Self exercising medical application for Coma patients

I had a strange idea. Given that electronic pulses when issued to the muscles cause them to twitch... and the fact nurses have to periodically move coma patients to prevent sores. What is the feasibility of hooking coma patients up into a self exercise machine, such that their body automatically perform some work out routines even when their brains are inactive? They might potentially become physically stronger than they were before they entered coma, if they do leave coma. If not, at least have less problems with their joints due to extensive periods of inactivity.