Integrative human cardiovascular function in hyperthermia

Integrative human cardiovascular function in hyperthermia

Speaker: Professor José González-Alonso, Brunel University London

Progressive whole body hyperthermia with passive heat stress is associated with a collection of physiological adjustments. These include large increases in peripheral blood flow and cardiac output and a smaller selective redistribution of blood flow from the cerebral and visceral tissues to the limbs, head and torso, with perfusion pressure being only slightly reduced. Although aerobic metabolism increases in these conditions, the magnitude is small in absolute terms, suggesting a predominant role of thermosensitive mechanisms in passive hyperthermia-induced cardiovascular adjustments. Exercise-heat stress can place substantially greater functional and regulatory demands on the cardiovascular system compared to passive heat stress. The combined cardiovascular responses to exercise-heat stress are drastically blunted or abolished, however, compared to those seen when either passive heating or exercise is experienced in isolation. As a result, submaximal exercise limb blood flow is only slightly higher during small muscle mass exercise in the heat and is similar to control conditions during whole-body exercise. When exercise intensity is increased further towards maximal levels, the superimposition of heat stress leads to earlier reductions in regional and systemic blood perfusion, compromised locomotor limb aerobic metabolism, and ultimately results in impaired endurance capacity. This seminar provides an integrative overview of the human cardiovascular response to passive heat stress and exercise-heat stress, with an emphasis on its consequences on exercise performance in the heat. 

Seminar organised by Dr Federico Formenti