I'm sprawled out on all fours, my hands sliding off the back of a sweat-soaked exercise mat as I desperately try to shift my legs back and forth behind me in a torturous series of moves called "mountain climbers." I'm flailing, dripping, red-faced, and gasping for breath. This may very well be the least graceful or attractive I've ever looked. Questions are running through my head at a pace as rapid as my pulse: Am I having a heart attack? Have I sweat out 14 pounds yet? How did I get here?