The sternal head of the pectoralis major is the muscle head which composes much of the bulk of the middle and lower portion of the chest. It is one of two muscle heads, with the other being the clavicular head which located to the upper region of the chest.
Spanning from the sternum (chest bone) to the humerus (upper arm bone), the sternal head is effectively targeted with traditional chest exercises, such as the bench press and chest fly which involve the transverse flexion of the shoulder. Unknown to many gym-goers, however, is the engagement of the sternal head during shoulder extension and adduction. This, in simple terms, means the sternal head is also actively involved during pull up exercises.