What does my body do when I run out into the snow?

Picture yourself pulling on your boots and running out into fresh white snow. Crunch, crunch go your steps, and the cold air nips at your nose and fingers. Can you feel that tingly, chilly tickle on your cheeks?

Out there, you stop to catch snowflakes and look all around, and it seems like nothing special is happening inside you. Yet your body is busy the whole time. So what does your body do when you run out into the snow?

Deep inside, you are warm, as warm as a cosy bath. Your heart, your lungs and your tummy sit in your core, which means the warm middle part of your body. Your core needs to stay warm so all those parts can keep doing their jobs.

When the cold air touches your skin, your skin sends a quick message to your brain. The message says that it is cold out here. Right away, your brain starts working to keep your core warm.

Your warm blood travels all around you inside blood vessels, which are tiny tubes that carry your blood. Many of these tubes run just under your skin, close to the snowy air. When warm blood flows there, the cold air takes away its heat.

So your brain tells the blood vessels in your skin to squeeze narrower. Less warm blood flows near the cold, and more of it stays deep in your core. That is why your fingers and toes feel chilly first, while your middle stays warm.

Narrow blood vessels help keep heat in, but they cannot make any new heat. Little by little, your body still loses warmth to the frosty air. What do you think your body could do to make more heat?

Your brain tells your muscles to shiver. They tighten and loosen fast, again and again, and all that tiny busy work makes heat. Your teeth chatter and your shoulders shake, and your blood carries the new warmth into your core.

When you run out into the snow, your skin tells your brain about the cold, and your brain works to keep your core warm. It squeezes your blood vessels narrower to hold warm blood deep inside, and it makes your muscles shiver to make new heat.

Out in the white snow, your boots crunch and your fingers tingle with cold. Yet deep in your middle, your core stays as warm as a cosy bath.