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Whole-body heat exchange in black-African and Caucasian men during exercise eliciting matched heat-loss requirements in dry heat.

Abstract

NEW FINDINGS

• What is the central question of this study? Black-African descendants are thought, by some, to possess genotypic adaptations conducive to survival in hot climates. We therefore assessed whether Canadian residents of black-African descent display enhanced whole-body total heat loss (evaporative + dry heat exchange) compared to Caucasian-Canadians during exercise eliciting matched heat-loss requirements in dry heat. • What is the main finding and its importance? Neither whole-body total heat loss nor body heat storage differed significantly between groups, irrespective of the exercise-intensity. Our findings indicate that genotypic adaptations associated with ethnicity do not appreciably modify whole-body heat exchange during exercise-heat stress.

ABSTRACT

Ethnicity has long been thought to modulate thermoregulatory function; however, an evaluation of whole-body heat exchange in men of black-African descent and Caucasian men (white-European descendants), born and raised in the same climate, during exercise eliciting matched heat-loss requirements remained unavailable. We therefore used direct calorimetry to assess whole-body total heat loss (evaporative + dry heat exchange) in young (18-30 years), second-generation (or higher) black-African (n = 11) and Caucasian (n = 11) men. Participants performed three, 30-min bouts of semi-recumbent cycling at fixed metabolic heat productions (and therefore matched heat loss requirements between groups) of 200 (light), 250 (moderate), and 300 W/m2 (vigorous), each followed by 15-min recovery, in dry heat (40°C, ∼13% relative humidity). Across all exercise bouts, dry (p = 0.435) and evaporative (p = 0.600) heat exchange did not differ significantly between groups. As such, total heat loss during light, moderate and vigorous exercise was similar between groups (p = 0.777), averaging (mean (SD)); 177 (10), 217 (13) and 244 (20) W/m2 in black-African men, and 172 (13), 212 (17) and 244 (17) W/m2 in Caucasian men. Accordingly, body heat storage across all exercise bouts (summation of metabolic heat production and total heat loss) was also similar between the black-African (568 (142) kJ) and Caucasian groups (623 (124) kJ; p = 0.356). We demonstrate that, when assessed in young, second-generation (or higher) black-African and Caucasian men during exercise eliciting matched heat-loss requirements in dry heat, ethnicity did not significantly modulate whole-body dry and evaporative heat exchange or the resulting changes in total heat loss and body heat storage. This article is protected by copyright. All rights reserved.

Authors+Show Affiliations

Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31628699

Citation

Muia, Caroline M., et al. "Whole-body Heat Exchange in black-African and Caucasian Men During Exercise Eliciting Matched Heat-loss Requirements in Dry Heat." Experimental Physiology, 2019.
Muia CM, Notley SR, Saci S, et al. Whole-body heat exchange in black-African and Caucasian men during exercise eliciting matched heat-loss requirements in dry heat. Exp Physiol. 2019.
Muia, C. M., Notley, S. R., Saci, S., D'Souza, A. W., & Kenny, G. P. (2019). Whole-body heat exchange in black-African and Caucasian men during exercise eliciting matched heat-loss requirements in dry heat. Experimental Physiology, doi:10.1113/EP088091.
Muia CM, et al. Whole-body Heat Exchange in black-African and Caucasian Men During Exercise Eliciting Matched Heat-loss Requirements in Dry Heat. Exp Physiol. 2019 Oct 18; PubMed PMID: 31628699.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Whole-body heat exchange in black-African and Caucasian men during exercise eliciting matched heat-loss requirements in dry heat. AU - Muia,Caroline M, AU - Notley,Sean R, AU - Saci,Samah, AU - D'Souza,Andrew W, AU - Kenny,Glen P, Y1 - 2019/10/18/ PY - 2019/08/13/received PY - 2019/10/08/accepted PY - 2019/10/20/entrez KW - ethnicity KW - exercise KW - heat stress JF - Experimental physiology JO - Exp. Physiol. N2 - NEW FINDINGS: • What is the central question of this study? Black-African descendants are thought, by some, to possess genotypic adaptations conducive to survival in hot climates. We therefore assessed whether Canadian residents of black-African descent display enhanced whole-body total heat loss (evaporative + dry heat exchange) compared to Caucasian-Canadians during exercise eliciting matched heat-loss requirements in dry heat. • What is the main finding and its importance? Neither whole-body total heat loss nor body heat storage differed significantly between groups, irrespective of the exercise-intensity. Our findings indicate that genotypic adaptations associated with ethnicity do not appreciably modify whole-body heat exchange during exercise-heat stress. ABSTRACT: Ethnicity has long been thought to modulate thermoregulatory function; however, an evaluation of whole-body heat exchange in men of black-African descent and Caucasian men (white-European descendants), born and raised in the same climate, during exercise eliciting matched heat-loss requirements remained unavailable. We therefore used direct calorimetry to assess whole-body total heat loss (evaporative + dry heat exchange) in young (18-30 years), second-generation (or higher) black-African (n = 11) and Caucasian (n = 11) men. Participants performed three, 30-min bouts of semi-recumbent cycling at fixed metabolic heat productions (and therefore matched heat loss requirements between groups) of 200 (light), 250 (moderate), and 300 W/m2 (vigorous), each followed by 15-min recovery, in dry heat (40°C, ∼13% relative humidity). Across all exercise bouts, dry (p = 0.435) and evaporative (p = 0.600) heat exchange did not differ significantly between groups. As such, total heat loss during light, moderate and vigorous exercise was similar between groups (p = 0.777), averaging (mean (SD)); 177 (10), 217 (13) and 244 (20) W/m2 in black-African men, and 172 (13), 212 (17) and 244 (17) W/m2 in Caucasian men. Accordingly, body heat storage across all exercise bouts (summation of metabolic heat production and total heat loss) was also similar between the black-African (568 (142) kJ) and Caucasian groups (623 (124) kJ; p = 0.356). We demonstrate that, when assessed in young, second-generation (or higher) black-African and Caucasian men during exercise eliciting matched heat-loss requirements in dry heat, ethnicity did not significantly modulate whole-body dry and evaporative heat exchange or the resulting changes in total heat loss and body heat storage. This article is protected by copyright. All rights reserved. SN - 1469-445X UR - https://www.unboundmedicine.com/medline/citation/31628699/Whole-body_heat_exchange_in_black-African_and_Caucasian_men_during_exercise_eliciting_matched_heat-loss_requirements_in_dry_heat L2 - https://doi.org/10.1113/EP088091 DB - PRIME DP - Unbound Medicine ER -