The influence of thermal inputs on brain regulation of exercise: An evolutionary perspective

The relationship between performance, heat load and the ability to withstand serious thermal insult is a key factor in understanding how endurance is regulated. The capacity to withstand high thermal loads is not unique to humans and is typical to all mammals. Thermoregulation is an evolutionary adaptation which is species specific and should be regarded as a survival strategy rather than purely a physiological response. The fact that mammals have selected ~37°C as a set point could be a key factor in understanding our endurance capabilities and strategy. Endurance presents a significant challenge to bodily homeostasis while our thermoregulatory strategy is able to cope exquisitely under the most unfavorable conditions. The ability of the CNS to regulate this strategy is key in athletic performance since the thermoregulatory center is located within the brain and receives input from multiple systems and deploys effector responses as needed. This chapter will discuss the evolution of thermoregulation in humans and propose that the brain is more than sufficiently capable of maintaining thermal-homeostasis because of its evolutionary path. As such, this is connected to our ability to modulate efferent drive during heat strain and in so doing provides us with the capability to pace during endurance events in the heat.