The pectoralis minor muscle is a small strip like muscle located underneath the pectoralis major. It functions to protect the shoulder and aid in scapular movement and stabilization. This muscle almost always has trigger points in it due to chronic poor posture where the shoulders are rounded. Federal pain from these trigger points will cause pain to be felt in the chest and down the arm.
The Infraspinatus muscle is part of the rotator cuff. It acts to move and stabilize the shoulder. This muscle is often chronically strained in people who have a rounded shoulder posture. With this type of strain trigger points can develop. These knots in the muscle will cause pain to be felt in the front of the shoulder and down the arm.
The supraspinatus muscle is one of your rotator cuff muscles in the shoulder. It helps to move and stabilize the shoulder joint. Poor posture can cause this muscle to become strained and irritated. Rounded shoulders can cause strain in this muscle and can even cause the tendon of this muscle to become impinged with overhead shoulder movement. Trigger points that form in this muscle will cause pain to be felt in the shoulder, elbow, and down the arm.
The scalenes muscles are located in the neck and help with neck movements and inspiration. The anterior scalene runs directly over the brachial plexus that gives nerve and blood supply to the arm. Poor neck and head posture as well as poor breathing mechanics can cause this muscle to become overloaded and develope trigger points. These points will refer pain into the shoulder, arm, and hand. As well as the shoulder blade. When tight, the anterior scalene muscle can put pressure on the brachial plexus causing numbness and tingling felt in the fingers and hand.