Your Rotator Cuff
By Coach Fox
Pretty often I hear these things…”I think it’s my rotor cuff”, or “rotary cuff”, or some other well intentioned but ill informed self-diagnosis. So let’s take a look at what the rotator cuff really is. Simply speaking, the rotator cuff is made up of 4 small muscles and their respective tendons. The main job of the rotator cuff is to optimally position and stabilize your humeral head within your glenoid fossa (or the ball at the top of your arm into the socket in your scapula) so that the larger muscles at the shoulder can do the real work.
Meet your rotator cuff (RC):
Supraspinatus – Initially ABducts your arm (raises to the side, away from the body)
Infraspinatus – Externally rotates the arm
Teres Minor – Externally rotates the arm
Subscapularis – Internally rotates the arm
Remember that while these are the joint actions the muscles of the RC effect, their main job is positioning and stabilizing. They are small muscles that cannot move much load. At first glance it seems that external rotation has an unfair advantage over the others. In fact there are larger “mover” muscles that also internally rotate the arm (pecs and lats mainly) and can overpower the small external rotators. In CrossFit we intentionally focus on compound, functional movement, and that includes lots of push-ups and pull-ups (read, pecs and lats). So what winds up happening in many of us is that internal rotation at the shoulder overpowers external rotation. This is on display anytime an athlete’s drop in and their elbows flare out during a DB Thruster or Push Press or the like. They don’t have enough external rotation force being generated to stabilize the arm. Enter the justification of isolation exercises.
Here’s a great movement to strengthen external rotation. Position yourself you’re your torso pretty horizontal to the ground as in the photo. Start with a light DB or change plate held at arms length toward the floor. Pull your elbow up until it is in the plane of your torso. Then, keeping your upper arm in the same plane, externally rotate at the shoulder until your forearm is in the same plane as your torso and upper arm (Think of your elbow pointing a laser straight out to the wall and not letting it deviate). Then reverse the motions in opposite order.
If you're not sure about your technique on this move, don't hesitate to ask any of the coaches at the gym.
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Run barefoot with Christopher McDougall, author of "Born to Run" from Harlem to Brooklyn!
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