How do muscles grow?
For grown-ups: the science
Muscles get signals when you move, then use materials from food to slowly grow thicker.
Muscles grow when exercise, including the force of movement, signals the body to make more muscle protein. Enough energy, protein, rest, and sleep support recovery and growth. For preschoolers, varied active play is better than hard strength training meant to build big muscles.
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Transcript
When you jump rope at the park, how do your muscles slowly get bigger?
When you move your body, your muscles squeeze to make strength. Using them a lot sends muscles a signal to grow stronger.
Inside muscles, a body building material called protein is used. When the signal comes, more material makes the muscles a little thicker.
Food gives your body materials, and your body works while you sleep. With exercise, food, and sleep, muscles grow slowly over time.
Muscles grow little by little with movement signals and materials from your body.