If the heat is not able to escape, we run the risk of overheating and potentially suffering the effects of heat injury. To get rid of the heat, blood is delivered to the skin surface where it can be dissipated. Most of the heat is lost from the surface through the evaporation of sweat. While exercising in hot, humid weather the sweating mechanism is heavily relied upon for the releasing body heat. If this fluid is not replaced, dehydration occurs and the body loses its ability to adequately dissipate heat.
Body temperature can then increase to dangerously high levels.
To prevent dehydration remember to drink plenty of water before, during, and after exercise. Don't rely upon sensations of thirst to tell you if you've had enough to drink. Thirst is satisfied well before the body has adequately replenished its fluid supply. Sugary drinks are not recommended because the sugar tends to delay the passage of fluids from the intestines to the rest of the body. If you experience cramping or muscle twitching after exercising in the heat you probably have not replaced enough fluids.