The fitness program created by Tony Horton that uses a 90-day calendar is P90X. The name is short for “Power 90 Extreme,” and the program was designed as an intensive home-training system built around scheduled workouts, nutrition guidance, and progression over roughly three months.
P90X became widely known through Beachbody’s marketing and workout-video business. Its approach uses cross-training and periodization, rotating among resistance training, cardio, martial-arts-inspired workouts, yoga, and flexibility sessions. The variety is intended to reduce routine stagnation and challenge different physical qualities across the calendar.
Tony Horton developed P90X after earlier work on the Power 90 program. A frequent mix-up is confusing P90X with Insanity, another well-known Beachbody program that emphasizes high-intensity cardio and was associated with trainer Shaun T. P90X is instead most closely identified with Horton, its structured 90-day schedule, and its “muscle confusion” marketing concept.