The Shoulder joint in Sports
The shoulder joint is a ball and socket joint involved in sports requiring overhead movements such as throwing, swimming, tennis, gymnastics to name a few. Hence, it is a very mobile joint with a wide range of motion. The structures that hold it in place are:
1) static structures – tense bands of ligaments and capsule that hold and encase the ball and socket joint in place
2) dynamic structures – the muscles that span the joint on all sides (like rubber bands) enervated by nerves that control motion between the neck, shoulder blade, trunk, shoulder and arm
When engaging in sports requiring force and repetition, it is crucial that there is an intricate balance between these static and dynamic structures to
1) maintain stability
2) prevent excessive translation of the ball on the socket
3) avoid subluxation or dislocation.
Such integration requires muscular coordination, strength, endurance, flexibility and neuromuscular control not only of the shoulder, but the trunk, shoulder blade and other parts of the body. A deficiency in any of these can result in shoulder instability, increased risk of injury and less than optimal performance.
Muscle fatigue is an important factor to consider as it diminishes the stabilizing effects of the dynamic structures. The rotator cuff muscles which are the key dynamic stabilizers of the shoulder joint are found to be active throughout the entire throwing motion with activity levels peaking at the cocking phase. Fatigue would lead to reduced muscle coordination and control resulting in excessive movement of the ball in the socket and stress on surrounding structures. Consideration should be made towards
1) pre-season screening and conditioning
2) adequate rest and recovery after training and competition
3) thorough post-injury rehabilitation
4) eccentric (resistance applied to muscle as it is lengthening) endurance training for the rotator cuff muscles