Fitness phenom P90X has sold more than 3 million DVDs since its 2004 debut—and this December, sales will surely rise with the holiday release of P90X2. But it's not as if creator Tony Horton invented anything new. He just repackaged established fitness principles. It's an old trick in the fitness industry: Take something gym rats have done for decades, give it a new name, and start selling. The innovation is in the pitch.
Rotating workouts continually introduce your muscles to new stimuli.
Knowing the audience.
"Muscle confusion is nothing new," says strength coach John Romaniello, owner of Roman Fitness Systems. "But people buying P90X are intrinsically more likely to get better results, because they go in knowing they're going to work hard."
Boot-camp-style workouts—including kettlebell swings, handstand push-ups, and jumping squats—target strength and flexibility.
"CrossFitters excel by rallying around each other," says Romaniello of the method's cultlike following. "Cross-Fitters and trainers alike defend it with a very high level of tenacity."
A lightweight canvas strap secures to anything from a gym machine to a hotel-room door; resistance changes based on the angle at which you stand or lay.
"TRX is popular because it's portable," says Romaniello. "Similar pieces of equipment [before TRX] were intimidating and hard to travel with. TRX made it user-friendly."
Cycling is amped up with dance moves, yoga breathing, positive exhortations, and a kick-ass playlist.
"Sex sells in fitness like it does in anything else," says Debora Warner, a personal trainer based in New York. "The vibe is great, from the candles to the music to the nice-smelling towels. It's solid on all levels of service."
A version of this article appeared in the December 2011/January 2012 issue of Fast Company magazine.