I'm 40 and set a fence post by myself yesterday. This involved digging a 20" deep hole and mixing and pouring two bags of concrete with the water source being thirty feet away from where i was working at. Also delivered 400 notebooks and six cartons of paper along with a bunch of other shyt across a large campus and my back feels perfectly fine. Just gotta keep it limber, strong, and always use proper lifting techniques (lift with your legs, never twist) and it should last for years to come.