Muscles

Muscles are special parts inside your body. They pull on your bones to make you move. You use muscles when you run, jump, smile, and even blink. People have more than 600 muscles. Muscles work hard every day to keep you going.

How Muscles Work

Muscles work by squeezing and then relaxing. When a muscle squeezes, it gets shorter and pulls a bone. This makes your arm or leg move. Muscles often work in pairs. One pulls while the other rests. Your brain sends fast messages to tell muscles what to do.

Tiny muscle fibers seen up close through a microscope.
Tiny muscle fibers seen up close through a microscope. (Community College Bioscience / Wikimedia Commons)

Types of Muscles

Your body has three kinds of muscles. Skeletal muscles help you run and play. Smooth muscles work inside your tummy to push food along. The heart muscle pumps blood all day and night. You do not have to think about smooth or heart muscles. They work on their own.

Fun Facts

  • The strongest muscle for its size is the one you use to chew.
  • Your tongue is made of many small muscles working together.
  • It takes more muscles to frown than to smile.

Did You Know?

The biggest muscle in your body is in your bottom! It is called the gluteus maximus, and it helps you stand up, walk, and climb stairs.