Shoulder Savers: Alterations of Traditional Exercises
Michael D. Rosenthal, PT, CSCS
Naval Medical Center
Athletic competition places extreme strength and mobility demands on the proximal joints of the upper extremity. The ball and socket configuration of the glenohumeral joint allows more motion to occur at the shoulder than any other joint in the body (10). Where mobility is so great, stability is often sacrificed.
Static, noncontractile tissue and dynamic, contractile tissue restraints provide stability of the shoulder joint. The capsule and ligaments of the glenohumeral joint serve as the static restraints.
The static restraints help maintain the joint congruency. The rotator cuff muscles function as dynamic stabilizers as they guide and fix the humerus during active and stationary movements. Mobility of the shoulder joint is a complex coordination of movements from the glenohumeral, sculpothoracic, acromioclavicular, and sternoclavicular joints (2). When so many joints work together to perform the highly specific motions required in sports, optimal function of the muscles is crucial (7) for preventing movement patterns that may result in injury.
In weight rooms from high school to professional sports athletes perform a variety of exercises that place great stress on the passive (static) restraints of the shoulder. Moreover, they place the muscles on the rotator cuff in a position that reduces their efficiency and may lead to impingement, a pinching of the tendons on the underside of the acromion.
While occasional performance of these lifts is unlikely to result in disabling shoulder pain, regular repetition of the lifts may cause subtle instability due to stretching of the capsule and ligaments, or impingement of the rotator cuff tendons.
This article discusses various exercises that may place excessive stress on the static dynamic stabilizers, and describes minor changes in technique that will decrease the strain on these structures.
Planes of Motion
The three planes of the body are sagittal, frontal (coronal), and transverse (horizontal) (8). The sagittal plane is a vertical plane that divides the body into left and right sides. The frontal plane divides the body into anterior and posterior portions and lies perpendicular to the sagittal plane. The horizontal plane is parallel to the ground. The scapular plane lies 30 degrees anterior to the frontal plane (5).
The ability of the capsule and glenohumeral ligaments to provide stability may be compromised as a result of an isolated trauma (e.g., frank dislocation of the glenohumeral joint) or from repetitive stress to a specific region of the capsule, usually anterior, which may result in progressive laxity of these structures (4). When the capsule and ligaments become less competent at providing stability, the rotator cuff muscles try to compensate as dynamic stabilizers.
Supraspinatus, infraspinatus, teres minor, and subscapularis are the four muscles of the rotator cuff. The primary function of the supraspinatus muscle is abduction and stabilization of the humeral head in the glenoid fassa. The infraspinatus and teres minor are the primary external rotators. The subscapularis muscle, along with the pectoralis major, teres major, and latissimus dorsi, perform internal rotation (9).
The deltoid, rhomboids, levator scapulae, superior trapezius, middle trapezius, inferior trapezius, serratus anterior, cobrachialis, pectoralis minor, and short head of the biceps brachii all have attachments to the scapula (15). The deltoid muscle serves as the primary mover of the humerus in the frontal (abduction) and sagittal planes (forward flexion) (9).
Precise interaction of the muscles of the glenohumeral and scapulothoracic joints is essential for producing pain-free motion at the shoulder joint. Impairment in any muscle due to weakness, injury, or poor training technique will produce increased demand on the assisting static and dynamic stabilizers, possibly resulting in further injury, impaired performance, and restriction from competition.
Numerous muscles are active during functional movement. For instance, during abduction in the scapula plane, the deltoid serves as the prime mover of the humerus while the rotator cuff muscle functions in stabilizing the head of the humerus on the glenoid. The serratus anterior and inferior trapezius act to rotate the scapula to maintain congruency between the glenoid and humeral head.
Functional activities rarely occur in isolated planes of motion. Most upper extremity activities are performed with the hand in front of the shoulder (12). Exercises performed in the scapular plane (scaption) have been advocated because the length/tension relationship of the shoulder abductors and rotators are optimum in this plane for elevation (14).
Exercise in the scapular plane maximizes glenohumeral joint congruity and avoids excessive tension of the static stabilizers (14). Research has also revealed higher external rotational strength values in the plane of the scapula than in the frontal plane (3).
Traditional Exercises and Minor Alterations
Lateral raises, behind-the-neck military presses, dumbbell flyes, and bench presses are exercises that have been shown to cause anterior shoulder instability and pain, resulting in limitations of function (4).
The lateral raise performed in the frontal plane with the arm extended reduces conformity of the joint surfaces, produces less than optimal alignment of the rotator cuff muscles (6), and increases the stress on the inferior glenohumeral ligament complex (13).
Performing this exercise in the scapular plane increases the activity of the external rotatory muscles (3). Flexion of the elbow to 90 degrees during this motion further reduces the glenohumeral forces (8, 14) and increases the demand on the infraspinatus and teres minor muscle due to the internal rotation moment (8).
The lateral raise in the scapular plane with external rotation (i.e., thumb up) minimizes impingement of the rotator cuff under the coracoacromial arch when performed beyond 90% of elevation. However, this is not the case with abduction performed in the frontal plane (11).
Behind-the-neck pulldowns and behind-the-neck military presses increase the stress on the anterior portion of the glenohumeral complex (4). Furthermore, with the humerus externally rotated to 90 degrees, the teres minor and infraspinatus muscles are in a shortened position and may be less effective at maintaining glenohumeral congruency based on the length/tension relationship (8).
Performing these exercises anterior to the shoulder joints results in less stress on the passive restraints of the anterior glenohumeral joint and is more consistent with functional movement.
Also, bench presses and dumbbell flyes (flat of incline bench) can produce excessive stress on the static stabilizers of the anterior glenohumeral joint. Performing the downward movement of dumbbell flyes to where the dumbbells are level with the shoulders (1) increases the anterior shear of the humerus. Minor modifications in technique can reduce these harmful forces while still effectively stressing the muscles.
Limiting horizontal abduction of the humerus so the elbow does not pass beyond the frontal plane will reduce on the static restraints. Performing the bench press with a towel on the chest will also reduce the anterior movement of the humerus on the glenoid. Upright rows and high pulls performed above 60-70 degrees of abduction may produce impingement of the greater tuberosity on the coracoacromial arch due to the inability of the humerus to externally rotate and clear the acromial arch during this movement (5).
Therefore, performing this exercise to 60 degrees of abduction will limit impingement of the rotator cuff.
Optimal performance of the shoulder complex is dependent on pain-free function. Traditional shoulder exercises can produce unwanted stress on the static stabilizers of the glenohumeral joint and also reduce the efficiency of the rotator cuff muscles, resulting in shoulder pain.
Given the intricate integrated function of the glenohumeral, scapulothoracic, and sternoclavicular joints, it is important to strengthen the muscles without producing pain. Pain will preclude one’s ability to strengthen the shoulder girdle complex, resulting in altered mechanics and microtrauma to the soft tissues.
Repeated microtrauma may eventually compromise the static and dynamic stabilizers of the shoulder joint complex and lead to joint instability and dysfunction.
The traditional exercises should not be discounted on the basis of this information. However, in athletes with a history of shoulder injury or recurrent pain, the aforementioned modifications of technique may allow exercise to be pain-free and prevent further complications.
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Michael D. Rosenthal is a lieutenant is the U.S.Navy and a staff physical therapist at the Naval Medical Center in Portsmouth, VA. He has a Master’s in physical therapy from Baylor U.