Sagittal Plane Trunk Tilt Is Associated With Upper Extremity Joint Moments and Ball Velocity in Collegiate Baseball Pitchers

BACKGROUND: The trunk is a major contributor to the kinetic chain during baseball pitching by helping to transfer energy from the lower limbs to produce the desired ball speed. However, most of the research detailing the trunk’s contribution to the pitch is focused on rotational timing and coronal plane lean, with little attention focused on sagittal plane positioning of the trunk. PURPOSE: To determine the association between sagittal plane trunk motion and elbow varus moment and ball velocity in collegiate baseball pitchers. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 99 collegiate pitchers were recruited for this study and underwent a comprehensive biomechanical assessment of their pitching motion using 3-dimensional motion techniques. A random-intercepts, mixed-effects regression model was used to determine whether statistically significant associations were noted between sagittal plane trunk motion and the ball velocity and elbow varus moment. RESULTS: There were a number of significant associations between sagittal plane trunk tilt and the elbow varus moment and ball velocity. Increased forward trunk tilt at the time of ball release was associated with an increase in elbow varus moment and a small increase in ball velocity; for every 10° of increased forward trunk tilt greater than 28° at ball release, the elbow varus moment increased by 2.9 N·m (P = .007), and the ball velocity increased by 0.7 m/s (P = .002). CONCLUSION: Sagittal plane positioning of the trunk plays a role in pitching mechanics, as it can affect both pitching performance and elbow moments. The results also indicated that there is a potential optimal trunk position and range of motion during the acceleration of the pitch that could limit the stress placed on the elbow joint. Implementing proper trunk mechanics from an early age could lead to a reduction in joint moments. CLINICAL RELEVANCE: The results provide evidence for coaches and trainers to emphasize the importance of proper trunk positioning through the inclusion of core strengthening and motor control in their practice and coaching sessions in an effort to reduce the moments placed on the elbow during the pitch.