Useless Fact

Ever wonder why we shiver? Because we're cold- d'uh. But what is the purpose of shivering?
I assume you're heard that if you're in very low temperatures, you need to move around to increase circulation. Shivering is the body's autonomic method of doing the same thing. It gets very cold and the body forces muscle groups to contact and relax very rapidly- more so than can be done consciously. These sudden bursts of muscle activity generate heat which causes your blood vessels to open. This is why you primarily shiver in your vital areas- head, torso, & abdomen.

Of course, this is only for shivering due to temperature. If you're shivering due to fear- well, you're just a pussy.