Contralateral Trunk Tilt in High School Baseball Pitchers: Comparison and Relationship with Trunk Rotational Mobility, Compensatory Lateral Flexion, and Performance
Hiromu Tanaka, Yoshinori KagayaBackground
Excessive contralateral trunk tilt (CLT), the lateral flexion angle of the trunk during pitching, increases torque on the shoulder and elbow. Although core muscle strength is known to influence CLT, the relationship between limited trunk rotational mobility and throwing injuries is unclear.
Purpose
To compare trunk rotational mobility and compensatory lateral flexion between pitchers with high and low CLT, and to examine the relationships between these factors, player characteristics, ball velocity, and elbow valgus torque.
Study design
Cross-sectional comparison study.
Methods
This study evaluated 19 male adolescent pitchers (aged 15–18 years) with ≥1 year of experience and no pain or surgical history. Participants were stratified into high (>30°) and low (≤30°) CLT groups based on two-dimensional analysis. Trunk rotational mobility was assessed using inclinometers in hand-to-knee and lumbar-locked positions. Compensatory contralateral trunk flexion during rotation was analyzed photographically in the hand to knee position. Primary outcomes compared were differences in trunk rotational mobility and compensatory trunk flexion between groups; secondary outcomes were correlations between primary outcomes and ball velocity and elbow valgus torque.
Results
No significant differences were observed between the high (n = 9) and low (n = 10) CLT groups in trunk rotational mobility in the LLP position on the dominant (62.8° ± 11.5° vs 64.5° ± 11.2°, p = 0.745) and non-dominant (58.3° ± 9.0° vs 60.0° ± 8.5°, p = 0.684) sides, nor in compensatory contralateral trunk flexion during rotation on the dominant (17.1° ± 7.6° vs 18.0° ± 2.5°, p = 0.705) and non-dominant (18.2° ± 7.6° vs 20.1° ± 6.5°, p = 0.576) sides. CLT at MER moderately correlated positively with ball velocity (r = 0.47, p = 0.004), which correlated strongly with elbow valgus torque (r = 0.69, p < 0.001).
Conclusion
Excessive CLT at MER in adolescent pitchers is not associated with limited trunk rotation or compensatory lateral trunk flexion.
Level of Evidence
3