Effect of Excessive Contralateral Trunk Tilt on Pitching Biomechanics and Performance in High School Baseball Pitchers

Background: There is a growing number of pitching-related upper extremity injuries among young baseball pitchers; however, there is a lack of data on the identification of injury prevention strategies, particularly the prevention of injuries through the instruction/modification of technique. The identification of technical parameters that are associated with increased joint loading is needed. Purpose: To investigate the effects of excessive contralateral trunk tilt, a common technique identifiable by video observation, on pitching biomechanics and performance in high school baseball pitchers. The hypothesis was that this strategy is associated with greater joint loading and poor pitching performance. Study Design: Descriptive laboratory study; Level of evidence, 3. Methods: The 3-dimensional pitching biomechanics, ball speed, and frontal view of the pitching technique from 72 high school baseball pitchers were captured on video and analyzed. The videos were reviewed to determine if the pitcher's trunk was excessively contralaterally tilted at the instant of maximal shoulder external rotation by examining whether the side of the pitcher's head ipsilateral to the throwing limb deviated by more than a head width from a vertical line passing through the pitcher's stride foot ankle. Upper extremity kinetics and upper extremity/trunk kinematics between pitchers with and without excessive contralateral trunk tilt were compared using independent t tests. Results: Compared with pitchers who did not demonstrate excessive contralateral trunk tilt, those with excessive contralateral trunk tilt pitched at a higher ball speed (mean, 32.6 2.2 vs 31.1 2.9 m/s, respectively; P = .019) and experienced a greater elbow proximal force (mean, 103.9 +/- 12.7 vs 93.2 +/- 13.9 %weight, respectively; P = .001), shoulder proximal force (mean, 104.8 +/- 14.1 vs 94.3 +/- 15.5 %weight, respectively; P = .004), elbow varus moment (mean, 4.29 +/- 0.73 vs 3.84 +/- 0.8 %height*weight, respectively; P = .017), and shoulder internal rotation moment (mean, 4.21 +/- 0.71 vs 3.75 +/- 0.78 %height*weight, respectively; P = .011). Pitchers with excessive contralateral trunk tilt demonstrated less upper torso flexion at stride foot contact, less upper torso rotation, and greater upper torso contralateral flexion at maximal shoulder external rotation and ball release (P < .05). Conclusion: Excessive contralateral trunk tilt is a strategy that is associated with higher ball speeds and increased joint loading. Clinical Relevance: Pitching with excessive contralateral trunk tilt, which can be identified through screening of the pitching technique, is associated with a benefit in performance and increased joint loading. Future study is warranted to determine if this strategy should be encouraged or discouraged by baseball coaches.