In Plain English
The lower chest is the lower portion of your chest, extending from the lower sternum and ribs to the upper arm. It’s part of the larger pectoralis major and helps bring your arm down, across your body, and inward while contributing to the fullness of the lower chest.
Technical Definition
The lower chest refers to the inferior fibers of the sternocostal head of the pectoralis major, originating primarily from the lower sternum, costal cartilages, and external oblique aponeurosis before inserting onto the lateral lip of the intertubercular groove of the humerus. Its inferior fiber orientation gives it greater mechanical advantage during shoulder adduction, shoulder internal rotation, and horizontal adduction, particularly when the arm moves from higher positions toward the torso.

















