Understanding the human heat stress response using whole-body calorimetry

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Prolonged exposure to hot environments/processes and or performing strenuous exercise can heat the body causing significant increases in internal body temperature. To offset this increase powerful and highly developed behavioral and autonomic thermoregulatory responses are activated to enhance whole-body heat loss. Independent of thermal control of heat loss responses, there is increasing evidence demonstrating that nonthermal factors [those associated with the activation of the body's sensory receptors (baroreceptors, metaboreceptors, etc.) as well as personal factors (sex, aging, hydration and acclimation status, etc.) can have profound consequences on the body's ability to dissipate heat during heat stress. My NSERC study program is directed at understanding the separate and combined contribution of these factors during heat stress. I am studying the mechanisms underlying the nonthermal modulation of the body's heat loss response using my world's only whole-body calorimeter (a device for making very precise measurements of the heat emitted by the body) to measure changes in the body's capacity to dissipate heat and therefore the level of thermal strain. To date, my calorimetry based studies have allowed me to make new and important advancements in our understanding of human heat stress response. The knowledge gained from this work serves as the foundation driving my team’s development of advanced solutions and technologies used to address real-world challenges faced by many industries (mining, electric utilities, others) and professional occupations (firefighters, warfighters, others) impacted by heat exposure issues. This has included 1) the development of an improved approach to estimate an individual’s level of heat stress, 2) assisting industry in developing new work uniforms that provide the necessary protection from the harsh environment while ensuring optimal heat dissipation, 3) the development of new personal cooling system options and technologies, 4) the establishment of job-specific work-rest schedules for the management of heat stress, and 5) others. Funds obtained as part of this grant will be used to replace the aging mechanical components that are critical and integral for the operation of our calorimeter. The newer technologies will help us achieve the highest possible level of control of ambient conditions and will allow us for the first time to conduct ramping protocols involving rapid changes in humidity and temperature. This will allow us to significantly increase our operational capabilities (by more closely simulating real-world conditions in a work environment) which will greatly benefit our research capacity and enhance the impact of our research work. Moreover, in partnership with our industry partners, the calorimeter will be used to develop and test a portable monitoring system that would define when a worker is at risk of a heat-related injury.