013 - Isolating the Infraspinatus: Are We Actually Testing the Right Muscle?
Traditional External Rotation Tests Activate More Than Just the Infraspinatus.
EMG studies confirm that the infraspinatus and supraspinatus coactivate in most external rotation tests.
If your goal is to isolate the infraspinatus, standard testing might not be giving you accurate data.
The Best Positions for Isolating the Infraspinatus
Prone external rotation with arm support produced the highest infraspinatus-to-supraspinatus (IS:SS) activation ratio (415%).
Resisted external rotation at 60–90° abduction also demonstrated high infraspinatus specificity (IS:SS = 286%).
Humeral longitudinal force (push-up position loading) significantly increased infraspinatus activation.
Tactical Fixes: How to Train & Test the Infraspinatus More Effectively
1. Modify Shoulder Testing for More Accurate Assessments
Use prone external rotation with arm support for clinical infraspinatus testing.
Incorporate resisted external rotation at 60–90° abduction for better specificity.
2. Use Humeral Loading in Strength Training
Push-up holds with feet elevated (IS:SS = 289%) and one-arm push-ups (IS:SSS = 297%) recruit more infraspinatus than supraspinatus.
Applying humeral compression (loading along the arm’s axis) enhances infraspinatus activation during external rotation exercises.
3. Leverage Faster, Isotonic Movements for Neuromuscular Training
High-speed external rotation exercises (e.g., baseball throwing mechanics) showed stronger infraspinatus activation (IS:SS = 275%).
Slower isometric contractions may increase supraspinatus coactivation, reducing infraspinatus specificity.
Thick Necks, Strong Shoulders, No Weak Links
A shoulder test that activates multiple muscles isn’t an isolated test—it’s a guessing game.
A weak infraspinatus masked by coactivation leads to poor rehab and failed return-to-sport outcomes.
If we’re not adapting clinical testing to match the latest research, we’re holding back recovery and performance.
A thick neck with weak external rotators is just waiting for an injury.
Fix the foundation!
Stay Thick.
Hughes P, Taylor NF, Green R. Identifying shoulder testing positions and movements that isolate infraspinatus from supraspinatus. Phys Ther Rev. 2015;20(2):73–85. doi:10.1179/1743288X15Y.0000000012