P90X, or Power 90 Extreme, is a commercial home exercise regimen created by Tony Horton. Developed as a successor to the program called "Power 90", it is designed to take 90 days, and consists of a training program that uses cross-training and periodization, combined with a nutrition and dietary supplement plan.
The system was developed by Tony Horton, Beachbody CEO Carl Daikeler, Beachbody Fitness Advisor Steve Edwards, nutritionist Carrie Wyatt, Creative Director Ned Farr, and workout video director Mason Bendewald.
In 2002, Daikeler requested that Horton create a fitness program for people who were already physically fit. Daikeler then hired Ned Farr to document the process of developing the new program. Horton consulted various fitness experts and experimented with several disciplines to help develop the workout program.
The program was promoted as using "Muscle Confusion" to emphasize the effectiveness of the workouts, using three phases that had different orders of workouts, so the body wouldn't get used to the workouts. The program also had three different schedules: Lean, for people looking to lose weight and fat; Classic, for people wanting to get both muscle mass and physical endurance; and Doubles, which was the Classic schedule with an extra cardio workout each day, for athletes to get in shape before a sports season begins.
Farr used a documentary approach when filming the infomercials, using raw home footage supplied by P90X graduates. "P90X: The Proof" infomercial won a Telly award in 2009 and "P90X: The Answer" infomercial won a Moxie award in 2010.
In 2011, the sequel to P90X was released, P90X2. Also a 90-day workout regimen, P90X2 focuses on an applied sports science called Muscle Integration. Instead of working one muscle group at a time, P90X2 uses resistance on unstable platforms to engage more muscles with each movement.
In December 2013, P90X3 was released and featured 30 minute workouts as opposed to hour-long ones. P90X3 includes 16 routines, and includes yoga, mixed martial arts, Pilates, and plyometrics with upper and lower body workouts.
In January 2015, P90X announced it will partner with EB Sport Group and enter the traditional retail marketplace. Together, Beachbody, LLC and EB Sport Group plan to launch a full range of P90X branded products.
P90X uses the term "muscle confusion" in their advertising to refer to their training methods. Their advertising claims that "muscle confusion" is believed to prevent the body from adapting to exercises over time, resulting in continual improvement without plateau.
There are several programs associated with the Power 90 name. Currently for sale are P90, P90X, P90X+, P90X One on One, P90X2, and P90X3. Several others were produced, but are out of print, such as the original Power 90 series that spawned P90X. 
P90X is a 90-day program with exercises six days per week. It combines a variety of exercise techniques, including strength training, cardio, yoga, plyometrics, and stretching. The program consists of a fitness test, nutrition guide, fitness plan, calendar, and series of DVDs demonstrating a variety of techniques. The video demonstrates moves at lower and higher levels of intensity.
Standard home gym equipment recommended for use with P90X: yoga blocks, yoga mat, dumbbells, resistance bands, pull-up/chin-up bar, push-up handles, heart rate monitor, and body fat tester. A chair, plastic plate, and wall are also things that can be used.
The nutrition plan is composed of three phases. The first 30 days emphasize higher protein and lower carbohydrates. The second phase increases the percentages of carbohydrates. The third phase further increases the carbohydrates.
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