I actually had the more common effect of getting a lower back pain after a ride or even a spinning class. I was going to the chiropractor a lot because my right hip was hitching up and rotating and causing my SI to get enflamed and spasm'd.

I knew that my left femur was shorter than my right by at least 1/8-1/4 inch. So, a few weeks ago we put shims under my left cleat - a little more than 1/8 inch. And, voila! No more back pain! Seems I was rocking my hips. My right leg was doing most of the work and my left leg was just keeping up. Now my left leg has to work as hard. It improved my power a tad also Cool, huh?