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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Physiol. | doi: 10.3389/fphys.2019.01381

How does a delay between temperate running exercise and hot-water immersion alter the acute thermoregulatory response and heat-load?

Storme L. Heathcote1, Peter Hassmen1,  Shi Zhou1,  Lee Taylor2 and  Christopher J. Stevens1*
  • 1School of Health and Human Sciences, Southern Cross University, Australia
  • 2School of Sport, Exercise, and Health Sciences, Loughborough University, United Kingdom

Hot-water immersion following exercise in a temperate environment can elicit heat acclimation in endurance-trained individuals. However, a delay between exercise cessation and immersion is likely a common occurrence in practice. Precisely how such a delay potentially alters hot-water immersion mediated acute physiological responses (e.g. total heat-load) remains unexplored. Such data would aid in optimising prescription of post-exercise hot-water immersion in cool environments, relative to heat acclimation goals. Twelve male recreational runners (mean ± SD; age: 38 ± 13 y, height: 180 ± 7 cm, body mass: 81 ± 13.7 kg, body fat: 13.9 ± 3.5%) completed three separate 40-minute treadmill runs (18°C), followed by either a 10 min (10M), 1 h (1H) or 8 h (8H) delay, prior to a 30-minute hot-water immersion (39°C), with a randomised crossover design. Core and skin temperatures, heart rate, sweat and perceptual responses were measured across the trials. Mean core temperature during immersion was significantly lower in 1H (37.39 ± 0.30°C) compared to 10M (37.83 ± 0.24°C; P = 0.0032) and 8H (37.74 ± 0.19°C; P = 0.0140). Mean skin temperature was significantly higher in 8H (32.70 ± 0.41°C) compared to 10M (31.93 ± 0.60°C; P = 0.0042) at the end of the hot-water immersion. Mean and maximal heart rates were also higher during immersion in 10M compared to 1H and 8H (P < 0.05), despite no significant differences in the sweat or perceptual responses. The shortest delay between exercise and immersion (10M) provoked the greatest heat-load during immersion. However, performing the hot-water immersion in the afternoon (8H), which coincided with peak circadian body temperature, provided a larger heat-load stimulus than the 1 h delay (1H).

Keywords: Heat acclimation, Heat stress, Hot bath, Passive heating, Endurance athletes

Received: 27 Jul 2019; Accepted: 21 Oct 2019.

Copyright: © 2019 Heathcote, Hassmen, Zhou, Taylor and Stevens. 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) and the copyright owner(s) 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: Dr. Christopher J. Stevens, School of Health and Human Sciences, Southern Cross University, Lismore, NSW 2480, Australia, Christopher.Stevens@scu.edu.au