Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 May 1;60(5):372-380.
doi: 10.4085/1062-6050-0448.24.

Combined Active and Passive Isothermic Heating Leads to Similar Core Temperature Compared With Exercise Alone

Floris C Wardenaar  1 , Sonia Navarro  1 , Rachel Caballero  1 , Kaila A Vento  1 , Stavros A Kavouras  1 , Jenni Vanos  2
Affiliations

Combined Active and Passive Isothermic Heating Leads to Similar Core Temperature Compared With Exercise Alone

Floris C Wardenaar et al. J Athl Train. .

Abstract

Context: The training stress of heat acclimatization optimizing exercise performance in a hot environment can be demanding.

Objective: This study evaluated the efficiency of different single heating protocols to elevate core temperature.

Design: Nonrandomized controlled trial.

Setting: Laboratory.

Patients or other participants: Ten male participants (age = 25 ± 3 years) performed 4 different 60-minute heating strategies at least 1 week apart.

Interventions: Sixty minutes passive heating (PAS), 30 minutes active heating using a high-intensity bike protocol (HIBP) in a hot environment with 30 minutes passive heating (EH-PAS), 60 minutes HIBP in a hot environment (EH), or 60 minutes HIBP at room temperature (EM).

Main outcome measure(s): Body core temperature and heart rate.

Results: The highest peak gastrointestinal temperature occurred in EH-PAS (39.1 ± 0.4°C), followed by EH (38.9 ± 0.3°C), EM (38.4 ± 0.3°C), and PAS (38.1 ± 0.5°C). The average heart rate, measured as a control for intensity, was not different between exercise strategies (EH-PAS = 142 ± 12.3 beats per minute [bpm], EH = 146 ± 9.7 bpm, and EM = 142 ± 13.3 bpm; P > .05), but was different for PAS (98 ± 15.2 bpm; P < .05).

Conclusions: Adding passive heating to a shorter exercise protocol can be just as effective in keeping core temperature elevated as exercise in the heat alone during a 60-minute session. Therefore, a single-bout combination of exercise and passive heating may result in a similar body temperature induction compared with exercise heat stress alone.

Keywords: acclimation; body temperature; extreme heat; heart rate; work performance.

PubMed Disclaimer

References

    1. Sawka M, Wenger C, Pandolf K. Thermoregulatory responses to acute exercise-heat stress and heat acclimation. In: Fregly MJ, Blatteis CM, eds. Handbook of Physiology, Section 4: Environmental Physiology. Oxford University Press; 1996:157–186.
    1. Willmott AGB, Hayes M, James CA, Gibson OR, Maxwell NS. Heat acclimation attenuates the increased sensations of fatigue reported during acute exercise-heat stress. Temperature (Austin). 2019;7(2):178–190. 10.1080/23328940.2019.1664370 - DOI - PMC - PubMed
    1. Bain AR, Nybo L, Ainslie PN. Cerebral vascular control and metabolism in heat stress. Compr Physiol. 2015;5(3):1345–1380. 10.1002/cphy.c140066 - DOI - PubMed
    1. Nybo L, Rasmussen P, Sawka MN. Performance in the heat—physiological factors of importance for hyperthermia-induced fatigue. Compr Physiol. 2014;4(2):657–689. 10.1002/cphy.c130012 - DOI - PubMed
    1. Adolph EF. The effects of exposure to high temperatures upon the circulation in man. Am J Physiol. 1924;67(3):573–588. 10.1152/ajplegacy.1924.67.3.573 - DOI