Hey I'm just wondering..if you were to try to gain mass with p90x do you use other equipment to make it hard at the 8-12 range? i could increase the dumbells, but how about for the pushups? there seems to be a lot in p90x, just doing 8-12 pushup won't do much? Did you use other equipment to make your pushups more harder?
@Carl: Yes, I would buy the right amount of dumbbells that allows you to get in the 8-10 rep range. I use Adjustable dumbbells. For all body weight exercises I would go to Failure. That is key. When you get up to over 20 pull ups and over 50-60 push ups then you might want to think about using a weighted vest. I have a 30lb weighted vest that I use now.