寒いと体が震える理由は？筋肉が熱を作るしくみ

Why Do We Shiver When We Are Cold?

On a cold morning, your body may suddenly start to shake.

This is called shivering.

Why does it happen?

Our bodies like to stay warm, at about 37°C.

But they lose heat to the outside air all the time.

When it gets cold, sensors in your body notice it, and your brain tells your muscles to start shivering.

Then your muscles tighten again and again, very quickly.

These movements do not move your body much.

But moving muscles make heat, and this heat warms you up.

Most of the time, you cannot control when you shiver.

Your brain decides for you.

You may get goosebumps at the same time.

Tiny muscles around your hairs tighten, and this helps to trap warm air and slow down heat loss.

Humans are not the only ones that shiver.

All mammals can shiver, so your cat or dog may shiver when it is cold. Even birds shiver.

You may also shiver when you have a fever, even in a warm room.

During a fever, your brain raises your body's target temperature, so you feel cold until your body reaches it.

Newborn babies cannot shiver to keep warm.

Instead, they use a special kind of fat, called brown fat, to make heat.

Shivering helps you warm up, but the best way to stay warm is to wear the right clothes. So next time you start to shiver, put on a coat!