Chest anatomy

Chest anatomy


The pectoralis major is a fan-shaped muscle that has two anatomic sections, or heads. The upper clavicular head arises from the clavicle (collarbone), and the lower sternal head arises from the sternum (breastbone). The two heads pass outward across the chest wall and merge into a single tendon that attaches to the humerus bone in the upper arm. As the muscle inserts, the tendon twists so that the upper head attaches beneath the lower head. When the pectoralis muscle contracts, movement takes place at the shoulder joint. Pectoralis major adducts, flexes, and internally rotates the arm, thus moving the arm forward and across the chest during movements such as a push-up or a bear hug. Even though the muscle has only two anatomic divisions, functionally it may be considered as having three sections (upper, middle, and lower), depending on the angle through which the arm is moved. As the position of the shoulder joint changes, certain fibers of the chest muscle have a better mechanical advantage to create motion. Other fibers of the chest muscle are still active but are not able to contract as much because of the shoulder position.



The side wall of the chest is formed by the serratus ant erior. This muscle arises f rom the scapula behind, and it passes forward around the chest wall to attac to the upper eight ribs. The serrated edge of this uscle emerges f rom beneath the outer margin of the pectoralis muscle. The serratus anterior pulls (protracts) the scapula forward, stabilizing it against the rib cage. The serratus anterior is active during most chest exercises and works especially hard during the lockout phase of a push-up or bench press. The pectoralis minor muscle lies deep beneath the pectoralis major and is not visible. It has only a minor function and does not contribute to the size of the chest.



Example of exercise for chest and anatomy focus.

1. While seated on an indine bench, take a shoulder-width overhand grip on the bar.
2. lower the weight slowly until the bar touches your upper chest.
3. Push the bar straight up until your elbows lock out

Muscles Involved
Primary: Upper pectoralis major.
Secondary: Anterior deltoid, triceps.

Anatomic Focus
Trajectory: The angle of incline determines trajectory. As the backrest is raised up and the incline increases, the focus shifts progressively higher up the pectoral muscle. The upper pectoral is best targeted when the backrest is inclined at 30 to 45 degrees to the floor. Steeper Inclines of 60 degrees or more switch the focus to the anterior deltoid.


 Increased incline shifts focus to higher up the pectoral muscle.

Hand spacing: A shoulder-width grip or slightly wider targets all areas of the upper pectoral muscle. Narrow hand spacing emphasizes the inner central portion of the chest and requires more effort from the triceps. Wider grips provide a greater stretch, targeting the outer portion of the muscle, and minimize triceps contribution; but as the hand spacing increases, so does the risk of injury.

Range of motion: To maximize pectoral work, flare your elbows out wide as the barbell is lowered. A shorter rep terminating the press just before lockout keeps tension on the pectorals and reduces triceps assistance.

Machine Incline press: This provides better stability and safety than the standard barbell press. Many machines offer a choice of grips. A neutral grip (thumbs up, palms facing together) emphasIzes the pectorals better than a pronated grip (palms forward).