Originally Posted by
cooleric1234
When my lower back hurt on my bike it was because I was too stretched out, once I got a shorter stem my back pain instantly went away.
I'm the opposite. I found slightly less back pain when I stretch out and flatten my back. I had my stem lowered to get a more flatten position. When I scrunch I hurt more. Also think pushing higher gears adds to more back pain. I think it's the side muscles, not sure the technical name, that hurt and get stiff.