Many thanks for the excellent tips!
As a matter of fact, I had two surgeries last year to cut out a herniated disk = 9 months of no riding and 4 months of not being able to sit in a chair, drive a car or eat in a restaurant. Been doing yoga since then and my back has been much better.
In addition to that, I had a partially-torn ACL and PCL (running is decidedly not as good for the body as cycling) in my left knee the year before that. Since then, I'd been favoring my left leg and it had grown weak.
Thanks again,
-CCinC