well, i was one of those when i had this surgery, could barely walk...i did what i could and that is/was good enough for me.....i say as long as one is moving in oxygen, at their fitness level, then its all good.
that is just how i see it...
i exercise at my fitness level and do not care how many calories i am burning as i know me moving/exercising is making a helluva difference...i am however, 100% aware to not take in more calories than i can burn off...
so far, so good.