Biomechanics of the press

[PatrickD]

Rip often mentions how the press is good for preventing and rehabbing shoulder injuries. While I have no doubt this is true, I'm a little skeptical of his proposed mechanism of action.

He credits the injury-preventing powers of the press to the shrug at lockout, claiming it strengthens the rotator cuff. The rotator cuff is made up of four muscles: two external rotators, an internal rotator, and an abductor. But shoulder elevation does not seem like rotation or abduction. So how does the shrug strengthen the rotator cuff? Is it the case that these muscles are merely being worked isometrically at lockout?

I was wondering if you could explain why the press is so good for shoulder prehab/rehab. Thanks!

[Austin Baraki]

You are focusing too much on the specifically named "primary" functions of each of the rotator cuff muscles. Yes, they do play a role in rotation and abduction, but as a "complex" the role of the rotator cuff is to stabilize the glenohumeral joint -- i.e., keep the humeral head held stable within the glenoid fossa. I saw a patient this past week who ruptured his subscapularis muscle in the setting of an anterior shoulder dislocation, for example.

The "shrug" is not the only component of the press that strengthens the rotator cuff -- the entire movement does, though admittedly with varying contributions from each of the individual muscles. The "shrug" does require isometric contraction to stabilize the lockout position (which, you'll recall, is arguably the "primary function" of the whole rotator cuff complex), along with contributions from the deltoid, trapezius, and other upper back musculature as well.

[PatrickD]

Thanks for your explanation!