Tony Horton used to be a stand-up comedian. Now he's the front man for P90X and a millionaire exercise guru. So is he an infomercial salesman? Or a fitness savior? ***** Beyond the compelling marketing, there are two reasons why P90X is so popular. First, Horton is the perfect front man. At 5´10* and 180 pounds with 9 percent body fat, he is genuinely ripped. He says he can consecutively do 110 pushups, 80 dips, 35 pullups, and eight 260-pound lat pulls. Plus, he can hold a handstand for a minute and even do a backflip off a wall. To...