Lesson 4 of 6

How muscles work

Goal: Describe how muscles cause movement.

Puzzles for this lesson

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A boy bending his arm to show the muscle in his upper arm

A muscle moves a bone by pulling on it. A muscle can pull, but it cannot push.

  • To pull, a muscle contracts. It gets shorter and fatter.
  • Tendons join muscles to bones. When the muscle contracts, its tendon pulls on the bone.
  • When a muscle relaxes, it stops pulling. It cannot push the bone back again.
  • Some organs contain muscle too. The muscle in the heart contracts to pump blood.
Children pulling on a rope in a tug of war
A muscle is like a rope. A rope can pull, but it cannot push.

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Key words in this lesson

Tendon Joins a muscle to a bone

Contract When a muscle gets shorter and fatter, and pulls

Relax When a muscle stops pulling

For teachers: AQA 3.8.1 · Cambridge 8Bs.01 in part