Invited Editorial Hot topic—cerebral hemodynamics in the heat

impairment such as dizziness, cognitive decline, and fatigue. These symptoms may reflect a mismatch of increased cerebral metabolic activity and impaired nutritive supply (8). Hyperther-mia challenges cerebral circulation by inducing hyperventilation, and in turn hypocapnia, the strongest cerebrovascular constrictor. For thermoregulatory purposes, a significant proportion of cardiac output is diverted to the skin. Under these circumstances a number of studies have examined the cerebral hemodynamic response to exercise and orthostasis, and it is a general finding that indexes of cerebral blood flow (CBF) decrease (1, 5, 13). In a study in the Journal of Applied Physiology, Fan et al. (4) demonstrate an impressive data set that indicates a heat-stress induced reduction in CBF in the resting supine human. The authors carefully investigated not only the effect of increasing core temperature but also examined the influence of two majo