Biological sex does not independently influence time-dependent changes in core temperature and sweating of children exercising in uncompensable heat stress

Thomas H Topham; James W Smallcombe; Harry A Brown; Brad Clark; Andrew P Woodward; Richard D Telford; Ollie Jay; Julien D Périard

doi:10.1152/japplphysiol.00877.2023

Biological sex does not independently influence time-dependent changes in core temperature and sweating of children exercising in uncompensable heat stress

J Appl Physiol (1985). 2024 Apr 25. doi: 10.1152/japplphysiol.00877.2023. Online ahead of print.

Authors

Thomas H Topham¹, James W Smallcombe², Harry A Brown¹, Brad Clark³, Andrew P Woodward⁴, Richard D Telford¹, Ollie Jay⁵, Julien D Périard⁶

Affiliations

¹ Research Institute for Sport and Exercise, University of Canberra, Bruce, Australia.
² Heat and Health Research Incubator, University of Sydney, Sydney, New South Wales, Australia.
³ Research Institute for Sport and Exercise, University of Canberra, Canberra, Australia.
⁴ Faculty of Health, University of Canberra, Bruce, Australia.
⁵ Heat and Health Research Incubator, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia.
⁶ Research Institute for Sport and Exercise, University of Canberra, Bruce, ACT, Australia.

PMID: 38660730
DOI: 10.1152/japplphysiol.00877.2023

Abstract

Purpose: To investigate the influence of biological sex, independent of differences in aerobic fitness and body fatness, on the change in gastro-intestinal temperature (∆T_gi) and whole-body sweat rate (WBSR) of children exercising under uncompensable heat stress.

Methods: Seventeen boys (mean±SD; 13.7±1.3 years) and 18 girls (13.7±1.4) years) walked for 45 min at a fixed rate of metabolic heat production per kg body mass (8 W·kg^-1) in 40°C and 30% relative humidity. Sex and V̇O_2peak were entered into a Bayesian hierarchical general additive model (HGAM) for T_gi. Sex, V̇O_2peak and the evaporative requirement for heat balance (E_req) were entered into a Bayesian hierarchical linear regression for WBSR. For 26 (12 M, 14 F) of the 35 children with measured body composition, body fat percentage was entered in a separate HGAM and hierarchical linear regression for T_gi and WBSR respectively.

Results: Conditional on sex-specific mean V̇O_2peak, ∆T_gi was 1.00°C [90% credible intervals: 0.84, 1.16] for boys and 1.17°C [1.01, 1.33] for girls, with a difference of 0.17°C [-0.39, 0.06]. When sex differences in V̇O_2peak were accounted for, the difference in ∆T_gi between boys and girls was 0.01°C [-0.25, 0.22]. The difference in WBSR between boys and girls was 0.03 L·h^-1 [-0.02, 0.07], when isolated from differences in E_req. The difference in ∆T_gi between boys and girls was -0.10°C [-0.38, 0.17] when sex differences in body fat (%) were accounted for.

Conclusion: Biological sex did not independently influence the ∆T_gi and WBSR of children exercising under uncompensable heat stress.

Keywords: fatness; fitness; pediatric; thermoregulation.

Abstract

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