Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements

Ashley Willmott, Mark Hayes, Carl James, Jeanne Dekerle, Oliver Gibson, Neil Maxwell

Research output: Contribution to journalArticleResearchpeer-review

Abstract

This experiment aimed to investigate the efficacy of twice-daily, nonconsecutiveheat acclimation (TDHA) in comparison to once-daily heatacclimation (ODHA) and work matched once- or twice-daily temperateexercise (ODTEMP, TDTEMP) for inducing heat adaptations, improvedexercise tolerance, and cytokine (immune) responses. Forty males,matched biophysically and for aerobic capacity, were assigned to ODHA,TDHA, ODTEMP or TDTEMP. Participants completed a cycling gradedexercise test, heat acclimation state test and a time to task failure(TTTF) at 80% peak power output in temperate (TTTFTEMP: 22°C/40%RH) and hot conditions (TTTFHOT: 38°C/20% RH), before and after 10-sessions (60-min of cycling at ~2W.kg-1) in 45°C/20% RH (ODHA andTDHA) or 22°C/40% RH (ODTEMP or TDTEMP). Plasma IL-6, TNF-α andcortisol were measured pre- and post-sessions 1, 5 and 10. ODHA andTDHA induced equivalent heat adaptations (P<0.05) (resting rectaltemperature [-0.28±0.22, -0.28±0.19°C], heart rate [-10±3, -10±4b.min-1] and plasma volume expansion [+10.1±5.6, +8.5±3.1%]) andimproved heat acclimation state (sweat setpoint [-0.22±0.18, -0.22±0.14°C] and gain [+0.14±0.10, +0.15±0.07g.sec-1.°C-1]).TTTFHOT increased (P<0.001) following ODHA (+25±4%) and TDHA(+24±10%), but not ODTEMP (+5±14%) or TDTEMP (+5±17%).TTTFTEMP did not improve (P>0.05) following ODHA (+14±4%), TDHA(14±8%), ODTEMP (9±10%) or TDTEMP (8±13%). Acute (P<0.05) butno chronic (P>0.05) increases were observed in IL-6, TNF-α or cortisolduring ODHA and TDHA, or ODTEMP and TDTEMP. Once- and twice-dailyheat acclimation conferred similar magnitudes of heat adaptation andexercise tolerance improvements, without differentially altering immune function, thus non-consecutive TDHA provides an effective, logisticallyflexible method of HA, benefitting individuals preparing for exercise-heatstress.
Original languageEnglish
Article numbere13936
JournalPhysiological Reports
Volume6
Issue number24
DOIs
Publication statusPublished - 21 Dec 2018

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Exercise Tolerance
Acclimatization
Hot Temperature
Interleukin-6
Immune Tolerance
Thermotolerance
Cytokines

Bibliographical note

© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Keywords

  • heat acclimatization
  • heat adaptation
  • immune
  • performance
  • thermoregulation
  • training

Cite this

@article{4d02cb2413594ea5b79bbbb84203cbc7,
title = "Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements",
abstract = "This experiment aimed to investigate the efficacy of twice-daily, nonconsecutiveheat acclimation (TDHA) in comparison to once-daily heatacclimation (ODHA) and work matched once- or twice-daily temperateexercise (ODTEMP, TDTEMP) for inducing heat adaptations, improvedexercise tolerance, and cytokine (immune) responses. Forty males,matched biophysically and for aerobic capacity, were assigned to ODHA,TDHA, ODTEMP or TDTEMP. Participants completed a cycling gradedexercise test, heat acclimation state test and a time to task failure(TTTF) at 80{\%} peak power output in temperate (TTTFTEMP: 22°C/40{\%}RH) and hot conditions (TTTFHOT: 38°C/20{\%} RH), before and after 10-sessions (60-min of cycling at ~2W.kg-1) in 45°C/20{\%} RH (ODHA andTDHA) or 22°C/40{\%} RH (ODTEMP or TDTEMP). Plasma IL-6, TNF-α andcortisol were measured pre- and post-sessions 1, 5 and 10. ODHA andTDHA induced equivalent heat adaptations (P<0.05) (resting rectaltemperature [-0.28±0.22, -0.28±0.19°C], heart rate [-10±3, -10±4b.min-1] and plasma volume expansion [+10.1±5.6, +8.5±3.1{\%}]) andimproved heat acclimation state (sweat setpoint [-0.22±0.18, -0.22±0.14°C] and gain [+0.14±0.10, +0.15±0.07g.sec-1.°C-1]).TTTFHOT increased (P<0.001) following ODHA (+25±4{\%}) and TDHA(+24±10{\%}), but not ODTEMP (+5±14{\%}) or TDTEMP (+5±17{\%}).TTTFTEMP did not improve (P>0.05) following ODHA (+14±4{\%}), TDHA(14±8{\%}), ODTEMP (9±10{\%}) or TDTEMP (8±13{\%}). Acute (P<0.05) butno chronic (P>0.05) increases were observed in IL-6, TNF-α or cortisolduring ODHA and TDHA, or ODTEMP and TDTEMP. Once- and twice-dailyheat acclimation conferred similar magnitudes of heat adaptation andexercise tolerance improvements, without differentially altering immune function, thus non-consecutive TDHA provides an effective, logisticallyflexible method of HA, benefitting individuals preparing for exercise-heatstress.",
keywords = "heat acclimatization, heat adaptation, immune, performance, thermoregulation, training",
author = "Ashley Willmott and Mark Hayes and Carl James and Jeanne Dekerle and Oliver Gibson and Neil Maxwell",
note = "{\circledC} 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.",
year = "2018",
month = "12",
day = "21",
doi = "10.14814/phy2.13936",
language = "English",
volume = "6",
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Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements. / Willmott, Ashley; Hayes, Mark; James, Carl; Dekerle, Jeanne; Gibson, Oliver; Maxwell, Neil.

