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Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements.
Physiol Rep 2018; 6(24):e13936PR

Abstract

This experiment aimed to investigate the efficacy of twice-daily, nonconsecutive heat acclimation (TDHA) in comparison to once-daily heat acclimation (ODHA) and work matched once- or twice-daily temperate exercise (ODTEMP, TDTEMP) for inducing heat adaptations, improved exercise 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-graded exercise 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 ~2 W·kg-1) in 45°C/20% RH (ODHA and TDHA) or 22°C/40% RH (ODTEMP or TDTEMP). Plasma IL-6, TNF-α, and cortisol were measured pre- and postsessions 1, 5, and 10. ODHA and TDHA induced equivalent heat adaptations (P < 0.05) (resting rectal temperature [-0.28 ± 0.22, -0.28 ± 0.19°C], heart rate [-10 ± 3, -10 ± 4 b·min-1 ], and plasma volume expansion [+10.1 ± 5.6, +8.5 ± 3.1%]) and improved heat acclimation state (sweat set point [-0.22 ± 0.18, -0.22 ± 0.14°C] and gain [+0.14 ± 0.10, +0.15 ± 0.07 g·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) but no chronic (P > 0.05) increases were observed in IL-6, TNF-α, or cortisol during ODHA and TDHA, or ODTEMP and TDTEMP. Once- and twice-daily heat acclimation conferred similar magnitudes of heat adaptation and exercise tolerance improvements, without differentially altering immune function, thus nonconsecutive TDHA provides an effective, logistically flexible method of HA, benefitting individuals preparing for exercise-heat stress.

Authors+Show Affiliations

Environmental Extremes Laboratory, University of Brighton, Brighton, Eastbourne, United Kingdom.Environmental Extremes Laboratory, University of Brighton, Brighton, Eastbourne, United Kingdom.Environmental Extremes Laboratory, University of Brighton, Brighton, Eastbourne, United Kingdom. Institut Sukan Negara (National Sports Institute), National Sports Complex, Kuala Lumpur, Malaysia.Environmental Extremes Laboratory, University of Brighton, Brighton, Eastbourne, United Kingdom.Centre for Human Performance, Exercise and Rehabilitation (CHPER), Brunel University London, Uxbridge, United Kingdom.Environmental Extremes Laboratory, University of Brighton, Brighton, Eastbourne, United Kingdom.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

30575321

Citation

Willmott, Ashley G B., et al. "Once- and Twice-daily Heat Acclimation Confer Similar Heat Adaptations, Inflammatory Responses and Exercise Tolerance Improvements." Physiological Reports, vol. 6, no. 24, 2018, pp. e13936.
Willmott AGB, Hayes M, James CA, et al. Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements. Physiol Rep. 2018;6(24):e13936.
Willmott, A. G. B., Hayes, M., James, C. A., Dekerle, J., Gibson, O. R., & Maxwell, N. S. (2018). Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements. Physiological Reports, 6(24), pp. e13936. doi:10.14814/phy2.13936.
Willmott AGB, et al. Once- and Twice-daily Heat Acclimation Confer Similar Heat Adaptations, Inflammatory Responses and Exercise Tolerance Improvements. Physiol Rep. 2018;6(24):e13936. PubMed PMID: 30575321.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements. AU - Willmott,Ashley G B, AU - Hayes,Mark, AU - James,Carl A, AU - Dekerle,Jeanne, AU - Gibson,Oliver R, AU - Maxwell,Neil S, PY - 2018/11/06/received PY - 2018/11/08/accepted PY - 2018/12/22/entrez PY - 2018/12/24/pubmed PY - 2019/9/17/medline KW - heat acclimatization KW - heat adaptation KW - immune KW - performance KW - thermoregulation KW - training SP - e13936 EP - e13936 JF - Physiological reports JO - Physiol Rep VL - 6 IS - 24 N2 - This experiment aimed to investigate the efficacy of twice-daily, nonconsecutive heat acclimation (TDHA) in comparison to once-daily heat acclimation (ODHA) and work matched once- or twice-daily temperate exercise (ODTEMP, TDTEMP) for inducing heat adaptations, improved exercise 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-graded exercise 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 ~2 W·kg-1) in 45°C/20% RH (ODHA and TDHA) or 22°C/40% RH (ODTEMP or TDTEMP). Plasma IL-6, TNF-α, and cortisol were measured pre- and postsessions 1, 5, and 10. ODHA and TDHA induced equivalent heat adaptations (P < 0.05) (resting rectal temperature [-0.28 ± 0.22, -0.28 ± 0.19°C], heart rate [-10 ± 3, -10 ± 4 b·min-1 ], and plasma volume expansion [+10.1 ± 5.6, +8.5 ± 3.1%]) and improved heat acclimation state (sweat set point [-0.22 ± 0.18, -0.22 ± 0.14°C] and gain [+0.14 ± 0.10, +0.15 ± 0.07 g·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) but no chronic (P > 0.05) increases were observed in IL-6, TNF-α, or cortisol during ODHA and TDHA, or ODTEMP and TDTEMP. Once- and twice-daily heat acclimation conferred similar magnitudes of heat adaptation and exercise tolerance improvements, without differentially altering immune function, thus nonconsecutive TDHA provides an effective, logistically flexible method of HA, benefitting individuals preparing for exercise-heat stress. SN - 2051-817X UR - https://www.unboundmedicine.com/medline/citation/30575321/Once__and_twice_daily_heat_acclimation_confer_similar_heat_adaptations_inflammatory_responses_and_exercise_tolerance_improvements_ L2 - https://doi.org/10.14814/phy2.13936 DB - PRIME DP - Unbound Medicine ER -