You don't even have to work out during the prep phase, I didn't. Actually I would advise either having a deload week, week off, or Shockwave during the prep phase. The last thing you want to do is have hard workouts when you are going low carb.However, if the ten day prep phase is over before you start working out, I would either do one of the following:1. If your next real workout is only a day or two after the 10 days are up, extend the prep phase until after that workout. That is have your backload/Carb Nite.2. If your next real workout is further in the future, have a Carb Nite on the night of the tenth day and go low carb again until after your next workout.3. Or have a Shockwave workout on the tenth day before your Carb Nite. Shockwave is very easy on your nervous system.If it were me I'd choose option 2 or 3. Option 1 is there really just for sanity's sake.