In: Physiological Reports, Vol. 6, No. 24, e13936, 21.12.2018.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements

AU - Willmott, Ashley

AU - Hayes, Mark

AU - James, Carl

AU - Dekerle, Jeanne

AU - Gibson, Oliver

AU - Maxwell, Neil

N1 - © 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

PY - 2018/12/21

Y1 - 2018/12/21

N2 - This experiment aimed to investigate the efficacy of twice-daily, nonconsecutiveheat acclimation (TDHA) in comparison to once-daily heatacclimation (ODHA) and work matched once- or twice-daily temperateexercise (ODTEMP, TDTEMP) for inducing heat adaptations, improvedexercise tolerance, and cytokine (immune) responses. Forty males,matched biophysically and for aerobic capacity, were assigned to ODHA,TDHA, ODTEMP or TDTEMP. Participants completed a cycling gradedexercise test, heat acclimation state test and a time to task failure(TTTF) at 80% peak power output in temperate (TTTFTEMP: 22°C/40%RH) and hot conditions (TTTFHOT: 38°C/20% RH), before and after 10-sessions (60-min of cycling at ~2W.kg-1) in 45°C/20% RH (ODHA andTDHA) or 22°C/40% RH (ODTEMP or TDTEMP). Plasma IL-6, TNF-α andcortisol were measured pre- and post-sessions 1, 5 and 10. ODHA andTDHA induced equivalent heat adaptations (P<0.05) (resting rectaltemperature [-0.28±0.22, -0.28±0.19°C], heart rate [-10±3, -10±4b.min-1] and plasma volume expansion [+10.1±5.6, +8.5±3.1%]) andimproved heat acclimation state (sweat setpoint [-0.22±0.18, -0.22±0.14°C] and gain [+0.14±0.10, +0.15±0.07g.sec-1.°C-1]).TTTFHOT increased (P<0.001) following ODHA (+25±4%) and TDHA(+24±10%), but not ODTEMP (+5±14%) or TDTEMP (+5±17%).TTTFTEMP did not improve (P>0.05) following ODHA (+14±4%), TDHA(14±8%), ODTEMP (9±10%) or TDTEMP (8±13%). Acute (P<0.05) butno chronic (P>0.05) increases were observed in IL-6, TNF-α or cortisolduring ODHA and TDHA, or ODTEMP and TDTEMP. Once- and twice-dailyheat acclimation conferred similar magnitudes of heat adaptation andexercise tolerance improvements, without differentially altering immune function, thus non-consecutive TDHA provides an effective, logisticallyflexible method of HA, benefitting individuals preparing for exercise-heatstress.

AB - This experiment aimed to investigate the efficacy of twice-daily, nonconsecutiveheat acclimation (TDHA) in comparison to once-daily heatacclimation (ODHA) and work matched once- or twice-daily temperateexercise (ODTEMP, TDTEMP) for inducing heat adaptations, improvedexercise tolerance, and cytokine (immune) responses. Forty males,matched biophysically and for aerobic capacity, were assigned to ODHA,TDHA, ODTEMP or TDTEMP. Participants completed a cycling gradedexercise test, heat acclimation state test and a time to task failure(TTTF) at 80% peak power output in temperate (TTTFTEMP: 22°C/40%RH) and hot conditions (TTTFHOT: 38°C/20% RH), before and after 10-sessions (60-min of cycling at ~2W.kg-1) in 45°C/20% RH (ODHA andTDHA) or 22°C/40% RH (ODTEMP or TDTEMP). Plasma IL-6, TNF-α andcortisol were measured pre- and post-sessions 1, 5 and 10. ODHA andTDHA induced equivalent heat adaptations (P<0.05) (resting rectaltemperature [-0.28±0.22, -0.28±0.19°C], heart rate [-10±3, -10±4b.min-1] and plasma volume expansion [+10.1±5.6, +8.5±3.1%]) andimproved heat acclimation state (sweat setpoint [-0.22±0.18, -0.22±0.14°C] and gain [+0.14±0.10, +0.15±0.07g.sec-1.°C-1]).TTTFHOT increased (P<0.001) following ODHA (+25±4%) and TDHA(+24±10%), but not ODTEMP (+5±14%) or TDTEMP (+5±17%).TTTFTEMP did not improve (P>0.05) following ODHA (+14±4%), TDHA(14±8%), ODTEMP (9±10%) or TDTEMP (8±13%). Acute (P<0.05) butno chronic (P>0.05) increases were observed in IL-6, TNF-α or cortisolduring ODHA and TDHA, or ODTEMP and TDTEMP. Once- and twice-dailyheat acclimation conferred similar magnitudes of heat adaptation andexercise tolerance improvements, without differentially altering immune function, thus non-consecutive TDHA provides an effective, logisticallyflexible method of HA, benefitting individuals preparing for exercise-heatstress.

KW - heat acclimatization

KW - heat adaptation

KW - immune

KW - performance

KW - thermoregulation

KW - training

U2 - 10.14814/phy2.13936

DO - 10.14814/phy2.13936

M3 - Article

VL - 6

JO - Physiological Reports

JF - Physiological Reports

SN - 2051-817X

IS - 24

M1 - e13936

ER -