Heat Reacclimation using Exercise or Hot Water Immersion

Nicola Gerrett, Puck Alkemade, Hein Daanen

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Introduction The aim of this study was to compare the effectiveness of exercise versus hot water immersion heat reacclimation (HRA) protocols. Methods Twenty-four participants completed a heat stress test (HST; 33°C, 65% RH), which involved cycling at a power output equivalent to 1.5 W·kg-1 for 35 min whereby thermophysiological variables were measured. This was followed by a graded exercise test until exhaustion. HST1 was before a 10-d controlled hyperthermia (CH) heat acclimation (HA) protocol and HST2 immediately after. Participants completed HST3 after a 28-d decay period without heat exposure and were then separated into three groups to complete a 5-d HRA protocol: A control group (CH-CON, n = 8); a hot water immersion group (CH-HWI, n = 8), and a controlled hyperthermia group (CH-CH, n = 8). This was followed by HST4. Results Compared with HST1, time to exhaustion and thermal comfort improved; resting rectal temperature (Tre), end of exercise Tre, and mean skin temperature (Tsk) were lower; and whole body sweat rate (WBSR) was greater in HST2 for all groups (P < 0.05). After a 28-d decay, only WBSR, time to exhaustion, and mean Tsk returned to pre-HA values. Of these decayed variables, only WBSR was reinstated after HRA; the improvement was observed in both the CH-CH and the CH-HWI groups (P < 0.05). Conclusion The data suggest that HRA protocol may not be necessary for cardiovascular and thermal adaptations within a 28-d decay period, as long as a 10-d CH-HA protocol has successfully induced these physiological adaptations. For sweat adaptations, a 5-d CH or HWI-HRA protocol can reinstate the lost adaptations.

Original languageEnglish
Pages (from-to)1517-1528
Number of pages12
JournalMedicine and Science in Sports and Exercise
Volume53
Issue number7
Early online date3 Feb 2021
DOIs
Publication statusPublished - Jul 2021

Bibliographical note

Funding Information:
This research was supported by both ZONMW and the Dutch Research Council (NWO) with grants held by Hein Daanen. Nicola Gerrett was funded by ZONMW (2019-30601) and Puck Alkemade through the Citius Altius Sanius project (P16-28) from NWO. The authors thank the following people for their assistance during the data collection: Lisa Klous, Mireille Folkerts, Guilio Tan, Romin Gaalman, Mae El Hamoud, Iris Dijkstra, Amber Berlijn, Michelle van Delden, and Emma Wiedenmann. Special thanks are given to the participants for their dedication and commitment to this long and challenging study.

Publisher Copyright:
© Lippincott Williams and Wilkins.

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

Keywords

  • ADAPTATION
  • ATHLETES
  • CONTROLLED HYPERTHERMIA
  • DECAY
  • PERFORMANCE

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