My muscles
How muscles pull on bones to move you, why they work in pairs, and the muscles that work all by themselves. With a feel-your-muscles experiment.
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Muscles help you move. They let you run, jump, wave, and even smile and talk![1]
Many muscles are joined to your bones by strong cords called tendons. When a muscle gets shorter, it pulls on the bone and the bone moves.[1][5]
A muscle can pull, but it cannot push. So muscles work in pairs: one pulls to bend your arm, the other pulls to make it straight again.[1][6]
In your arm, the biceps at the front bends your elbow. The triceps at the back straightens it.[1]
Some muscles work all by themselves, without you thinking. Your heart is a muscle, and muscles in your tummy help move your food along.[1]
Running, jumping and playing help keep your muscles and your body fit and healthy.[1]
Try it: Feel your muscles pull
You need
- Your own arms
- A table to put your hand under
- Two strips of card and a split pin (for the teacher's model arm)
- A piece of string
Safety
Move slowly and gently, and only press on your own arm. Press up under the table only softly. Pupils with a hurt arm can watch the model arm and do the feeling part with the other arm, or be the helper.
What to do
- Put your left hand on the front of your right upper arm. Slowly bend your right arm. What does the muscle under your hand do?
- Now put your hand on the back of your upper arm. Straighten your arm slowly. What do you feel now?
- Put your hand flat under the table top and gently press upwards. Feel the front of your arm again.
- Watch the teacher's model arm: card strips are the bones, the split pin is the elbow and the string is the muscle. Pull the string. Does the arm bend?
- Can you make the model arm straight again by pushing the string? Why not?
What happens, and why?
When you bend your arm, the biceps at the front gets shorter and fatter, and you can feel it get hard. It pulls on the bone to bend the elbow. To straighten the arm, the triceps at the back pulls instead. A string, like a muscle, can only pull, not push, so you need a second muscle to pull the other way.[1][6]
Play: I choose, or all by itself?
Read each card. Do you choose to make these muscles work, or do they work all by themselves?
Your best score is kept only on this device. Nothing is sent anywhere.
Quiz
Other ages: Ages 10–11 · Ages 15–16