Not to be confused with an inflated exercise ball, a medicine ball is a weighted ball used in fitness workouts for strength-building and to increase flexibility. Balls are leather or vinyl with nylon cloth and filled with materials to make them heavy. Most have a rubber outer shell, though they do not bounce. Weight ranges from 2 to 25 pounds, and some have handles.
Medicine balls are used when performing exercises like sit-ups and leg raises to increase stress on muscles. They are also commonly used in rehabilitation practices for athletes.