The relationship between shoulder external rotation strength, horizontal abduction, and glenohumeral distance ratios in professional baseball pitchers.
Masaki Tamura, Takuya Aso, Tomoyuki Takahashi and 8 others
PMID 40757016WHAT IT FOUND
In 18 professional baseball pitchers, weaker shoulder external rotation strength at a specific position correlated with greater horizontal abduction and poorer humeral head alignment on MRI.
This suggests strength deficits may be linked to structural changes associated with posterosuperior impingement, but the study did not prove cause and effect.
Key findings
01Zero-position external rotation strength (normalized to body weight) showed a significant negative correlation with shoulder horizontal abduction angle (r = -0.61, p = 0.006) and the glenohumeral distance ratio (rho = -0.58, p = 0.01).
02Pitchers in the low-strength group had significantly greater horizontal abduction angles (9.9° vs 2.0°) and higher glenohumeral distance ratios (1.3 vs 0.9) compared to the high-strength group.
03The study was limited by its retrospective design, small sample size (n=18), and reliance on static MRI measurements rather than dynamic pitching analysis.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study had a very small sample size of 18 participants. It was a retrospective design, which limits the ability to establish causality. Measurements were taken in static positions (standing strength test and supine MRI) rather than during the dynamic pitching motion. The reliability of single-measurement strength testing was insufficient (ICC 0.66), requiring the use of averaged trials. The study did not assess pain, function, or actual injury incidence, only structural and strength parameters.
Declared interests
The study received no funding, and the authors declared no conflicts of interest.
The easy way to misread this
Do not assume that strengthening the shoulder in this specific position will prevent injury or improve symptoms. The study only showed an association between strength and static MRI measurements in a small group of pitchers; it did not test whether changing strength changes outcomes.