Although many people are familiar with the Pec muscles, what they often don't realise is that there are actually 2 of them. The Pec major is the large one that you see blokes in the gym tensing in front of the mirror after working them on a Friday evening before going for a night out ;-)
The pec minor however doesn't get quite as much publicity as it hides completely underneath the pec major. It also has a very different orientation and attachment points which means it does a completely different job to Pec Major.
That being said, although it is a smaller muscle, it can still be very strong and thick.
The Pec minor attaches to the coracoid process which is an odd little piece of the shoulder blade that sticks out through to the front of the shoulder. It then attaches at the other end to 3rd, 4th and 5th ribs.
So where as the Pec Major is responsible for moving the arm, the job of the pec minor is to pull down on the coracoid process (on the scapular) and to fix the shoulder blade in place whilst the arm then moves. It also moves the scapular downwards.
So you can see that the pec major and pec minor (despite having similar names) actually do very little together. That being said, they are so close to one another and being aware of fascial connections, you really can't move one without moving the other.
But did you know that the pec minor also has another job? Of course it moves the scapula. But remember it is also attached to the ribs so it also plays a part there too. The pec minor pulls up on the ribs to help to expand the chest during breathing, especially during forced breathing such as during high intensity activity, coughing, or sneezing.
This means that when we over-train or have a persistent cough then the pec minor can sometimes become shortened and irritated, leading to pain in the front of the shoulder, referred pain to other areas as well as many other symptoms occurring.
So as the pec minor tightens this can then cause compression of the arteries and nerves just under it. This then causes a restricted blood flow to the arm and hand as well as the pressure on the nerves causing tingling and numbness. When this happens it can often be mistaken for Carpal Tunnel Syndrome.
As the pec minor shortens it can cause a rounded shoulder position. This can then cause a dull ache in the midback due to strain on the posterior muscles. It can also cause a restricted movement in the shoulder when reaching up.
The opposite can happen too. If we constantly sit with our shoulders rounded (as we often do at the computer or at our desk) then this can lead to the Pec Minor becoming shortened. After all, just as structure dictates function, so can function dictate structure.
Trying to stretch this muscle in the traditional sense is usually useless as this can also place more compression on the nerves and blood vessels. And if the muscle is in a shortened protective state for a reason then it's not going to give up it's position lightly.
Instead try using Muscle Energy Techniques or Trigger Point work to release the Pec minor as in the videos. Completing these daily as well as developing strength in the upper back can often may a huge difference.