Exploring the pectoralis major muscle
Pectoralis major is one of the muscles that move the humerus at the shoulder joint. It’s a broad, powerful muscle and the larger of the two pectoralis muscles. Everyone is familiar with bodybuilders squeezing their arms in front of their body to show off their big “pecs”! That is the very same pectoralis major muscle we’re talking about here.
We show you some yoga postures below related to this muscle. I’ll also mention that this muscle is what the beginner’s body is after when they try to do a posture such as chaturanga dandasana, but can’t keep their elbows in. Their body is moving their elbows out to take advantage of this larger muscle in its action of horizontal abduction!
What does pectoralis major mean?
The name pectoralis major describes the general location of this muscle.
Pectoralis comes from the Latin word “pectus” meaning breast.
Major comes from Latin and means “greater than”.
Where does the pectoralis major attach?
The clavicular portion originates on the medial (inner) half of the clavicle (collar bone).
The sternal portion originates on the sternum and the upper 6 ribs.
The two divisions of pectoralis major come together to insert on the lateral (outside) lip of the bicipital groove. The bicipital groove is the groove at the top of the humerus that the biceps tendon passes through.
What actions does the pectoralis major do?
Fiber direction from origin to insertion is important in understanding how this muscle creates its actions.
The origin of pectoralis is broad and its insertion is small. This means that pec major can create opposite actions depending on the circumstances.
It can create a number of actions including:
- medial rotation
- horizontal flexion
It assists in adduction.
The lower fibers can create extension from a flexed position if there is a resistance to movement.
Because of this last muscle movement, the pectoralis major could be seen to be an antagonist to itself.