Sex-Specific Responses of Heat Acclimation on Running Performance in Cool Environmental Conditions

Authors

Marcos S. Keefe, Texas Tech UniversityFollow
Ryan A. Dunn, Texas Tech UniversityFollow
Kelly B. Elliott, Texas Tech UniversityFollow
Ruben E. Moya, Texas Tech UniversityFollow
Yasuki Sekiguchi, Texas Tech UniversityFollow

Abstract

Training and competing in the heat negatively impact athlete performance and health. Heat acclimation (HA) involves repeated heat exposures that many endurance athletes use to optimize performance and safety when competing in the heat. Although HA has been shown to improve endurance performance in the heat, contention remains whether it may confer these adaptations to a cool environment. PURPOSE: To Investigate physiological and performance adaptations in a cool environment following HA in endurance athletes. METHODS: Eleven high-level endurance runners (4 males [age: 21 ± 4 years; body mass: 78.63 ± 9.01 kg; height: 182.55 ± 3.97 cm; maximal oxygen uptake {VO_2max}: 73.93 ± 9.69 ml·kg^-1·min^-1]; 7 females [age: 22 ± 5 years; body mass: 64.30 ± 7.97 kg; height: 168.00 ± 6.43 cm; VO_2max: 58.30 ± 4.28 ml·kg^-1·min^-1]) participated in this study. At baseline, participants completed a combined VO_2max and lactate threshold (LT) test, followed by an 8-km time-trial (TT) in cool conditions (ambient temperate [T_amb], 11°C; relative humidity [RH], 40%). Following this, participants completed a 7-day protocol consisting of 60-min running at 50% velocity at VO_2max in a hot environment (T_amb, 40°C; RH, 35%). Physiological variables (i.e., heart rate [HR], core temperature [T_c], sweat rate [SR], plasma volume change [ΔPV]) were assessed on days 1 and 7. A post-testing visit that followed the same protocol as the pre-testing visit was conducted to determine performance changes. A two-way repeated measures ANOVA was conducted to assess physiological and performance changes from pre- to post-testing for performance variables, and from days 1 to 7 for physiological variables, between sexes. Cohen’s d classification of effect sizes was calculated. RESULTS: In a cool environment, a significant interaction between males and females from pre- to post-testing was observed for VO_2max, (p = 0.005) but not for velocity at LT or 8-km TT (p > 0.05). Particularly, females demonstrated improvements in VO_2max (57.62 ± 5.49 to 61.81 ± 6.16 ml·kg^-1·min^-1; p = 0.01; d = 0.68), but males did not (p > 0.05). Regardless of sex, velocity at LT was improved from pre- to post-testing (10.5 ± 0.3 to 11.0 ± 0.3 mi·h^-1; p = 0.05; d = 1.67), whereas TT remained unchanged (p > 0.05; d = 0.14). From day 1 to 7 of HA, there were no significant interactions between males and females in maximum HR, maximum T_c, ΔPV, and SR (p > 0.05). Irrespective of sex, maximum HR was reduced (183 ± 3 to 175 ± 2 bpm; p = 0.014; d = 3.14), whereas maximum T_c, ΔPV, and SR were unchanged (p > 0.05; d = 0.38 - 1.86). CONCLUSION: The present findings indicate that HA may procure adaptations to improve endurance performance in cool temperatures in both male and female endurance runners.

Recommended Citation

Keefe, Marcos S.; Dunn, Ryan A.; Elliott, Kelly B.; Moya, Ruben E.; and Sekiguchi, Yasuki (2025) "Sex-Specific Responses of Heat Acclimation on Running Performance in Cool Environmental Conditions," International Journal of Exercise Science: Conference Proceedings: Vol. 2: Iss. 17, Article 8.
Available at: https://digitalcommons.wku.edu/ijesab/vol2/iss17/8