Mike Marschall, one time pitcher, PHD id how the body works, and also a different thinker wrote this: Baseball pitchers tear the connective tissue fibers of their Ulnar Collateral Ligament from mis-use. That mis-use starts with taking the baseball out of their glove with the palm of their pitching hand on top of the baseball. As a result of taking the baseball out of their glove with the palm of their pitching hand on top of the baseball, baseball pitchers cannot swing their pitching arm downward, backward and upward to driveline height in one, smooth, continuous movement. Instead, with the palm of their pitching hand on top of the baseball, baseball pitchers can only swing their pitching arm downward and backward to forty-five degrees behind their body. From this position, to move their pitching arm to driveline height, baseball pitchers have to raise their pitching forearm vertically upward. When their pitching forearm approaches pointing vertically upward, the baseball pitchers’ glove foot lands and baseball pitchers immediately and powerfully start to rotate their hips and shoulders forward. This means that baseball pitchers start pulling their pitching upper arm forward. Unfortunately, with the pitching forearm pointing vertically upward and the pitching upper arm jerking horizontally forward causes the pitching forearm to dramatically move downward to the height of the pitching elbow. When the pitching arm reaches horizontal, without the protection of the muscles that attach to the medial epicondyle of the pitching elbow, their Ulnar Collateral Ligament alone absorbs the force of the downward bounce of the pitching forearm. With each ‘Reverse Pitching Forearm Bounce,’ baseball pitchers tear some of the connective tissue fibers of their Ulnar Collateral Ligament. After thousands of ‘reverse bounces,’ the Ulnar Collateral Ligament ruptures. Unfortunately, unlike tendons, ligaments do not have pain sensors. Therefore, baseball pitchers have no idea that they are tearing their Ulnar Collateral Ligament. Fortunately, to prevent Ulnar Collateral Ligament tears, when baseball pitchers take the baseball out of their glove, baseball pitchers only need to turn the palm of the pitching hand from on top of the baseball to under the baseball. With the palm of the pitching hand under the baseball, baseball pitchers can vertically pendulum swing their pitching arm downward, backward and upward to driveline height in one, smooth, continuous movement. This pitching arm action activates the muscles that attach to the medial epicondyle, such that the Ulnar Collateral Ligament does not receive any stress.