Also, as you ride, every so often sit up straight, and put your left arm behind your back in an "L" shape so that the part of your arm from your elbow to your hand basically rests along your waist in the back. You might slowly tip your head from side to side too, and make sure to drop your shoulder as you do this.

Doing that takes away the numbness in your hands, and also gives your body a bit of a stretch. It even feels good if you're just sitting at the computer for any length of time too.