How many of you currently train clients who experience shoulder pain? How many of you reading this article currently experience soreness or discomfort in your own shoulders? As training and conditioning specialists, we routinely encounter clients and athletes who experience shoulder dysfunction. While shoulder dysfunction is most often multi-faceted in nature, several of the more common causes include muscle imbalances, overuse injuries and/or poor exercise selection. Regardless of the cause, one movement dysfunction that is common in the large majority of clients experiencing shoulder dysfunction is downward rotation and destabilization of the scapula. This article will provide a brief discussion of shoulder mechanics and describe a corrective exercise strategy to improve this common movement dysfunction.
The shoulder joint is comprised of four articulations; the sternoclavicular (SC), acromioclavicular (AC), glenohumeral (GH) and scapulothoracic (ST). The SC joint is made up of the proximal end of the clavicle and the sternum forming the only bony attachment of the upper extremity to the axial skeleton. The GH joint is an inherently unstable joint due to the size of the humeral head related to the glenoid fossa. The head of the humerus sits against the glenoid fossa similar to a golf ball sitting on a tee. Therefore, it relies on stability provided by the rotator cuff muscles (subscapularis, infraspinatus, teres minor and supraspinatus) along with the long head of the biceps brachii to maintain the integrity of the “ball in the socket.” The ST articulation is a functional joint formed by the scapula sitting on the thoracic cage. Although it is not a true joint (it lacks a joint capsule and synovial fluid), it is an important contributor to proper stabilization and movement patterns of the upper extremity.
The range of motion for GH flexion and abduction is about 180 degrees (120 degrees of humeral motion and 60 degrees of scapula motion). During the setting phase (the first 90 degrees of GH abduction) the axis of rotation begins at the superior angle of the scapula. The serratus anterior and upper trapezius help maintain stability and upward rotation of the scapula at this range and the levator scapula holds the superior angle of the scapula in a stable position. The humerus has approximately a 2:1 ratio of motion compared to the scapula. For every two degrees of humeral motion, there is one degree of scapular motion. However, these actual numbers may vary according to what is in the hand and how fast the arm is moving. From 90 to 150 degrees of abduction, the axis of rotation shifts to the AC joint due to the change in arm position relative to the scapula as well as the pull of the clavicular ligaments fixing the AC joint. During this phase, the lower trapezius pulls the spine of the scapula inferiorly to aid in upward scapular rotation while the serratus anterior pulls the inferior angle of the scapula around the rib cage. During the final 30 degrees of abduction (150 to 180 degrees) the axis of rotation shifts back to the superior angle of the scapula as the clavicular fibers of the pectoralis major complete the motion. The major muscles that contribute to these scapular movements are listed in the table below.
|Table 1: Scapula Rotators
|Upper and lower trapezius
|Clavicular fibers of pec major through the humerus
||Latissimus dorsi through the humerus
||Lower fibers of pec major through the humerus
Dysfunction of the Upward Rotators
Weakness and/or inhibition of any one of the upward rotators will potentially lead to impingement issues to both the supraspinatus as it passes under the acromium process and the soft tissue structures including the subacromial bursa and long head of the biceps brachii. Prolonged weakness/inhibition of the upward rotators causes motor control issues in which humeral motion dictates motion of the scapula. In the presence of prolonged inhibition of the upward rotators, the deltoid will jam the head of the humerus superiorly under the acromion process as it attempts to assist humeral elevation. This action will eventually overpower the rotator cuff muscles which exert an inferior force to counteract the superiorly directed pull of the deltoid complex creating impingement of the aforementioned structures. Trigger points and myofascial tension will often be noted in the rotator cuff secondary to weakness/inhibition of the scapular upward rotators and stabilizers. This most likely occurs secondary to up-regulation of the rotator cuff muscles in an attempt to stabilize the GH in light of scapular destabilization. This also results in increased activation and myofascial tension in the synergists of elevation, particularly the levator scapula, rhomboids and middle trapezius. Over-activation of the levator scapula and rhomboids coupled with inhibition of the upper trapezius, lower trapezius and serratus anterior additionally place stress on the cervical spine as stability will be compromised due to the cervico-scapular relationship between these muscles. This is a common cause of neck tension, headaches and cervical discogenic issues and contributes to the perpetuation of chronic neck and shoulder issues.
Biomechanics or Neuromechanics?
The forward head and winged scapula are common postural faults typically blamed on biomechanical causes including but not limited to:
- Muscle imbalances secondary to improper exercise selection (focus on anterior musculature at the expense of posterior musculature).
- Poor ergonomics (computer work and other occupations that require prolonged sitting and flexed postures).
- Breast implants in female clients.
- Guarding postures secondary to emotional stress that favor the protected position (flexion of the head and trunk and flexion and adduction of the extremities).
While these causes are valid causes and may contribute to common postural alterations, can it really be that simple? Is the nervous system really so easily programmed that it will modify its entire alignment in order to perform activities such as working on a computer or in a garden? If that is the case, then shouldn’t the postural work we do easily improve our clients’ posture? As most trainers will attest, it is very hard work and usually takes a long time to improve any client’s posture. In fact, it is common to see our clients return to their chronic postures as soon as they leave the gym door despite all the postural work and cues that occurred during the preceding hour. So why is this?
What we must come to realize as a profession is that neurology dictates function. In other words, the nervous system will alter the muscular response based upon the information it receives from the proprioceptive system. For example, if information is received that the tissues are being improperly oxygenated, the CNS will respond by increasing its respiratory efforts. This will result in the following postural changes:
- An increase in thoracolumbar extension to increase the lower diameter of the thoracic cage.
