SPORT SPECIFIC groups can lead to a variety of injuries to the labrum capsule or the rotator cuff itself. EXERCISE SELECTION How can all this data affect the exercise prescriptions you provide to pitchers? Obviously, the answer varies depending on training goals, existing symptoms of deficiency, weakness, or movement compensation, and past or present injuries. But in general, the research suggests special emphasis should be given to the supraspinatus, infraspinatus, and
teres minor, as well as the scapula stabilizer muscles. They lay the foundation upon which optimal power and sound technique are built. As for which exercises are best, there’s some controversy about the ideal way to position, isolate, and strengthen the supraspinatus muscle, and this has led several study authors to use EMG analysis in an attempt to resolve the issue. There is no consensus yet, and one of the main points of contention involves the relative value of “empty can” and “full can” exercises.
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Frank Jobe, MD, pioneer of Tommy John ligament replacement surgery, was the first to recommend empty can exercises for strengthening the supraspinatus. This involves elevation in the scapular plane (30 degrees anterior to the frontal plane) with glenohumeral IR to shoulder height only. Meanwhile, others believe in the full can position (see Figure One on page 47), which involves elevation in the scapular plane with glenohumeral ER to shoulder height. We recently conducted a study of the supraspinatus and deltoid musculature using EMG during full can, empty can, and prone full can exercises. We found that all three provided a similar amount of supraspinatus activity (ranging from 62 to 67 percent of maximal voluntary isometric contraction). However, we did observe one key difference: The full can exercises resulted in significantly less middle and posterior deltoid activity. This led us to conclude that the full can may be a superior exercise, since it is able to strengthen the supraspinatus while minimizing potentially damaging superior shear force due to deltoid activity. The two other key muscles targeted in the overhead throwing athlete are the infraspinatus and teres minor. These comprise the posterior cuff, providing glenohumeral compression and resisting superior and anterior humeral head translation by exerting an inferoposterior force to the humeral head. The posterior cuff muscles also provide glenohumeral external rotation, and pitchers rely on them to maintain adequate glenohumeral joint congruency during each throw. Some researchers have found that overhead throwers most often experience rotator cuff tears from the mid-supraspinatus posterior to the midinfraspinatus area, which they surmise is a result of compressive force produced to resist distraction, horizontal adduction, and internal rotation at the shoulder during arm deceleration. Thus, the external rotators often appear weak and affected by different shoulder pathologies such as internal impingement, joint laxity, labral lesions, and rotator cuff lesions—particularly in pitchers. To head off these potential problems, some studies suggest emphasizing ER strengthening for throwing athletes to enhance muscular strength, endurance, and dynamic stability. This is another area where the best exercises are not universally agreed upon, so we recently
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