What is a stress ball? How does it work?

A stress ball is a malleable toy no bigger than 7cm in diameter.  Some stress relievers are made from closed-cell polyurethane foam rubber. These are made by injecting the liquid components of the foam into a mold. The resulting chemical reaction creates carbon dioxide bubbles as a byproduct, which in turn creates the foam. When you exercise pressure on a stress ball, the nerves and the muscles stimulate and contract, making them stronger. This, in turn, improves nervous system functioning and reduces essential hormones, which control and curb stress levels.

this is true my friend.