Kinesiology THURSDAY – Pec Minor v Lower Trapezius (Tug-o-War Series)

Skeleton with highlighted chest and back muscles

The tug-o-war between pectoralis minor (PM) and lower trapezius (LT) lies at the root of rotator cuff tendonitis or impingement. The attachment of PM on the coracoid process produces an anterior/inferior pull on the scapula, while the LT opposes this with a posterior/inferior pull. If PM is tight, a rounded-shoulder posture will be seen. Rounded shoulder posturing has been shown to limit shoulder flexion by limiting upward rotation of the scapula.

Let’s take a look at how the PM v. LT tug-o-war may be contributing.

PM is a protractor and downward rotator of the scapula. If it is short/tight, it will limit upward rotation and retraction needed for normal scapulohumeral rhythm
LT is a retractor of the scapula and works in conjunction with serratus anterior and upper trapezius to upwardly rotate the scapula.
LT becomes long/weak with a thoracic kyphosis
LT is activated best with arm elevation past 90˚
Studies show improvement in arm elevation with stretching of PM and strengthening of LT

Here’s a simple fix. (If you aren’t a clinician but have shoulder pain, this is the part you want to pay attention to).

Man in athletic shorts showing muscular back.

Stretch the PM with a single arm doorway stretch. Make sure the arm is elevated approximately 100˚. Lean forward and hold for 30 seconds. You should feel a stretch in the upper chest region. This stretch was shown to be more effective than manual stretches for pec minor performed by a clinician.
This self-mobilization of pec minor (placing deep pressure on the muscle) while actively performing flexion is a great way to actively release this muscle.
Performing one arm dumbbell overhead presses will activate the lower trapezius.

Why does this matter?

Rounded shoulder posturing often lies at the root of shoulder pain, specifically rotator cuff tendonitis or impingement. Addressing the tug-o-war between pec minor and lower trapezius is one of the most successful ways to improve arm elevation and open up subacromial space for the rotator cuff to pass underneath. A successful program requires stretching or releasing pec minor and strengthening lower trapezius.

Because nobody has time to be in pain.

Until next time…