Exertional Heat Illness

Exertional heat illness is a spectrum of conditions caused by the body overheating during exercise, from heat exhaustion to exertional heat stroke (EHS), a life-threatening emergency.

It occurs wherever people work hard in heat and humidity, from endurance events and team sports to military and occupational training, and it can occur in cool UK conditions too. Exertional heat stroke is a recognised cause of collapse and death in sport.

One rule runs through the topic: cool first, transport second. Survival depends on how quickly the core temperature is lowered, core temperature is measured rectally, and the main mimic, exercise-associated hyponatraemia, needs the opposite approach to fluid.