A medicine ball (also known as an exercise ball, a med ball, or a fitness ball) is a weighted ball roughly the diameter of the shoulders (approx. 13.7 inches), often used for rehabilitation and strength training. The medicine ball also serves an important role in the field of sports medicine. However, it should not be confused with the larger, inflated exercise ball.
Medicine balls are usually sold as 2–25 lb (1–11 kg) balls and are used effectively in plyometric weight training to increase explosive power in athletes in all sports. Some medicine balls are up to 14″ wide and up to 14 lbs weight, or in the form of weighted basketballs. Modern exercise balls are larger, up to 36″ diameter.
A med ball is used for children training as the best way to overcome fear of free weights exercises.