Skeletons can be remarkably flexible but muscles are needed to move them. Various sports competitors and athletes are seen in action using their muscles. Muscles are used every time we move. There are more than 600 muscles in the human body. Muscles are attached to the bone by tendons and work in pairs to allow for smooth movement. To move a joint, one muscle contracts while the other muscle relaxes and becomes longer.
After watching the explanation of the muscles working to raise or lower the forearm, children could make a model of a human arm using card for the bones and string to act as the muscles. If the arm is hinged (using a split pin) at the elbow, the children could experiment in getting the string to control the elevation of the arm - like a muscle. The children could draw diagrams of their favourite sports stars, annotating the muscles used and in which direction a contraction or extension causes movement.