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Muscles help you move. They let you run, jump, wave, and even smile and talk!

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.

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.

In your arm, the biceps at the front bends your elbow. The triceps at the back straightens it.

Experiment: Feel your muscles pull

1. 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?
2. Now put your hand on the back of your upper arm. Straighten your arm slowly. What do you feel now?
3. Put your hand flat under the table top and gently press upwards. Feel the front of your arm again.
4. 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?
5. Can you make the model arm straight again by pushing the string? Why not?

	Front muscle (biceps)	Back muscle (triceps)
Bending my arm	Guess: which muscle gets hard when you bend your arm?
Straightening my arm	Guess: which muscle gets hard when you bend your arm?

Questions

1. Draw your arm. Draw the biceps at the front and the triceps at the back.

   🍎

2. When I bend my arm, the muscle that gets hard is the…

   biceps / triceps

3. Can a muscle push?

   yes / no

4. Name one muscle that works all by itself.

Sources for every fact on this sheet: echoesof.science/school/muscles/sources/

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