I've pretty much achieved a ride set-up and fitness levels which have overcome lower back pain problems which I've experienced previously on my regular training rides and smooth surface crit racing, but when I race one particular track, which has quite a lumpy surface, I get serious lower back pain. The circuit is also undulating and has lots of turns as it winds it's way through parkland.
I think the pain is a result of holding myself more rigid to maintain control over the bumps, particularly in the quickest part of the circuit.
Is there a good exercise I can do to strengthen my lower back to help ease this problem? I would appreciate any help I can get.