I was getting a lot of lower back pain on the second half of my laps on Saturday's BigDog, enough that it spoiled the fun a little. It's happened before when racing but I don't usually get it on general rides. It's a muscle strain type pain, central, just above the base of the spine. It stops when I stop riding.
Is that just a case of DogTFU, or is there likely to be something specific I can change such as seat height, lower gearing etc? Thoughts appreciated, it's a bit of an issue for me with racing.
I ride a couple of times a week, plenty of hills and some SS, not at plod pace, so it's not a "total lack of fitness" issue. My body's used to riding.