The best exercise for infraspinatus

We all know that the rotator cuff muscles of the shoulder are crucial in the prevention and rehabilitation of shoulder injuries. Among other mechanisms these muscles help to centre the humeral head in the socket and prevent superior migration during arm elevation.

Strength of the external rotators of the shoulder, particularly infraspinatus, is critical for a healthy shoulder. In overhead athletes exercises to strengthen this muscle is advisable due to the strength ratio imbalance that occurs over time, with the internal rotators becoming stronger relative to the external rotators.

Research has shown that the side-lying shoulder external rotation evokes the greatest EMG activity of the infrapsinatus compared with other exercises. The superior, middle and inferior heads of infraspinatus have the largest moment arm and generate the greatest torque at 0 degrees abduction. As abduction increases, the moment arm of the superior head gradually reduces. This does mean that external rotation exercise at 45 degrees and 90 degree abduction angles should not be performed however. Greater degrees of abduction still evokes significant rotator cuff activity, and also is a more specific position for the throwing athlete. However the side-lying exercises is best performed in the early stages of rehabilitation and also reduces the potential for excessive upper trapezius activity. Images below depict the exercise

Side lying shoulder external rotation 1Side lying shoulder external rotation 2

When performing the exercise many clinicians believe it is better to place a rolled towel between the elbow and the patient’s side. This may help to reduce capsular strain in the shoulder and lead to higher activity of the external rotators.

Cools , A. M.. ( 2007) Rehabilitation of Scapular Muscle Balance: Which Exercises to Prescribe? The American Journal of Sports Medicine 35 ( 10) ,  1744- 1751
De Mey , K.. ( 2012) Scapular Muscle Rehabilitation Exercises in Overhead Athletes With Impingement Symptoms: Effect of a 6-Week Training Program on Muscle Recruitment and Functional Outcome The American Journal of Sports Medicine 40 ( 8) , 1906- 1915
Reinold , Michael M.. ( 2004) Electromyographic Analysis of the Rotator Cuff and Deltoid Musculature During Common Shoulder External Rotation Exercises  Journal of Orthopaedic & Sports Physical Therapy 34 ( 7) ,  385- 394 

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