The Shoulder

Unlike any other non-contact field based sports, contact sports like rugby (both codes) places an incredible amount of force and trauma on the shoulders of the athletes that play them. Typical accelerations on the field can be over 2.5m/s/s, players can easily weigh above the 110kg mark, and running speeds often reach above 30kph. Running at this speed, with that momentum to stopping in a fraction of a second leads to forces of above 270N and an average of 22G. And the shoulder deals with a large proportion of these forces! Just to add a bit of context a 30mph car crash creates roughly 30G in a one off event. You are involved in more than one tackle per game (unless you play in the halves….)!

Over this programme, our interactive injury prevention E-book will give you all of the tools to get yourself in a great position to prevent any shoulder injuries or get you back on track if you have had trouble with your shoulders in the past.

The shoulder can be seen as quite a complex region of the body. Developing strength and range of movement in the shoulder complex and having the ability to control both qualities will create a robust shoulder to use on the rugby field.

When we talk about the shoulder we are talking about the union of the humerus (upper arm), clavicle (collar bone), scapula (shoulder blade), and the thorax (rib cage) and all the soft tissue that connects them. Due to the interaction of all these bones and structures the shoulder complex actually involves 4 joints; the gleno-humeral joint, acromio-clavicular joint, sterno-clavicular, and scapulo-thoracic joint.

The gleno-humeral joint is what you would describe as the true shoulder joint, the one with the greatest available range of movement. The range of movement the shoulder has was a key evolutionary advancement for humans when we went from a quadruped (on all fours) to bipedal (two footed) gait and allowed to us to interact with our environment in a fuller manner giving us the ability to manipulate and reach objects with our hands. And then, we created Rugby!

The gleno-humeral shoulder joint is a ball and socket joint, just like your hip, but the shoulder has sacrificed stability for range of movement. So unlike the hip the shoulder socket is far shallower which is why on occasion the stabilisers we do have, fail. As a result we suffer shoulder subluxations and dislocations of the shoulder far more frequently than we do for the hip. The primary stabilisers of the joint are the ligaments and the shape of the joints just like in other joints of the body but the muscular secondary and tertiary stabilisers of the shoulder are especially important due to the joint’s lack of bony stability.

The Glenohumeral Joint

Primary Stabilisers

The primary stabilisers of the gleno-humeral joint can be summarized as the architecture of the gleno-humeral joint where you get the convex surface of the humerus held in place by the bowl like shape of the concave glenoid cavity of the scapula. The cavity is deepened slightly by a cartilage ring around the socket that is called the labrum. The glenohumeral ligament complex further supports this joint, within this ligament complex you have 3 ligaments;

Superior Glenohumeral Ligament

Middle Glenohumeral Ligament

Inferior Glenohumeral Ligament

Secondary Stabilisers

Within the shoulder there are some key players to be aware of that will help stabilise and secure the shoulder in its socket. The shoulder is heavily reliant on muscles to stabilise the joint due to the reduced stability it has. The muscles that cross the shoulder joint all work together to keep the head of the humerus where it should be – in it’s socket. The relative contribution of each muscle across the shoulder will vary depending on the position of the arm relative to the body and the load that it has to control.

The rotator cuff is a key stabiliser of the shoulder; a group of four local stabilizer muscles that sit around the shoulder joint. These muscles are responsible for securing the humerus in the joint of the shoulder. It is comprised of four muscles, the supraspinatus, infraspinatus and teres minor muscles that all sit on the posterior (back) aspect of the joint, and the subscapularis that sits at the front of the joint between the scapula and the torso.

Tertiary Stabilisers

There are also a number of other key muscles and structures that help the mechanics of the shoulder and add tertiary stability. A few of these will be familiar to you. The Levator Scapulae, the upper, middle and lower trapezius, the rhomboids on the posterior (back) aspect of the body that influence the scapula and its movements, the Serratus anterior that crosses from the back of the scapula to the flank of the body, the Latissimus Dorsi, the deltoids, pectoralis major and finally the pectoralis minor muscles that move and stabilise the humerus and scapula. Moving down into the upper arm, we will find the biceps, triceps and corracobrachialis that also influence the shoulder complex.

The Acromio-Clavicular & Sterno-Clavicular Joints

Both of these joints sit on each end of the collarbone (clavicle).

The Acromio-clavicular joint (ACJ) joins the clavicle to the acromium process of the scapula (shoulder blade). The joint is supported by a number of ligaments;

Coraco-clavicular

Acromio-clavicular

This joint can be particularly susceptible to injury when you suffer a heavy impact directly on the joint when the arm is by your side.

The Sterno-clavicular joint (SCJ) sits at the opposite end of the clavicle joining it to the sternum, close to the midline of the body. This joint is supported by the following ligaments;

Sterno-clavicular ligaments; anterior and posterior

These two joints, ACJ and SCJ both work together to allow the arm to be coupled to the shoulder blade. The coupling of the arm to the shoulder blade further adds to the arms ability to move through full ranges of motion. In fact as your arm moves above 90° from the vertical the clavicle has to rotate backwards to allow the movement to happen.

The Scapulo-Thoracic Joint

The scapulo-thoracic joint describes the joint between the shoulder blade and the thorax. This joint rarely suffers from direct impact related trauma but it can be implemented in conditions like shoulder impingement and tendinopathies in the shoulder. It can contribute to these conditions due to poor force coupling between the muscles that act on controlling the position of the scapula during movement of the arm.

I’m sure you can now start to appreciate just how wonderful your shoulders really are. Wonderful and complex! But complex doesn’t mean complicated– a well rounded program will give you the opportunity to develop strength and range of movement and the ability to control the two in the rugby environment.

Joint Ranges of Motion

All of the joints described above work together to allow the shoulder to move through wide ranges of motions. The available movements available at the joint are;

Gleno-humeral Joint

Flexion

Extension

Abduction

Adduction

Internal Rotation

External Rotation

Scapula

Upward Rotation

Downward Rotation

Protraction

Retraction

Any loss of range or poor control of any of these movements could lead to repetitive overload or compensatory movements.

Putting it all together

When we consider all of the joints of the shoulder, the different levels of stabilisers and muscles around the joints we need to consider all of their contributions to normal joint motions.

The shoulder is heavily reliant on force couples. A ‘Force couple’ describes phases of movement that all have varying contributions from different tissues to achieve the desired motions. All joints rely on balance between the muscles that act on them to work and move efficiently but for the shoulder, balance is especially important due to the movements of the scapula, humerus and clavicle that all contribute to the overall movement of the upper limb. This is similar in a lot of ways with the muscles that act on the back, which also need balance across the numerous joints and muscles of the spine.

A very important consideration when training the shoulder is the health and the positioning of the neck. Many of the muscles that influence the shoulder can also directly or indirectly influence the neck. The neck musculature already has a 4.5-5kg head to manage; they shouldn’t have to work for the shoulder too. Whenever you are training we would advise a neutral position for the head and neck. An overly protracted (pointing) chin or overly retracted (tucked) chin could lead to trouble. Find a comfortable mid point and control your breathing and your trunk stability throughout your lifts.

An unbalanced training programme can lead to imbalance across the joints that make up the shoulder. Some of these will be discussed in more detail in the next chapter but for a healthy shoulder your training needs to have an appropriate balance of push and pull exercises, horizontal and vertical movements, upper body, lower body and full body exercises and of course, appropriate loading vs appropriate recovery.