Understanding the interplay of thermal and non-thermal factors on whole-body heat exchange during heat stress

温度调节是人类生存的一个重要方面。然而，暴露在炎热的环境中（较高的环境温度增加了身体散热的需求）和/或代谢过程产生的热量（代谢率的增加增加了身体产生的热量，从而增加了热量必须消散的速度）会导致体温的危险升高。为了抵消这种增加，高度发达的自主热效应反应（皮肤血管舒张和出汗）被激活，以促进热应激期间全身的热量损失。然而，热效应反应的生理控制以及因此导致的全身热损失可能会随着以下因素而变化：1)个体间（年龄、性别、其他）和个体内部因素（健康、水合作用、其他）以及个体控制范围之外（暴露次数、睡眠状态、其他）；2)与感觉受体（压力受体、代谢受体、渗透受体等）激活相关的非热因素的作用。新出现的证据表明，这些散热调节剂之间的相互作用可能对个体的生理散热能力产生深远的影响。然而，我们对这些因素之间相互作用的理解仍然不完整。因此，本研究的主要目的是阐明个体内因素（适应度、水合作用、热暴露时间）的复杂相互作用，以及与压力受体、代谢受体和渗透受体相关的感觉受体激活对散热的作用，以及性别和年龄等个体间因素的作用。这包括解释热损失响应的非热调节中介机制。这些目标将通过我们研究部门开发和研究的实验范例来解决，该实验范例独特地集成了我们独一无二的空气热量计（精确测量人体散热和储存热量的设备）的使用，从全身角度研究控制散热的机制。表征这些因素对人体生理耗散能力的生理相互关系，是推进我们对人体热应激反应理解的重要一步。通过全面了解影响人们在高温下生活和工作能力的生理因素，我们可以制定新的热保护策略，包括监测和管理解决方案和技术，为所有加拿大人和加拿大工人提供最大程度的保护，以应对日益严重的人类安全威胁-热。重要的是，拟议的研究活动将吸引一批新骨干学员，推动新一代和科学发展文化，以应对工业和其他受地球变暖引发的极端高温影响的人群所面临的现实挑战。

Temperature regulation is a vital aspect of human survival. However, exposure to hot environments (higher ambient temperatures increase the requirements for the body to dissipate heat) and/or heat generated from metabolic processes (increases in metabolic rate augments the heat produced by the body and thus rate that heat must be dissipated) can lead to dangerous increases in body temperature. To offset this increase, highly developed autonomic thermoeffector responses (cutaneous vasodilation and sweating) are activated to facilitate whole-body heat loss during heat stress. However, physiological control of thermoeffector responses and therefore whole-body heat loss can vary as a function of: i) inter-individual (age, sex, other) and intra-individual factors both within (fitness, hydration, other) and beyond (number of exposures, sleep state, other) an individual's control, and ii) the actions of nonthermal factors associated with activation of sensory receptors (baroreceptors, metaboreceptors, osmoreceptors, etc.). Emerging evidence indicates that an interplay between these modulators of heat dissipation may have profound effects on an individual's physiological capacity to dissipate heat. However, our understanding of the interplay between factors remains incomplete. Thus, the main goals of this proposal is to expound the complex interplay of intra-individual factors (fitness, hydration, heat exposure duration) as well as the role of sensory receptor activation associated with baroreceptors, metaboreceptors and osmoreceptors on heat dissipation as a function of inter-individual factors of sex and age. This includes explicating the mechanisms mediating the nonthermal modulation of heat loss responses. These goals will be addressed using an experimental paradigm developed and studied at our research unit which uniquely integrates the use of our one-of-a-kind air calorimeter (device to accurately measure the heat dissipated and stored by the human body) to investigate the control mechanisms governing heat dissipation from a whole-body perspective. Characterizing the physiological interrelations of these factors on the body's physiological capacity to dissipate represents an important step toward advancing our understanding of human heat stress response. By obtaining a comprehensive understanding of the physiological factors affecting a person's ability to live and work in the heat we can generate novel heat protection strategies consisting of monitoring and management solutions and technologies that will provide the maximum level of protection to all Canadians and Canadian workers against the rising threat to human safety - heat. Importantly, the proposed research activities will attract a new cadre of trainees and drive a new generation and culture of scientific growth to address real-world challenges faced by industry and other sectors of our population affected by extreme heat spurred by a warming planet.