I took on a sandwich student for a year and he had sufficiently bad chronic back pain that we had to buy him a special chair. It was being treated by … wait for it … counselling.
He was surprised to find that I cycled to work but, all credit to him, he decided that in an effort to lose some weight he might give it a go. After 3-4 months he said that the cycling must have strengthened some muscle group somehwere, or maybe just altered his posture, but in any case his back pain was essentially cured. Result !