Anker: Shoulder Horizontal Adduction Strength Test

The Shoulder Horizontal Adduction Strength Test measures the maximum isometric force produced as the arm moves across the body in the transverse plane. Using the Anker, the assessment provides an objective and repeatable measure of shoulder horizontal adduction strength in a standardised position.

Horizontal adduction strength contributes to pushing movements, tackling, throwing follow-through, racquet sports, swimming, pressing exercises and upper-limb force production. The assessment is useful for baseline strength profiling, side-to-side comparison and monitoring changes over time.

The primary muscles assessed include the pectoralis major, anterior deltoid and coracobrachialis, with assistance from the short head of biceps brachii during stabilisation.

When used with Measurz, the Anker records peak force and can calculate additional metrics including 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 Horizontal Adduction Strength Test?

The Shoulder Horizontal Adduction Strength Test is an isometric assessment where the client attempts to move the arm across the chest while maintaining a stable shoulder and trunk.

The test is typically performed with the shoulder abducted to 90° and the elbow flexed to 90°, allowing force to be generated primarily through the horizontal adductors while minimising compensatory movement.

The fixed resistance provided by the Anker allows consistent testing when the same positioning, anatomical landmarks and instructions are reproduced during each assessment.

Step-by-Step Protocol

1. Prepare the client

Explain that the assessment measures how strongly they can bring their arm across their body.

Record any:

• shoulder pain

• chest pain

• previous shoulder injury

• previous surgery

• stiffness

• neurological symptoms

• fatigue

Complete one or two familiarisation trials before maximal testing.

2. Position the client

Position the client:

• seated upright

• feet flat on the floor

• trunk supported

• shoulder abducted to 90°

• elbow flexed to 90°

• forearm in neutral rotation

Maintain identical positioning during every reassessment.

3. Position the testing limb

Ensure:

• the scapula remains in a neutral position

• the humerus is level with the shoulder

• the elbow remains aligned with the shoulder

• the wrist remains relaxed

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

Avoid placing the load cell directly over the elbow joint.

Record the contact point to improve repeatability.

4. Stabilise the client

Prevent movement of:

• trunk

• scapula

• opposite shoulder

• pelvis

The effort should come from shoulder horizontal adduction rather than trunk rotation.

5. Testing instructions

Use consistent verbal instructions.

"Push your arm across your body."

"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 either:

• highest force value, or

• average of recorded trials

Use the same scoring method during reassessment.

7. Repeat the trial if

• the trunk rotates

• the shoulder elevates

• the elbow changes position

• the scapula excessively protracts

• the load cell slips

• pain limits maximal effort

• the client starts before instructed

Why It Is Used

The assessment may be useful for:

• baseline shoulder strength assessment

• side-to-side comparison

• athlete profiling

• monitoring strength over time

• objective reporting using Measurz

• monitoring response to exercise

• client education

The assessment should not be used as a stand-alone diagnostic or return-to-sport assessment.

What It Measures

The primary outcome is peak isometric shoulder horizontal adduction 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:

• shoulder stability

• rotator cuff integrity

• shoulder mobility

• throwing mechanics

• sporting performance

Understanding the Result, Reference Values and What to Look For

Higher force values generally indicate greater horizontal adduction strength.

Lower values may reflect:

• pain

• previous injury

• fatigue

• reduced effort

• inconsistent positioning

• movement compensation

Interpret results by considering:

• previous assessments

• left versus right comparison

• symptoms during testing

• movement compensations

• functional demands

Published Anker-specific normative values are currently unavailable.

Upper-limb dynamometry has demonstrated excellent reliability when joint position, stabilisation and lever arm are standardised. Baseline comparison and repeated testing using identical procedures are generally more meaningful than comparing absolute force values between different devices.

A side-to-side difference greater than approximately 10% may warrant further assessment when accompanied by symptoms or reduced function.

Assessing Different Client Populations

Youth

Interpret relative to growth, coordination and sporting participation.

Adults

Useful for baseline strength assessment and monitoring progress.

Older adults

Interpret alongside upper-limb function and activities of daily living.

Athletes

Useful for throwing, racquet sports, swimming, rugby, AFL, combat sports and strength athletes.

Clients with persistent symptoms

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

Common Errors and Limitations

Common errors include:

• trunk rotation

• shoulder elevation

• elbow movement

• inconsistent load cell placement

• scapular compensation

• inconsistent verbal cueing

Limitations include:

• results are specific to the testing position

• pain may reduce force production

• strength alone does not determine shoulder function

• published Anker-specific normative values remain limited

Practical Applications

The assessment may be useful for:

• baseline shoulder assessment

• athlete monitoring

• side-to-side comparison

• progress tracking

• Measurz reporting

• client education

FAQs

What does this assessment measure?

Maximal isometric shoulder horizontal adduction strength.

Which muscles are primarily assessed?

Pectoralis major, anterior deltoid and coracobrachialis.

Which metric should be used routinely?

Peak force.

Should both shoulders be tested?

Yes. Bilateral assessment provides meaningful comparison.

Can this assessment diagnose shoulder injuries?

No. It measures muscle force only.

Key Takeaways

• Measures maximal isometric shoulder horizontal adduction strength.

• Primarily assesses the pectoralis major and anterior deltoid.

• Peak force is the primary outcome measure.

• Consistent positioning improves repeatability.

• Measurz provides additional force-time metrics.

• Compare with previous assessments and the opposite limb.

References

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

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

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.