Why Does Your Heart Beat Faster When You Run? A Pulse Experiment for Kids

Run across the playground and you can feel your heart thumping. It’s one of the first things children notice about their own bodies, and a good reason to run a real experiment.

Find your pulse

Press two fingers (not your thumb, which has its own pulse) gently on the inside of your wrist, below the thumb, or on the side of your neck. You’ll feel a regular beat.

The experiment

Question: How does exercise change heart rate, and how long does it take to recover?

You need: a clock with a second hand or timer, a data table, squared paper for a graph and water.

Rest. Sit quietly for two minutes. Count your pulse for 30 seconds and double it for beats per minute. Do this twice and take the typical number.
Exercise. Do star jumps (or jog on the spot) for one minute.
Recover. Immediately sit down and count your pulse for 15 seconds, multiplying by 4. Repeat every minute until your pulse returns near your resting number.
Graph. Time (minutes) on the bottom, beats per minute up the side.

Make a prediction before you start.

What the graph shows

Heart rate jumps up after exercise, then drops quickly at first and more slowly later, until it’s back near your resting rate. Heart rates vary a lot between people, so compare each person’s graph with their own resting number, and don’t turn it into a contest.

Why it speeds up

Your heart is a pump. It sends blood around your body through blood vessels. Blood carries oxygen and nutrients to your cells and takes waste away. When you run, your muscles use oxygen and food much faster. Your breathing speeds up to take in more oxygen, and your heart beats faster to deliver it to the muscles quickly.

When you rest, demand falls, so your heart rate comes back down.

Questions kids ask

Does a faster heart mean a stronger heart? Not necessarily. People who exercise regularly often have a lower resting pulse, because their hearts pump more with each beat.

Why can I feel it in my neck? Large blood vessels near the surface carry the pulse of each heartbeat.

Is it dangerous? A faster heartbeat from play is normal. A child with a heart condition or who feels unwell should skip the exercise part and just measure resting pulse.

Safety and sensitivity

Make exercise optional and gentle, and let students choose another action if they prefer. Avoid pressing hard on the neck. Never tell students a “good” or “bad” number.

The full lesson is Why does your heart beat faster when you run? in How Your Body Works, alongside What happens to your lunch? and How does your arm bend? Sign up for three lessons free.