Not only is this one of the toughest triathlons, it's one of the hardest in which to to earn a spot. For athletes lucky enough to toe the line, the mass swim start is a telling precursor for a treacherous day but the intensity only picks up on the bike and run courses where athletes face harsh wind, heat and humidity. By the time you hit the Energy Lab, about halfway into the run, it threatens to zap any energy you have left. For many, it's pure will that gets them through the lab, where road temps can hit 115 degrees, to the home stretch. But waiting there is a spectator reception that's unmatched at any other race.