Abstract
Training in a hot environment (heat acclimation) elicits beneficial physiological and thermoregulatory adaptations that enhance subsequent exercise in the heat; however, additional strain from exertional heat stress may negatively influence sleep duration and quality. Although sex differences in sleep have been observed relative to exercise, it remains unclear if training in the heat exacerbates sex-specific responses. PURPOSE: Investigate the effect of heat acclimation on sleep in highly trained male and female endurance runners compared to training in a temperate environment. METHODS: 17 highly trained endurance runners (males: n = 8, age, 21 ± 3 years, maximal oxygen uptake [VO2peak], 66.5 ± 11.0 mL∙kg-1∙min-1; females: n = 9, age, 24 ± 7 years, VO2peak, 55.3 ± 6.0 mL∙kg-1∙min-1) completed two separate interventions in a randomized, counterbalanced order: 7 days of 60 min running at 50% velocity VO2peak in hot (HEAT) (40 °C, 35 % relative humidity [RH]) and temperate (TEMP) (22 °C, 35 % RH) environmental conditions. A validated smart ring was worn continuously throughout the training interventions and recorded sleep metrics. Furthermore, subjective sleep data was collected each day using the Karolinska Sleep Diary (KSD) questionnaire. Linear mixed effects models with Tukey post hoc analyses were performed to examine sex differences across HEAT and TEMP interventions. Participants were categorized as the random effect, and sex and environmental condition were classified as fixed effects. Data are presented as estimated marginal means and 95% confidence intervals. RESULTS: Significant main effects were observed only for average resting heart rate (RHR). Post hoc analyses revealed that in females, HEAT (55 [50, 60] bpm) led to greater RHR compared to TEMP (52 [47, 57] bpm; p < 0.001), but not in males (p > 0.05). For all other sleep metrics from both the smart ring and KSD questionnaire, there were no differences between males and females (p > 0.05), nor between HEAT and TEMP (p > 0.05). CONCLUSION: Sleep responses to running in the heat compared to a temperate environment were not significantly different. Furthermore, there were no differences between male and female endurance runners between environmental conditions. Taken together, while sleep is an important variable to track throughout training, it appears that highly trained endurance runners are not negatively affected by training in the heat.
Recommended Citation
Waller, Sophia; Keefe, Marcos S.; Mccollum, Tyler B.; Dunn, Ryan A.; and Sekiguchi, Yasuki
(2026)
"Sex-Specific Responses in Sleep Metrics throughout Heat Acclimation in Highly Trained Endurance Runners,"
International Journal of Exercise Science: Conference Proceedings: Vol. 2:
Iss.
18, Article 43.
Available at:
https://digitalcommons.wku.edu/ijesab/vol2/iss18/43