The Powerball is both a toy and an exercise tool. Spinning a powerball lets you relieve muscle and tendon tension and exercise your wrist after a hard day’s work at your computer. Additionally, it relaxes and strengthens shoulders, fingers, and arms. The Powerball is a recommended rehab tool for people who play a woodwind or string instrument, keyboardists, tennis and golf players, cyclists, and rock climbers. It is also suitable for virtually everybody else.