Everyone sits still and finds a pulse. Notice how fast the beat feels. Now everyone jumps or marches in place for a bit. Find your pulse again. Is it faster or slower? Sit and rest together. Check your pulse one more time. Each person checks only their own pulse.
Safety first
Clear a space so nobody trips. Jump on a soft, flat floor. Stop and rest if you feel too tired.
For a grown-up
This is about noticing a pattern, not numbers. Do not compare people. If you have health questions, ask a doctor or nurse.