Originally posted by: esun
Too easy. I figured this little trick out a long time ago:
Try putting your thumb across your palm (but not touching your palm), then bending the first joint on the thumb. Now, point your palm downward and try bending your wrist down. You'll notice you can't bend past a certain point. If you start your wrist in that position bent down, then try moving your thumb across your palm and bending the first joint, you'll also notice you can't do it. It's an interesting limitation of the hand/wrist, but I'm not sure how it works.