The pectoralis minor is a small muscle that lies underneath the large pectoralis major, right against the rib cage and just below the clavicle (collar bone). It originates on the third, fourth, and fifth ribs and inserts on the coracoid process of the scapula (a part of the shoulder blade). The pecoralis minor depresses the scapula (pulls it down), abducts the scapula (pulls it out to the side), and anteriorly tilts the scapula. When the scapula is fixed, the pec minor can also assist in forced inhalation by pulling up on the ribs
Postural positions that include rounded shoulders and forward head position are an indication that the pec minor may be in chronic contraction. Another sign may be difficulty or even pain with pulling the shoulder blades together. Pec minor can also be injured by trauma to the neck or arm or fall victim to repetitive strain injuries from sports or daily tasks. Pain from the pectoralis minor may be felt in the chest, shoulder, inner arm, palm, and even into the fingers.
The major artery and vein of the arm as well as the nerve bundle known as the brachial plexus which serves the arm, all pass underneath the pecoralis minor, creating the potential for this muscle to compress the nerve and blood vessels if it becomes too tight. This condition is called pectoralis minor syndrome and its symptoms are very similar to and often exist alongside thoracic outlet syndrome. Symptoms of pectoralis minor syndrome include pain, weakness, numbness, and tingling in the arm and hand as well as tenderness in the chest and armpit. Massage therapy and physical therapy are the first steps towards resolving this issue.
Here is a quick video explaining a simple pec minor stretch (with fun accent!). It is just a slight variation on the pec major stretch that you may have seen me demonstrate before