Anker: Wrist Radial Deviation Strength Test

The Wrist Radial Deviation Strength Test measures the maximum isometric force produced when the wrist moves towards the thumb side of the forearm. Using the Anker, the assessment provides an objective and repeatable measure of wrist radial deviator strength in a standardised testing position.

Radial deviation contributes to grip stability, lifting, carrying, racquet sports, golf, baseball, climbing, manual handling and many occupational tasks requiring controlled wrist positioning. It also assists with stabilising the wrist during gripping activities by balancing the action of the wrist flexors and extensors.

The primary muscles assessed include extensor carpi radialis longus, extensor carpi radialis brevis and flexor carpi radialis.

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, wrist mobility, grip strength and functional performance.

What Is the Wrist Radial Deviation Strength Test?

The Wrist Radial Deviation Strength Test is an isometric assessment where the client attempts to move the hand towards the thumb side while maintaining a stable forearm and elbow.

The assessment is typically performed with the forearm resting comfortably, the elbow flexed to approximately 90° and the wrist beginning in a neutral position. Standardising forearm position reduces compensatory movement and improves repeatability.

The fixed resistance provided by the Anker allows the assessment to be reproduced consistently when positioning, anatomical landmarks and verbal instructions remain unchanged.

Step-by-Step Protocol

1. Prepare the client

Explain that the assessment measures how strongly they can move their hand towards the thumb side without moving their forearm.

Record any:

• wrist pain

• thumb pain

• forearm pain

• previous wrist injury

• previous surgery

• neurological symptoms

• fatigue

Complete one or two familiarisation contractions before maximal testing.

2. Position the client

Position the client:

• seated upright

• forearm fully supported

• elbow flexed to approximately 90°

• forearm in neutral rotation

• wrist in neutral

• fingers relaxed

Maintain identical positioning during every reassessment.

3. Position the testing limb

Ensure:

• the forearm remains supported

• the elbow remains still

• the wrist begins in neutral

• the hand remains relaxed

Position the Anker load cell against the radial border of the second metacarpal, just proximal to the metacarpal head.

Avoid direct pressure over the thumb or wrist joint.

Record the contact point for future testing.

4. Stabilise the client

Prevent movement of:

• forearm

• elbow

• shoulder

• trunk

The movement should occur only as an isometric wrist radial deviation effort.

5. Testing instructions

Use consistent verbal cues.

"Move your hand towards your thumb."

"Increase the pressure smoothly."

"Push as hard as you can."

"Hold."

"Keep breathing."

Repeat the same wording 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:

• the highest force value, or

• the average of the recorded trials

Maintain the same scoring method during future assessments.

7. Repeat the trial if

• the forearm lifts

• the elbow moves

• the shoulder compensates

• the wrist flexes or extends

• the load cell slips

• pain limits maximal effort

• the client starts before instructed

Why It Is Used

The assessment may be useful for:

• establishing baseline wrist strength

• comparing left and right limbs

• monitoring strength over time

• upper-limb strength profiling

• athlete performance assessment

• objective reporting using Measurz

• monitoring response to exercise

• client education

The assessment should contribute to a broader physical assessment and should not be used as a stand-alone diagnostic assessment.

What It Measures

The primary outcome is peak isometric wrist radial deviation 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:

• wrist joint stability

• ligament integrity

• wrist range of motion

• grip endurance

• hand dexterity

• readiness for work or sport

Understanding the Result, Reference Values and What to Look For

Higher force values generally indicate greater radial deviation strength.

Lower force values may reflect:

• pain

• fatigue

• previous injury

• reduced confidence

• inconsistent positioning

• movement compensation

Interpret results by considering:

• previous assessment results

• left versus right differences

• symptoms during testing

• grip strength

• occupational and sporting demands

Published Anker-specific normative values are currently unavailable.

Handheld dynamometry has demonstrated good reliability for wrist strength assessment when forearm position, wrist position and lever arm are standardised. Because testing protocols vary between devices, comparison with the client's own baseline and repeated assessments using the same protocol are generally more meaningful than comparison with published force values.

A side-to-side difference of approximately 10% or greater may warrant further assessment when accompanied by symptoms 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 grip strength, hand function and activities of daily living.

Athletes

Particularly useful for racquet sports, golf, climbing, baseball, cricket and strength athletes.

Clients with persistent symptoms

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

Common Errors and Limitations

Common errors include:

• forearm lifting

• elbow movement

• wrist flexion or extension

• excessive finger gripping

• inconsistent load cell placement

• inconsistent verbal cueing

Limitations include:

• results are position-specific

• pain may reduce maximal force production

• muscle strength alone does not determine upper-limb function

• published Anker-specific normative values remain limited

Practical Applications

The assessment may be useful for:

• establishing baseline wrist strength

• monitoring progress

• side-to-side comparison

• upper-limb performance profiling

• objective reporting within Measurz

• educating clients using measurable outcomes

FAQs

What does the Wrist Radial Deviation Strength Test measure?

It measures maximal isometric wrist radial deviation strength.

Which muscles are primarily assessed?

Extensor carpi radialis longus, extensor carpi radialis brevis and flexor carpi radialis.

Which metric should be used routinely?

Peak force is the primary outcome measure.

Should both wrists be tested?

Yes. Bilateral testing provides meaningful side-to-side comparison.

Can this assessment diagnose wrist pathology?

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

Key Takeaways

• Measures maximal isometric wrist radial deviation strength.

• Primarily assesses the radial wrist deviators.

• Peak force is the primary routine outcome measure.

• Consistent positioning and metacarpal contact point improve repeatability.

• Measurz provides additional force-time metrics.

• Compare results with previous assessments and the opposite limb.

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.