What It Is and Symptoms:
Heat cramps are painful, involuntary muscle spasms that usually occur during intense exercise in a hot climate. Symptoms include muscle cramps and/or spasms, heavy sweating, normal body temperature. Heat cramps may happen in any muscle group involved in exercise, but the most commonly affected muscles are calves, arms, abs, and back.
Severe cramping may occur when you have been sweating excessively and losing electrolytes.
The easiest way to avoid heat disorders is to keep your body hydrated by drinking fluids before, during, and after exercise. The body's fluid needs vary with exertion, weather, terrain, and other factors. Fluid recommendations for runners say that they should "obey your thirst" and drink when their mouth is dry and they feel the need to drink. Drink before workouts and make sure you have access to fluids if exercising more than 30 minutes. During longer workouts, some of your fluids should include a sports drink to replace lost salt and electrolytes.
If you're suffering from heat cramps, stop running immediately and drink fluids (especially a sports drink to replace electrolytes). Get in the shade and try cooling your body with cold water and wet towels. Gently massage the affected area. Contact your doctor if your cramps don't go away within an hour.