Muscle: Pectoralis Major, clavicular head
Origin: At the medial two-thirds of the anterior border of the clavicle (this is the inside two-thirds of the front edge of your collar bone).
Insertion: At the crest of the greater tuberosity of the humerus, along the bicipital groove (this is located just below the top of your arm bone, along the outside edge of the bone).
Function: Adducts the humerus (upper arm) horizontally across the front of the chest and also assists in flexion of the humerus (elevating the arm). The clavicular head works closely with the sternal head when the arm extends back in a dumbbell or cable fly.
In the fully extended position the stress is primarily on the sternal head, as the arms begin flexing forward the stress begins to shift from the sternal head to the clavicular head. With the arms held in the front at the completion of the movement, the stress is shifted almost completely to the clavicular head.
Muscle: Sternal Pectoralis Major
Origin: At the anterior and lateral surface of the sternum (front and side of the breast bone), the costal cartilage’s of the first six ribs (top ribs that connect into breast bone) and the aponeurosis of the external abdominal oblique and rectus abdominus muscles (area along the rib line coming off the base of the breast bone).
Insertion: At the crest of the greater tuberosity of humerus, along the bicipital groove.
Function: The sternal head adducts the humerus across the front of the chest so that the arm comes across and downward toward the opposite hip. It also assists in humerus flexion, arm inward rotation and arm adduction. Both the sternal and clavicular head work with the anterior deltoid to flex the arm horizontally from the side to the front in exercises such as bench presses or push-ups.
Muscle: Pectoralis Minor
Origin: At the anterior surface of the third, fourth and fifth ribs near the junction of the rib and its costal cartilage (approximately 4 – 6 inches away from the breast bone).
Insertion: At the coracoid process of scapula (inside, outer, upper notch of the shoulder blade).
Function: Very limited motion that is used in forced inspiration and stabilizes the scapula by flexing the shoulder joint and drawing the scapula anteriorly and inferiorly (forward and down).
Indications of Weakness
If either, or both, the sternal or clavicular heads become shortened, shoulder ROM in flexion and abduction decreases. This will make all bench press and fly exercises difficult and painful to do. If the clavicular head is weak, the athlete may experience pain around the clavicle, particularly when doing incline presses, flyes or overhead lifts.
If the sternal head is weak, the shoulder may appear to be posterior and slightly superior from its normal position. If both heads are shortened, the arm internally rotates so that the palms face backwards, instead of toward the thigh, when the arms are in a relaxed standing position. If the pectoralis minor is shortened, it can cause winging of the scapula. It can also draw the glenohumeral joint forward, creating a biomechanical shoulder problem for weight training.
Whether the pectorals have shortened due to crouching over a computer key board all day or have become out-of-balance due to improper weight training program design (focusing on your bench press and chest development while neglecting the back muscles is a recipe for dysfunction), the effect is the same. The imbalance must be corrected to regain optimal performance and prevent pain and injury.
Optimal Training Principles
Grip width is very important in all bench press movements. Even a one-inch change in grip width in the bench press can significantly change the level of muscle involvement. One of the best methods for determining your athletes “natural grip width” is to have them stand at the end of the bench, facing and centered on the bar. Have them close their eyes with their arms hanging relaxed at their sides. Then have them bring their hands forward and where they touch the bar is their “natural grip”.
Now, to double check they got it right mark the bar with chalk, or at least note where their hands touch by distance to the knurled section. Have them perform a bench press with this grip. If they got it right, you will observe that their forearm is perpendicular to the floor at the bottom of their lift. This position stresses the pectorals while minimizing the stress on both the shoulder and wrist joints.
Wide grip bench presses increase the stress on the pectorals, but dramatically increase stress on both the shoulder and wrist joints. The wide grip involves the pectorals as well as the anterior deltoid, it allows the pectorals and anterior deltoid to lengthen to a far greater degree and therefore allows more force activation. It also allows a decrease in the total distance the bar must move to complete the lift.
All of these factors allow for greater loads and makes the wide grip position a favorite among many powerlifters. The pectorals are most active during the first two-thirds of the bench press. You can take advantage of this by performing partial reps. The partial rep is from the bar touching the chest to a point two-thirds of the way up. Use spotters when performing partial reps, because, done correctly, when you complete the set, you will not be able to get the bar back on the uprights.
The narrow grip bench press takes the stress off the pectorals and shifts the stress on to the triceps. When the bar is first pressed off the chest, there is a large burst of energy from the triceps, pectorals and anterior deltoid, then the pectorals and anterior deltoid take over and do most of the work during the final one-third of the lift till lockout.
There is still an ongoing debate between the researchers performing MRI analysis and bodybuilders. The MRI research shows you cannot move stress on the pectorals from the medial fibers (inner) by performing narrow grip chest presses, or to the lateral fibers (outer) by performing wide grip chest presses.
The reason is that the pectoral fibers run from clavical to humerus as a single fiber. You can move stress upward, to the clavicular head with incline presses and lower, to the inferior sternal fibers, but research says you cannot move stress medially or laterally on the chest. However, many bodybuilders disagree, they have found that they can develop medial or lateral pectoral fibers.
Bodybuilders claim that the wide grip chest press works the lateral fibers and narrow grip chest presses, with the elbows flared at 45 degrees work the medial fibers. I would like to hear from the athletes performing these movements and see what results they get. There is another debate on the incline press. Some claim that the bench has to be at least 30 degrees to stress the clavicualr head.
While others say that 30 degrees is the ideal angle for clavicular head development since any angle above 30 degrees increases stress on the anterior and then the lateral deltoid as the angle increases above 30 degrees. I would like to hear from the athletes and see what results they get. After the grip, the next consideration is elbow placement.
Elbows flared to the 3 o’clock / 9 o’clock position place maximal stress on the pectorals, but dramatically increase stress on the shoulder joint. Elbows at 45 degrees to the body place adequate stress on the pectorals and greatly reduce the stress on the shoulder joint.
It is recommended that you start with compound movements (bench presses) to strengthen and develop the pectorals. The flyes put more stress on the pectorals and less on the triceps, but also increase stress on the shoulder capsule (use GPO when starting beginners on flyes).
Use a wide variety of exercise, angles and variations. The pectorals are a very large muscle that operates a wide range of movements. You will need a wide range of exercises and angles to fully develop the chest.
Important Safety Notes:
1. Do not bounce at the bottom of the barbell bench press
2. Use knowledgeable spotters when going heavy
3. Do not arch the back during any bench press to protect the vertebrae
4. Do not exceed a comfortable ROM. Particularly if you are flaring your elbows straight-out to the sides (3 O’clock and 9 O’clock)
5. Train the external rotators of the rotator cuff (teres minor and infraspenatus) to prevent shoulder problems.
6. Train the body: upper/lower, front/back in balance.
Dr. Jim Bell