Form tip

When I get tired on the bike, I tend to hunch up and round my back which leads to soreness stiffness and general crumminess. Just read this from a link in RoadBikeRider's newsletter:

Quick Tip: Back Talk. A flat back is the picture-perfect road cycling posture, but physiology seems to be as important as riding position. Witness Lance Armstrong, whose position on the bike was the result of many hours of wind tunnel testing and yet his back was more humped than flat. Obviously, it didn't slow him down. So if your back looks more like Lance's than an ironing board, don't sweat it as long as you know your overall position is correct. A stretching program may help you sit longer and lower without strain, as will this tip: Imagine touching your belly button to the top tube. This rotates your hips forward and takes some roundness out of your back.

Also strengthen your core. That'll help you avoid that kind of fatigue for a longer time.

Actually, I don't like rotating my hips forward (which I naturally do) because it puts too much pressure on my delicate girl soft tissue. I focus on keeping my pelvis upright and well supported on the sit bones, and bending at the waist. Core class helped make that more possible. :p No, I am not perfect in this posture, but the closer I am to that position, the faster and more comfortable I am. It doesn't seem like a flat back to me, but it seems to work....

H&B
~T~

Lance actually had something wrong with his back. I think that is why his riding form is a bit off.

I sorta tried it out on my ride early this morning. I don't think you have to do it to any extreme. Just pop your belly button out a bit and it straightens your back and, importantly for me, pulls your shoulders down and back.

The Queen of Slouchiness

This is how I attempt to ride when I'm consciously thinking about it. I was taught this when we had the tandem fitted to us and dh and I were just discussing it recently.