Medicine Ball Training (From: New Functional Training For Sports - Mike Boyle - 1st Edition) - very simple and safe way to develop total body power, rotary power, and anterior-core power. Med ball training helps the athlete develop power in the hip internal and external rotation and move that power from the ground through the core (very similar to that in which a baseball player throws a ball).
Why we like them so much: Med ball training teaches the summation of force, from the ground through the legs, through the core, and finally out through the arms. This transfer process is the essence of core function. The athlete learns to transfer force from the ground to the ball, with core as the vital link.
Rotary power does not mean lumbar rotation (we want a relatively stable lumbar spine)
Rotary power lies in the hips (not core)
Med ball movements should be fluid and include explosive concentric contractions
Allows the muscle to contract at speed similar to that encountered in sports
Speed of movement is key - not weight (remember Force = Mass X Acceleration)
Overhead throws can help throwing athletes work on the declarative capability of the shoulder musculature and force acceptance in the lead leg