FOGGY AND BREEZY SOUTHWEST ENGLANDis hardly the place for Chris Byrne to study the human response to extreme heat. So Byrne, an exercise physiologist at the University of Exeter, traveled to sweltering Singapore to study soldiers running a half-marathon. His research recorded one of the highest internal body temps ever (107°F) and demonstrated that hydration during exercise doesn't decrease core temperature. To keep your body comfortably near 98.6°F, Byrne recommends these strategies.
Expose as little of your upper body to direct sunlight as possible.
Wear a wide-brimmed hat and loose-fitting, light-colored shirts and pants. In hot and dry conditions, breathable cotton fabrics will keep you cooler.
Open or make vents at the ankles, inseams, and armpits to generate airflow and enhance sweat evaporation.
Take a break
Active muscles generate tremendous heat, so rest in a shady place if you begin to feel uncomfortably hot.
Don't force an overheated person to drink: Both heat exhaustion and heat stroke can occur without dehydration. Let your thirst level, not your body temperature, determine your rate of fluid intake.
Water absorbs body heat about 23 times faster than air. If you're getting hot, says Byrne, pour water over your skin, or wet a cloth and apply it to the neck, armpits, and groin. The cooling effect is maximized in places with high concentrations of blood vessels, like the neck's carotid arteries and jugular veins.
In case of heat exhaustion, cool the body as rapidly as possible using a combination of shade, fanning, and water.