I walk a lot to and from work (choose further stations if neccessary) and I carry a backpack that has a laptop and one or two heavy books so that my body muscle

I walk a lot to and from work (choose further stations if neccessary) and I carry a backpack that has a laptop and one or two heavy books so that my body muscles have some balancing work to do. It works. I only had back pain once when I rented a furnished apartment with soft comfy furniture. Once I realized that the furniture was bad, I added some pillows to give lumbar support, and spent a few days standing to watch TV. Of course I sleep on a thin futon and mostly sit on wooden chairs or directors chairs. But I do think the walking is essential to building up muscle strength to begin with. Unless you want to lift free weights...