Scapulo-Thoracic (Shoulder) Complex - Rhythm Matters

Like the hips, the shoulders are a woefully misunderstood part of the body. The shoulder, or glenohumeral joint (GHJ), is a combination of the shoulder blade (scapula) and the humerus (upper arm bone), and even the clavicle (sort of). The GHJ has the highest range-of-motion of any other joint in the body and it is because of the way the scapula moves to accommodate the rotation, flexion, and extension of the arm. The reason we are talking about the shoulder today is to highlight the importance of the scapula itself in anything that your upper body does, from putting dishes up on a rack to doing a weighted pushup or bench press.

In the current highly-ergonomic nature of society, the arm does not necessarily need to access high ranges of motion to accomplish most daily tasks, which means the scapula isn’t moving much. As is all things in the body, the movement of the scapula is use it or lose it. If you’ve been training with us for longer than 120 seconds, we’ve probably told you to draw the shoulder blades down and back in a lot of exercises. But why? Get ready for a quick anatomy lesson!

Scapular Movement IS Shoulder Movement

Take a look at Figure 1 below. The glenoid cavity is the seat where the humerus rests its funny little head and is why the GHJ is called a “ball and socket” joint, where the scapula is the socket. If the scapula moves, the entirety of the shoulder moves with it. You can also see that the head of the humerus and the glenoid cavity have cartilage that protects the joint from excess friction - we are only born with so much cartilage and it will deteriorate with age and use. That deterioration is accelerated by poor

mechanics, which are exceptionally common when someone first begins training.

Figure 1: Anatomy of the glenohumeral joint

To answer the question of why we keep the shoulder blades down, we have to consider what is happening when the scapula moves. In Figure 2, you can see the four different actions of the shoulder blade, which inevitably produce movement in the humerus: 

•  Depression is when the scapulae slide down the back of the ribcage and elevation is the upward slide. 

• Protraction is when the scapulae slide away the spine, and retraction is when they slide toward the spine. 

• Winging, or rotation is when the scapulae slide by rotating up or down, and has components of both protraction and elevation (similar muscles work to help). 

Figure 2: Scapular Actions

When we are trying to do pulling exercises, we want to make sure that the scapulae are not getting in the way of the humerus trying to move. Due to lack of use, many of the smaller muscles that create the scapular action we want are weak and the body will instead compensate by using larger muscles, like your trapezius muscles (AKA the traps, the big muscle on the upper back and shoulders). If you are pulling, and feeling it in your traps, you are likely compensating and causing an accidental scapular elevation, when we instead want depression. The depression of the scapula moves the GHJ in such a way that the humerus experiences the least friction forces and allows the appropriate muscles to be targeted, strengthened, and reduce the likelihood of cartilage damage. In an exercise like the bench press which can get very heavy, if you are compensating through the traps then you are significantly more likely to see injury in the shoulder. That is why we are always emphasizing your shoulder blade position, every degree of movement matters here!

Coordinating the Scapula - Feel the Rhythm

We call the coordinated movement between the scapular, humerus, and all associated muscles in the shoulder joint “scapulohumeral rhythm”. This coordination is usually poor for someone who has not practiced it - a keyboard and driving a car don’t exactly tax these areas. So when we train, we try to create awareness of what this rhythm feels and looks like by doing different exercises that isolate the scapula: 

• Scap Retractions/Pulls - practicing retraction on the TRX or rings

• Scap pushups or Pushup Plus - practicing protraction in a pushup position or bear crawl position

• Scap Pullups - practicing winging and depression with the arm overhead while hanging on a bar or using the lat pulldown machine

  
  

Click to see the exercise examples

These are just a few examples of exercises you may have done or will do at some point in your training, but we are always trying to bring awareness of what is happening. This can take weeks, months, or even years to master, but the time taken to master scapulohumeral rhythm keeps you safe, strong, and doing it for years to come! 

Image References: 

• Cambridge Shoulder. (n.d.). SLAP tears. Cambridge Shoulder 

• BodyParts3D. (n.d.). Anterior view of human skeleton showing scapular location [Digital image]. Tennis Fitness Love. https://www.tennisfitnesslove.com/2016/11/scapular-exercises-for-the-health-of-your-shoulders/ (Original work licensed under CC BY-SA 2.1 JP)