When you first start lifting weights, your body makes more of the tiny machines that build muscle proteins, which helps your muscles grow. But after a while, your body shifts focus and gets better at using those machines more efficiently instead of making more of them.

When you lift weights, your muscles make more of the tiny molecular machines that build proteins, which helps them grow bigger.

When you lift weights, your muscles grow bigger because your cells first make more protein-making machines (ribosomes) — and the more of these machines you build, the more your muscles grow.

When people lift weights and their muscles get bigger, their cells make more of the tiny machines (ribosomes) that build muscle proteins — and the people who gain the most muscle tend to make the most of these machines.

When you lift weights, your muscles grow bigger because your body makes more tiny protein-making machines inside muscle cells, which helps build more of the proteins that make muscles strong and bulky.

Lifting weights makes your muscles bigger and stronger, and this happens because your muscle cells start making more of the tiny machines that build proteins.