Why does heart rate slow down?

Your heart slows down when it doesn’t need to work as hard.

Imagine your heart is like a toy car that keeps moving forward, you push it, and it goes faster. When you're running, playing tag, or climbing the stairs, your body needs more energy, so your heart pushes harder and beats faster. But when you sit down to read a book or take a nap, your body doesn’t need as much energy. That means your heart can relax and take it easy, just like your toy car would if you stop pushing it.

Your brain sends messages to your heart, telling it when to speed up or slow down. These messages are like notes in a game: “Go faster!” or “Take a break!”

When you're calm and relaxed, your brain says, “You’ve had enough, slow down.” So the heart listens and beats more slowly, just like a clock that ticks slower when it’s not rushing.

Sometimes, your lungs also help out. If you’re breathing deeply or taking shallow breaths, your body knows how much energy it needs, and tells the heart what to do next!