Medical College Study on Pitching Mound Height Provides Insight into Baseball Injuries

A study involving several Major League Baseball (MLB) pitchers indicates the height of a pitcher's mound can affect an athlete's throwing arm motion. This alteration in arm motion may lead to stress on the shoulder and elbow thereby increasing the potential of injuries.

The study was led by William Raasch, M.D., associate professor of orthopedic surgery at the Medical College of Wisconsin in Milwaukee. Dr. Raasch is also the head team physician for the Milwaukee Brewers, a major league baseball team. The study was funded by Major League Baseball to help prevent injuries among professional baseball players.

The results of the study were presented at the 2007 MLB Winter Meetings at a joint session of the Major League Baseball Team Physicians Association and Professional Baseball Athletic Trainers Society.

The researchers recruited 20 top-level pitchers from Major League Baseball organizations and Milwaukee-area NCAA Division I-A college pitchers for the study which was conducted during 2007 spring training in Arizona and at the Froedtert & Medical College Sports Medicine Center in Milwaukee.

"Our researchers employed a motion analysis system using eight digital cameras that recorded the three-dimensional positions of 43 reflective markers placed on the athletes' bodies. Then we analyzed pitching motion using the regulation 10-inches of mound height along with eight-inch and six-inch mounds as well as having the athletes throw from flat ground," Dr. Raasch explains.

The study focused on determining if there is increased stress on the shoulder or the elbow based on the height from which the pitcher has thrown. A kinematic analysis provided information regarding pitching motion (position and velocity), while the kinetic analysis determined the forces and torque generated at the shoulder and elbow.

"We found that compared to flat ground, pitchers using a 10-inch mound experience an increase in superior shear and adduction torque in the shoulder - meaning there's a greater amount of stress on the joint surface and surrounding structures. That greater stress may result in injury to the shoulder including tearing of the rotator cuff or labrum which may result in surgery and long-term rehabilitation. It also can make it difficult for the athlete to replicate the same throw and develop a consistent strike," Dr. Raasch says.

"The most notable kinematic difference was the increase in shoulder external rotation at foot contact. This probably represents a change in the timing of the foot contact relative to arm position, because the foot lands earlier in the pitch delivery during flat ground throwing than with a slope," he says.

While the study did not result in enough data to recommend reducing the 10-inch mound height which became standard in 1968 and is also used in college and high school baseball, Dr. Raasch says the findings give trainers information that can help them determine if pitchers would be better off practicing on flat ground, especially after an injury.

"Nolan Ryan, who played major league baseball for 27 years often threw pitches more than 100 mph, even past the age of 40, and he liked to throw on flat ground in his waning years. I think others might follow his lead," Dr. Raasch says.