Science
How do muscles work?
Muscles work by contracting — shortening to pull on bones and create movement. When a nerve signal arrives, tiny protein filaments inside the muscle slide past each other, pulling the muscle tight, and let go when the signal stops.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a muscle works.
Step by step
- 1A nerve signal tells the muscle to contract.
- 2Inside, protein filaments (actin and myosin) ratchet past each other.
- 3This sliding shortens the muscle, pulling on the bone it's attached to.
- 4Muscles can only pull, not push, so they work in opposing pairs.
- 5Contracting uses energy (ATP) from the food you eat.
Frequently asked questions
- How do muscles create movement?
- They contract, pulling on bones across a joint; because muscles only pull, pairs work in opposition — one bends a joint, the other straightens it.
- Why do muscles get tired?
- Sustained contraction uses up energy stores and builds byproducts faster than the body clears them, reducing force until you rest.
- How do muscles get stronger?
- Exercise causes tiny damage that the body repairs by adding muscle protein, gradually making the fibers thicker and stronger.