I've got 2 slipped discs in my back so certain exercizes are limited to me, so i basically have to do everything on machines. I'm wondering if its better that i do different body parts once a week, Chest/Back on monday, Legs on Wednesday, and shoulders/arms on friday like THIS says. Or should i continue working out my whole body 3 times a week? I've been doing this with 3 sets of 8-10 reps. Which would be more benficial to do? Also how many sets should i be doing?