Mechanisms of Cross-tolerance between Heat and Hypoxia Acclimation

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The goal of our proposed research is to understand how human beings respond to a combination of heat and simulated altitude at the same time. To date, very little research has looked at this question. Most research has focussed on one environmental condition at a time. However, there is some recent research that indicates that exposure to heat and exposure to altitude might act synergistically. Specifically, if one becomes acclimated to heat, it appears they do better in simulated altitude. At altitude, the oxygen level in the surrounding air is low (this is called hypoxia), and it is very stressful on the body, leading to poor performance, poor ability to think and learn, and sometimes even illness. ***If there is an interaction between heat acclimation and hypoxia acclimation, it could have the potential to prepare people to better adapt to these harsh conditions. ******The goal of this research is to thoroughly investigate this interaction. The first step to confirm its existence and its extent. Secondly, we aim to try to understand the mechanisms responsible for this interaction. Are there common mechanisms by which humans react to heat and to hypoxia? Can heat acclimation can be used to improve hypoxia acclimation? ******It seems that if there is an interaction it might relate to exercise performance, in that if people become acclimated to high heat, their exercise performance in the heat gets better. We suspect that their exercise performance at altitude (or simulated altitude) might also get better. Improving exercise performance under these conditions is important for all people that work and play in the outdoors, from casual exercisers, to athletes, to military personnel, to workers that work in hot, high environments. ******Interestingly, there is some recent evidence that this heat acclimation might also improve cognition. We also aim to investigate the effects of heat and hypoxia on cognition, to determine if there truly is an interaction here. We will test cognition by looking both at blood markers of cognitive health, but also by performing a battery of cognitive tasks.******Participants will visit the lab on multiple occasions partaking in heat, hypoxia and sham (placebo) exposures to acclimate them to heat, and to test their response to the hypoxia.