The Ankle Eversion Strength Test measures the maximum isometric force produced when the client pushes the outside of the foot against the Anker. It is used to objectively assess ankle evertor strength, monitor changes over time and compare left and right limbs using a consistent testing setup.

The primary muscles assessed include the fibularis longus, fibularis brevis and fibularis tertius. These muscles contribute to lateral ankle stability, foot positioning during gait, balance and change-of-direction movements.

When used with Measurz, the Anker can record peak force and additional force-time 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 strength only and should always be interpreted alongside symptoms, functional performance and other assessment findings.

What Is the Ankle Eversion Strength Test?

The client performs a maximal isometric ankle eversion contraction by pushing the outside of the foot into the Anker without allowing visible movement at the ankle.

Because the Anker provides fixed resistance using four independent load cells, testing is highly repeatable when the same client position, foot placement and load cell contact are reproduced.

Step-by-Step Protocol

1. Prepare the client

Explain that the assessment measures how strongly they can push the outside of their foot into the Anker.

Record any pain, swelling, stiffness, recent injury, neurological symptoms or fatigue before testing.

Allow one or two practice contractions so the client becomes familiar with the movement.

2. Position the client

Seat the client with:

• hips flexed approximately 90°
• knees flexed approximately 90°
• pelvis against the backrest
• trunk upright
• feet facing forwards

Maintain the same position during every reassessment.

3. Position the foot

Place the testing foot so that:

• the heel is centred on the footplate
• the second metatarsal aligns with the centre of the platform
• the ankle begins in a neutral position
• the tibia remains vertical

Position the lateral load cell against the lateral border of the fifth metatarsal head. Avoid contact with the lateral malleolus or toes.

Record the exact setup so it can be reproduced during future testing.

4. Stabilise the client

Prevent movement of the pelvis, knee and trunk throughout the contraction.

Only the ankle should generate force against the load cell.

5. Testing instructions

Use consistent verbal cues.

"Push the outside of your foot into the pad."

"Build the pressure smoothly."

"Push as hard as you can."

"Hold."

"Keep breathing."

6. Record the assessment

Use:

• 1–2 practice trials
• 2–3 maximal trials
• 3–5 second contraction
• 30–60 seconds rest

Record either the highest value or the average of the recorded trials and use the same method at every retest.

7. Repeat the trial if

• the heel lifts
• the foot rotates
• the knee moves
• the trunk leans
• the load cell loses contact
• pain limits maximal effort
• the client starts before instructed

Why It Is Used

The assessment may assist with:

• baseline ankle strength assessment
• left versus right comparison
• monitoring rehabilitation progress
• athlete profiling
• lower-limb strength assessment
• objective progress tracking
• monitoring response to exercise
• performance testing

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

What It Measures

The primary outcome is peak isometric ankle eversion 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 ankle stability, ligament integrity, tendon pathology, range of motion, balance or gait quality.

Understanding the Result, Reference Values and What to Look For

Higher force values generally indicate greater ankle eversion strength in the tested position.

Lower force values may be influenced by pain, fatigue, apprehension, previous injury, reduced effort or inconsistent positioning.

When interpreting the assessment:

• Compare with the client's previous results.
• Compare the left and right limbs.
• Consider symptoms during testing.
• Review movement quality and compensations.
• Relate the findings to functional goals.

Published Anker-specific normative values are currently unavailable.

Research using handheld and fixed dynamometry demonstrates that ankle eversion strength can be measured reliably when the testing position is standardised, although force values vary considerably between protocols and devices. For this reason, baseline measurements and repeated testing using the same protocol are generally more valuable than comparing absolute values with other studies.

Healthy adults typically demonstrate less than a 10% side-to-side difference in ankle strength. Larger asymmetries may warrant further assessment when they correspond with symptoms or functional limitations.

Assessing Different Client Populations

Youth: Use additional practice trials and interpret results relative to growth and physical development.

Adults: Useful for baseline assessment and monitoring changes over time.

Older adults: Consider results alongside walking ability, balance and daily function.

Athletes: Assess as part of a broader lower-limb strength profile for running, jumping, cutting and landing activities.

Clients with persistent symptoms: Interpret findings alongside pain, confidence and functional performance rather than strength alone.

Common Errors and Limitations

Common errors include:

• inconsistent foot placement
• heel lifting
• excessive toe gripping
• trunk movement
• pelvis shifting
• incorrect load cell contact
• inconsistent verbal instructions

Limitations include:

• results are specific to the testing setup
• pain may reduce force production
• strength alone does not determine functional performance
• published Anker-specific normative data are currently limited

Practical Applications

The assessment is useful for:

• establishing a baseline
• monitoring progress over time
• comparing left and right limbs
• athlete screening
• lower-limb strength profiling
• objective reporting in Measurz
• client education

FAQs

What does this assessment measure?

Maximum isometric ankle eversion strength.

Which metric should I use routinely?

Peak force is the primary outcome measure.

Can this assessment diagnose ankle instability?

No. It measures strength only.

Should both sides be tested?

Yes. Bilateral comparison is recommended.

Why is standardised positioning important?

Small changes in foot position or load cell contact can significantly influence force measurements.

Key Takeaways

• Measures maximal isometric ankle eversion strength.
• Peak force is the primary outcome.
• Four independent load cells provide repeatable testing conditions.
• Standardised positioning improves consistency.
• Compare results with previous assessments and the opposite limb.
• Interpret strength alongside symptoms and function.

References

Alfuth, M., & Hahm, M. M. (2016). Reliability, comparability, and validity of foot inversion and eversion strength measurements using a hand-held dynamometer. International Journal of Sports Physical Therapy, 11(1), 72–84.

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.

World Journal of Orthopedics. (2025). Normative values of ankle strength and its importance for rehabilitation and return to sport.