Understanding the physiological factors affecting human heat dissipation

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Temperature regulation is a vital aspect of human survival as relatively small deviations in internal body (i.e. core) temperature can lead to profound disruptions in whole-body homeostasis. Prolonged exposure to hot environments and/or performing strenuous exercise can heat the body causing significant increases in internal body temperature. This heat is lost by contact with cool air and by sweat production, which cools your body as the sweat evaporates. However, when the body is unable to cool itself by sweating, several heat-induced illnesses such as heat stress or heat exhaustion and the more severe heat stroke can occur, and can result in death. Our work has demonstrated that there are a number of nonthermal factors (sensory end organs: metaboreceptors, baroreceptors, etc. and intrinsic factors: sex, aging, hydration status, fitness, etc.) that can have profound effects on the body's physiological capacity to dissipate heat. Our work is directed at understanding the separate and relative contribution of these factors during challenges to human heat balance associated with progressive elevations in environmental (elevated ambient temperature) and/or metabolic (exercise) heat load. To achieve an advanced understanding of the changes that nonthermal factors may elicit in the body's physiological capacity to dissipate, we are using the world's only whole-body calorimeter (a device for measuring heat emitted by the body) to measure how much heat the body is loosing. By understanding the precise combination of environmental and metabolic heat loads where physiological differences in the body's capacity to dissipate heat occur, we can begin to develop a better understanding of how heat stress develops. Funds obtained as part of this grant will be used to purchase research instruments that will help to maintain the operation of the world's only calorimeter (dew point mirror: used to regulate ambient humidity and measure whole-body sweating response) and increase capacity for research (laser-Doppler flowmetry: used to measure skin blood flow and therefore local heat loss).