IRRST (Internal Rotation Resisted Strength Test): Subscapularis and Posterior Cuff Strength

This test has a confusing name in some translations ("Hawkins internal rotation compression test"), but it's not a variant of the Hawkins-Kennedy test. It's actually the IRRST (Internal Rotation Resisted Strength Test), a resisted strength test that helps differentiate between external subacromial impingement and internal (posterosuperior) impingement—something especially relevant in overhead/throwing sports.

What does this test measure?

The IRRST compares external rotation strength versus internal rotation strength of the shoulder in a position of 90° abduction with slight external rotation (the "cocking" position of a throw). A marked relative weakness in internal rotation compared to external rotation, especially if accompanied by pain, points toward internal (posterosuperior) impingement rather than classic subacromial impingement.

Equipment needed

• None (optional: a hand-held dynamometer to quantify strength)

Step-by-step protocol

1. The subject is positioned with the shoulder abducted at 90°, the elbow flexed at 90°, and the shoulder externally rotated about 80-90° (the "cocking" position)
2. First, ask for isometric resistance in external rotation: the subject pushes against your hand trying to rotate the shoulder outward while you resist. Assess pain and strength
3. Then, ask for isometric resistance in internal rotation from the same position: the subject pushes inward against your resistance. Assess pain and strength
4. Compare both: if internal rotation is clearly weaker and/or more painful compared to external rotation, the test is considered positive
5. Repeat on the contralateral side for comparison

Common mistakes

• Not maintaining the 90°/90° (cocking) position during both resistance tests, which completely changes what's being assessed
• Not comparing both directions (external vs. internal)—the value of the test lies in the comparison, not a single direction
• Confusing weakness due to pain (the subject "holds back" because it hurts) with true strength deficits

How to interpret the result

Result	Interpretation
Similar strength in internal and external rotation, no pain	Negative
Internal rotation clearly weaker and/or more painful than external	Positive—suggests internal (posterosuperior) impingement, common in overhead/throwing sports

As with other shoulder tests, this is a screening test that guides clinical suspicion, not a definitive diagnostic tool.

Relationship with other tests

• Hawkins-Kennedy test — assesses "external" subacromial impingement; if Hawkins is negative but pain occurs during throwing motions, the IRRST helps point toward internal impingement
• Jobe test — complements the rotator cuff strength assessment, in this case focused on the supraspinatus

Why tracking it matters

In overhead athletes (handball, volleyball, tennis, baseball), internal impingement usually responds well to specific posterior cuff strengthening and scapular control programs—but you need to measure the strength asymmetry between rotations to know if the program is working. In Movalytics you can record the IRRST result alongside the rest of your shoulder tests and track progress session by session.

Frequently asked questions

Is the IRRST the same as the Hawkins-Kennedy test? No, even though they share part of their name due to a confusing translation. Hawkins-Kennedy is a passive impingement test (you move the arm); the IRRST is a resisted strength test comparing internal and external rotation. Who is this test most useful for? Especially athletes with repetitive overhead motions (throwing, serving, spiking), where internal impingement is more common than in the general population. Do I need a dynamometer to do this? It's not essential. Manual resistance and comparing both sides already gives you useful information, though a dynamometer lets you quantify the strength difference more precisely. Note: this test is a screening tool for guidance only and does not replace a medical diagnosis or imaging study.