The Shoulder Muscle: Basics, Training and Treatment.

The first part of this piece will give you a basic understanding of how the shoulder muscles work. The second part is a little more detailed for those that want to better understand the anatomy.

The Basics of Shoulder Function

The shoulder is the most mobile joint in the body. In this blog, we look at how the muscles in the shoulder work to provide us with strength and mobility in this joint. We will also examine why we can get shoulder pain. Then, we’ll delve into a little more detail for those that want to better understand the anatomy of the shoulder.

The most prominent muscles of the shoulder are the deltoid and the rotator cuff. The deltoid is the power house. It produces the force behind large amplitude shoulder movement. The rotator cuff has four smaller muscles. It provides stability to the shoulder. It also helps us to control movement at this joint (glenohumeral joint AKA GHJ). It may be easier to liken this to a car. The deltoid is the motor that powers the car along. The rotator cuff is the steering wheel which helps us to guide it in the right direction.

The “Powerhouse” Muscle

The main factors that allow the deltoid to work as the power house are as follows:

It is a large, broad muscle;
It attaches to the arm (humerus) about a third of the way down the arm. This means it is able to produce more force than it would if it attached at the very top of the arm; and
Its attachment is a ‘V’ shape and covers a large area, kind of like a hand gripping a club.

The Rotator Cuff

The rotator cuff muscles are more refined. They attach over a much smaller area at the very top of the humerus. The shoulder is a ball and socket joint (GHJ) with a small socket and ball that sits on top, like a golf ball on top of a tee. These muscles attach to this ball. They control and refine movement at the shoulder to maintain control and stability.

So, can the rotator cuff muscles move the shoulder in the same way as the deltoid? Well, the reality is that these muscles try to take over when the deltoid is weak. But, they are not very efficient at doing so. There are two reasons for this. The muscles and their attachments are small and they attach right at the top of the humerus. As a result, they cannot produce the same amount of force as the deltoid.

The Shoulder and Strength Training

It is not uncommon to see people training their rotator cuffs at the gym. Before you do this, ask yourself a few questions. “Is my shoulder sore because my rotator cuff is weak? Or is it sore because my rotator cuff is trying to take on more load than should?” In some instances, it is often the case that the deltoid is actually the weakened structure. It’s a bit like a lazy colleague that isn’t doing its fair share of the work. The rotator cuff muscles become sore and remain that way because they are trying to pick up the slack. They are simply overworked.

Strengthening the rotator cuff muscles when the deltoid is weak can set people up to fail. By doing this we:

Ask our rotator cuff to perform tasks that it is not designed to do;
Teach ourselves to move with poor biomechanics; and
Continue to work on a structure that may not even be the cause of the pain.

If you’ve been suffering from shoulder pain and haven’t gotten results you’ve wanted, come down and see us. Our approach to shoulder pain targets the compromised tissue. So doing, it reduces your symptoms and allows you to improve your strength and mobility.

Let us treat your pain so you can train!

A More Detailed Explanation

The Muscles

The Deltoid has three components that cover the shoulder joint, like a hood:

An anterior component at the front of the shoulder which helps us to lift our arm up in front of us (flexion);
A middle component on the side of the shoulder which helps us to lift our arm up to the side (abduction); and
A posterior component at the back of the shoulder that helps us to push our arm behind us (extension)

The rotator cuff provides us with stability and movements that do not need a great deal of force. The muscles themselves attach underneath the muscle belly of the deltoid. This then encapsulates the GHJ like a hood. The rotator cuff is the four following muscles:

Supraspinatus – External rotation and stability through abduction
Infraspinatus – External rotation
Subscapularis – Internal rotation
Teres Minor – External rotation and adduction

The Muscles in Motion

Essentially, the deltoid will lift your arm up either in front of you, behind you or to your side. Once your arm is where it needs to be, the rotator cuff plays a role in producing some of the finer movements. It also provides the required stability to do things like screw in a light bulb or reach for a jar at the back of the cupboard on the top shelf.

Luke O’Neill is a physiotherapist with a keen interest in treating the upper body. He has dealt with his own injuries in the past. And he understands the frustrations of not getting results from treatment and training. He has undertaken specialized training in the USA to allow him to bring a unique approach to treating problems of the neck and shoulders.