Human thermoregulation: separating thermal and nonthermal effects on the body's capacity to dissipate heat

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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 (i.e., baroreceptors, metaboreceptors, etc.) as well as personal factors (i.e., aging, acclimation, 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 measuring the heat emitted by the body) to measure changes in the body's capacity to dissipate heat. A critical component of my work is the ability to integrate the simultaneous measurement of responses of other physiological systems (cardiovascular, metabolic, etc.). This has enabled me to achieve an unprecedented insight into the complex interplay between thermal and nonthermal controllers of human thermoregulation. Funds obtained as part of this grant will be used to replace and upgrade critical instruments uniquely integrated for use in my calorimeter. This includes 1) a laser-Doppler flowmetry unit for assessing skin blood flow, 2) a non-invasive hemodynamic system to measure multi-hemodynamic parameters, and 3) gas analyzers for measuring oxygen consumption and carbon dioxide production (used to quantify and/or regulate rate of heat production). My study findings will help in developing management tools to control or eliminate heat stress conditions and protect the health and safety of individuals during heat-stress conditions. It can also be used to stimulate the development of technologies/solutions to improve industry process efficiencies (ventilation systems, new clothing designs, personal cooling systems, etc.).