agrajag said:But I've always been told that you need to take breaks in between workouts anyway, so your muscles can recover?
Right, that's why with P90X you only do dedicated resistance training for a muscle group once per week. Just because you exercised your chest on Monday doesn't mean you have to wait until Wed or Thurs to exercise a completely separate part of your body.
I finished my first round of P90X about two weeks ago and lost close to 30 pounds during the process. I gained a lot more muscle definition, but I did lose some overall muscle size in my chest since even though doing a ton of push-ups is good, it's not the same as bench-pressing twice a week which is what I was doing before. I'm just now starting up a second pass of the program, but this time I'm going to throw in some bench-pressing on chest days.