Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.
Exp Physiol. 2020 Jan;105(1):7-12. doi: 10.1113/EP088091. Epub 2019 Nov 19.
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 plus dry heat exchange) in comparison 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.
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 plus dry heat exchange) in young (18-30 years of age), 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 m (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 m in black-African men and 172 (13), 212 (17) and 244 (17) W m 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 demonstrated 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.
这项研究的核心问题是什么？有人认为，黑非洲后裔具有有利于在炎热气候中生存的基因型适应。因此，我们评估了在干热环境中进行运动以产生匹配的热量损失要求时，加拿大黑非洲裔居民的全身总热量损失（蒸发加干热交换）是否与加拿大白种人不同。主要发现及其重要性是什么？无论运动强度如何，两组之间的全身总热量损失或身体热量储存均无显着差异。我们的研究结果表明，与种族有关的基因型适应不会显着改变运动热应激期间的全身热交换。
长期以来，人们一直认为种族会调节体温调节功能；然而，对于在相同气候中出生和长大的年轻（18-30 岁）第二代（或更高）黑非洲裔（n=11）和白种欧洲裔（白种人）男子，在进行运动以产生匹配的热量损失要求时，仍无法评估全身热量交换。因此，我们使用直接量热法评估了 11 名年轻的第二代（或更高）黑非洲（n=11）和 11 名白种人（n=11）男子在固定代谢产热（因此组间热量损失要求匹配）下的全身总热量损失（蒸发加干热交换）。在 30 分钟的半卧位自行车运动中，每个运动阶段持续 30 分钟，然后进行 15 分钟的恢复期，每个运动阶段的代谢产热（因此组间热量损失要求匹配）为 200（低）、250（中）和 300Wm（高），均在干热（40°C，相对湿度约为 13%）中进行。在所有运动过程中，两组之间的干热（P=0.435）和蒸发（P=0.600）热量交换没有显着差异。因此，两组在轻、中、高强度运动期间的总热量损失相似（P=0.777），黑非洲男性的平均（SD）分别为 177（10）、217（13）和 244（20）Wm，白种男性为 172（13）、212（17）和 244（17）Wm。相应地，在所有运动过程中，身体热量储存（代谢产热和总热量损失的总和）也相似，黑非洲组为 568（142）kJ，白种人组为 623（124）kJ；P=0.356）。我们证明，在年轻的第二代（或更高）黑非洲裔和白种人男子中，在干热环境中进行运动以产生匹配的热量损失要求时，种族不会显着调节全身干热和蒸发热量交换或总热量损失和身体热量储存的变化。
