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Bend and Stretch: How Our Muscles Move Our Bones
by My Book Hub Team
At the school science fair, Dr. Flex shows how muscles pull on bones to make us bend, stretch and move.
What your child will learn
Explains how muscles help bones move.
Genre: educational
For ages 6-9
A peek inside
Welcome to the school science fair! Dr. Flex waves and smiles. She wears a white lab coat and big round glasses. Today she will show how our muscles help our bones move. Come closer and watch her special project. It is all about bend and stretch.
Dr. Flex points to a tall skeleton model. Bones make a strong frame inside your body. They hold you up and give your body its shape. Without bones, you would be soft like jelly. Your skeleton has many bones that join together. They protect soft parts inside you too.
Next, Dr. Flex holds up bright red muscle shapes. Muscles cover your bones like soft, stretchy layers. They attach to your bones in many places. When a muscle works, it can pull on a bone. That pull is what starts a movement. Muscles and bones are a team.
Dr. Flex tugs a string on her model arm. Muscles can only pull. They cannot push bones by themselves. When a muscle gets shorter, we say it contracts. Contracting makes the muscle pull hard on the bone. Then the bone moves at a joint. Watch carefully as the model arm bends.
Muscles work in pairs to move your bones. One muscle contracts while its partner relaxes. The contracting muscle pulls the bone one way. Later the other muscle contracts to pull it back. Working together, the pair lets you bend and stretch. Dr. Flex shows two rubber bands as a pair.
Feel your upper arm and bend your elbow. The muscle on the front is called the biceps. When the biceps contracts, it shortens and bulges. It pulls your lower arm bones upward. Your elbow joint lets the bones swing smoothly. Dr. Flex flexes her arm and grins.
Now straighten your arm again slowly. The muscle on the back is the triceps. The triceps contracts and pulls the lower arm bones down. At the same time, the biceps relaxes and lengthens. That is how the pair works. Dr. Flex straightens her arm for the class.
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