During my first Master-Cleanse last year I did all my workouts (aerobic and weight training) but at 75% intensity and duration and was fine. My workouts were originally 2 hour, so I dropped down to 1.5 hours total, dropped the intensity of the aerobic machine 2 levels, did slightly less weights/reps.
You have figure out what your limit is and err on the side of caution. But most of all, listen to your body and what it is telling you. Drink extra water.