Normalized Isometric Shoulder Strength as a Predictor of Ball Velocity in Youth Baseball Players.
Amanda J Arnold, Charles A Thigpen, Paul F Beattie and 4 others
PMID 35136695WHAT IT FOUND
Normalizing shoulder strength by ulnar length is the most reliable method for tracking changes in youth baseball players.
This method, along with height normalization, shows that dominant shoulder strength predicts ball velocity, with scaption and external rotation at 0 degrees being the strongest predictors.
Key findings
01Ulnar length normalization was the only method to consistently detect changes in strength over six months, exceeding minimal detectable change values with medium effect sizes.
02Normalized dominant shoulder scaption and external rotation at 0 degrees strength were significant predictors of ball velocity, explaining 27% and 23% of the variance respectively when using ulnar length normalization.
03Strength measures taken at 90 degrees of shoulder abduction showed high inter-subject variability and were not predictive of ball velocity in this youth population.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study was cross-sectional for velocity and had a small subset (n=58) for the longitudinal strength change analysis. Isometric testing does not fully capture the dynamic nature of throwing. High variability in neuromuscular control at 90-degree positions limited the usefulness of those measures. Only male participants aged 9-12 were included, so results may not generalize to females or older adolescents. No external stabilization was used during testing, which may affect reliability compared to lab settings.
Declared interests
All authors declare no conflicts of interest.
The easy way to misread this
Do not assume that increased shoulder strength directly prevents injury or that all strength measures are equally useful. The study found that strength measures at 90 degrees were unreliable due to variability, and while strength predicts velocity, the relationship with injury risk was not examined here.