First successfully used in Eastern Europe, plyometrics is now generally accepted as a key to the training of successful championship athletes.
The idea behind plyometrics is simple: exploit the muscles' cycle of lengthening and shortening to increase power. Plyometric exercises start with rapid stretching of the muscle, follwed by a shortening of the same muscle - the goal being to train the nervous system to react quickly to he lengthening of the muscle by rapidly shortening the same muscle with maximum force.
Plyometric exercises have long been used to develop power using the body weight as the resistance force. The medicine ball is the perfect device for imposing plyometric loads on the upper extremeties and trunk and legs, and its versatility means you can develop a varied and sport-specific programme of throwing and catching movements for the upper extremeties, rotational exercises for the trunk, extension exercises for the lower extremeties and total body exercises.
Dr. Donald Allan Chu's classic work on the subject is informed by his experience training national level US high-jumpers and figure skaters.