i'm in 10th week of p90x (last phase, 3rd month). i haven't missed a single day and on the day of rest, i either jog or do my wifes cardio dvd.
i'm on atkins for 3 years now.
with the p90x, i used to do it midday because of work schedule so that helped with my energy but now i do it at night after the kids are in bed and its tough! i just finished plyometrix 10 minutes ago and that is no joke.

you should eat 5 small meals a day while doing this routine. I have been using the atkins shake as a supplement after the exercises.

i only had one issue and it was last week. i did the legs and back routine and really pushed the calf raises. that night 4am i awoke to horrendous charlie horse cramp in the calf. it was killing me for 4 minutes. solid as a rock. i didn't drink enough water and maybe didn't stretch enough. so drink plenty of water and for now on, on leg days, i will also look for a low carb gatorade for electrolytes. do the same.

bring it!