and what the research says
The primary role of the external rotators is to provide a braking force for the arm, which EMG studies show is the most strenuous part of the throwing motion. Weak or fatigued external rotators have been linked to an increase risk of both shoulder and elbow injuries.
Analyzing External
Rotation Strength
compares external rotation strength:
1. Percentile
Percentile compares your external rotation strength to other players your age. If you are in the lower third for players your age, you know that this is an area that you need to improve.
2. Symmetry
Symmetry compares the internal rotation strength of your throwing side to your non-throwing side, in which most players are the same or slightly weaker on their throwing arm.
2. Symmetry
Symmetry compares the internal rotation strength of your throwing side to your non-throwing side, in which most players are the same or slightly weaker on their throwing arm.
3. Trend
Trend analyzes how your strength has changed compared to previous tests. It’s normal for a player’s strength to fluctuate throughout the season, but these changes should be monitored and addressed.
If the strength score has decreased by 10% or more, the app will automatically modify your arm care to a recovery-based program that reduces training loads & volume. Along with your symmetry score, the trend score is an excellent marker to identify arm fatigue.
- A 5-year study of Major League Baseball Players found that preseason external rotation weakness was a good predictor of in-season injuries that required surgery (Byram, 2010).
- Baseball players who had UCL injuries had a 30% deficit in external rotation rotator cuff strength compared to healthy players (Garrison, 2015).
Byram IR, Bushnell BD, Dugger K, Charron K, Harrell FE Jr, Noonan TJ. Preseason shoulder strength measurements in professional baseball pitchers: identifying players at risk for injury. Am J Sports Med. 2010;38(7):1375–1382.