The 2018 heatwave has seen soaring temperatures across much of the world, resulting in many cases of heat stroke and even deaths. Heat stroke has become a popular topic, yet the mechanisms behind it are rarely mentioned. Dr Keiji Hayashi, Associate Professor at the University of Shizuoka, Japan, has spent many years investigating the causes of heat stroke and the ways in which the body manages rising temperatures. His research focuses on hyperthermia-induced hyperventilation. Hayashi explains, ‘when body temperature rises, minute ventilation (hyperventilation) also increases. This causes a reduction in partial pressure of arterial CO2 (PaCO2), resulting in a reduction in cerebral blood flow. Cerebral blood flow, generated in the brain, is a key factor in removing heat. Therefore, a reduction in cerebral blood flow leads to an accumulation of heat in the brain and that is very dangerous for us.’ When the body’s temperature rises, breathing patterns become more rapid, especially with an increase in blood flow into the brain. Where this process is not managed effectively, heat stroke can occur. Hayashi and his team have examined the relationship between hyperthermia-induced hyperventilation and heat stroke through exercise. However, the mechanisms and countermeasures of hyperthermia-induced hyperventilation are uncertain as there is a great deal of variation in responses to increased temperatures. Hayashi explains, ‘because hyperthermia causes hyperventilation, temperature input should be an important factor causing hyperthermia-included hyperventilation in humans.’ Thus, we are left with the question, do individual experiences of hyperthermia-induced hyperventilation differ due to the ways in which humans absorb temperature? Hayashi examined the relationship between skin temperature and its effect on the body. ‘We plotted minute ventilation against core temperature, and found that differences in skin temperature did not influence the relationship between ventilation and core temperature,’ explains Hayashi. This discovery shifted Hayashi’s focus towards investigating how the core of the body absorbs heat, as it is that affects the ventilator response. Exercise provoked the most rapid increase in body core temperature. The body’s response to the changes in carbon dioxide (CO2), hydrogen ions, and oxygen (O2) levels in the blood is called the chemoreflex. He predicts that this may be another influence on the ventilatory response to the rising body temperature. By studying how the body incorporates heat, Hayashi seeks to understand how exercise affects these chemical reactions that result in hyperthermia-induced hyperventilation. By looking closely at the ways in which our bodies change through exercise in the heat, Hayashi is dedicated to better understanding hyperthermia-induced hyperventilation in order to develop effective methods of coping with heat stroke and central fatigue.