And although there is plenty of anecdotal evidence that suggests the program is effective, no scientific studies have been published to determine the true energy cost and exercise intensity of P90X.
Those who stick with the very intense P90X program and “keep pressing play” (as P90X devotees say) six sessions per week for the full 90 days are a loyal group. This, in turn, means the body burns more fat and builds more muscle, more quickly. Exercise scientists call it daily undulating periodization, which is the principle that by changing up workouts regularly, the body doesn’t have time to adapt and become efficient at the exercise. It was Idol who gave Horton the nickname “Muscle Confucius,” a tip of the hat to Horton’s favorite fitness concept, muscle confusion, which is at the heart of the P90X program.
Horton, the quirky yet motivating star and creator of P90X, first made a name for himself as a trainer for Hollywood’s elite, including actors Sean Connery and Ewan McGregor, musicians Sheryl Crow, Usher and Bruce Springsteen, and ‘80s rocker Billy Idol. Have a hankering for more Horton-isms? The sequel, P90X2, will be on sale by late December 2011. “Keep your bucket nearby my friends, because this routine is X City.” "Yes, I know it’s hard! It’s supposed to be!” “Oh, dude, this is going to hurt so much.” “Like a pterodactyl backing out of trouble.” “Oh yeah, gonna burn off some goo today! Get rid of the goop because we don’t want it.” Eleven phrases that trainer Tony Horton uses famously in the P90X workout videos: