28 April 2020
Shoulder mobility- do you have scapula rhythm?
The shoulder is a complex structure. It is made up of 3 joints that allow us a great deal of movement.
The biggest of these is a ball and socket joint, similar to the hip joint, but with a few differences. The socket is a lot shallower than the hip, this is to allow for more range of movement (ROM). However, the sacrifice for more ROM comes at a cost of less stability. But, the body is very clever and has adapted to allow as much ROM as possible with the most amount of stability possible. It achieves this through small muscles called the rotator cuff, through its ligaments, and through a collar of cartilage called the labrum.
When our ancestors began walking on two legs on the plains of Ethiopia, 3.2 million years ago, things had to change. The angles of hip joint had to change. The pelvis became narrower. And the hip joint became deeper because it was now taking the full weight of their bodies. Shoulder mobility was necessary to return to the safety of the trees at night.
During that time, our ancestors developed tools and weapons for hunting, they needed good shoulder mobility to throw the spears and catch their dinner. The shoulder joint became less of a weight bearing joint, and more functional and mobile.
These days I am willing to bet that you don’t sleep in a tree or throw spears. I would say that 98% of the time your shoulders are below 90 degrees. We aren’t getting the full 180 degree range of shoulder mobility and strength that we would have had when hanging from branches.
As you can see from the picture, sitting at a desk causes our upper backs, shoulders and necks to become restricted. The muscles around the shoulder and chest will become chronically shortened, affecting our scapula rhythm.
As the diagram shows, when the arm moves to an over head position of 180 degrees, 120 degrees of that movement comes from the ball and socket joint. The remaining 60 degrees comes from the movement of the shoulder blade (scapula). For every 2 degrees of movement at the joint, there is 1 degree of movement at the scapula. That means that the rhythm is 2:1.
But as I mentioned before, if we sit at a desk for hours, the muscles around the shoulder blade will become shortened and contracted. This will affect the 2:1 rhythm. When the shoulder blade is not doing its fair share of the work, then the shoulder joint has to compensate. If left alone, this could lead to more serious injuries of the shoulder. So it is vital to address the movement of the scapula before injury happens.
As Osteopaths we are trained to assess the movements of the shoulder complex. We will check the scapular rhythm. Through treatment we will address the complex interplay between the shoulder, thoracic and cervical spine by working on the joints, muscles, and tendons. We will then prescribe exercises for you to help maintain a healthy shoulder.
One such exercise is the ‘passive hang’. This is best performed before you have a shoulder injury. Performing it when injured may cause pain. But performed regularly ‘ hangs’ can be of real benefit to the shoulder.
As the name suggests you need to find a stable horizontal bar at home or the gym where you can reach both arms above your head and simply hang in that position. If you can’t support your entire weight yet, modifications can be used. For example, a chair under the feet in order to offload some of the weight.