Quick question: Is there any benefit to doing forward and backward lunges as opposed to just doing standing (stationary) lunges? I have been doing the Muscle Max workout for a couple of weeks (my first Cathe) and would like to replace the leg exercises of that workout with the standing legs from Gym Style Legs... the only problem is the "moving" lunges. I feel all wobbly and unbalanced and they seem to make my knees hurt more. Can I just sub without losing too much benefit?