Comparison of OnBaseU Tests with Biomechanical Motion Analysis in Youth Baseball Pitchers

BACKGROUND: The OnBaseU screen was developed to evaluate a baseball pitcher’s ability to perform movement patterns key to pitching. However, due to lack of validation, it is unclear what application is ideal for this screen. PURPOSE: To compare four OnBaseU tests to relevant pitching mechanics measured using 3D motion capture to evaluate if the OnBaseU screen can be used to assess pitching mechanics. The secondary purpose was to compare OnBaseU and 3D motion capture seated trunk rotation test results to determine the validity of the OnBaseU test. METHODS: OnBaseU screening and 3D motion capture pitching evaluations were completed for 103 adolescent pitchers (age = 15.2 ± 1.29 years; height = 1.80 ± 0.0866 m; weight = 76.2 ± 13.8 kg). A motion capture seated trunk rotation test was also conducted on 80 of the 103 youth players (age = 15.2 ± 1.32 years; height = 1.80 ± 0.0889 m; weight = 75.7 ± 13.9 kg). RESULTS: Stride length and OnBaseU side step walkout test data were moderately correlated, and all other comparisons were not correlated or were minorly correlated. No significant differences were found between kinematics from players who obtained different OnBaseU scores, except for stride lengths during pitching of players who scored a 1 or 3 on the OnBaseU side step walkout test (p<0.01). Further, OnBaseU and motion capture seated trunk rotation tests were not correlated (r = 0.003) and not found to be statistically associated (p = 0.83). CONCLUSION: Results from this study indicate that the OnBaseU clinical assessment screen may not have use in assessing pitching mechanics and that visual grading criteria used in the OnBaseU seated trunk rotation test may not be accurate. LEVEL OF EVIDENCE: 3