insanity is an intense cardio workout program. The strength training moves that are incorporated in it are plyometric based and body weight only (pushups) there is not enough outside resistance to actually build muscle. These workouts are truely designed to shread fat off your body. I absolutely love them. I have never done such a hard workout in my life. As far as the ab workout with insanity, during the 1st month you do an ab workout once a week for the first 3 weeks and twice for the 4th week and during the second month you do an ab workout about 2 times per week however, all the insanity workouts work the abs so actually your abs are being incorporated in each workout. You can also add an extra day of abs if you truely want to. I think if you want to add some muscle, use insanity as your cardio and keep going with P90x. Hope this helps
