"It's HOW hot in here?" I'm no stranger to sweating. As a competitive roller derby athlete, I spend hours a week racing around the track and smashing into my friends (and rivals), often amid sweltering NYC summers. But this time, I was locked in, literally harnessed to a giant industrial-looking cardio machine at the high-tech Gatorade Sports Science Institute as part of an exclusive battery of tests normally reserved for performance-maxxing professional athletes . The 45-minute sweat test was