<p>I have p90X and haven't done it. The equipment is kind of off-putting for me. I just finished 2 months of INSANITY workouts and found that I was only able to run 2x a week (I was also swimming 2x). However, at least with INSANITY, I didn't feel like I lost any cardio vascular fitness. P90X isn't nearly as cardio heavy as INSANITY is though. I dunno, I think you should be able to run 3-4x a week but they might not be real quality runs as you will likely have some fatigue.</p>