Muscles Targeted: If you are rehabilitating a rotator cuff injury or simply want to build strength in the small muscles of your shoulders, then external rotations are an excellent exercise to perform with resistance bands. The benefit of this exercise is that it isolates the small muscles of the shoulder and strengthens them without bringing other muscle groups in at the same time. When you have more strength in the shoulder, you’ll want to add in more movements, but this is a good starting point.
Exercise Instructions: Follow these steps to complete this exercise correctly, especially when you are recovering from an injury. It is extremely important to use proper technique at all times so that you do not make an existing injury worse. Secure one of the ends of the band around a doorknob, pole or other secure object, at about elbow height. Keeping the height at the right level ensures that the movement with the band will be consistent on the same plane. Grab the handle on the other end of the band with one hand. Hold your arm straight out from your side and bend your elbow at a right angle. 
Stand with your forearm and hand pointing toward the fixed object which is securing the other end of the band. Make sure that there is enough tension in the exercise band to allow some resistance during the movement. Holding your upper arm still and tucked into your side, pull your arm away with the band to the point where your lower arm points the other way. If you feel pain beginning to go beyond the typical “burn” sensation, do not extend your arm any further. Bring your upper arm back to its starting position. Repeat the movement several times for one side. Release the band, and turn in the other direction so that you can do the exercise with the other arm.
Things To Avoid: You don’t need to use a band with a lot of resistance to make this an effective exercise because you are isolating the smaller muscles within the shoulder. If you keep your wrist straight and envision your shoulder as a hinge that is closing and opening while you perform this exercise, that will help you get the most benefit out of this movement. Do not allow your elbow to swing out away from your side and make sure to anchor it by tucking your elbow into your side throughout the entire movement. Do not use any part of your shoulder to move. Everything should be still except for your forearm moving back and forth.
Reps and Sets: This really varies with your strength and ability. Because this is typically either a rehabilitative or maintenance exercise, we recommend beginning with 2-3 sets of 20-30 repetitions. As you build strength and endurance, you should aim to perform 4-5 sets of 40-50 repetitions per set.
Other Exercises To Use: If you get to a point where you find that this exercise is becoming too easy for you, it may be a good idea to transition from the external rotation to some different exercises and drills. The shoulder is one of the weaker joints in the body and incorporating some additional exercises that strengthen neighboring muscle groups and increase thoracic spine mobility, you can improve overall performance in the shoulder region and throughout the upper body.
One of these drills involves lying on your left side and bringing your right knee across to rest on a medicine ball. Then, without any resistance, hold your right arm out straight, and bring it back behind your head, turning your head as it goes back. Bring your left arm up so that it is perpendicular to the floor. When you reach your maximum range of motion, slowly bring your right arm back up to its original position. Repeat, and then turn over to perform the same routine on your left shoulder.
The shoulder is a fragile and often tricky joint. Even if you aren’t a baseball pitcher, the rotator cuff can give you trouble, particularly as you get older. Try internal rotations with an exercise band and other exercises to keep the shoulder joint as strong as possible while always remembering its fragility.
