THE RELATIONSHIP OF RANGE OF MOTION, HIP SHOULDER SEPARATION, AND PITCHING KINEMATICS.

BACKGROUND

When pitching a baseball, pelvic and trunk pitching kinematics play an integral role in momentum transfer from the lower extremity to the upper extremity. However, it is unknown how hip and trunk ROM and hip shoulder separation interplay with pelvic and trunk pitching kinematics.

HYPOTHESIS/PURPOSE: To determine the relationship between clinical trunk and hip range of motion (ROM) and pitching biomechanical pelvis and trunk kinematics, and kinematic sequencing.

STUDY DESIGN

Controlled biomechanical study.

METHODS

High school pitchers were assessed for trunk rotation via motion capture and hip ROM via a goniometer prior to pitching. Trunk rotation was designated as dominant and non-dominant sides, and hips as stance and lead limbs. Pitchers threw four fastballs during three dimensional biomechanical assessment. Spearman's Rho correlations were performed between trunk and hip ROM, and trunk and hip biomechanical kinematics, and kinematic pitching sequence.

RESULTS

Thirty-two pitchers (mean age: 16.3 ± 1.2 years, height = 184.0 ± 6.9 cm, mass = 76.8 ± 20.8 kg) were included in this study. Their mean pitch velocity was 34.7 ± 2.3 m/s, peak pelvis rotation velocity: 669.1 ± 95.5 deg/s, and peak trunk rotation velocity: 1084.7 ± 93.0 deg/s. There were no differences between dominant and non-dominant side trunk rotation, or between stance and lead hip ROM. There were no significant relationships between trunk or hip ROM and pitching kinematics. There was a significant relationship between hip shoulder separation and peak trunk rotation velocity (r = 0.390, p=0.027). There was a significant relationship between pitch velocity and peak trunk rotation velocity (r = 0.478, p = 0.006). There were no other significant relationships between pitching kinematics or kinematic sequencing.

CONCLUSION

Hip shoulder separation is related to trunk rotation velocity, and ultimately pitch velocity. These ROM measurements can be used as normative values for hip shoulder separation in high school pitchers.

LEVEL OF EVIDENCE