I pulled a muscle in my back yesterday and can barely walk, for some reason it doesn't bother me on the bike. I rode in today against a fairly strong headwind, I had to stop about half way in to take off my jacket, felt like a summer morning ride to work. The ride turned out great, I took the back way in down by a winding river that has a bit of wildlife to entertain me. The back made it, I'm in no worst shape than I was when i left the house.