While sometimes it may not feel like it, your shoulders are the most flexible joint in your body. The joint is formed by the union of the humerus, scapula (or shoulder blade) and the clavicle (or collarbone). While we normally think of it as a single joint, it is actually three joints
- glenohumeral joint
- sternoclavicular joint
- acromioclavicular joint.
These three joints work together to allow the arm both to circumduct in a large circle and to rotate around its axis at the shoulder. As with most joints it is stabilised by ligaments. However the shoulder joint is unique in that it is strengthened posteriorly and superiorly by the rotator cuff muscles, which act as "active and relaxable ligaments". Unlike most joints which have a high degree of passive stability the shoulder joint depends largely on the active stability of the rotator cuff muscles. As soon as you move your arm joint stability is provided by the rotator cuff muscles alone. The muscular action of the joint is more complex to move the joint in numerous directions.
This design of the shoulder joint makes it the most flexible joint giving us a high degree of mobility & power. This great range of movement comes at the cost of reduced stability. A key benefit of the design is it does reduce the risk of arthritis in the shoulder when compared to other joints.
Given the additional importance of muscles in shoulder's design when in the gym, it is important to:
- Work all joint articulations - if it moves that way, strengthen it.
- If you do a pushing exercise, counter it with a pulling exercise.
- Always use proper exercise form - control the resistance.
And don't neglect the smaller stabilizing shoulder muscles that make up the rotator cuff. Spend time fortifying them via internal and external rotation exercises with the upper arm at various positions.
