How does the arm move?
The arm bends at the elbow to make a hinge joint – a bit like the hinge on a door. Two muscles move the arm, the biceps and the triceps. The biceps muscle is at the front of the arm and the triceps is at the back. Tendons attach the biceps to the shoulder blade at the top and the radius (one of the bones in the forearm) at the bottom. When the biceps contracts, it becomes shorter, pulls on the radius and arm moves up.
