How Your Rotator Cuff Muscles Function

My online and Seattle Pilates and fitness community has been asking me a lot of questions about shoulder function and pain. I’ve already covered how poor shoulder function relates to neck pain, but today I’m going to go more in depth on how the rotator cuff muscles function, since they are a big part of shoulder health.

First, how do the rotator cuff muscles function and why is it important?

The rotator cuff muscles are responsible for shoulder stability. In laymen’s terms this means the rotator cuff holds your upper arm bone or humerus in its socket, which, is sort of crucial for anything and everything you could ever do with your arms.

The rotator cuff is made up of four muscles: the supraspinatus, infraspinatus, teres minor and subscapularis. I’ve simplified this, but here are the cliff notes on what they do.


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The supraspinatus is the small muscle at the top of your shoulder. It is responsible to externally rotating (turning out) humerus and for initiating lifting the arm away from the body.

It is also responsible for resisting the downward pull of gravity on your arms. Considering we tend to use our arms with poor mechanics and gravity works, you can see why this little guy is inhibited and frequently injured!

The infraspinatus and teres minor help externally rotate or turn out the upper arm bone. Like the supraspinatus, they help keep your arm in its socket.

The subscapularis is responsible for internal rotation of the arm and for preventing excessive forward motion of the humeral head (the ball part of the ball and socket joint).

Oftentimes, the subscap is inhibited, because the big mover muscles of the shoulder like the pecs, lats and biceps are over recruited. If this happens, the big muscles begin to pull the shoulder forward and down.

Subsequently, the subscapularis (and other rotator cuff muscles) do their best to “suck” the arm bone up and back into its socket. However, they’re stabilizers, so power is not on their side.

If we use our big movers for too long in a poor joint position (think bad push-up form or slouching in front of a desk), eventually the rotator cuff muscles will become exhausted and give up, which can lead to injury, neck pain and shoulder pain.

Now that we know how the rotator cuff muscles function, how do we know if we need to strengthen them?

Maybe you’ve never had a shoulder injury that was bad enough to see a PT and you think rotator cuff exercises are part of rehabilitation, not fitness. How do you know if you can benefit from spending some time getting to know the rotator cuff muscles?

The short answer is that the rotator cuff is so important for shoulder health that everyone can benefit from some rotator cuff work, if only for maintenance. However, here are a few signs that you may have some rotator cuff weakness.

– Your shoulders frequently roll forward and in when you do exercises like rows, push-ups.

– You have neck and shoulder tension or pain.

– You feel tightness or soreness predominantly in the front of your shoulder after you workout.

– You sometimes feel like your arm is “hanging” from the joint or feels excessively heavy.

If any of these apply to you, there is no need to panic. They’re common experiences. However, it is a sign that you could benefit from a little mindfulness around how to position your shoulders and some corrective exercises to get the rotator cuff muscles back online.

To learn about how to do rotator cuff exercises with good form, please visit part two of this article “How to Strengthen Rotator Cuff Muscles.”

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