Open the Door: External Rotation for Infraspinatus and Rhomboids

The shoulder blade (scapula) is a flat bone on your upper back.

The infraspinatus is one of the four rotator cuff muscles. It helps turn the arm outward, a motion called external rotation.

The rhomboid major sits between the shoulder blade and the spine. It helps pull the shoulder blade back toward the ribs.

Open the Door works both areas. To learn more, see the 17 muscles of the shoulder blade.

• Exercise with resistance that builds gradually is the type most likely to help rotator-cuff-related shoulder pain. Gentle movement alone probably does little for pain [R01].
• A 2025 review found that scapular stabilization exercise improved pain and function [R03].
• Programs that teach control may work a little better than generic exercise, though we do not fully know why [R02].
• Two-arm training research comes mostly from stroke rehabilitation. It is an interesting idea, but it does not prove that any device works [R14].

1. Sit tall in an armchair with back support and both feet flat. Hold the trainer with both hands, elbows close to your sides.
2. Let one arm guide the other. Swing the working forearm outward slowly, only as far as feels comfortable.
3. Pause, then return slowly. Repeat a few slow times, then rest.
4. Stop if you feel sharp pain, numbness, or pain that lingers after you finish.

For a gentler warm-up that works the same general area, try SeeSaw.