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Woman Lifting Weight
The Complexity of GH Joint Stability
by: Dr. Steve Young

What does the typical chest workout consist of? Typically it consists of three sets of flat bench, three sets of incline bench, three sets of flys, and three sets of dips. This type of training leads to bigger muscles now, but what is it really doing to your joints? Unfortunately, many people involved in weight training will experience some type of shoulder pain in their 30’s or 40’s. With smart training, you can avoid the pain and inability to weight lift from a rotator cuff tear, bursitis, impingement, or inflammation. In this article, I will elaborate on the anatomy and biomechanics of the glenohumeral (GH) joint and how to train without injury or accelerated joint degeneration.

The Acromioclavicular Joint (AC)

The AC joint at the shoulder is where the clavicle (collar bone) connects with the shoulder blade at the Acromion. The two joints are connected by ligaments and an articular disk. The articular disk goes through wear and tear with repeated overhead lifting and excessive shoulder extension. Common exercises that typically accelerate AC joint degeneration include dips and shoulder presses. Over time, the joint becomes arthritic and painful with touch, reaching across the body, and with overhead lifting.

The Scapulothoracic Joint and Glenohumeral Joint

When referring to the shoulder, one has to consider mainly the Scapulothoracic joint (the shoulder blade in reference to the posterior aspect of the ribs) and the GH joint (the actual ball and socket joint of the shoulder). During any large shoulder movements, the GH and scapulothoracic joints must work in synergy for proper joint mechanics. Typically, the first 30 degrees of shoulder elevation is achieved through the GH joint only. After 30 degrees, the scapula (shoulder blade) will upwardly rotate in a ratio of 2:1 with GH joint elevation. This important mechanism (scapulohumeral rhythm) and synergy must occur to avoid problems in the GH joint.

Shoulder JointIf normal scapulohumeral rhythm does not occur, the ball of the joint will elevate and rub against the undersurface of the Acromion. The area under the Acromion and the head of the Humerus contains many soft tissues such as the GH joint capsule, the rotator cuff tendons, a bursa, and the long head of the biceps. So, if the head of the Humerus rubs the Acromion repeatedly, inflammation, tearing, or bone spurring can occur. Under normal conditions, we have muscles that minimize the superior translation of the head of the Humerus on the Glenoid (i.e. the ball of the socket joint does not go up and hit the Acromion bone).

The Active Stabilizers

The four (RTC) rotator cuff muscles (Supraspinatus, Infraspinatus, Subscapularis, and Teres Minor) in the shoulder work to keep the head of the Humerus down during shoulder elevation. The Supraspinatus initiates initial abduction (arm going out to the side). The Infraspinatus and Teres Minor externally rotate the shoulder joint while the Subscapularis assists with internal rotation. During active arm movements such as the bench press, the RTC muscles work together to actively keep the GH joint stable. If excessive rotational forces or weakness in the RTC muscles occur, the head of the Humerus will move superiorly and impinge with the Acromion. This motion is what leads to impingement and RTC tears. Minor adjustments in technique with all pushing exercises can minimize the impingement effect.

Weight Room Mistakes

The answer to minimizing joint pain and degeneration in the shoulder lies in correct exercise selection and execution. With simple changes in body and hand positioning, the adverse forces applied to the shoulder can be largely minimized or avoided. The typical culprits that accelerate shoulder degeneration and arthritis include the bench press, shoulder press, and dips. With minor modification to these exercises, the risk of shoulder pain can be lessened.

Bench Press

The typical bench press technique starting from the wrist to the chest consists of: wrist extension, elbows half way out from the torso, and the bar traveling from neck to lower chest level as the bar descends. This technique is the most common because you can bench press the most weight with it. It allows more force contribution from the Deltoid and Triceps. There are several problems with this technique.

First, the wrist extension places the bar behind the elbow – draw a line from the bar down, and the line is behind the elbow. This places an external moment on the shoulder – the force of the bar wants to externally rotate the shoulder. This position places more force requirement and stresses on the RTC muscles to stabilize the shoulder. If the RTC muscles (especially the Subscapularis) are not able to accommodate the force requirement, then the head of the Humerus will travel up and make contact with the Acromion.

Secondly, the path of bar movement down to the lower chest level leads to shoulder extension instead of horizontal abduction. The fan shaped muscle of the Pectoralis Major is optimally taxed with horizontal adduction (i.e. the motion you make when you do a pec deck machine). With bench pressing to the lower chest level, the elbows are closer to the torso and the Deltoid takes more workload instead of the chest. So how do you correct the biomechanical mistakes and bench correctly?

The key to shoulder joint preservation during the bench press is technique and tempo. The wrists need to be neutral while gripping the bar. The bar should be directly over the wrist joint, not behind it. During the pressing motion, keep the bar inline with the shoulders. For example, the bar should make a straight line and be directly over the shoulders during the entire set. If you do this correctly, the bar should touch down at the Sternoclavicular joint (where the collar bone meets the sternum). From an overhead view, the bar, wrists, elbows, and shoulder should all be in the same plane of motion. When this happens, all rotational moments are excluded during the motion, and stability requirements of the RTC muscles are minimized. Once you have the technique down, work on the tempo. Try to perform the entire set without acceleration and pausing. Imagine a pendulum swinging at a 1 second pace (1 hertz). The bar should elevate and descend at one-second intervals without pause at either end and without acceleration. This takes some practice. I would suggest starting with a much lighter weight and perfect the technique first.

Shoulder Press

If you took the time to read the above, you’re in luck .The same exact principles can and should be applied to the shoulder press. The wrists should be straight, and it, the bar, the elbows, and the shoulders should all be in the same plane. To preserve the AC joint, limit the bottom position to ear level. This will limit the tension and shearing forces on the AC joint. To tax the muscles optimally with the least amount of forces, follow the same tempo as the bench press.


Dips are great for overall chest, shoulder, and triceps development. However, they should never be performed with your feet forward on a bench and your hands behind you. (i.e. bench dips). That version of dips touted for triceps development is horrendous for your AC joint. Normal shoulder extension is limited to 30 degrees. When you do bench dips, the shoulder extends to 30 degrees and the rest of the motion comes from anterior tilting of the scapula. The scapula (shoulder blade) has to tilt forward because the GH joint itself will not allow you to go any lower. This motion places direct shearing forces on the AC joint. Repetitive shearing forces on the AC joint cause degenerative changes and arthritis. If you are performing dips on a V bar, lean forward 45 degrees to avoid the excessive shoulder extension movement. Do not stay totally upright like most pictures in magazines and even on the V bar machine itself illustrates. The tempo for dips should be the same as the bench press. If fact, that tempo can be used for all exercise to minimize joint forces and optimize muscle tension.


The above techniques do not apply if you are training for power lifting or athletics. The goal of the techniques is to tax the muscles and make them grow with the least amount of joint stress. It can be viewed as a muscular workout, not an ego workout. If applied correctly, you can work your muscles harder with 30-40% less weight. Overtime, your joints are exposed to less stress and degeneration.