Muscle guide · Chest and shoulders
Also called pecs, chest muscle
The pectoralis major is the large, fan-shaped muscle across the front of the upper chest, under the breast tissue. It forms the front wall of the armpit and has two heads: a clavicular head from the collarbone (the 'upper chest') and a larger sternocostal head from the breastbone and ribs.
Its fibres converge on one tendon at the front of the upper arm, so together they bring the arm across and down the body, which is the work of every press, push-up and fly.
| Part | Starts at | Attaches to | What it does |
|---|---|---|---|
| Clavicular head | Inner half of the collarbone | Front of the upper arm bone, just below the shoulder | Lifts the arm forward, as in raising a glass for a toast |
| Sternocostal head | Breastbone, upper rib cartilages and a sheet from the abdominal wall | Same tendon, front of the upper arm bone | Brings the arm across the body and pulls a raised arm down |
Flat pressing worked the sternocostal head most. Inclines of about 30 to 45 degrees shifted some work to the clavicular head and, in one 8-week trial, grew the upper chest more; above 45 degrees the front deltoid takes over.
3D demoBarbell bench pressIntermediate · A barbell + A bench or box
3D demoPush-upIntermediate · No equipment
3D demoIncline barbell bench pressIntermediate · A barbell + A bench or box
3D demoIncline dumbbell pressIntermediate · A dumbbell + A bench or box
3D demoDumbbell bench pressIntermediate · A dumbbell + A bench or box
3D demoCable flyIntermediate · A cable machine
3D demoChest dip (forward lean)Intermediate · Pull-up barTaking the arm out to the side and back, as in a doorway stretch, reverses its main action.
Rare, and almost all in men aged 20 to 40. Nearly half of 365 published cases happened during weight training, and about half of all tears happen on the bench press, as the loaded arm lowers and turns out while the muscle lengthens under strain. Anabolic steroid use is a known association. Complete tears are usually repaired surgically, ideally within 6 weeks.
Each grade rates the evidence for the correction.
No study has measured 'inner' or 'outer' chest. Grip width changed chest activity little or not at all; what reliably changes with a narrower grip is more triceps work.
EMG studies and one small training study suggest a 30 to 45 degree incline shifts some work toward the clavicular head. The effect is real but modest.
A gym chest workout: bench press, incline dumbbell press, cable flyes, dips and a push-up finisher.
45 minIntermediate7 movesA band, A barbellA push day workout for chest, shoulders and triceps: bench press, overhead press, incline dumbbell press, lateral raises and pushdowns.
55 minIntermediate10 movesA band, A barbellWork up to full push-ups: wall, incline and knee push-ups, then the floor push-up and harder variations.
15 minBeginner8 movesA wall, A bench or boxIt brings the arm across the body, lifts it forward, pulls a raised arm down and turns it inward. Every press, push-up and fly uses it.
Press on an incline of about 30 to 45 degrees. Above that, the front deltoid does more of the work.
Very little. Studies found chest activity similar across grip widths; a narrower grip mainly adds triceps work.
The clavicular head from the collarbone (the upper chest) and the larger sternocostal head from the breastbone and ribs.
Anatomy and movement education, not a diagnosis or treatment plan. If you have pain that follows an injury, is severe or getting worse, or comes with numbness, weakness or swelling, get it assessed. Health disclaimer.
