As the body’s core temperature increases, athletic performance declines. Lately, cooling vests have been used by athletes in an attempt to pre-cool their bodies prior to competition. Does this work? Somewhat. But research indicates that the best way to deal with the heat is to be aerobically fit and to spend time acclimatizing to training and racing in the heat. If you can’t do that, be careful when exercising in the heat: any signs of dizziness, light headedness or nausea can mean you need to get inside and rehydrate NOW.