Effects of 8-week core training program on lumbopelvic-hip muscle function and pitching biomechanics in adolescent pitchers

ABSTRACT Context: The lumbopelvic-hip musculature plays a critical role in controlling trunk movement during pitching. Training interventions targeting these muscles have been shown to enhance muscle function and increase ball speed. However, evidence linking improvements in lumbopelvic-hip strength and power to changes in trunk kinematics and joint moments during pitching is lacking. Objective: To investigate the effects of an 8-week strength training intervention targeting the lumbopelvic-hip muscles on muscle function and pitching biomechanics in adolescent pitchers. Design: Controlled Laboratory Study. Setting: Research laboratory / Training facility Patients or Other Participants: Fifty-four high school pitchers enrolled into either an intervention or a control group. Intervention: Eight-week training targeting lumbopelvic-hip muscles. Main Outcome Measures: Changes in lumbopelvic-hip muscle function, trunk kinematics during pitching, joint loading, and ball velocity. Results: The intervention resulted in greater improvements in trunk rotation strength and power (p = 0.002 -0.017) and increases in elbow varus moment (p = 0.046) and ball speed (p = 0.014). Although no significant between-groups differences were observed in pitching kinematic correlated with a smaller pelvis rotation (a more “closed” pelvis) at lead foot contact, smaller trunk separation angle at lead foot contact, and later timing of peak upper torso rotation velocity (|r| = 0.436 - 0.566). Conclusion: The intervention effectively improved trunk rotational strength and power and ball speed, but also increased elbow stress. This finding underscores the importance of reducing pitch counts or extending rest periods as ball speed increases. The intervention produced only limited changes in pitching kinematics. Enhanced trunk rotational strength and power in the intervention group were associated with positive changes in trunk kinematics, but no other kinematic adjustments. Combining strength training with technical feedback and extending the intervention duration may lead to greater biomechanical adaptations.