Anker: Shoulder External Rotation Strength Test – 0° Shoulder Abduction

The Shoulder External Rotation Strength Test measures the maximum isometric force produced during shoulder external rotation with the shoulder positioned at 0° of abduction. Using the Anker, the assessment provides an objective and repeatable measure of shoulder external rotator strength in a standardised position.

The shoulder external rotators play a critical role in glenohumeral stability by controlling humeral head position during arm movement. They are heavily involved in throwing deceleration, overhead sports, rowing, swimming and posture, making this assessment valuable for both athletic performance profiling and upper-limb strength monitoring.

The primary muscles assessed include the infraspinatus and teres minor, with assistance from the posterior deltoid depending on shoulder position.

When used with Measurz, the Anker records peak force and can calculate force relative to body weight, impulse, torque (when the lever arm is entered), rate of force development, time to peak and fatigue index.

The assessment measures muscle force only and should always be interpreted alongside symptoms, shoulder mobility and functional performance.

What Is the Shoulder External Rotation Strength Test?

The Shoulder External Rotation Strength Test is an isometric assessment where the client attempts to rotate the forearm away from the body while the elbow remains flexed to 90° and the upper arm stays against the trunk.

Testing at 0° shoulder abduction provides a stable and repeatable position that is commonly used when assessing rotator cuff strength. This position reduces compensatory movement and allows consistent assessment across repeated testing sessions.

The Anker's fixed resistance allows objective strength measurement when positioning, anatomical landmarks and instructions remain consistent.

Step-by-Step Protocol

1. Prepare the client

Explain that the assessment measures how strongly they can rotate their forearm away from their body without moving their elbow.

Record any:

• shoulder pain

• neck pain

• previous shoulder injury

• previous surgery

• neurological symptoms

• stiffness

• fatigue

Complete one or two familiarisation contractions before maximal testing.

2. Position the client

Position the client:

• seated upright

• feet flat on the floor

• trunk supported

• shoulder adducted against the side of the body

• elbow flexed to 90°

• forearm in neutral rotation

A towel between the arm and trunk may improve consistency by maintaining the shoulder in a neutral position.

Use the same setup during every reassessment.

3. Position the testing limb

Ensure:

• the humerus remains against the trunk

• the elbow remains flexed to 90°

• the forearm begins in neutral

• the wrist remains relaxed

Position the Anker load cell against the dorsal (posterior) aspect of the distal forearm, approximately 3–5 cm proximal to the radial and ulnar styloid processes.

Avoid positioning directly over the wrist joint.

Record the contact point for future testing.

4. Stabilise the client

Prevent movement of:

• trunk

• shoulder girdle

• scapula

• elbow

The effort should come from shoulder external rotation only.

5. Testing instructions

Use consistent verbal cues.

"Rotate your forearm away from your body."

"Increase the pressure smoothly."

"Push as hard as you can."

"Hold."

"Keep breathing."

Repeat the same instructions during every reassessment.

6. Record the assessment

Use:

• 1–2 familiarisation trials

• 2–3 maximal trials

• 3–5 second contractions

• 30–60 seconds rest between trials

Record either:

• highest force value, or

• average of recorded trials

Maintain the same scoring method during future testing.

7. Repeat the trial if

• the elbow lifts away from the trunk

• the shoulder abducts

• the trunk rotates

• the shoulder elevates

• the load cell slips

• pain limits maximal effort

• the client starts before instructed

Why It Is Used

The assessment may be useful for:

• baseline rotator cuff strength assessment

• side-to-side comparison

• athlete performance profiling

• monitoring progress over time

• objective reporting using Measurz

• monitoring response to exercise

• client education

The assessment should not be used as a stand-alone diagnostic or clearance assessment.

What It Measures

The primary outcome is peak isometric shoulder external rotation force.

When analysed in Measurz, additional metrics may include:

• Peak force

• Force relative to body weight

• Impulse

• Torque

• Rate of force development

• Time to peak

• Fatigue index

The assessment does not directly measure:

• rotator cuff integrity

• shoulder instability

• movement quality

• shoulder mobility

• overhead throwing mechanics

• readiness for sport or work

Understanding the Result, Reference Values and What to Look For

Higher force values generally indicate greater shoulder external rotation strength.

Lower force values may reflect:

• pain

• fatigue

• previous injury

• reduced confidence

• poor familiarisation

• inconsistent positioning

• movement compensation

Interpret results by considering:

• previous assessment results

• left versus right differences

• symptoms during testing

• movement compensations

• occupational, sporting or daily-life demands

Published Anker-specific normative values are currently unavailable.

Shoulder external rotation strength has been extensively studied using handheld dynamometry and demonstrates excellent reliability when joint position, elbow position and stabilisation are standardised. As testing methods differ between devices, comparing results with the client's own baseline and repeated assessments using the same protocol is generally more meaningful than comparing absolute force values with external reference data.

A side-to-side difference of approximately 10% or greater may warrant further investigation when accompanied by symptoms, previous injury or functional limitations.

Assessing Different Client Populations

Youth

Interpret relative to growth, coordination and sporting participation.

Adults

Useful for baseline assessment and monitoring progress.

Older adults

Interpret alongside upper-limb function and daily activities.

Athletes

Particularly useful for overhead sports, throwing athletes, swimmers, racquet sports and climbers.

Clients with persistent symptoms

Interpret alongside pain, confidence and functional performance rather than strength alone.

Common Errors and Limitations

Common errors include:

• elbow lifting from the trunk

• shoulder abduction

• trunk rotation

• shoulder elevation

• inconsistent load cell placement

• inconsistent verbal cueing

Limitations include:

• results are specific to the testing position

• pain may reduce maximal force production

• muscle strength alone does not determine shoulder function

• published Anker-specific normative values remain limited

Practical Applications

The assessment may be useful for:

• establishing baseline rotator cuff strength

• monitoring progress

• comparing left and right limbs

• athlete profiling

• objective reporting using Measurz

• educating clients using measurable outcomes

FAQs

What does the Shoulder External Rotation Strength Test measure?

It measures maximal isometric shoulder external rotation strength with the shoulder positioned at 0° abduction.

Why is external rotation commonly tested?

The external rotators are essential for shoulder stability and are frequently assessed in overhead athletes and individuals with shoulder symptoms.

Which metric should be used routinely?

Peak force is the primary outcome measure.

Should both shoulders be tested?

Yes. Bilateral testing allows meaningful comparison.

Can this assessment diagnose rotator cuff tears?

No. It measures muscle force only and should always be interpreted alongside other assessment findings.

Key Takeaways

• Measures maximal isometric shoulder external rotation strength.

• Primarily assesses the infraspinatus and teres minor.

• Peak force is the primary routine outcome measure.

• Consistent positioning and forearm contact point improve repeatability.

• Measurz provides additional force-time metrics.

• Baseline comparison and repeated testing are generally more valuable than broad population norms.

References

Bohannon, R. W. (1997). Reference values for extremity muscle strength obtained by hand-held dynamometry from adults aged 20 to 79 years. Archives of Physical Medicine and Rehabilitation, 78(1), 26–32.

Stark, T., Walker, B., Phillips, J. K., Fejer, R., & Beck, R. (2011). Hand-held dynamometry correlation with the gold standard isokinetic dynamometry: A systematic review. PM&R, 3(5), 472–479.

Mentiplay, B. F., Perraton, L. G., Bower, K. J., Adair, B., Pua, Y. H., Williams, G. P., McGaw, R., & Clark, R. A. (2015). Assessment of lower limb muscle strength and power using hand-held and fixed dynamometry: A reliability and validity study. PLOS ONE, 10(10), e0140822.