat adaptation in females, there was a reduction in resting T_core (Effect size (ES) = -0.45; 95%CI -0.69, -0.22; p < 0.001), exercise T_core (ES = -0.81; 95%CI -1.01, -0.60; p < 0.001), T_sk (ES = -0.64; 95%CI -0.79, -0.48; p < 0.001), HR (ES = -0.60; 95%CI -0.74, -0.45; p < 0.001), and an increase in SR (ES = 0.53; 95%CI 0.21, 0.85; p = 0.001). There was no change in PV (ES = -0.03; 95%CI -0.31, 0.25; p = 0.835), whilst performance test outcomes were improved following heat adaptation (ES = 1.00; 95%CI 0.56, 1.45; p < 0.001). Across all moderators, physiological adaptations were more consistently observed following heat adaptation protocols that had durations of 451 – 900 min and/or 8 to 14 days, EI ≥ 3.5 kcal^.min^-1, TEE ≥ 3038 kcal, consecutive (daily) frequency, and total heat dose ≥ 23,000 °C^.min. 

CONCLUSION: Females using heat adaptation regimens can experience benefits to their physiology and performance test outcomes. Sport coaches and sports scientists may consider heat adaptation regimens that include training in the heat for 451 – 900 min and/or 8 to 14 days, EI ≥ 3.5 kcal^.min^-1, TEE ≥ 3038 kcal, consecutive (daily) frequency, and total heat dose ≥ 23,000 °C^.min to attain physiological adaptations and improvements in performance test outcomes. 

Disclosure(s):The authors have nothing to disclose.