Impingement and the press. Selected excerpts from Starting Strength: Basic Barbell Training, 3rd ed.
“An injury usually attributed to the press is the situation called shoulder impingement. Folks advise against using the press because of the supposed tendency of the tendons of the rotator cuff muscles to become trapped between the head of the humerus and the bony projections on the scapula - the coracoid and acromion processes.
This dogma ignores the anatomical facts about a properly performed press. The scapula is attached to the rest of the shoulder girdle at only one point, the clavicle at the AC joint. Except for the acromioclavicular ligament, the scapula essentially “floats” freely through its range of motion in a sheath of fascia and muscle, so that its position can change relative to all the other structures of the back and humerus.
When you press overhead, you finish the movement by shrugging your shoulders up toward the bar. This motion engages the trapezius muscles that connect the spinous processes of the vertebral segments in the neck and upper back to the scapulas, and this actively reinforces the traps’ support for the shoulders and the bar. In effect, the bar is supported overhead by the locked-in-line arms, the scapulas hold up the arms, and the traps hold up the scapulas, so the shrugged traps actively support the weight of the bar. When the traps contract, they pull the scapulas together at the top so that they rotate medially, and the shrug pulls them upward. This motion points the glenoid cavity upward to directly support the humerus from below, and pulls the acromion and coracoid processes away from the humerus.
The claim that presses impinge the shoulder is therefore not correct. Pressing incorrectly is not the same thing as pressing - you don’t get to redefine the exercise and then claim that it’s dangerous.”