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Muscles Pull on Bones to Make You Move · How My Body Moves · muscles · bones

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Muscles Pull on Bones to Make You Move

with Medi

Medi stands in a sunny gym, flexing one arm and pointing at a big, friendly drawing of a muscle hugging a bone on the wall behind her.

Identify muscles as the soft parts of your body that make you move.
Explain that muscles pull on bones to bend and straighten your body.
Identify at least two everyday actions that use muscles pulling on bones.
Predict which muscle gets shorter when you bend your arm.

Key terms

muscle: A soft body part that pulls on bones to make you move.
bone: A hard part inside your body that a muscle can pull on.
contract: When a muscle gets shorter and tighter to pull a bone.
tendon: A tough cord that attaches a muscle to a bone.

Muscles Attach to Bones

Your muscles are soft and stretchy, and they wrap around your hard bones. They are tied to bones by tough cords called tendons, a bit like a rope tied to a stick. Because muscles are connected to bones, when a muscle moves it can tug the bone it is attached to and make a part of your body move.

Pulling, Never Pushing

A muscle works by contracting, which means it gets shorter and tighter and bunches up. That squeeze pulls on the bone and moves it. A key fact is that muscles can only pull, never push. So to bend and then straighten a body part, you need muscles on both sides of a joint that take turns pulling.

Muscles Everywhere

You use muscles every single time you move. Muscles bend your arm to hug, push off the ground when you walk, swing your leg to kick a ball, and lift your backpack. Even smiling and blinking use muscles. The more you practice and move, the stronger many of your muscles become over time.

Worked examples

Predict what the front upper-arm muscle does when you bend your elbow.

Bending the elbow lifts your lower arm bone upward.
A muscle must contract, getting shorter, to pull that bone up.
The front upper-arm muscle is the one that contracts to do this.

Answer: The front upper-arm muscle gets shorter and squeezes up to pull the bone.

Decide whether a still rock shows muscles pulling bones.

Muscles pulling bones must cause movement in a living body.
A rock is not alive and has no muscles or bones.
So a still rock does not show muscles pulling on bones.

Answer: No, a still rock does not show muscles pulling on bones.

Hi! I am Medi, and today we are going to learn about muscles and bones! Your bones are the hard parts inside your body. They hold you up, like a frame. Your muscles are the soft, squishy parts that wrap around your bones. Muscles are attached to bones. That means they are connected, like a rope tied to a stick. Here is the cool part: muscles can PULL. When a muscle pulls, it gets shorter and squeezes up. That squeeze tugs the bone, and the bone moves! Muscles can only PULL — they cannot push! Try this: put one hand on the upper part of your other arm, above your elbow. Now bend your arm up slowly. Do you feel something getting tight and bumpy? That is your muscle squeezing and pulling the bone in your lower arm UP! Muscles help you bend your arm, walk, kick a ball, and even pick up your backpack. Every time you move, muscles are doing the pulling!

Activity

Sort each action into the box that shows muscles pulling on bones.

Practice

Name two everyday actions that use muscles pulling on bones.

Why do you need muscles on both sides of a joint to move it back and forth?

Common mistakes to avoid

Muscles push bones to move them.Muscles can only pull by getting shorter; they never push, so opposite muscles take turns.
Muscles stay the same shape while moving.A working muscle gets shorter, tighter, and bumpier as it contracts to pull a bone.

Check your understanding

What do muscles do to bones to make your body move?

You bend your arm to pick up a toy. What happens to the muscle on the front of your upper arm?

Which of these body parts is SOFT and helps you move?

Recap

Muscles are the soft parts that attach to bones with tendons. They work by contracting, getting shorter to pull bones and make you move. Muscles can only pull, so opposite muscles take turns to bend and straighten you.

Reflect

Which muscle do you notice getting tight when you climb stairs, and what is it pulling?