Anker: Forearm Supination Strength Test

The Forearm Supination Strength Test measures the maximum isometric force produced when the forearm rotates so the palm faces upward. Using the Anker, the assessment provides an objective and repeatable measure of forearm supination strength in a standardised position.

Supination strength is important for gripping, lifting, carrying, using tools, opening doors, racquet sports, climbing and many occupational tasks. It also contributes to efficient hand positioning during activities requiring precision and force generation.

The primary muscles assessed are the biceps brachii and supinator, with assistance from the brachioradialis when moving towards a neutral forearm position.

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, elbow and wrist mobility, grip strength and functional performance.

What Is the Forearm Supination Strength Test?

The Forearm Supination Strength Test is an isometric assessment where the client attempts to rotate the forearm so the palm turns upwards while maintaining a stable elbow and upper arm.

The assessment is commonly performed with the elbow flexed to 90° and the upper arm positioned against the trunk. This position reduces compensation from the shoulder while allowing consistent loading of the supinator muscles.

The Anker provides fixed resistance, allowing repeatable testing when client positioning, anatomical landmarks and verbal instructions remain consistent.

Step-by-Step Protocol

1. Prepare the client

Explain that the assessment measures how strongly they can rotate their palm upwards without moving the elbow or shoulder.

Record any:

• elbow pain

• forearm pain

• wrist pain

• previous upper-limb injury

• previous surgery

• neurological symptoms

• fatigue

Perform 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

• elbow flexed to 90°

• forearm in neutral rotation

• wrist maintained in a neutral position

Maintain identical positioning during every reassessment.

3. Position the testing limb

Ensure:

• the humerus remains against the trunk

• the elbow stays flexed to 90°

• the wrist remains neutral

• the hand remains relaxed

Position the Anker load cell against the palmar surface of the distal forearm, immediately proximal to the radial and ulnar styloid processes.

Avoid positioning directly over the wrist joint or hand.

Record the contact point to improve repeatability.

4. Stabilise the client

Prevent movement of:

• trunk

• shoulder

• upper arm

• elbow

The movement should occur only as an isometric forearm supination effort.

5. Testing instructions

Use consistent verbal cues.

"Turn your palm upwards."

"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 testing.

7. Repeat the trial if

• the elbow moves

• the shoulder rotates

• the trunk leans

• the wrist flexes or extends excessively

• 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 forearm strength

• comparing left and right limbs

• monitoring changes 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 or clearance test.

What It Measures

The primary outcome is peak isometric forearm supination 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:

• elbow joint stability

• tendon integrity

• forearm 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 forearm supination strength.

Lower force values may reflect:

• pain

• fatigue

• previous injury

• reduced effort

• inconsistent positioning

• movement compensation

Interpret results by considering:

• previous assessment results

• left versus right differences

• symptoms during testing

• grip strength

• functional demands

Published Anker-specific normative values are currently unavailable.

Forearm rotational strength has demonstrated good reliability using handheld dynamometry when elbow position, forearm position and stabilisation are standardised. Because force values differ between devices and testing methods, comparison with the client's own baseline and repeated testing using the same protocol are generally more meaningful than external normative values.

A side-to-side difference of approximately 10% or greater may warrant further investigation 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 strength over time.

Older adults

Interpret alongside grip strength, lifting ability and daily activities.

Athletes

Particularly useful for racquet sports, climbing, throwing sports, gymnastics 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:

• shoulder rotation

• elbow movement

• wrist flexion or extension

• gripping excessively during the test

• 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 upper-limb function

• published Anker-specific normative values remain limited

Practical Applications

The assessment may be useful for:

• establishing baseline forearm strength

• monitoring progress

• side-to-side comparison

• upper-limb performance profiling

• objective reporting within Measurz

• educating clients using measurable outcomes

FAQs

What does the Forearm Supination Strength Test measure?

It measures maximal isometric forearm supination strength.

Which muscles are primarily assessed?

The biceps brachii and supinator.

Which metric should be used routinely?

Peak force is the primary outcome measure.

Should both forearms be tested?

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

Can this assessment diagnose tendon injuries?

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

Key Takeaways

• Measures maximal isometric forearm supination strength.

• Primarily assesses the biceps brachii and supinator.

• Peak force is the primary routine outcome measure.

• Consistent positioning and forearm 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.