A stress ball is a small ball designed to help relieve stress by exercising the muscles in the hand. Actually, a stress ball does not necessarily have to be shaped like a ball, and a wide variety of shapes can be found on the market. The main defining characteristic is that it can fit easily in a hand, and it is malleable, allowing a user to squeeze it out of shape while providing some resistance to force the muscles of the hand to work.

Stress balls are supposed to be very useful for mental stress relief, by giving people a tool with which to work out physical aggression and stress. Squeezing a stress ball while imagining a reduction in stress is a frequently-recommended stress management tool for people in demanding jobs, and stress balls are often given away at conferences and other corporate events as promotional tools, reflecting their widespread use.

In addition to being useful for emotional strain, a stress ball can be useful for physical strain. Physical therapists use a very similar tool to help people flex and stretch the muscles in their hands. Squeezing a stress ball can reduce the amount of strain associated with repetitive tasks like typing, and it can also help to develop hand strength. For people who have experienced strokes and other neurological problems, stress balls can also be used as part of a physical therapy plan to help the patient recover his or her hand and finger mobility.

A variety of things can be used to fill a stress ball. The idea is that the filling should be firm, with a slight give to it, forcing people to work to deform the stress ball. Foam is a common choice, as is gel, or a powder enclosed in a latex packet. You can even make your own basic stress ball by filling a balloon with corn starch. Beans and plastic granules may also be used, although these fillings are less smooth.

Using a stress ball doesn't require any particular instructions or skills: all you need to do is pick the ball up and squeeze it. Repeated use of a stress ball can, of course, cause the same problems that other repetitive motions are associated with, but taking breaks from typing and other repetitive tasks to squeeze a stress ball a few times can be beneficial. For people who are stressed or who have problems with anger management, a stress ball can be a great focusing tool: for example, you can say that you will squeeze your stress ball 10 times before responding to a situation, to make sure that you do not act in haste.