- from Muscles
If a Halloween skeleton is hanging from a string and you cut that string, the skeleton falls to the ground in a heap. That’s exactly what would happen to you if you had no muscles to hold you up.
Muscles are the parts of the body that let you stand, walk, run, bend, reach, smile, and even roll your eyes. They get involved when your mouth waters at the thought of your favorite food.
Muscles are what make it possible for you to move your body in so many different ways. And they do it all so simply—just by contracting and relaxing. When they contract, muscles pull on the bones or tissue where they’re attached, and that pulling is what enables you to move. When they relax, your muscles enable you to rest.
Every human body contains more than 600 muscles. Some are small, thin, and delicate, while others are tough and sturdy. Together, your muscles make up from 25 to 45 percent of your weight, and each muscle plays a role in keeping you alive and healthy.