What is the pectoralis major muscle?
The pectoralis major is a large muscle located in the chest that is responsible for movement of the arm, specifically adduction and medial rotation of the humerus (upper arm bone).
It is the largest and most superficial muscle in the pectoral region. There are 2 heads of the pectoralis major, the clavicular and the sternocostal. (1)
Origin, insertion and function
Origin:
The pectoralis major muscle heads originate from two parts:
- Clavicular head – originates from the anterior surface of the medial half of clavicle.
- Sternocostal head – is the larger of the two heads and originates from :
- The anterior surface of the manubrium and body of sternum,
- The anterior surface of the superior six costal cartilages.
- Superior part of the aponeurosis of external oblique muscle.
Insertion:
The muscle inserts on the greater tubercle humerus (upper arm bone).
Function:
The pectoralis major muscle is responsible for adduction and medial rotation of the humerus. It also plays a role in shoulder flexion, which is the movement of bringing the arm forward, and in horizontal adduction, which is the movement of bringing the arm across the front of the body. It also helps to keep the shoulder blade pressed against the rib cage during certain movements, this is called scapulothoracic muscle.
Common signs of weak pectoralis major muscles
Signs that you may have weak pectoralis major muscles include:
- Inability to perform exercises such as push-ups or the bench press with proper form
- Shoulder pain or instability during chest exercises or other upper body movements
- Poor posture, with the shoulders rounding forward and the chest sinking in
- Limited range of motion in the shoulders
- Difficulty reaching overhead or behind the back
- Noticeable asymmetry in muscle development between the left and right sides of the chest
- General weakness or fatigue in the chest and shoulder area during daily activities
- “winged” scapula, which is when the shoulder blade sticks out from the back rather than lying flush against the rib cage
Exercises that strengthen the pectoralis major
Exercises that help strengthen your pectoralis major muscles include:
Push-ups:
- Place hands shoulder-width apart on the floor, with the fingers facing forward.
- Begin in a plank position with the body straight and core engaged.
- Lower the body towards the floor by bending the elbows, keeping the body straight throughout the movement.
- Push back up to the starting position by straightening the elbows.
Dumbbell press:
- Sit on a bench with a dumbbell in each hand at shoulder level with your palms facing forward.
- Press the dumbbells up, extending the arms fully, then lower to the start position
Barbell bench press:
- Lie on a flat bench with feet flat on the floor and grip the barbell at shoulder-width apart.
- Lower the barbell to the chest while keeping the elbows close to the body
- Press the barbell back up to the starting position
Dumbbell fly:
- Lie on a flat bench holding dumbbells at shoulder level with your palms facing each other
- Slowly lower the dumbbells out to the sides in a controlled motion, keeping the elbows slightly bent
- Bring the dumbbells back to the starting position, squeezing the chest muscles at the top of the movement.
Cable crossover:
- Stand between two high pulley cables, with a handle in each hand.
- Step forward to create tension on the cables
- Bring your hands together in front of your body, squeezing the chest muscles at the top of the movement.
- Return to the starting position with control.
Dips:
- Support yourself on parallel bars
- Lower your body until your upper arms are parallel to the floor
- Push back up to the starting position
It is important to use proper form and to start with a weight that allows you to perform the exercises with control and good form, then gradually increase the weight as your strength improves.
References:
- Solari F, Burns B. Anatomy, Thorax, Pectoralis Major Major. [Updated 2022 Jul 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK525991/