ORIGINAL RESEARCH article
Front. Physiol.
Sec. Exercise Physiology
Volume 16 - 2025 | doi: 10.3389/fphys.2025.1581594
Four-week heat acclimation lowers carbohydrate oxidation of trained runners during submaximal exercise in the heat
Provisionally accepted
- 1Shanghai University of Sport, Shanghai, China
- 2Fudan University, Shanghai, Shanghai Municipality, China
- 3Macao Polytechnic University, Macau, Macao, SAR China
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Purpose: This study examined the effect of 4 weeks of heat acclimation (HA, 39 °C ≤ target Tc < 40 °C) on aerobic capacity in middle-and-long distance runners, with a focus on metabolic adaptation. Methods: Eighteen male middle-and long-distance runners were randomized into exercise group (C group, n = 9) or heat acclimation group (HA, n = 9). The runners in the C group performed regular exercise training in a thermoneutral environment (20 °C < wet bulb globe temperature ≤ 25 °C), whereas the runners in the HA group underwent four-week heat acclimation (39 °C ≤ target coer temperature < 40 °C), 5 days a week, once a day, for a total of 20 sessions over 4 weeks. Results: After 4 weeks of interventions, the core temperature after incremental treadmill test in the HA group (38.2 °C ± 0.1 °C vs. 38.6 °C ± 0.1 °C, p = 0.045) was significantly lower than that in the C group. The 4-week HA decreased the 0.4 °C core temperature. The VO2 (44.7 ± 1.6 vs. 43 ± 2.9 ml/min/kg, p = 0.008) and velocity (12.9 ± 0.7 vs. 12.4 ± 0.9 km/h, p = 0.02) at the first ventilation threshold and the VO2 (55.9 ± 2.3 vs. 53.9 ± 3.1 ml/min/kg, p = 0.03) at second ventilation threshold increased compared with those in the C group. The carbohydrate oxidation (2.5 ± 0.1 vs 3.1 ± 0.2 g/min, p = 0.01) at 75% V ̇O2max and 85% V ̇O2max exercise (3.4 ± 0.1 vs. 4 ± 0.2 g/min, p = 0.02) in the HA group decreased compared with that in the C group.Four-week heat acclimation reduced carbohydrate oxidation during submaximal exercise in the heat, indicating improved muscle glycogen utilization efficiency, which supports the enhancement of ventilatory thresholds and thermoregulatory adaptation, thereby improving aerobic capacity in the heat.
Keywords: Heat acclimation, Carbohydrate oxidation, Trained runners, aerobic capacity, Exercise
Received: 22 Feb 2025; Accepted: 03 Jun 2025.
Copyright: © 2025 Xu, Ye, Ma and Gao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Binghong Gao, Shanghai University of Sport, Shanghai, China
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