I havn't stretched extensively since I played soccer a lot. I can touch my toes but can't hold it there for more than a few seconds. I rode today again (without stretching, I hadn't read your responses) and I got even worse pain in my back and I had to ride back very slowly. I noticed it worse when I would go over a bump or when I was pedalling in a very hard gear (which I like to do most of the time) The only way I could ease the pain a bit was to sit straight and arch my back backwards, but of course I couldn't go very fast doing that. I'll try stretching my hammys and everything else tomorrow before I go out. On the side of the road today I did touch my toes among other things and it seemed to alleviate it for a few minutes when I got back on, or it could have been that I just rested up. In any case, thanks.