Although it’s designed to facilitate movement, the shoulder joint is unique due to its requirement of stabilizing structures. In addition, since it is a relatively small muscle group, the shoulder is more prone to stress.
Just sitting at your desk in class can add tension, so sports movements like pitching a baseball, serving a tennis ball or swinging a golf club can be a major challenge—especially if your shoulders or their stabilizing structures are weakened. Shoulders are essential for sports movements, so weak shoulders are an athlete’s worst nightmare.
This scenario is easily preventable as long as the shoulders and their stabilizing structures are well cared for. (See Build Balanced Shoulder Strength.) Here’s a look at the various stabilizers of the shoulders.

Bones

The shoulders are comprised of the humerus (upper arm bone), scapula (shoulder blade) and clavicle (collar bone). These bony connections look like a golf ball on a tee. Alone, they provide very little stability.

Joints

The shoulder contains three major joints—glenohumeral, acromioclavicular and sternoclavicular—which work together to allow the arm to move in all directions.

Ligaments

These tough fibrous structures connect the shoulder bones and joints together. Several ligaments—above, below, in front of, and behind the joints—stabilize the shoulder at rest.

Shoulder Joint Capsule

While also a fibrous structure, the capsule is more flexible than a ligament. It completely surrounds the joint instead of providing small strategic connections of the ligaments. It’s loose enough to allow the shoulder to have a wide range of motion, allowing the bones to separate by as much as an inch.

Labrum

The labrum is a cuff of cartilage ringing the outer portion of the scapula where the humerus connects. It forms a cup for the end of the arm bone to move within, making the shoulder socket deeper and providing more surface area, wider range of motion and stability.

Scapular Muscles

The scapula has 16 muscular connections. They don’t all attach directly to the joint, but even those that don’t are secondary stabilizers to the shoulder. Some assist with stabilizing the neck and secondary respiratory muscles—and even aid in swallowing.

Rotator Cuff

When a shoulder is injured, it’s often a torn rotator cuff. This a bit misleading, because the rotator cuff is really four muscles; and when someone has a “torn rotator cuff,” it’s usually just one torn muscle out of the group. The main jobs of the rotator cuff are to create stability and to place the arm in the proper position to rotate. To perform these jobs, the muscles of the rotator cuff need to be balanced in strength and flexibility. (See How to Keep Your Shoulders Healthy, Part 3: Rotator Cuff Strength.)
When the labrum is intact and the rotator cuff muscles are working properly, a suction force is created that assists in holding the arm bone stable against the scapula.

Outside Influencers

Many other bodily functions and parts provide stability for the shoulder, including:

Breathing

Improper breathing adversely affects the shoulder by changing the shape of the rib cage, changing the position of the scapula and inhibiting correct function of the shoulder muscles. Breathing should come from the diaphragm, creating a small expansion outward, not a raising of the rib cage or a stiffening of the neck, which is an improper pattern. Fixing breathing patterns is a good place to start stabilizing the shoulder, and working on breathing is best performed while training other muscles.

Thoracic Mobility

An inability to move at the thoracic spine (mid back), especially extension and rotation, puts the muscles of the shoulder in a disadvantageous position and functionally weakens them. It’s a tricky issue with 12 different segments. Many times one end of the chain is stiff and the other is loose.
Thoracic rotation can be fixed in multiple positions and should be. For general mobility of the thoracic spine, foam rolling is a great technique. You can also try this simple way to begin any rotational exercise:

• Stand up and lock your hands behind your head
• Begin rotating your upper body toward the ceiling

Imbalances in Shoulder Mobility

Throwers and golfers tend to be unbalanced and asymmetrical. They perform such violent rotational movements at the shoulder that one side of the joint gets plenty of mobility and the opposite side stiffens. The dominant shoulder in athletes, especially throwers and golfers, tends to excessively rotate externally (away from the body), which, if unchecked, limits the motion of the posterior capsule (back of shoulder) and the shoulder’s ability to rotate internally (towards the body). (Read How to Keep Your Shoulders Healthy, Part 1: Mid-Back Mobility.) Athletes do not need to be mirror images, right to left. Rather, they need comparable amounts of strength and range of motion when measuring one side against the other. The side lying sleeper stretch, passive internal rotation stretching and crossed arm horizontal stretching are effective for this.

Non-Traditional Shoulder Strengthening

Strengthening the shoulder can be difficult, but it’s essential to make the shoulder both strong and functional. Think outside the box when working to maximize effectiveness. The key to non-traditional strengthening exercises is to avoid strengthening muscles only once in an early rehabilitation phase. Instead, focus on training the rotator cuff and scapular musculature to perform their other important function of stabilizing the humeral head dynamically.
Options include:
Manual resistance with PNF patterns.
Single arm cable strengthening versus standard tubing or band exercises.
Photo: jimmysmithtraining.com