Fierce and Fab in 14 Days: Tony Horton's P90X-Inspired Workout

Pudge-proof your winter with this two-week tighten-it-up blast from the transformation master himself, Tony Horton. "This is one routine you will not blow off, because it delivers the greatest amount of change in the shortest amount of time," says Horton, who gave FITNESS an exclusive look at the P90X class he's bringing to a gym near you. Based on his blockbuster workout DVD sets, this quick circuit is your perfect antidote for the holiday slide. By using different muscles in Horton's signature UIML (upper body, interval, middle, lower body) pattern, "you don't need any downtime between moves," he says, thereby amping your fat burn as you firm all over. Warm up for five minutes, then grab a three- to six-pound medicine ball and do the moves in order, taking a breather only between rounds one and two. Repeat the entire circuit for a 24-minute trimmer you can do up to four days a week. (On alternating days, try some light cardio or yoga.) Reboot the 14-day routine whenever you could stand to lose a few!