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Muscles: Facts


Wiggle your toes. Now smile. Wave your hand. Pat your stomach while rubbing your head. Were you able to do these things? Thank your muscles. We have over 600 muscles in our bodies. Many of our muscles allow us to move. And they couldn't help us move without the assistance of our skeletal system. But not all of our muscles are responsible for movement. Some of our muscles have other jobs. Let's take a look at the types of muscles we have.

Types of Muscles

Our bodies have three kinds of muscles. The smooth muscles, the cardiac muscles and the voluntary muscles.

Smooth muscle tissue
Each of these three muscle types have a specific job to do and each of them look entirely different under microscopes.

The smooth muscles are the ones that are responsible for parts of the body like the digestive system, the blood vessels, and the kidneys. You have no conscious control of the smooth muscles or the jobs that they do. Our nervous system controls the smooth muscles.

Cardiac muscle

We don't control the cardiac muscles either. These are the muscles of the heart. They keep our hearts beating every single day of our lives. They squeeze blood through our bodies continuously in a rhythm called our heartbeat.

Arm muscles

The voluntary muscles are attached to our bones and allow us to run, hop, swim, kick, dance, write and smile. And that's just the beginning. We have control over most of these muscles. That's why they are called voluntary. These are often referred to as the skeletal muscles and they attach to the bones of the skeleton at each end of the muscle by tendons.

The voluntary muscles work very closely with the skeletal system. Together they make up the musculoskeletal system. Many scientists and doctors do not separate the two into distinctly different systems, but think of them as one.

How Muscles Work

Muscles have two basic movements. They can tighten up (contract) or they can relax. So they always work in pairs. When you move your arm up to your mouth to get a drink of water, some muscles contract to move your hand closer to your face. Others are relaxing. When you are ready to put the glass back on the table, a different set of muscles contract so that your arm moves away from your face. The first set then needs to relax so that the contracting muscles can do their job. It sort of works like two people holding a rope. Imagine one person pulling on the rope to get the rope closer to themselves. The other person needs to relax in order for the rope to move. Then when the rope is moved toward the second person, the first person must relax.

Tug o'war

Muscles Have Names

The voluntary muscles of your body have a huge job.

Ear anatomy
They must be available all of the time to get you moving at the smallest of a need. Like when that mosquito lands on your arm and you slap it. Or you jump up to answer the phone. Many times we don't plan in advance to do the moving we do. But our muscles are ready anyway.

Some of the muscles in our body can be very long — like the sartorius muscle which runs from the hip all the way down to the knee. Or very short — like the stapedius muscle which is in the middle ear and contributes to our ability to hear.


Our muscles are grouped by names for the jobs that they need to perform. The deltoids are located in the shoulders. They allow you to throw a ball or swim or do pull ups on the monkey bars. They move your arms back and forth and around.


Your pecs or pectorals are the large muscles in your chest. These help you lift things. Many body builders work out these muscles so that they become very large. Boys tend to get larger pecs than girls.

In your abdomen area are the abs, as they are often called. These are the ones that you tighten when you do sit-ups.


Your arms and legs have some very strong muscles. The bicep are the ones you flex when you do that "muscle showing thing" with your arm. Your quadriceps are the thick muscle on the front part of your thigh. When you run that muscle gets to going.

And let's not forget the gluteus maximus. That is the big muscle that you sit on. And so much fun to say!!

Seated elephant

Muscles Have Needs

Bowl of fruit

Good, healthy muscles help us to move, help our heart to beat and our other organs to function properly. So how do we make sure that the muscles are healthy?

First of all, your muscles need good healthy food choices. The food you eat feeds your muscles. You might not think of it that way, but truly that is why we eat. Not just to taste good or to fill your stomach. So eat a balanced diet of fruits and vegetables with some good protein choices. To learn more about healthy eating, visit the Science Trek Nutrition site.

Muscles are always in need of water. Let's face it, our bodies are mostly water. So be sure to drink lots of water during the day. More if you are doing lots of physical exercise or it is hot.

Girl jumping rope

You also need to keep those muscles in good shape by exercising them regularly. Run, play games, play in a sport, walk, climb, throw a ball, jump, swim, and make sure to move those muscles often. This includes your heart muscle which also needs exercise. When you do activity that makes your heart beat faster, you are giving it the needed workout too.

Muscles use a lot of energy and oxygen. That is why we feel tired after a huge work out. We also breathe heavily to replace the necessary oxygen that the muscles use. Run a lap or two around the school ground. You will be breathing faster and be more tired than you were when you started.

When you work out, you need to make sure to do it correctly. Do a warm up and a cool down when you take on a physical activity. This allows your muscles to break into it gently and to relax gently. This prevents injury to muscles. Don't keep working a muscle if you have pain. Pain can be part of exercise, but it might be due to injury. So be cautious and seek help from an adult if you need to.

Woman and man wearing bicycle helmets

Be extra cautious when lifting. A person can do serious injury to themselves when lifting heavy objects such as furniture or boxes. Always use the knees to get that object off the floor, not the back!! For more information about lifting, check out this slide show from the Mayo Clinic.

Wear protective gear! Be sure to put on a helmet before riding a bike or playing a sport where a helmet is part of the game gear. Don't forget the knee and shin pads. Always make sure to cover the parts of your body that might take the most physical abuse from your sport or activity. This helps to keep the bones and muscles safe and lets you play again.

Muscle Injury

Injuries can sometimes happen when we play hard. But knowing how and why can be helpful.

Cartoon figure of football player on crutches

During exercise, our muscles can be susceptible to tiny tears. These tears heal up in a very short time, but they can make us feel some pain in the meantime. A little ice on the painful spot and staying off of it for a while will usually do the trick.

But sometimes, a more severe form of this injury, known as a sprain can occur. Most of us have sprained an ankle at one time or another. This likely happened by twisting the ankle or can even happen to a knee or a wrist. A trip to the doctor might be in order just to make sure that no bones are broken.

The doctor will probably take an x-ray to see into the painful spot. They can see what damage has occurred and know what form of treatment must take place. An x-ray is not painful, but you might have to move your painful body part for the x-ray technician and that might hurt some.

X-ray of two hands

Muscles Fun Facts

Rapid muscle contractions
  • There are 40 plus muscles in the face
  • Not everyone has the same number of muscles
  • There is some confusion about how many muscles are needed to smile and frown
  • The biggest muscle is the gluteus maximus
  • The hardest working muscle is the heart
  • The masseter muscle in the jaw can have a force as great as 200 pounds when a person bites down
  • Goose bumps happen when tiny muscles at the bottom of the hair follicle contract
  • Rapid muscle contractions when the body gets cold is called shivering
  • The tongue is a muscle and has its own "fingerprint" or "tongueprint"

Muscles Quiz

Now that you know everything there is to know about muscles, take this quiz and see if you can answer all of the questions. The quiz is online and part of the National Institute of Arthritis and Musculoskeletal and Skin Diseases — find the red box and click on it.

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