When most people think “muscle,” they think of the big visible ones in their arms and legs. Those are skeletal muscles, and they’re just one of three completely different muscle types in your body.
Skeletal muscles are the ones you control consciously. They’re attached to your bones, and they move when you decide to move them - picking things up, walking, smiling. They make up most of the visible “shape” of your body. They’re also the only muscle type you can deliberately strengthen by exercising.
Smooth muscle lines your internal organs - your stomach, intestines, blood vessels, even your eyeballs. It works without you thinking about it. When your gut digests a meal or your blood vessels widen, that’s smooth muscle. It moves more slowly than skeletal muscle but doesn’t get tired the same way.
Cardiac muscle is the rarest type. It only exists in your heart. It’s similar to skeletal muscle in structure but works involuntarily like smooth muscle - and it has been contracting roughly once a second since before you were born. Over a lifetime, your heart beats about 2.5 billion times without ever taking a break.
