Externall Rotation Range of Motion

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

Externall Rotation Range of Motion

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

Why it matters
Baseball players often have greater external rotation range of motion on their throwing arm. These are often normal adaptations to throwing, but significant changes following an outing or a progressive loss throughout a season may be early signs of an injury, fatigue, or a response to muscle soreness. When participating in a velocity program using weighted balls, external rotation increases and needs to be monitored.

Research shows that these changes can affect performance and increase the risk of both shoulder and elbow injuries.

In addition to the normal increase in external rotation on the throwing arm, it’s usually paired with a decrease in internal rotation as well. For that reason, it’s common to look at the total arc of motion (external rotation + internal rotation = total arc motion) rather than movement in just one direction.

The total arc should remain within 5-10 degrees between the throwing and non-throwing sides.

Analyzing External

Rang of Motion (ER ROM)

There are two ways that we look
at external rotation ROM:

1.SYMMETRY

Symmetry compares your throwing arm external rotation range against your non-throwing shoulder. Most players have more external rotation range in their throwing arm than their non-throwing arm.

2. Trend

Trend looks at how your range changes when compared to previous tests. Decreased range of motion by more than 10% will automatically modify your arm care and provide a recovery-based program focused on mobility.

2. Trend

Trend looks at how your range changes when compared to previous tests. Decreased range of motion by more than 10% will automatically modify your arm care and provide a recovery-based program focused on mobility.

Summary of Research
    • Pitchers usually have greater external rotation and less internal rotation of their throwing arm due to bone and soft-tissue adaptations to the throwing motion (Hellem, 2019).
      • Pitchers with an external rotation deficit of more than 5 degrees on their throwing arm compared to the non-throwing arm were  2.2x more likely to be placed on the disabled list for a shoulder injury and were 4x more likely to require shoulder surgery (Wilk, 2015).
    • Pitchers who have ER deficit have a moderate increased risk of shoulder injury and a significant increased risk of elbow and UCL injuries.  (Camp, 2017).

TAKE HOME MESSAGE: Maintaining external range of motion is essential for health and performance. When using the ArmCare app, if you notice a trend that your throwing arm’s external rotation range of motion is increasing more than 10 degrees, ensure that you are addressing muscular imbalances to support the range of motion increase. If your external rotation is not greater than your non-throwing arm by more than 5 degrees, you may want to consult a clinical professional to help you with soft-tissue restrictions that are impeding layback of your throwing arm.

Research
Research
Hellem A, Shirley M, Schilaty N, Dahm D. Review of Shoulder Range of Motion in the Throwing Athlete: Distinguishing Normal Adaptations from Pathologic Deficits [published online ahead of print, 2019 Jul 1]. Curr Rev Musculoskelet Med.

Wilk KE, Macrina LC, Fleisig GS, et al. Deficits in Glenohumeral Passive Range of Motion Increase Risk of Shoulder Injury in Professional Baseball Pitchers: A Prospective Study. Am J Sports Med. 2015;43(10):2379–2385.

Camp CL, Zajac JM, Pearson DB, et al. Decreased Shoulder External Rotation and Flexion Are Greater Predictors of Injury Than Internal Rotation Deficits: Analysis of 132 Pitcher-Seasons in Professional Baseball. Arthroscopy. 2017;33(9):1629–1636.