Pectoralis major
Musculus pectoralis major
// Structure & location
The pectoralis major is flat and fan-shaped and covers much of the front of the chest. It has an upper (clavicular) part arising from the collarbone and a larger lower part from the sternum and rib cartilages. All fibres converge on one tendon that inserts on the front of the humerus. On the way they twist: the lower fibres insert higher up than the upper ones.
// Function
The muscle brings the arm towards the midline (adduction), rotates it inwards and moves it forward. The upper part also helps raise the arm forward and up, while the lower part pulls a raised arm back down. According to OpenStax, it is one of only two trunk muscles that move the humerus, together with the latissimus.
// For training & sport
- Pressing movements like bench press, push-ups and dips train it as the prime mover.
- On an incline bench the upper part works harder, because the arm presses more forward and up.
- Flyes and cable crossovers load it especially in the stretched position, with the arms wide open.
// Good to know
A pec tendon tear is rare but almost only affects men and typically happens during heavy bench pressing at the bottom of the lift. The pectoralis minor lies underneath and pulls on the shoulder blade, not the arm.