Sex differences in the thermoregulatory and cardiovascular response to exercise in hot environmental conditions

Costa, JG ORCID: 0000-0002-4452-3255, Locatelli, JC, Wigati, K ORCID: 0000-0002-8542-5934, Criddle, JL ORCID: 0000-0002-0913-7754, Xu, X, Collis, J ORCID: 0009-0005-9626-1321, Naylor, LH ORCID: 0000-0002-6210-912X, Haynes, A ORCID: 0000-0001-7312-8265, Maloney, SK, Carter, HH ORCID: 0000-0001-9617-2744, McLaughlin, RA ORCID: 0000-0001-6947-5061, Jones, H ORCID: 0000-0001-8282-1459, George, KP ORCID: 0000-0002-5119-6651 and Green, DJ ORCID: 0000-0003-3226-2921 (2025) Sex differences in the thermoregulatory and cardiovascular response to exercise in hot environmental conditions. American journal of physiology. Regulatory, integrative and comparative physiology. ISSN 0363-6119

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Abstract

Exercise during heat exposure induces skin microvascular and systemic cardiovascular changes. When standardised exercise tasks are completed, such as during military training or in workplace settings, sex differences in responses may be apparent. Nineteen males and 19 females participated in a set-pace laboratory walking test (treadmill walking 5 km/h; 2% incline) in a climate chamber (40°C; 50% RH) for 90 minutes. Body composition (DXA) and VO2 max were measured in a preliminary session. Metabolic heat production, skin blood flow (SkBF; laser Doppler flowmetry), limb blood flow (Doppler ultrasound), stroke volume, cardiac output (CO), heart rate (HR), oxygen consumption (VO2), and core temperature (Tc) were measured at baseline, 30, 60, and 90 minutes. No sex difference in Tc at 90 min was evident (♂38.3±0.5 vs ♀38.5±0.4°C; p=0.403) and a similar change from baseline to 90 min (Δ♂1.40 vs 1.28°C; p=0.447) occurred, despite males producing more heat (3.4±1.0 vs 2.1±0.7 W/kg; p=0.001), exhibiting higher SkBF (192±50 vs 160±21 PU; p=0.026), and higher sweat production rate (16.5±5.1 vs 12.3±3.3 ml/min; p=0.009). Males also had higher CO (7.25±1.38 vs 6.11±1.72 L/min; group p=0.026), and femoral blood flow (1.00±0.23 vs 8.22±0.19 L/min; p=0.026) responses than females. Males compensated for more lean mass and higher metabolic heat production via a larger increase in cardiac output, with more blood flow distributed to active muscle and, as heat and exercise exposure continued, to the skin. Tc in females did not rise more than males, possibly due to body size and/or anthropometric factors.

Item Type:	Article
Uncontrolled Keywords:	Heat stress; exercise; sex difference; skin blood flow; thermoregulation; 32 Biomedical and Clinical Sciences; 3202 Clinical Sciences; Physical Activity; Cardiovascular; Cardiovascular; 06 Biological Sciences; 11 Medical and Health Sciences; Physiology; 31 Biological sciences; 32 Biomedical and clinical sciences; 42 Health sciences
Subjects:	Q Science > QP Physiology R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions:	Sport and Exercise Sciences Vice-Chancellor's Office
Publisher:	American Physiological Society
Date of acceptance:	28 September 2025
Date of first compliant Open Access:	14 October 2025
Date Deposited:	14 Oct 2025 09:34
Last Modified:	14 Oct 2025 09:45
DOI or ID number:	10.1152/ajpregu.00139.2025
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27329

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