Dooley Noted: 10/4/2017
The External Abdominal Oblique (EAO) is an extrinsic core muscle that is meant to take intrinsic force (from structures like diaphragm and innermost abdominal muscles) and send it to the limbs. This muscle starts at rib 5, where it interdigitates with the Serratus Anterior muscle at ribs 5-9 laterally.
These two muscles work together to send out force through the scapula, during activities like the initiation phase of gait, lunging, and throw delivery.
The elasticity of these muscles on eccentric load is crucial to the backswing of a golf, hockey, and throwing. As they achieve this elastic, eccentrically loaded moment arm, they can then be recruited for acceleration in their concentric loading.
In other words: EAO and serratus anterior must first load in order to then explode with more force.
The most common factor to get in the way is the levator scapula and pectoralis minor on the same side. This is mostly due to our “tech necks” and “tech pecs,” where we load ourselves into a scapula that’s elevated and then protracted through the coracoid process.
The common observational mistake is assuming the person overly protracts.
They don’t – at least not with serratus, the scapular protractor thats actually attached to the entirety of the medial scapular border.
Instead, they protract through the coracoid process in an elevated position, meaning they are using pectoralis minor to do the job. This creates a potential for subacromial bursitis as the space between the coracoid, humerus, and scapula decreases. It also creates the potential for coracopectoral tunnel syndrome
Protract with pec minor solely, and you get potential pain and potential nerve entrapment.
Protract with pec minor, and now it’s unavailable for scapular depression, its seldom-discussed job. This unchecked scapular elevation leads to pathologies like SLAP tears, bicipital tendinitis, and rotator cuff tears.
So, to prevent these scapular-driven issues, one must learn to protract WELL.
And that protraction comes from a down-regulated levator scapula and pec minor and an up-regulated serratus anterior and EAO.
When retraining this anterior oblique subsystem of tissues, make sure that the scapula is not being dominated by levator scapula and pec minor. Don’t let these overeager pair dominate protraction and rotation of your trunk to the opposite side.
As always, it’s your call.
– Dr. Kathy Dooley