What is a heartbeat?
Every heartbeat is one squeeze of your heart. Squeeze, and blood rushes out. Relax, and the heart fills up again.
Each squeeze sends a wave of blood down your arteries, the tubes that carry blood away from the heart. The artery walls stretch a tiny bit as the wave goes by. That stretch is what you feel as your pulse.
So when you feel your pulse in your wrist, you are feeling your heart at work, even though your heart is in your chest!
How fast does it go?
Heart rate means how many times your heart beats in one minute. When a school-age kid sits still, their heart usually beats about 70 to 100 times a minute. Younger kids' hearts often go a little faster.
A grown-up's resting heart usually beats about 60 to 100 times a minute. A baby's heart is the fastest of all, often over 100 times a minute.
Every body is a little different, so your number might not match a friend's. That is normal.
Faster and slower
When you run, jump or swim, your muscles need extra oxygen. Your heart speeds up to bring it to them.
Your heart also speeds up when you feel scared, nervous or excited, like before a big race or at the top of a slide. That is your body getting ready for action.
When you rest, read or sleep, your heart slows down. Slow, deep breaths can help it calm down too.
The heart's own spark
What tells your heart when to beat? A tiny spot in the top right room of the heart makes a little electric signal, over and over. It is called the SA node, and people call it the heart's natural pacemaker.
The spark spreads across the top rooms, then down to the bottom rooms, like a wave. Wherever it goes, the heart muscle squeezes.
Your brain can tell the spark to go faster or slower, but the spark itself comes from the heart.
Doctors can see these sparks with a test called an ECG. Little stickers go on your chest, and a machine draws your heartbeat as a wiggly line. It does not hurt.
Try it: find your pulse
Turn one hand palm up. Put the first two fingers of your other hand on the inside of your wrist, just below your thumb. Press gently. Don't use your thumb to feel, because your thumb has a pulse of its own that can mix you up.
You can also find a pulse on your neck. Put two fingers gently on one side of your neck, in the soft spot beside your windpipe. Only press on one side.
Feel the little taps? Now count them for 15 seconds while a grown-up watches a clock. Multiply your number by 4. That is your heart rate for one whole minute!
Here is an example: if you count 22 taps in 15 seconds, 22 times 4 is 88 beats a minute.
Try it: jump and count again
Now jump up and down 20 times, or run in place for one minute. Then quickly find your pulse and count again for 15 seconds.
Is the number bigger? Your heart sped up to send more oxygen to your working muscles.
Sit quietly for a few minutes and count one more time. Watch your heart slow back down. Hearts that get lots of exercise often slow down faster after playing.