Medicine ball training is one of the oldest forms of strength and conditioning training – the first reference to wrestlers training with sand filled bladders appears in Persia nearly 3000 years ago. In ancient Greece the physician Hippocrates had them sewn out of animal skins and stuffed with sand. His patients threw them back and forth for injury prevention and rehabilitation.
In the late nineteenth century and early twentieth century, the words "health" and "medicine" were synonymous. The so-called "Four Horsemen of Fitness" were the dumbbell, the Indian club, the wand and the medicine ball. This is where the beginnings of the modern medicine ball originate.
Inner core and outer rubber shell of air filled medicine ballMedicine balls are generally constructed of a leather or vinyl covered nylon cloth, and filled with impact absorbing materials to give them weight. Vinyl covered medicine balls typically are sand filled and are not used for exercises requiring bouncing. Sand or steel shot filled neoprene bags are also used for medicine ball exercises not requiring bouncing.
Some medicine balls have an inner half sphere of dense material in varying thicknesses and seamed together with an outer rubber shell. Other medicine balls have a thin rubber bladder covered by a thick rubber outer surface. Medicine balls that are constructed with an inner rubber bladder and rubber outer surface incorporate an air valve to pump up the ball and increase the bounce. The outer rubber surface has indented designs for easy handling. Over time the rubber surface may wear down if the medicine ball has been used on rough surfaces.
Other types of medicine ball include balls made of gel-filled polyvinyl chloride shells, balls made of solid polyurethane, and neoprene bags filled with sand or steel shot. The materials can vary depending on the desired weight and density.
https://en.wikipedia.org/wiki/Medicine_ball
