Notley Sean R, Lamarche Dallon T, Meade Robert D, Flouris Andreas D, Kenny Glen P
Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada.
FAME Laboratory, Department of Exercise Science, University of Thessaly, Trikala, Greece.
Exp Physiol. 2019 Jul;104(7):1038-1050. doi: 10.1113/EP087666. Epub 2019 May 6.
What is the central question of this study? The aim was to identify the greatest contributor(s) to the variation in whole-body heat exchange, as assessed using direct calorimetry, among young men and women with heterogeneous characteristics during exercise at increasing metabolic heat production rates in dry heat. What is the main finding and its importance? The evaporative heat loss requirement, body morphology and aerobic fitness made the greatest contributions to the individual variation in evaporative and dry heat exchange, with the variance explained being exercise intensity dependent. These findings provide a foundation on which to build our ability to explain the individual variation in heat exchange during exercise-induced heat stress.
Numerous individual factors (e.g. fitness, sex, body morphology) are known to independently modulate heat exchange during exercise in the heat. However, in our view, the individual factor(s) making the greatest contribution to the variation in heat exchange among men and women remains poorly understood, despite several studies. We therefore sought to revisit this question by assessing whole-body dry and evaporative heat exchange using direct calorimetry in a heterogeneous sample of 100 young men (n = 57) and women (n = 43). Participants performed three 30 min bouts of cycling at very light (men/women; 300/250 W), light (400/325 W) and moderate (500/400 W) metabolic heat production rates, separated by a 15 min recovery, in dry heat (40°C, ∼12% relative humidity). Positive associations were observed between the evaporative heat loss requirement (metabolic heat production ± dry heat exchange) and evaporative heat loss (all P < 0.01), especially during moderate exercise (men, r = 0.62; women, r = 0.82), which explained 19-67% of individual variation. Peak aerobic power (in millilitres per kilogram per minute) was also positively related to evaporative heat loss in both sexes, albeit only during light and moderate exercise (r = 0.33-0.43; all P < 0.05), explaining a further 5-9% of individual variation. Dry heat exchange shared negative associations with body mass and surface area during all exercise bouts in both sexes (r = -0.29 to -0.55; all P < 0.05), explaining 9-30% of individual variation. We therefore demonstrate that the evaporative heat loss requirement, peak aerobic power and body morphology are the greatest contributors to the variation in whole-body heat exchange among young men and women exercising in dry heat, with the strength of those relationships being heat-load dependent.
本研究的核心问题是什么？目的是确定在干热环境中，随着代谢产热率增加，使用直接量热法评估的全身热交换变化中最大的影响因素，研究对象为具有不同特征的年轻男性和女性。主要发现及其重要性是什么？蒸发散热需求、身体形态和有氧适能对蒸发和干热交换的个体差异贡献最大，所解释的方差取决于运动强度。这些发现为我们解释运动引起的热应激期间热交换的个体差异提供了基础。
已知许多个体因素（如适能、性别、身体形态）在热环境中运动时会独立调节热交换。然而，在我们看来，尽管有多项研究，但对男女热交换变化贡献最大的个体因素仍了解不足。因此，我们试图通过使用直接量热法评估100名年轻男性（n = 57）和女性（n = 43）的异质样本的全身干热和蒸发热交换来重新审视这个问题。参与者在干热环境（40°C，相对湿度约12%）中进行了三轮30分钟的骑行，代谢产热率分别为非常轻（男性/女性；300/250瓦）、轻（400/325瓦）和中等（500/400瓦），每轮之间有15分钟的恢复时间。观察到蒸发散热需求（代谢产热±干热交换）与蒸发散热之间存在正相关（所有P < 0.01），尤其是在中等强度运动期间（男性，r = 0.62；女性，r = 0.82），这解释了19 - 67%的个体差异。峰值有氧功率（毫升/千克/分钟）在男女中也与蒸发散热呈正相关，尽管仅在轻度和中等强度运动期间（r = 0.33 - 0.43；所有P < 0.05），进一步解释了5 - 9%的个体差异。在男女所有运动回合中，干热交换与体重和表面积呈负相关（r = -0.29至-0.55；所有P < 0.05），解释了9 - 30%的个体差异。因此，我们证明蒸发散热需求、峰值有氧功率和身体形态是干热环境中运动的年轻男女全身热交换变化的最大贡献因素，这些关系的强度取决于热负荷。
