Make a Model Hand
What you'll need:
The muscles in your body are there to shorten or contract, a simple but very important task. Every movement you make is driven by the muscular system, from a simple smile to lifting a heavy box.
The muscles inside your forearm have long tendons running through ligament fibers, known as the carpal tunnel, in the wrist. These muscles allow you to flex your fingers, bending the tips towards your palm, as your fingers do when giving the thumbs up. This is what happens when you pull on the strings of your model hand.