How heavy should the dumbbell be?

Start with a very light weight, typically 2 to 5 pounds, as the muscles of the rotator cuff are small and easily overpowered by larger muscle groups if the load is too high.

Why is the towel under the arm necessary?

The towel provides a pivot point that keeps the humerus centered in the joint and ensures the rotator cuff is performing the work rather than the deltoids.

Can I do this exercise every day?

While it is a corrective movement, these muscles still require recovery; performing it 2 to 3 times per week is usually sufficient for most strength programs.

Side-lying External Rotation Guide | Shoulder Stability

Learn the correct form for side-lying external rotations to strengthen the rotator cuff, prevent injury, and improve shoulder mobility.

How to Perform

Lie on your side on a flat bench or a comfortable mat with your legs stacked and hips neutral.
Place a small folded towel between your upper arm and your ribcage to maintain proper alignment and tension.
Hold a light dumbbell in your top hand with your elbow bent at a strict 90-degree angle.
Rest your forearm across your stomach with your palm facing inward to establish the starting position.
Slowly rotate your forearm upward toward the ceiling while keeping your elbow pressed firmly against the towel.
Pause for one second at the top of the movement when your forearm is roughly parallel to the floor.
Lower the weight back to the starting position under control to complete one repetition.

Common Mistakes

Using excessive weight that forces the use of momentum.
Allowing the elbow to lift away from the torso during the rotation.
Rotating the torso backward to help lift the weight.
Rushing the eccentric lowering phase of the movement.

Muscles Worked

Primary movers

Shoulders

Stabilizers

Infraspinatus
Teres minor
Rear deltoid

Related Guides

2 Handed Kettlebell Swing — Strength
3D lunge warmup — Strength
4-count burpees — Strength

Shoulders · Strength