Shoulder Press - Behind the Neck
By Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS
This exercise requires beyond optimal flexibility from the glenohumeral (shoulder) joint. To perform this exercise with optimal shoulder girdle (scapulothoracic joint) mechanics would require more than optimal external rotation (95°) and horizontal abduction of the shoulder(100°) (gleno-humeral joint). This implies that we must sacrifice the optimal length of soft tissues (hyper-mobility), or adopt a compensatory pattern at the shoulder girdle and spine.
Since most of us are not hyper-mobile at the shoulder, it is more common to adopt a compensatory movement pattern. In this scenario the scapula assume a position of downward rotation, anterior tipping, and elevation to allow external rotation of the glenohumeral joint without restriction from the subscapularis and pectoralis major. Further, the cervical and thoracic spine flex to "move the head out of the way."
The new position adopted by the scapula creates a potentially dangerous environment for subacromial tissues. The downward rotation and anterior tipping of the scapula press the acromion process into the humeral head and compresses the soft tissues between them (specifically the biceps tendon, supraspinatus tendon, and subacromial bursa). This greatly increases the risk of developing shoulder impingement syndrome (anterior shoulder pain).
The position of the scapula also changes the position of the glenoid fossa and creates a potentially unstable environment for the glenohumeral joint. Specifically, the anterior tipping of the scapula leads to a superior and anterior glide of the humeral head (anterior subluxation) in the glenoid fossa. Although I have not heard of a dislocation occurring from this position, the mechanical force imposed on the shoulder capsule could lead to adaptive length changes that lead to long term mechanical change. Further, the lack of stability created by lengthening of the shoulder capsule and the decrease in mechanical support from the glenoid fossa (there is no portion of the glenoid fossa inferior to the humeral head to “bolster” the humerus) will lead to altered recruitment patterns.
The downward rotation and anterior tipping of the shoulder girdle reinforces faulty recruitment patterns that could lead to adaptive shortening, and altered length/tension relationships. Specifically, the anterior tipping and downward rotation leads to adaptive shortening of the pec minor and levator scapulae, and the change in gleno-humeral position (anterior subluxation) leads to adaptive shortening of the supraspinatus, subscapularis, and posterior capsule. The adaptive shortening is matched by lengthening and weakness of the teres minor, infraspinatus, and traps. This pattern is reinforced when loaded and repeated.
The forward head position and kyphotic thoracic spine lead to the reinforcement of a compensation pattern similar to the postural dysfunction - forward head tilt. Adaptive shortening of the cervical extensors, scalenes, sternocleidomastoid, upper trapezius, and a concurrent lengthening of longus coli, longus capitis, lower trapezius and thoracic extensors. Forward head tilt is a common compensatory pattern adopted by desk workers that should not be reinforced by an exercise program whenever possible.
The forward head position and increased kyphosis of the thoracic spine often leads to fixated facet joint in the cervical and thoracic spine. This can be both painful and extremely disruptive to shoulder girdle mechanics. A decrease in thoracic extension, decreases upward rotation of the scapula and forces the body to adopt the compensatory shoulder girdle movement pattern discussed above (anterior tipping, and downward rotation).
© Brent Brookbush 2011
Questions, comments, and criticisms are welcomed and encouraged –