INVESTIGATING THE EFFECTS OF HEAT STRESS ON HUMAN ENDURANCE CAPACITY, BRAIN AND MUSCLE PHYSIOLOGY USING MRI METHODS

Abstract

Heat stress is a potent stressor for the human body where it can be presented as an environmental stress or as a priming/training factor. Under a hot environment, exertional hypohydration and hyperthermia can impair exercise performance and these factors may affect the brain function too. Our findings showed that exertional hypohydration (-3% body mass) led to a reduction of total brain volume with expansion of brain ventricles while functional activity and cerebral perfusion remained unperturbed. Exertional or passive hyperthermia were shown to impair cerebral perfusion and diminished the functional activity of primary motor cortex. This depressed central drive may limit endurance performance. In contrast, the induction of acute hyperthermia prior to exercise could be beneficial to exercise performance with the release of heat shock proteins (p-HSP27) that could have protected against muscle damage. However, the pre-exercise heating did not provide ergogenic gains for endurance capacity after a damaging eccentric run.