In my opinion, anterior -superior shoulder migration is the most common posture abnormality among tennis players. And there is a good reason to be so, but on the other hand, this also can be a major cause of shoulder joint aches and pains.
What is a shoulder anterior-superior translation?
* example of the left shoulder in anterior migration
It is a position in which a glenohumeral joint is not properly centered in the glenoid fossa. In a normal situation, the ball is kept in the center of the socket by the ligaments and rotator cuff tendons.
During the regular postural assessment, it is possible to control the position of the GH joint while an athlete is standing in front of you. As you can see in these two pictures in the middle, the center of the shoulder joint is moved forward. The posture plumb line is an imaginary straight line from the top of the head to the floor. Good posture represents our ears, shoulders, hips, knees, and ankles stacked up along this line.
But the question is, can we look for a perfect plumb line in our tennis athletes?
My straight answer is no. Why? Because of the repetitive nature of the sport where there is present overuse of some muscles and tissues at the expense of others.
During all tennis strokes, there is a domination of the pushing over pulling movements, adduction over abductions, and internal rotations over external ones.
In this slow-motion video is easy to notice another important factor, there is no real use of a stretch-shortening cycle before every shot. Every swing is starting from almost a dead start, which means there is present a violent concentric contraction of one tissue system, while antagonist tissues are working much more in decelerating or eccentrically to stop the momentum of the arm. As these gestures are repeated many times during practice and matches, it is normal that some adaptations of the tissues, joints, and eventually posture will occur with time.
The tissues that are more concentrically stimulated have a predisposition to become short and stiff with time, while those that are eccentrically stressed become elongated and weak.
Regarding the tennis player’s shoulder joint, there is a constant battle between tissues that are responsible for extension/adduction/internal rotation versus flexors/abductors/external rotators.
And it’s not a fair battle at all, let’s have a look at shoulder Intra vs. extra rotators:
|GH INTRA ROTATORS
|GH EXTRA ROTATORS
Pecs and lats are big and strong muscles, prime movers, they have much better leverage to create force compared with infra and supraspinatus, teres minor. Because of that our training interventions must be adequate to balance these forces.
As we all already know there are four rotator cuff muscles. One of them is an internal rotator – subscapularis, the other three are external rotators of the shoulder joint – infraspinatus, teres minor, and supraspinatus.
Their main job is to keep the ball (head of the humerus) into the socket (glenoid). But these guys are playing a pretty unfair game with some other much more powerful muscles which can pull the shoulder joint out of the position – pec major and latissimus dorsi.
Moreover, it is well documented using MRI and CT scans that the humerus of the dominant arm is more retroverted than the non-dominant arm. This is a structural adaptation where humerus bone twists (torque effect) at the growth plate and causes permanent adaptations of the bones – humeral retroversion – this is called adaptation to imposed demand.
Shoulder anterior-superior translation is a normal finding among tennis players and overhead athletes in general. We can’t expect a perfectly positioned shoulder when athletes are continuously repeating movements that are causing permanent adaptations, both structural and functional. There is no exact formula for how much of this anterior-superior migration is a limit and when excited put someone in a more vulnerable position for injury. I worked with a tennis player with a hugely anteriorly positioned shoulder and yet no shoulder problem throughout their whole career.
What you can do is on a day-to-day basis control these important factors:
*photo: Neil Hallinan, CSCS, PRT