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ORIGINAL RESEARCH

The Relationship between Passive Glenohumeral Total Rotation and the Strength of the Internal and External Rotator Muscles: A Preliminary Study.   

Authors: Cibulka MT,  Enders G, Jackson A, Maines S, Von der Haar J, Bennett J

There is little research on how the amount of shoulder joint range of motion, specifically glenohumeral rotation, may be related to the strength of the rotator cuff muscles. A long held belief is that a joint with excessive range of motion needs sufficient muscular strength for stability to exist. However, no studies have examined this concept. Therefore, the purpose of this study was to see if total arc of glenohumeral joint rotation (External rotation [ER] + Internal rotation [IR]) could predict peak isometric muscle strength of the IR or ER muscles of the shoulder. The authors found that those with an increased total arc of motion of glenohumeral rotation (greater than 165.0°) had less isometric rotator cuff muscle strength in all test positions than those with less glenohumeral rotation.  Decreased force of the ER and IR muscles of the shoulder was noted in those with increased total arc glenohumeral rotation (> 165.0°); specifically those with increased glenohumeral internal rotation (> 80.0°) when compared to those with glenohumeral rotation < 165.0° and glenohumeral internal rotation < 80.0°.   

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