After doing a hilly century over Memorial Day followed a week later by a flat metric, I had a couple bad weeks of pain and numbness in the left side of my butt and upper thigh. I would describe the pain as burning followed by numbness. It hurt to sit for long stretches of time, and it would get particularly bad about 10-15 miles into most, though not all, rides. I assumed that my sciatic nerve was involved in some way, which of course worried me. Before I had a chance to go to the doctor, I found relief by stretching my piriformis muscle. I concentrated on it during my regular yoga classes and did a lot of stretching before, during and after rides. The worst of the pain is now gone. I would note, ironically, that I have a Terry Butterfly Tri Gel saddle. I've been riding it w/o incident for about a year now, so I think my pain was caused by doing a ride that was hard on my back followed by a ride where I sat in a static position on my bike for long stretches of time. I need to remember to move around a bit more during long, flat rides.
I found the following site to be helpful for understanding what can cause sciatic nerve issues and for a list of stretches/exercises: http://www.spine-health.com.
Kate
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher