Pectorals

Pectorals: what are they?

Pectoralis major has two heads with different fibre directions. The clavicular head runs from the collarbone downwards and outwards to the humerus; the sternocostal head runs from the sternum and upper ribs upwards and outwards to the same point. Because the fibres come from different angles, the arm path decides which head does more work: pressing on an incline biases the clavicular head, pressing flat or on a decline biases the sternocostal head. Underneath, pectoralis minor attaches to the coracoid process of the scapula and tilts it forward, which is why a short pec minor affects shoulder position rather than pressing strength.

What the pecs do

The main actions of pectoralis major are horizontal adduction, bringing the arm across the body, shoulder flexion in the clavicular head, and adduction and internal rotation. A bench press combines horizontal adduction with elbow extension; a fly isolates the horizontal adduction.

Pectoralis minor does something different. It pulls the coracoid process down and forward, tilting the scapula anteriorly. When it is short and the upper back is undertrained, the shoulder blade sits tipped forward, which reduces the room the arm has to travel overhead. That is a positional issue, not a pressing-strength issue.

How to train the pectorals

Vary the angle and vary the resistance profile. Barbell and dumbbell pressing loads the mid-range heavily; cables and machines can keep tension where free weights lose it, particularly in the stretched position at the bottom of a fly.

Bench press technique that protects the shoulder

A bench press with the elbows flared to 90 degrees puts the shoulder in the position with the least room and the most stress. Tucking the elbows to roughly 45 to 70 degrees from the torso, and keeping a small arch with the shoulder blades set on the bench, gives the shoulder a better position without costing much load.

Grip width interacts with this. A very wide grip shortens the range and increases the flare; a narrower grip lengthens the range and shifts more work to the triceps. Somewhere between shoulder width and one and a half times shoulder width suits most clients, adjusted for arm length and comfort.

The bar path is not straight up. It travels from the lower chest at the bottom to over the shoulders at the top, in a shallow arc. A client trying to press in a perfectly vertical line usually ends up starting too high on the chest.

What goes wrong in practice

The first pattern is a client who feels bench press entirely in the front delts and triceps. Usually the shoulder blades are not set, the elbows flare too much, and the bar starts too high. Setting the shoulder blades down and back on the bench, tucking the elbows and lowering to the lower chest usually changes the sensation in one session.

The second is a program with three pressing exercises and one row. Pressing volume that outruns pulling volume by that much builds a front-heavy shoulder over months. Match the two at minimum, and favour pulling for a client who already has plenty of pressing.

The third is skipping the stretched position. Dumbbell and cable flies load the pec where a barbell cannot, and cutting that range to protect the shoulder often just removes the most useful part of the exercise. Reduce load rather than range, and only limit range if a specific position actually provokes symptoms.