Beijing Olympians can count on being cool as cucumbers in Nike's PreCool Vest, a specially designed piece of clothing that lowers the body's core temperature. Much like computers, muscles perform better when they're not dedicating most of their resources to cooling down. Used about an hour prior to a competition, it can help an athlete last up to 21% longer out in the field. The vest is made of two layers of material: the inner one is filled with frozen water and the outer layer is coated with aluminum to act like a thermos, trapping cold in while reflecting radiant heat. Unfortunately, the PreCool is only available for Olympic athletes, so us normal folk will have to find other ways to chill out this summer. []