I take yoga once a week and walk several times in the neighborhood each week. Three loops around our neighborhood is a mile but I have to admit that I am lazy in winter and only do one or two each day. If you are having back trouble, "legs up the wall" and "cows and cats" are two good yoga poses that may help you. My knees are quite creaky these days, so I am trying to lose a little weight in hopes of helping them. I'm going to try walking backwards in the house before I go outside to do it!