P90X Classic takes advantage of the full realm of P90X workouts. No muscle is left behind! The only workout you won’t encounter here is Cardio X. That being said, you can still incorporate Cardio X into the Classic plan without going totally insane with Doubles (see below). For example, on days when I feel like I have some extra time and energy, I will do Cardio X in the evening after doing my regular scheduled workout earlier in the day. The main thing is to only add Cardio X on days when you do the strength training workouts. On days when I feel a little guilty about what I’ve eaten I also like to add Cardio X.
The P90X Doubles plan kicks it up another notch. Doubles adds another cardio workout to the Classic plan three or four days a week. The Doubles plan is for those who want some extra cardiovascular exercise, either for performance or weight loss. If you plan on doing Doubles, you’ll definitely need to be careful while you plan out your diet, schedule and laundry! On certain days of the week you’ll be working out both in the morning and the afternoon or evening.
The P90X Lean plan has more cardio and less resistance for those who for whatever reason don’t feel like they’re ready to tackle the Classic plan. I find that a lot of women like to flock to the Lean plan because they’re afraid of “bulking up” with the resistance workouts.