The intensity is not matched by any other workout program on the market today. From the time you pop in the DVD it is non-stop movement, pushing, pulling, lifting, squatting, jumping, running. By the time the workout is over, if you make it that far, you will be absolutely exhausted. Studies have shown this is the most effective muscle building (German: effektiver Muskelaufbau) program on the market today. People are transforming their bodies and their lives in 90 days with P90X. Personally I experienced weight loss of 15lbs along with a substantial drop in body fat and increase in muscle mass.