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要求)和/或代谢过程产生的热量(代谢率的增加会增加身体产生的热量，从而增加热量必须散失的速度)可能会导致危险的体温上升。为了抵消这种增加，高度发达的自主神经温度效应器反应(皮肤血管扩张和出汗)被激活，以促进在热应激期间全身的热量损失。然而，温度效应器反应的生理控制和全身热损失可以根据以下因素而变化：i)个体之间(年龄、性别、其他)和个体内部因素(健康、水合等)和个体控制之外(暴露次数、睡眠状态等)，以及ii)与感觉受体(压力感受器、代谢性感受器、渗透感受器等)激活相关的非热因素的作用。新出现的证据表明，这些散热调节器之间的相互作用可能会对个体散热的生理能力产生深远的影响。然而，我们对因素之间的相互作用的理解仍然不完整。因此，这一建议的主要目的是阐明个体内因素(健康、水合、热暴露持续时间)的复杂相互作用，以及与压力感受器、代谢性感受器和渗透感受器相关的感觉受体激活在散热中的作用，作为性别和年龄的个体间因素的函数。这包括解释调节热损失反应的非热调制的机制。这些目标将使用我们研究单位开发和研究的实验范例来实现，该范例独特地整合了我们独一无二的空气热量计(精确测量人体散热和储存的热量的装置)的使用，以从全身的角度研究控制热量散失的机制。表征这些因素对身体的生理消散能力的生理相互关系是推进我们对人类热应激反应的理解的重要一步。通过全面了解影响人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防护策略，包括监控和管理解决方案以及技术，这些策略将为所有加拿大人和加拿大工人提供最大程度的保护，使其免受日益严重的人类安全威胁-高温。重要的是，拟议的研究活动将吸引新的受训人员，并推动新一代科学增长和文化，以应对受全球变暖刺激的极端高温影响的工业和其他人口部门面临的现实世界挑战。

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.