Anker: Shoulder Horizontal Abduction Strength Test

The Shoulder Horizontal Abduction Strength Test measures the maximum isometric force produced as the arm moves away from the body's midline in the transverse plane. Using the Anker, the assessment provides an objective measure of posterior shoulder strength in a repeatable testing position.

Horizontal abduction strength contributes to rowing movements, throwing preparation, swimming, climbing, posture and scapular control. Assessing this movement complements horizontal adduction testing and provides a broader profile of shoulder strength.

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

When used with Measurz, the Anker records peak force and additional force-time metrics including force relative to body weight, impulse, torque, rate of force development, time to peak and fatigue index.

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

What Is the Shoulder Horizontal Abduction Strength Test?

The Shoulder Horizontal Abduction Strength Test is an isometric assessment where the client attempts to move the arm backwards in the transverse plane while maintaining a stable trunk and shoulder.

The test is commonly performed with the shoulder abducted to 90° and the elbow flexed to 90°, allowing consistent loading of the posterior shoulder musculature.

The fixed resistance of the Anker provides repeatable testing when positioning, anatomical landmarks and instructions remain unchanged.

Step-by-Step Protocol

1. Prepare the client

Explain that the assessment measures how strongly they can move their arm backwards.

Record any:

• shoulder pain

• upper back pain

• previous shoulder injury

• previous surgery

• neurological symptoms

• stiffness

• fatigue

Perform one or two familiarisation trials.

2. Position the client

Position the client:

• seated upright

• trunk supported

• feet flat on the floor

• shoulder abducted to 90°

• elbow flexed to 90°

• forearm neutral

Maintain identical positioning during every reassessment.

3. Position the testing limb

Ensure:

• scapula remains neutral

• humerus remains level

• elbow aligns with the shoulder

• wrist remains relaxed

Position the Anker load cell against the posterior aspect of the distal humerus, approximately 5 cm proximal to the olecranon.

Avoid direct contact over the elbow joint.

Record the contact point for future testing.

4. Stabilise the client

Prevent movement of:

• trunk

• pelvis

• opposite shoulder

• scapular elevation

The effort should come from shoulder horizontal abduction rather than trunk extension or rotation.

5. Testing instructions

Use consistent verbal cues.

"Push your arm backwards."

"Increase the pressure smoothly."

"Push as hard as you can."

"Hold."

"Keep breathing."

6. Record the assessment

Use:

• 1–2 familiarisation trials

• 2–3 maximal trials

• 3–5 second contractions

• 30–60 seconds rest

Record the highest force or average of recorded trials.

7. Repeat the trial if

• trunk rotates

• shoulder elevates

• elbow changes position

• load cell slips

• pain limits effort

• client starts before instructed

Why It Is Used

The assessment may be useful for:

• baseline posterior shoulder assessment

• side-to-side comparison

• athlete profiling

• monitoring progress

• objective Measurz reporting

• client education

What It Measures

Primary outcome:

• Peak isometric shoulder horizontal abduction force.

Additional Measurz metrics 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 joint stability, movement quality or sporting performance.

Understanding the Result, Reference Values and What to Look For

Higher force values indicate greater posterior shoulder force production.

Lower values may reflect:

• pain

• fatigue

• previous injury

• reduced effort

• inconsistent positioning

Interpret findings using:

• baseline comparison

• left versus right comparison

• symptoms

• functional demands

Published Anker-specific normative values are currently unavailable. Consistent testing procedures and repeated assessments are generally more valuable than external reference values.

Assessing Different Client Populations

Youth: Interpret relative to development.

Adults: Useful for baseline assessment.

Older adults: Consider daily upper-limb function.

Athletes: Particularly useful for throwing, swimming, rowing, climbing and racquet sports.

Clients with persistent symptoms: Interpret alongside symptoms and function.

Common Errors and Limitations

Common errors include:

• trunk extension

• trunk rotation

• shoulder elevation

• inconsistent load cell placement

• inconsistent cueing

Limitations include:

• position-specific results

• pain may reduce force

• strength alone does not determine shoulder function

Practical Applications

Useful for:

• baseline assessment

• monitoring progress

• athlete profiling

• Measurz reporting

• client education

FAQs

What does this assessment measure?

Maximal isometric shoulder horizontal abduction strength.

Which muscles are primarily assessed?

Posterior deltoid, middle trapezius, rhomboids and infraspinatus.

Should both shoulders be tested?

Yes.

Which metric should be used routinely?

Peak force.

Can this diagnose shoulder pathology?

No.

Key Takeaways

• Measures maximal shoulder horizontal abduction strength.

• Primarily assesses the posterior shoulder musculature.

• Peak force is the primary outcome.

• Consistent positioning improves repeatability.

• Measurz provides additional force-time metrics.

• Compare results with previous assessments and the opposite shoulder.

References

Bohannon, R. W. (1997). Archives of Physical Medicine and Rehabilitation, 78(1), 26–32.

Stark, T., et al. (2011). PM&R, 3(5), 472–479.

Mentiplay, B. F., et al. (2015). PLOS ONE, 10(10), e0140822.