I slept for three years on a slab of concrete with a folded wool fire blanket as a mattress. On top of it I had sheets and a top blanket and a regular pillow. My roommates thought I was crazy, but after a few days of adjusting to it, I found it to be the most comfortable sleep I had experienced up until that time. All back pain disappeared. That was thirty years ago. I sleep on a regular American bed now, but any time I’ve had any issue with back pain or core muscle strain, I think back on that concrete slab with fond memories.