The pectoralis major muscle originates from multiple locations, including the costal cartilage of ribs two through six, the sternum, the medial half of the clavicle and the external oblique fascia.

Mark S., a 27-year-old male, is complaining of left shoulder weakness. Mark trains with weights regularly (3-4 times each week) and has done this for 10 years. Six months ago, while doing the bench ...