The musculus pectoralis major represents the large chest muscle. It covers almost the entire chest (thorax) and attracts much interest among athletes. But the chest muscles not only consist of the musculus pectoralis major.
Musculus pectoralis major
Underneath the musculus pectoralis major the musculus pectoralis minor, or the small chest muscle, can be found. Beside the musculus pectoralis major the musculus serratus anterior can be found. It covers the lateral chest wall. Together they form the chest muculature.
Musculus pectoralis major
The musculus pectoralis major can be divided into three different parts: an upper part (pars clavicularis), a middle part (pars sternocostalis), and a lower part (pars abdominalis). The upper part originates from the clavicle (clavicula), the middle part from the breastbone (sternum), and the lower part from the aponeuroses of the musculus rectus abdominis (rectus sheath). The musculus pectoralis major inserts into the crista tuberculi majoris of the humerus. The functions of the large chest muscles are:
- pulling the arm toward the body (adduction),
- the internal rotation of the arm,
- conducting the arm to the front (anteversion), and
- lowering the arm from raised position.
Musculus pectoralis minor
The musculus pectoralis minor originates from the 3rd, 4th, and 5th rib and the aponeuroses. The small chest muscle inserts into the processus coracoideus of the scapula. Its function is pulling down the shoulder blade caudally, medially and ventrally.
Musculus serratus anterior
Like the musculus pectoralis major the musculus serratus anterior can be divided into three parts: the pars superior, pars intermedia, and pars inferior.
- The pars superior originates from the 1st to the 2nd rib and inserts into the angulus superior of the scapula. Its function is to lift the shoulder.
- The pars intermedia originates from the 2nd to the 3rd rib and inserts into the medial edge of the scapula. Together with the pars superior it moves the scapula ventrally.
- The pars inferior originates from the 4th to the 9th rib and inserts into the margo medialis and the angulus inferior of the scapula. It moves the angulus inferior laterally and allows the elevation of the arm.
Musculus pectoralis major – importance and training
The musculus pectoralis major is one of the most effectual muscles of the shoulder joint. A lot of importance can be attached to this muscle from an aesthetic, as well as from a functional point of view. It is involved in almost all arm movements and essential for throwing competitions, swimming, pole vault, etc. The musculus serratus anterior is one of the most important stabilizers of the shoulder blade (scapula). Also, all chest muscles serve as respiratory musculature when the arms are resting.
We should be careful when we work out the musculus pectoralis major. Especially the exercise bench press bears quite some risk of injuries when we lower the barbell too far with high weights. Here, the head of the humerus presses against the connective tissue of the shoulder joint (ligaments, capsule, etc.). If we don’t bring down the barbell all the way to the chest but stop the down movement with our elbows on shoulder level (or slightly below) injuries can be avoided. The same applies for fly exercises.
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