When you lift weights, your muscles release special signaling molecules that might help your body build bigger muscles and get stronger overall.

Lifting weights helps people build bigger, stronger muscles, probably because it makes their muscles produce more protein and release helpful signaling molecules that help them grow and work better.

When your muscles get tired and burn during exercise, they release signaling chemicals (like IL-6) that might help repair and grow muscle by activating nearby stem cells — but we’re still figuring out if this really happens in people.

When you do weightlifting with changing resistance (like bands or machines that get harder or easier), your muscles briefly turn on a growth signal called MyoG more than with regular weights—but this doesn’t mean you’ll end up bigger in the long run.