P90x is an at home exercise system developed by Tony Horton. It claims to significantly improve physical fitness in 90 days through a rigorous segmented training program. P90X's emphasizes "muscle confusion", a method of cross-training and periodization achieved through switching the order of exercises and incorporating new and varied movements. Muscle confusion is said to prevent the body from adapting to exercises over time, resulting in continual improvement without plateaus. There are various exercise techniques in this workout series including strength training, cardio, yoga, plyometrics, and stretching.