When it comes to summer test labs, Arizona’s Big Ditch takes the prize. Dr. Tom Myers, a guide and medical advisor for the Grand Canyon Association Field Institute, faces triple-digit temps every season. Follow his advice to keep cool.
1 ) Drink what you need.
Stop for water when you’re thirsty, Myers says, but don’t force fluids—everyone has different water needs (though a good baseline is a half liter per hour at 80°F, and a liter per hour at 100°F). Like dehydration, which affects most endurance athletes on some scale, hyponatremia (diluted salt levels due to overhydration) is a serious risk: It affects 10 to 30 percent of athletes, according to some studies.