Descriptive Strength and Range of Motion in Youth Baseball Players.
Ross M Nakaji, Todd S Ellenbecker, Kevin M McClenahan and 3 others
PMID 33604150WHAT IT FOUND
Youth baseball players aged 5-12 already show shoulder adaptations similar to adults: greater external rotation and internal rotation strength in the throwing arm.
However, total range of motion remains symmetrical between arms, suggesting these changes are normal development rather than immediate injury risk.
Key findings
01The throwing arm had significantly greater external rotation range of motion and significantly less internal rotation range of motion compared to the non-throwing arm.
02Total arc of motion (sum of external and internal rotation) did not differ significantly between the dominant and non-dominant arms.
03Internal rotation strength was significantly greater in the throwing arm, but external rotation strength was not different between arms.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
Small sample size of 50 participants. Wide age range (5-12 years) prevented analysis of specific age groups. Single trial measurements may have increased error. No data on height, weight, years of experience, or injury history. All participants were male, so findings may not apply to female youth athletes.
Declared interests
The authors declared no financial interests or affiliations.
The easy way to misread this
Do not interpret the loss of internal rotation range of motion in the throwing arm as a definitive injury risk. The study found that total range of motion remained symmetrical between arms, which suggests these changes are normal adaptations in youth athletes rather than pathological deficits.