Thanks everyone for your feedback. I may seek a second opinion, not just because of his bike recommendations, but because I hope another doctor might have some different ideas about treatment and prevention.

maggieH, thanks for the ideas about modifying the bike. I'll definitely think about what I can do. I'm going to raise the handlebars up the two spacers I have left and see if that helps some. I'm also considering a set of those short reach brake levers so I can reach the brakes from the top of the bars without having to stretch out so much to ride on the hoods. Maybe an extender to raise the bars would be a good idea too.

My goals are to continue to improve on my long weekend rides, become a better climber, lose some weight, and ride a (fast) century in the fall. Being in the most aero position possible isn't as important to me as being able to comfortably stay on the bike for a long time. But I have to admit, speed is part of what makes riding fun. And getting a new bike right now isn't really an option, because I just bought this one a few months ago, and I love my bike.

I guess I'm most frustrated by his answer of "nothing" when I asked how I could prevent this in the future. This flare up was most likely caused by biking, but many, many flare ups in the past weren't caused by biking, because I've only been riding again for 8 months or so, and seriously riding the road bike for three months. So it's not like the bike is 100% of the problem. There must be other options for decreasing the frequency that my back goes into crazy muscle spasms. My doctor doesn't seem to view this as a very serious problem, because 99% of the time it isn't. He does understand that I want to keep active, but for whatever reason he thinks the road bike posture isn't very back friendly and doesn't understand why a hybrid or a recumbent just isn't the same as my road bike.

I'm going to work on my core strength with "The Core Program" by Peggy Brill and Pilates. One of the guys I ride with has been doing lots of core strength work (at physical therapy for a knee injury) and he says it has made a huge difference in his riding. Irulan, thanks for the reminder that there are many contributing factors in back pain. Honestly stress and anxiety are probably the biggest triggers for me. Since cycling helps with both, I really think it is probably helping more than it is hurting. If my back continues to be a problem, I'll probably seek a second opinion from another doctor, and look into phyisical therapy.

I'm partially just venting, as this is one of those things that isn't catastrophically bad, just really annoying and persistant. I'm 25 and the prospect of this continuing to be a problem for the rest of my life, with no real prevention or permanent treatment, is too much for me to even think about.