The pectoral group is the primary pushing muscle of the torso. They protect the rib cage from frontal impacts. They have a very high aesthetic value for men. With women, the Pectoralis Major muscle lies hidden under the breasts. The training of your pectorals is crucial for functionality, as increase in the strength of this muscle increases the pushing strength of the body. The Pectoralis muscles consist of the Pectoralis Major and Pectoralis Minor muscles.
The pectoralis major muscle is a strong, fan-shaped muscle of the shoulder joint. The function of pectoralis major is to horizontally adduct the humerus at the shoulder joint. The pectoralis major is further subcategorised into 3 heads:
Clavicular head- Popularly known as the Upper Pecs, It originates from the medial half of the clavicle and also inserts into the bicipital groove of the humerus. This head contains almost 1/4 fibers of the pectorals. Incline presses involves more of the clavicular head.
Sternocostal head- This would constitute what can be called as the Mid-Chest. It originates from the sternum, 2nd to 7th coastal cartilage and inserts into the bicipital groove of the humerus. Almost 3/4 fibers of the whole pectorals muscle come under this head. Decline press or the flat press involves much of the sternocostal head than the clavicular head.
Head arising from the Aponeurosis of the External Oblique – Typically this is the head that would constitute what we call as the Lower Pecs. These fibers arise out of the External Oblique via an aponeurosis (Connective tissue that connects one muscle to another.). Even these fibers share the same insertion as the above 2 heads, which is – The Bicipital Groove of the Humerus. This head is normally hit along with the sternocostal head while doing presses on a -15* Decline angle. This head is solely hit without much of involvement from the Sternocostal head in the instance of doing a parallel bar dip.
The pectoralis minor is a flat fan-shaped muscle of the shoulder girdle. It originates from the 3rd to 5th ribs, and inserts on the coracoid process of the scapula. It lies beneath the pectoralis major muscle and is the smaller of the two pectoral muscles. It stabilises the scapulae by drawing it inferiorly and anteriorly against the anterior wall.