External Rotation Strength
Why it matters, how it’s analyzed
and what the research says
External Rotation Strength
Why it matters, how it’s analyzed and what the research says
Why it matters

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

There are three ways that the app compares external shoulder rotation strength (ER 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.

A solid goal would be to raise your strength to the 80th percentile or better. That means that your strength is better than 80% of the population.

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.

In some cases, pitchers can show greater non-throwing side strength in their shoulder. When this is noticed, our customized training program becomes modified to correct imbalance.

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.

In some cases, pitchers can show greater non-throwing side strength in their shoulder. When this is noticed, our customized training program becomes modified to correct imbalance.

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.

Decreased strength by more than 10% will automatically modify your arm care and provide a recovery-based program of reduced training load. Along with your symmetry score, the trend score is an excellent marker to identify arm fatigue.

Summary of Research

 

 

    • 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).

 
TAKE HOME MESSAGE: ER strength in relation to IR strength is critical for arm health. Use the ArmCare App to determine if your muscles are out of balance.

Research
Research
Jobe FW, Moynes DR, Tibone JE, Perry J. An EMG analysis of the shoulder in pitching. A second report. Am J Sports Med. 1984;12(3):218–220.

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.

Garrison JC, Johnston C, Conway JE. Baseball players with ulnar collateral ligament tears demonstrate decreased rotator cuff strength compared to healthy controls. Int J Sports Phys Ther. 2015;10(4):476–481.