---
title: "How Muscles Move Bones"
description: "Describe how muscles pull on bones at joints, how the biceps and triceps help bend and straighten the elbow, and how chosen movements differ from automatic muscle activity in the heart and digestive s"
canonical: https://lightmysky.com/learn/science/how-muscles-move-bones-mt_6N-4TqCleR
source: https://lightmysky.com/learn/science/how-muscles-move-bones-mt_6N-4TqCleR.md
retrieved: 2026-11-12
---

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# How Muscles Move Bones

Describe how muscles pull on bones at joints, how the biceps and triceps help bend and straighten the elbow, and how chosen movements differ from automatic muscle activity in the heart and digestive system.

Subject: Science · Area: The Human Body · Ages 7 to 9
Page: https://lightmysky.com/learn/science/how-muscles-move-bones-mt_6N-4TqCleR

## Ready when they can

- Describe how the biceps and triceps help bend and straighten the elbow, and explain that muscles can also pull while holding a joint still
- Explain voluntary control and involuntary muscle activity, including that skeletal muscles can also act without a conscious choice
- Name the heart and muscles of the digestive system as examples of involuntary muscles

## Lesson: How Muscles Move Bones

Bones meet at joints. Many muscles attach to bones through tough bands called tendons. Muscles move bones by pulling, not pushing. When a muscle contracts, it tightens and pulls. It often gets shorter, but it can also pull while staying the same length. That is how a muscle can work while you hold something still.

*(drawing: For a movement, follow the pull through these word boxes. They are not a drawing of an arm.)*

**Example.** The biceps is at the front of your upper arm. The triceps is at the back. To actively bend your elbow, the biceps pulls more and the triceps relaxes more. To straighten it, the triceps pulls more and the biceps relaxes more. Both can pull together to steady the joint. Different joints allow different moves, such as bending, turning or swinging.

You can choose to move skeletal muscles in your arms and legs. We call this voluntary control. These muscles can also act without a choice, such as when you shiver. Smooth muscle in your stomach and intestines squeezes and moves food. Cardiac muscle in your heart pumps blood. Smooth and cardiac muscles are involuntary: they work without you deciding, even while you sleep.

**Recap.** Muscles pull to move bones at joints or hold them still. You can choose many movements, while heart and digestive muscles work without that choice.

*Original lesson, questions and flashcards written for this learning dataset.*

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Bones & Muscles](https://lightmysky.com/learn/science/bones-and-muscles-mt_SdIWVjzopp)

## Optional connections

- [Naming Major Bones](https://lightmysky.com/learn/science/naming-major-bones-mt_OMmiuv9ZLH)

## Opens up

- [Bone, Cartilage and the Mechanics of a Joint](https://lightmysky.com/learn/science/bone-cartilage-and-the-mechanics-of-a-joint-mt_1_q3aL7E5D)