The shape of the scapula can vary quite substantially depending on your genetic makeup. This influences how well it fits together with the humerus at the glenohumeral joint & the associated ROM due to the amount of space or restriction as created by the shape of the bones. Because of the composition of this joint, it is important to note that when the scapula moves, the humerus also moves.
The scapula floats along the ribs as it moves, sometimes referred to as scapulothoracic movements. It elevates (moves up), depresses (moves down), protracts (moves toward the front of the rib cage), retracts (slides back & towards the other scapula), rotates upwards (moves sideways & up),& rotates downwards (moves sideways & downwards). As is often seen in plank pose, the scapula can also tilt, lifting its medial border off the rib cage & protruding from our back. Several muscles collectively aid in the variety of movements the scapula are capable of:
- The trapezius muscle, divided into upper, middle, & lower sections, covers a good deal of the upper back. The upper section is able to depress the scapula & all sections contribute to the upward rotation of the scapula.
- The rhomboid muscles, which sit between the shoulder blades, assist with downward rotation & retraction of the scapula.
- The levator scapulae can downwardly rotate & elevate the scapulae.
- Pectoralis minor, along the front of the rib cage, is a depressor & downward rotator of the scapula.
- Serratus anterior “the upper-cut muscle”, is attached to the jagged-line attachment on the side of the ribs in front of the scapula. It then goes between the scapula & rib cage to attach onto the medial border of the scapula. This muscle helps protract & upwardly rotate the scapula. It is also a powerful stabilizer of the scapula. In our yoga practice, we target the engagement of this muscle in down dog, handstand, headstand, & forearm balance. Engagement of this muscle in high-plank & chaturanga allows the rib cage & entire torso to be lifted up between the shoulder blades.