Hence you had back surgery!!! I felt more pain after I walked from one store to another and back to the first one. The distance between two stores was about 50 meters. I am afraid to have the surgery because there is likelihood of paralyze. Mine is a combination of aging and others. You look very fit in your photos. Walking about one km when I was young (from toddler to 30s) could cause my body more pains (back, hips, knees, ankles, feet).