Mark Prior - Pitching Mechanics

Pitching Mechanics

Mark Prior's pitching mechanics have been the subject of much attention throughout his career. As a prospect, his symmetrical, seemingly effortless delivery was widely regarded as mechanically efficient and sound. Prior's former personal pitching coach Tom House labeled the right-hander a "can't-miss" prospect. However, after Prior suffered a series of debilitating arm injuries, many experts have re-examined Prior's delivery.

As easy and flowing as Prior's pitching mechanics seem to be, his arm action contains elements that some analysts believe to be hazardous. According to Chris O'Leary, a pitching mechanics analyst, Prior's injury problems are largely derived from his arm action. More specifically, they are due to Prior's Inverted W arm action, in which he lifts his elbows above and behind the level of his shoulders, with the forearm pointing down. According to O'Leary, this creates a timing problem that places an undue stress on the muscles and ligaments of the shoulder and elbow because the arm gets up to the "cocked position" too late.

Similarly, Dick Mills, a former major league pitcher and co-author of The Science and Art of Baseball Pitching and Pitching.com, has speculated that Prior's injuries were a result of a movement known as scapular loading. Scapular loading is a movement in which a pitcher's shoulder blades are pinched together and elbows are taken behind, and sometimes above, their shoulders. The idea that scapular loading is dangerous has been disputed by some in the field of athletic training.