Timo van den Bogaard, Lisa Klous, Rachel M Cottle, Jan Van Erp, Hein A M Daanen
{"title":"The effect of heat acclimation on critical environmental limits and rate of rectal temperature change.","authors":"Timo van den Bogaard, Lisa Klous, Rachel M Cottle, Jan Van Erp, Hein A M Daanen","doi":"10.1152/japplphysiol.01004.2024","DOIUrl":null,"url":null,"abstract":"<p><p>Quantifying the effect of heat acclimation (HA) on critical wet-bulb globe temperature (WBGT<sub>crit</sub>) and rate of rectal temperature change (vT<sub>re</sub>) is relevant for developing guidelines with regards to occupational safety while working in warm environments. This study quantified the effect of HA and the period following cessation of the HA protocol on WBGT<sub>crit</sub> and vT<sub>re</sub>. Twenty-eight non-acclimatized participants were divided into a HA (<i>n</i> = 15) and control (CON; <i>n</i> = 13) group. The HA group underwent a warm-humid (35°C, 65% relative humidity) controlled hyperthermia HA protocol (5-9 days of achieving T<sub>re</sub> ∼38.5°C for 60 min) and four progressive heat stress tests (HSTs) to identify WBGT<sub>crit</sub> and examine vT<sub>re</sub>: pre-, after 5 and 9 days of HA, and 4 to 8 days of no heat exposure following HA. CON performed two HSTs on average 13 days apart without heat exposure in between. HA increased WBGT<sub>crit</sub> after nine (28.5 ± 2.7°C vs. 30.5 ± 2.0°C; <i>P</i> = 0.016) but not 5 days (28.5 ± 2.4; <i>P</i> > 0.05). No effect of HA on vT<sub>re</sub> was observed (<i>P</i> > 0.05). Four-to-eight days post-HA, WBGT<sub>crit</sub> and vT<sub>re</sub> did not differ compared with 9 days of HA (<i>P</i> > 0.05). However, a reduction in vT<sub>re</sub> (-0.4 ± 0.3 °C/h) was observed when comparing 4 to 8 days post-HA to pre-HA. In conclusion, our results demonstrate that more than 5 days of HA are required to increase WBGT<sub>crit</sub> and indicate that 9 days of HA proceeded by adequate recovery reduced vT<sub>re</sub> during exercise in the heat.<b>NEW & NOTEWORTHY</b> We assessed the effect of heat acclimation (HA) on critical environmental limits and rate of rectal temperature change. We show that more than 5 days of heat acclimation are required to increase critical environmental limits and that 9 days of HA proceeded by adequate recovery reduces the rate of rectal temperature change. These findings enhance our understanding of heat acclimation's effect on work capacity in the heat and may be used to design occupational guidelines.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1150-1160"},"PeriodicalIF":3.3000,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of applied physiology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1152/japplphysiol.01004.2024","RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/4/7 0:00:00","PubModel":"Epub","JCR":"Q1","JCRName":"PHYSIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Quantifying the effect of heat acclimation (HA) on critical wet-bulb globe temperature (WBGTcrit) and rate of rectal temperature change (vTre) is relevant for developing guidelines with regards to occupational safety while working in warm environments. This study quantified the effect of HA and the period following cessation of the HA protocol on WBGTcrit and vTre. Twenty-eight non-acclimatized participants were divided into a HA (n = 15) and control (CON; n = 13) group. The HA group underwent a warm-humid (35°C, 65% relative humidity) controlled hyperthermia HA protocol (5-9 days of achieving Tre ∼38.5°C for 60 min) and four progressive heat stress tests (HSTs) to identify WBGTcrit and examine vTre: pre-, after 5 and 9 days of HA, and 4 to 8 days of no heat exposure following HA. CON performed two HSTs on average 13 days apart without heat exposure in between. HA increased WBGTcrit after nine (28.5 ± 2.7°C vs. 30.5 ± 2.0°C; P = 0.016) but not 5 days (28.5 ± 2.4; P > 0.05). No effect of HA on vTre was observed (P > 0.05). Four-to-eight days post-HA, WBGTcrit and vTre did not differ compared with 9 days of HA (P > 0.05). However, a reduction in vTre (-0.4 ± 0.3 °C/h) was observed when comparing 4 to 8 days post-HA to pre-HA. In conclusion, our results demonstrate that more than 5 days of HA are required to increase WBGTcrit and indicate that 9 days of HA proceeded by adequate recovery reduced vTre during exercise in the heat.NEW & NOTEWORTHY We assessed the effect of heat acclimation (HA) on critical environmental limits and rate of rectal temperature change. We show that more than 5 days of heat acclimation are required to increase critical environmental limits and that 9 days of HA proceeded by adequate recovery reduces the rate of rectal temperature change. These findings enhance our understanding of heat acclimation's effect on work capacity in the heat and may be used to design occupational guidelines.
期刊介绍：
The Journal of Applied Physiology publishes the highest quality original research and reviews that examine novel adaptive and integrative physiological mechanisms in humans and animals that advance the field. The journal encourages the submission of manuscripts that examine the acute and adaptive responses of various organs, tissues, cells and/or molecular pathways to environmental, physiological and/or pathophysiological stressors. As an applied physiology journal, topics of interest are not limited to a particular organ system. The journal, therefore, considers a wide array of integrative and translational research topics examining the mechanisms involved in disease processes and mitigation strategies, as well as the promotion of health and well-being throughout the lifespan. Priority is given to manuscripts that provide mechanistic insight deemed to exert an impact on the field.
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