Zen...You're right...I didn't use the right term! My BF encouraged me a few months ago to start doing 'core' strengthening exercises because he, too, thinks that's where I'm missing strength. Besides the 'holding myself up' issue, I often have a sore lower back now that I'm riding 20+mi. He attributes the soreness to having built up my quads faster than the other parts that need to be strong to counterbalance the new quad strength. (At least I think I've got that right, LOL!)