Some people call the large exercise balls described above , but the real medicine balls are the smaller heavy ones that aren't meant to roll. Typically 8 - 15 pounds, medicine balls are used for throwing, catching, and other moves where the momentum of the heavy ball adds to the challenge. Medicine balls have been around a very long time. Wikipedia, an unreliable but adequate source for this kind of anecdote, says that there are references to people training with sand-filled bladders 3,000 years ago.
Mini balls are similar to large exercise balls in that they add leverage and instability challenges to exercises. However, at 9 to 12 inches around, the mini ball is not usually a whole body balance challenge. They are very good for other kinds of stability work. For example, one hand on a mini ball during a push up calls on even more . Or, a seated side bend like with one hand rolling out on the ball is quite different than being supported by the floor.
Makes moving “hard-to-handle” big balls easy. Stores and safely transports large exercise balls (16” dia. and larger) plus fitness accessories such as jump ropes, stretch bands and resistance loops. Generous spacing allows easy access to all of the equipment on the cart.