oldbobcat

The Cobb videos are helpful, but my approach has more to do with balance and a straight spine.

Try this. First, stand straight and tall, shoulders back, head level, neck stretched upward. Feel the relative straightness of the back from the pelvis to the base of the skull. Next bend forward at the hips, maintaining the straightness of the torso. Notice that the hips move back to keep your weight centered over your feet. Try different levels and notice how the lower you go, the farther back the hips go. Also try raising your arms as if grasping a handlebar. Notice that your hip position instinctively responds to this small shift in the center of your upper body gravity. Last, from this bent at the hips position, raise your head enough to focus on a point across the wall. Notice that it doesn't require a whole lot of effort or strain.

Next, for contrast, do the same exercise but with bending throughout the entire length of the back. You might notice that breathing feels a little constricted because your torso is essentially curved around your diaphragm. Raising your head in this position is more stressful because your shoulders are level or or even aimed downward. To raise your head easily you need reduce the bend in the neck by raising the angle of the shoulders.

I arrived at my theory of fit through several influences. First, I swam competitively in high school, the butterfly. With a horizontal torso and shoulders, it isn't difficult at all to raise the head enough to see where you're going and inhale through the mouth and nose. The second was through observing riders who appeared to be most comfortable on the bike. One model was "Smilin'" George Mount, a national team racer of the late 70s. I believe that one reason Mount was always seen with a smile on his face is because he was supremely comfortable on his bike. While his torso angle was low, his shoulders were always aimed slightly upwards and his eyes focused far up the road ahead. His saddle was also far back enough to be balanced over the saddle so he didn't need to support his upper body with his arms.

I maintain that a moderately flat, horizontal back is best on the bike mainly because it reduces direct jolts up the spinal column. Road shock doesn't have a chance get transmitted up your spine if you're almost lying down. But any way you cut it, a straight back better than a hump.

Your mother says straighten your back!

And eagle, it's amazing that we arrived at a similar place intuitively and independently. Common sense and listening to your body really works.