The Physiology of Thermoregulation in Exercise

Abstract

During physical exercise, the production of heat in the working skeletal muscles increases, imposing heat stress on the body. Thermoregulatory mechanisms induce adjustments of cutaneous vascular conductance and thus skin blood flow (SkBF), sweating rate, and increased cardiac output to achieve thermal homeostasis. The response depends on the intensity, type, duration of exercise, and environmental temperature: during extreme exercise in a hot environment SkBF can attain up to 7 L/min compared to 300 mL/min at rest whereas the sweating rate can reach as high as 4 L/h. Due to opposing non-thermal reflexes, the thermoregulatory response of SkBF during exercise differs from that at rest: the threshold to induce vasodilation in the skin is shifted to higher body core temperature and the sensitivity of the “SkBF to-core temperature” slope is altered. Regular training induces better adaptations to physical stress which enable sportsmen to eliminate additional heat more optimally. The review emphasizes physiological mechanisms involved in thermoregulation during exercise and exposes some thoughts regarding the estimation t of the core temperature in humans, as well as some new approaches for an up-to-date assessment of parameters important for appropriate heat dissipation thereby maintaining core temperature.