A Biomechanical Comparison of Pitching From a Mound Versus Flat Ground in Adolescent Baseball Pitchers

BACKGROUND: Baseball professionals believe that pitching from a mound can increase the stresses placed on the body. HYPOTHESIS: There is no difference in kinematics or kinetics in pitching from a mound versus flat-ground conditions in adolescent baseball pitchers. STUDY DESIGN: Laboratory investigation. METHODS: The fastball pitching motions of 15 adolescent baseball pitchers, including upper extremity kinematics and kinetics and lead- and trail-leg kinematics, were evaluated while pitching from the mound and flat ground. Student t tests were used to determine the differences between the 2 testing conditions. RESULTS: Maximum external glenohumeral rotation was similar between the 2 conditions (134° ± 14° mound vs 133° ± 14° flat ground, P = 0.10). Ankle plantar flexion of the lead leg at ball release was greater in the flat-ground condition (−20° ± 10° mound vs −15° ± 12° flat ground, P = 0.01). A statistically significant increase in glenohumeral internal rotation moment (33.6 ± 12.1 Nm mound vs 31.7 ± 11.6 Nm flat ground, P = 0.01) and an increase in elbow varus moment (33.3 ± 12.3 Nm mound vs 31.4 ± 11.8 Nm flat ground, P = 0.02) was measured when pitching from the mound as compared with flat ground. CONCLUSION: Pitching from the mound causes increased stress on the shoulder and elbow of adolescent pitchers as compared with that from flat ground. CLINICAL RELEVANCE: The differences in kinematics as well as increased moments in the shoulder and elbow are helpful for pitchers and their coaches to know at the beginning of their season or as they return from injury or surgery. Pitchers in these situations should start their pitching progression on flat ground and progress to the mound.