Whenever I ride over a couple of hours the back of my neck and the upper part of my back hurts. It comes, of course, from holding my head up so I can see where i'm going as I ride.

Does anyone know of any exercises, or stretches, I can do to help with this?

Right now I'm stuck with just trying to ignore it.

I'm sure I could solve it by getting a bike with a more upright posture, but I'd rather do it with exercises, if possible.