The pectoralis minor is a small strap like muscle that is underneath (deep) to the pectoralis major. It originates on the third to fifth rib, near the costal cartilages. It’s insertion is on the coracoid process of the scapula. It acts to draw the scapula forward, downward, and inward at nearly equal angles ( think of rounding or shrugging your shoulders forward). This muscle is very often shortened and tight in people due to the high prevalence of desk jobs. This muscle pulls the shoulder blade forward resulting in the muscles in the back(rhomboid and mid traps) being chronically strained. Trigger points that form in the pec minor primarily refer pain over the anterior chest and shoulder, with spillover down the medial arm. Trigger points in the left side can mimic angina. 
Repetitive Stress Injury
Trigger points in the pectoralis Major muscle.
The pectoralis major or “pecs” is commonly thought of as the chest muscle. It originates on the clavicle, sternum, costal cartilage , and the external oblique aponeurosis. It inserts on the intertubercular groove of the humerus. Its main actions are to adduct the shoulder and to internally rotate the humerus. This muscle gets chronically shortened by a rounded shoulder forward posture such as from prolonged sitting. Tightness in this muscle can cause strain in the rhomboids and traps. When trigger points form in this muscle they refer pain into the anterior shoulder, as well as the anterior chest and medial aspect of the arm. Trigger points in the pecs can also cause nipple hypersensitivity. Trigger points in the left pec muscle can mimic heart pain.
Trigger points in the rhomboid muscles.
This is another common muscle to get trigger points. It originates on the spinous processes of the T2-T5 vertebrae. It inserts on the medial border of the scapula. It’s main actions are to adduct the scapula pulling it back toward the spine, and to rotate the glenohumeral joint downward. This muscle also prevents wining of the scapula. This muscle is often overloaded by a sitting posture where the shoulders are rolled forward such as when using a computer. The Rhomboids are often weak and under trained in people. Trigger points in this muscle cause pain and ache in the upper back between the shoulder blade. Strength trading for this muscle is necessary to help prevent postural overload. 
Trigger points in the trapezius muscle.
The trapezius muscle is a large diamond shaped muscle in you mid/upper back and neck. This muscle is one of the most common sites where trigger points can form. This muscle originates on the Nuchal ligament and the spinous processes of C6-T12. It inserts on the spine of the scapula, the acromion process, and the distal clavicle. The upper fibres elevate the shoulder and rotate the glenoid fossa (shoulder socket) upward. The lower fibres assist this motion as well as help depress the shoulder. The middle fibres of this muscle strongly adduct the scapula. This muscle is susceptible to postural overload such as sitting at desk all day. Trigger points on the lateral upper edge refer into the lateral neck and temples, causing “tension neck ache”as well as headache pain.Trigger points in the middle and lower fibres refer pain into the posterior neck and shoulder. 
Our Condition of the Month: ITB Syndrome
Iliotibial Band Syndrome
Your iliotibial band is a fibrous band of tissue running from the crest of your hip, down to your knee. A muscle near the crest of your hip called the tensor fascia lata, attaches to this band to help control movements of your leg. Your iliotibial band passes over the point of your hip and over another bony bump on the outside of your knee called the lateral epicondyle. When the band is too tight, it can become painfully inflamed as it repeatedly rubs over the top of either of these bony projections. Irritation at the bony bump near the knee is called iliotibial band friction syndrome.
The condition usually presents as pain on the outside of your knee that becomes worse with repetitive knee flexion or extension. This condition is the leading cause of lateral knee pain in runners, especially slower “joggers.” The pain usually develops 10-15 minutes into the workout. You may sometimes feel or hear a click during movement. Symptoms generally ease at rest. Running on slick “wintry” surfaces may aggravate the condition. Excessively worn running shoes may be a culprit.
This problem is commonly caused by weakness in your gluteal muscles. When these muscles are weak, the muscle that attaches to your iliotibial band must contract harder to stabilize your hip. Having one leg longer than another is a known aggravating factor.
Runners should minimize downhill running and avoid running on a banked surface like the crown of a road or indoor track, as well as wet or icy surfaces. Runners should reverse directions on a circular track at least each mile. Bicyclists may need to adjust seat height and avoid “toe in” pedal positions. Avoid using stair climbers or performing squats and dead lifts. Sports cream and home ice massage may provide some relief of symptoms.
Trigger points in the masseter muscle
The masseter is the main muscle that moves your jaw. It originates on the zygomatic arch and maxilla, and inserts on the coronoid process and Ramus of the mandible. It’s actions are to elevate the mandible and close the jaw. The deep fibres of this muscle also retrude the mandible. This muscle commonly harbours trigger points as a result of teeth grinding. Trigger points in this muscle are often also associated with tmj dysfunction. Trigger points in the upper part of this muscle will refer pain to the upper molars and maxilla often felt as sinusitis. Trigger points in the lower portion of this muscle refer to the lower molars and temple. All trigger points can cause tooth sensitivity
Aberdeen Chiropractic 