What is shivering? Why our bodies shake when it's cold.

Why our bodies shake when it's cold. Involuntary muscle contractions keep us warm and even fight infections. "Shivering is a way for our bodies to generate heat when we are cold," says Dr. Natasha Bhuyan, a family physician based in Phoenix, Arizona. Breakthroughs, discoveries, and DIY tips sent every weekday. You're walking down a Chicago street on a blustery winter day, when a particularly strong wind almost whips you off of your feet.