How to make rotator cuff strengthening work for you 👇 Assessing humeral internal rotation (IR) and external rotation (ER) can help to reveal what is happening in the scapula. However, sometimes the movement of the humerus itself still needs to be addressed. Let’s explore the rotator cuff to decrease tension in the shoulder complex for improved function. The rotator cuff includes muscles that do IR and ER. Balance in their movement facilitates joint centration (keeping the humeral head centered