At Least Your Shoulder Has Rhythm

Regardless of your musical ability, one part of you has at least a little bit of rhythm. Your Scapulohumeral joint, or where your humerus meets your scapula at the glenoid fossa, moves in synchronous harmony every time you move your shoulder.

This dance of the upper extremity allows for the best opportunity to have the greatest range of motion in your shoulder. The dance is a simple 1-2 step. When you abduct your shoulder your scapula tilts up one degree at a time. For every 1 degree it moves, the humerus can flex 2 degrees.

Now don't run off but we are going to do some math to really let this sink in. If our shoulder can abduct 180 degrees, remembering our 1-2 step would mean that 120 degrees of that motion would be from the humerus and 60 degrees would be from the scapula. Now, that's what I call team work. 

This scapulohumeral rhythm is important for two main reasons. 

The first one has to do with the fact that the scapula is a little bit of an oddly shaped bone. It has two extensions that come off of it right by the glenoid fossa, the acromion and coracoid process. These two bony landmarks are extremely important for attachments to your clavicle and a bunch of shoulder muscles, but they can sometimes get in the way of shoulder abduction. To prevent your humerus from sliding right off the glenoid fossa and impinging on the acromion, the scapula has to tilt. This small tilt helps the head of the humerus remain in contact with the glenoid fossa as it continues to increase in abduction. 

The second reason your shoulder has rhythm is to maintain the length-tension relationship  of muscles in your shoulder. As you abduct your shoulder muscles like the deltoid are concentrically contracting, or shortening. Without the scapulahumeral rhythm, the muscles would not be able to shorten completely and maintain the motion required for shoulder flexion, decreasing the available range of motion. 

If our shoulders didn't have any rhythm not only would putting your hands in the air and waving them like you just don't care but difficult, it might even be painful or lead to injury. Without the tilt of the scapula to support shoulder abduction, a client would experience impingement between the humerus and acromion, this would cause pain during abduction and might lead to swelling or even tearing. 

This lack of rhythm can happen in individuals with weak rhomboids causing scapular winging or poor coordination between the muscles in your shoulder like the rotator cuff muscles, trapezius or even the pectoralis muscles. So when you are the gym, don't pick favorites, make sure to work or stretch them equally to maintain proper body positioning. 

The moral of the story is, everyone has a little bit if rhythm in their bones.