- The head will shift forward to place the accessory muscles such as the scalenes and sternocleidomastoid in a preferential position to elevate the 1st and 2nd ribs and sternum to increase the volume of the thoracic cage.
- The scapula will tilt anteriorly to place the pectoralis minor in a preferential position to aid in elevation of ribs 2-5.
Interestingly, these are the postural alterations most commonly seen clinically in individuals who demonstrate shoulder dysfunction. Therefore, prolonged sitting and working on a computer may be looked at as merely perpetuating the forward head and shoulder patterns rather than being the driving force that actually initiates these patterns. These neuromechanical causes of the forward head and shoulder positions will include:
- Inhibition of the muscles that control upward rotation and posterior tilting of the scapula (primarily the serratus anterior, upper trapezius and lower trapezius) secondary to cervical or thoracic nerve irritation.
- Improper respiratory mechanics favoring utilization of the pectoralis minor and scalenes over the diaphragm and intercostals for thoracic expansion.
- Reflexive inhibition of the shoulder stabilizers secondary to weak foot intrinsics, decreased ankle dorsiflexion and/or poor core stability. Although the discussion of respiratory mechanics is beyond the scope of this article, no movement pattern can be considered ideal until respiratory mechanics are normalized.
Improving Shoulder Function
Improving shoulder function must begin with improving stabilization and upward rotation of the scapula. Isometric contractions are stressed in the beginning corrective phases for five important reasons:
- Isometric contractions are performed sub-maximally as the goal is to improve the stabilization function of the inhibited muscle.
- Sub-maximal isometric contractions place the least amount of stress upon the inhibited muscle and surrounding joint structures.
- Isometric contractions increase the sensitivity of the muscle spindle and therefore improve proprioceptive feedback to the CNS.
- There is a strength increase of 15 degrees in either direction during isometric contractions. For example, an isometric contraction held at 150 degrees of shoulder abduction will improve strength from 135 to 165 degrees.
- Isometric contractions will best isolate the inhibited muscle. Concentric and eccentric contractions will preferentially recruit the strong muscles while the inhibited muscles will remain less active.
As with all exercises, stress quality over quantity. The scapulae and thorax must remain neutral during each of the movements described below.
The client lies on his back with the spine in a neutral position. To prioritize the serratus anterior, the arm is lifted straight overhead with the elbow locked and the palm facing up. Depending upon the client’s available pain-free range of motion, the client pushes into either the side of a bench, stability ball, foam roller or the floor with 25 percent of his maximum strength and holds this position for five to 10 seconds for five repetitions (see Figure 1). To prioritize the lower trapezius, the arm is abducted to approximately 135 degrees with the thumb side of the hand facing towards the floor. The client pushes into a bench, ball, foam roller or the floor with approximately 25 percent of his total strength and holds this position for five to 10 seconds for five repetitions (see Figure 2). Remember the goal of these isometric holds is to activate the low level stabilization fibers so ensure that the contractions are sub-maximal in nature. If the range of motion increases and is pain free, the percent of effort may be increased by 10 percent with each successive repetition.
|Figure 1. Serratus Anterior
||Figure 2. Lower Trapezius Isometrics
Once the individual demonstrates control of the serratus anterior and lower trapezius with proper diaphragmatic breathing in the supine position, the client is moved into the upright position to challenge the scapula stabilizers during arm movements. The client faces the wall with his arms at shoulder height and pinky side of the hand resting against the wall (see Figure 3). The client activates his core and steps toward the wall as he slides his arms up the wall in a “V” type position (see Figure 4). The client returns to the starting position by eccentrically controlling his arms as they are lowered. Perform 10 to 20 reps before moving on to the next progression. The trainer must place his or her hands on the scapula to monitor for proper upward rotation during arm elevation and eccentric control as the client lowers his arms.
Figures 3-4. Wall slides (facing the wall)
For increased focus on the serratus anterior, the client stands with his back against the wall. His feet are about 12 inches from the wall, and the thorax is stabilized over the pelvis. Do not allow the individual to arch his back away from the wall. The hand is placed next to the head with the elbow in line with the hand and shoulder (see Figure 5). The client inhales and slides the hand up the wall. The arm is returned to the starting position by eccentrically controlling the descent of the upper extremity. The arm is raised only to the point at which the shoulder, elbow and wrist remain in a straight line (see Figure 6). Perform 10 repetitions. The trainer must place his or her hands on the scapula to monitor for proper upward rotation of the scapula during overhead motion and eccentric control during the lowering of the arms.
Figures 5-6. Wall slides (back to wall)
This article has outlined the fundamentals of shoulder function and discussed several biomechanical and neuromechanical causes of shoulder movement dysfunction. Improving upward rotation and stabilization of the scapula are vital to restoring proper function of the upper extremity. The next article in this series will cover several upper extremity patterns designed to integrate the scapular upward rotators into functional movement patterns and restore pain-free function in any of your clients experiencing shoulder issues.
- Liebenson, Craig. Rehabilitation of the Spine. 2nd Edition. Lippincott Williams and Wilkins, Baltimore MD, 2007.
- Osar, Evan. Complete Core Conditioning DVD. Fitness Education Seminars, Chicago, IL 2007.
- Osar, Evan. Complete Rotary Conditioning, Fitness Education Seminars, Course Handouts, Chicago IL, 2007.
- Osar, Evan. Complete Shoulder and Upper Extremity Conditioning, Fitness Education Seminars, Chicago IL, 2005.
- Roskopf, G. Muscle Activation Techniques. Upper Body Function, Course Handouts, Muscle Activation Techniques, Greenwood Village CO, 1999.