I was a runner at that time and had to lighten up on my workouts. By the end of the Water Fast I was only doing light workouts, 30 minutes of walking a few times a week. My suggestion is just to listen to your body. Bodies respond very differently to Water Fasts and it is best not to overdo it. Some days I felt full of energy and ready to run a 5K, other days it took all my energy to get around the house. I found it best to just workout according to my energy level. Hope that answered the question. Happy fasting :-)
-catyrpel