Road Cycling - back pain...but only on hills?

I recently came back from vacation at the beach, where I rode my bike nearly every day. I was vactioning in delaware, and it is incredibly flat there. I was averaging 20 mph on most of my rides, and my distances picked up. (how's 50 miles at 19 mph sound?)

AFter coming back, though, I noticed that around my area, a 30 mile ride would bring back pain (fatigue) that I hadn't seen for months. Is there some back muscle used when climbing? whats the deal?

I have the same problem, it occurs mostly on hills when I a pushing hard. It's like a deep ache in my lower back. I try to stretch out before riding but it doesn't seem to matter. If I spin in a lower gear and just keep a high cadence it seems to help. but the harder I push the worse it gets. Does anyone else have this problem, or any solutions.

Phatman, how strong are your abdominal muscles? They help support your back. Do you arch your back as you are going up the hills? This would indicate your abdominal muscles may be weak causing mechanical low back pain. Pilates is by far the most effective form of abdominal exercise that I have seen.

I heard somewhere that tight hamstrings can cause lower back pain. I had this often when I was running, so I decided to really concentrate on my hamstrings. Lo and behold my back pain ceased. This may or may not help, but a lot of info is better than none.

I agree. Tight hamstrings and psoas muscles may contribute to the problem. They are often tighter in those with weak abdominals.