Dumbbell Internal Rotation

Dumbbell internal rotation is another great exercise for the rotator cuff muscles. You cannot perform internal rotation with a dumbbell while standing upright, because gravity does not provide resistance for the rotator cuff. You have to lie across a flat exercise bench. While standing upright you can perform only cable internal rotation.

This exercise develops the muscles that cause the shoulder to rotate inward – the subscapularis. The muscles responsible for internal rotation are strong and generally well trained in contrast to those involved in external rotation. The most comfortable and effective position for this exercise is to lie on your back, but you can also lie on your side.

Dumbbell Internal Rotation Exercise Guide

STARTING POSITION (SETUP): Lie across a flat exercise bench (or on the floor) resting on your upper back, keeping your elbow in contact with the bench. Begin with your forearm out to the side, almost parallel to the floor.

MOVEMENT (EXECUTION): Keeping your upper arm in tight to your body, raise the dumbbell in a forward arc toward vertical position. In other words, rotate your shoulder so that your forearm moves in an arching motion from the bench to the vertical position. Hold for a one-count at the top and then return to the start position and repeat for the desired amount of repetitions. Then switch to the other arm.

Exercise Tips & Key Points

• In starting position your forearm in almost parallel to the floor. At the top of the movement your forearm is vertically upright – perpendicular to your abdomen (perpendicular to the floor).
• Your hand moves through a horizontal arc (90-degree arc).
• Maintain a 90-degree angle between your upper and lower arm throughout. Keep your upper arm motionless and in tight to your body.
• You may place a rolled up towel under your armpit (or under the elbow) for better isolation of the subscapularis.
• Common mistakes: using too much weight; too fast a movement; giving this exercise priority over outward/external rotation (which is more important); and poor technique.
• You can combine the external and internal rotation exercise and complete an entire 180-degree sweep with your arm.

Variations

• Side Lying Dumbbell Internal Rotation – Lie sideways on a flat bench or on the floor. The position is the same as for the outward (external) shoulder rotation, but in this case you hold the dumbbell in the lower hand. Rotate the shoulder that is resting on the floor or bench inward. Breathe naturally. Working elbow can be held with opposite hand for additional support.

Muscles Engaged in Dumbbell Internal Rotation

The subscapularis is the final and largest of the rotator cuff muscle. It is located on the anterior side of the scapula, which is the side that runs along the ribs. If you were lying on your belly, you would have to go through the scapula to get to this muscle.

Main muscles: subscapularis, pectoralis major
Secondary muscles: (latissimus dorsi, teres major), deltoid (front), biceps (long head), (serratus anterior and pectoralis major)
Antagonists: infraspinatus, teres minor