The Ankle Inversion Strength Test measures how much force a client can produce when turning the sole of the foot inward against resistance. It is commonly used to assess inversion force output from muscles such as tibialis posterior, tibialis anterior and related medial ankle contributors in a controlled isometric setup.
The Muscle Meter is a handheld dynamometry tool used to measure force output during push, pull and isometric strength assessments. When used on its own, the Muscle Meter primarily measures peak force, which is the highest force value produced during the test. When used with Measurz, Muscle Meter data can be recorded and analysed with a broader set of strength and force-time metrics, including peak force, impulse, torque, rate of torque development, rate of force development, time to peak and fatigue index.
For routine ankle inversion testing, peak force is usually the main metric. Force as a percentage of body weight may be useful if it is directly calculated from the test force and the client’s body weight. Rate of force development and time to peak may be useful when rapid ankle control is relevant, such as cutting, landing, change-of-direction or reactive balance tasks. Impulse may be useful if sustained force over a defined time window is intentionally tested. Fatigue index is only relevant if repeated or sustained inversion efforts are part of the protocol.
The result can support baseline assessment, side-to-side comparison and progress tracking, but it does not diagnose ankle pathology, tendon dysfunction, instability, injury status or readiness for sport or work on its own.
The Ankle Inversion Strength Test is an isometric force assessment where the client attempts to turn the foot inward into the Muscle Meter without visible ankle movement. The device is usually placed on the medial side of the foot, commonly around the medial forefoot or first metatarsal region.
The movement direction is ankle inversion. The purpose of the test is to measure force output in an inward-turning direction at the ankle and foot.
Consistent setup matters because ankle angle, foot position, contact point, lower-leg stabilisation, strap angle and compensation can all change the result. This test does not fully measure dynamic ankle control, balance, walking, running, cutting, landing or sport performance on its own.
Explain that the test measures how strongly they can turn the foot inward against the Muscle Meter. Record baseline symptoms, medial ankle discomfort, arch discomfort, tendon-region symptoms, recent activity, fatigue and confidence with maximal effort.
Use at least one submaximal practice trial so the client understands the direction of force.
A common setup is seated with the hip and knee flexed and the ankle near neutral. Supine or long-sitting setups can also be used, but the same position should be repeated at retest.
Record:
Seated, supine or long-sitting position
Knee angle
Ankle start position
Foot position
Whether footwear was removed
Whether the lower leg was stabilised
For a handheld setup, the professional resists the inversion force with the Muscle Meter. For stronger clients or improved repeatability, a strap-stabilised or fixed setup may be used.
If using a strap, record the anchor point, strap angle, strap length, foot position and whether the anchor stayed stable.
Place the Muscle Meter against the medial side of the forefoot, commonly near the first metatarsal region. Avoid pressure over sensitive bony areas or painful tendon regions.
The force direction should oppose inversion. The client attempts to turn the sole inward into the device without lifting or twisting the entire leg.
Stabilise the lower leg so the client does not compensate with hip rotation, knee movement, toe curling, ankle plantarflexion, dorsiflexion or whole-leg movement. The aim is controlled ankle inversion force.
Use consistent instructions such as:
“Turn your foot inward into the device as hard as you can and hold.”
“Build up smoothly, then push hard.”
“Keep the knee and leg still.”
“Try not to curl your toes or twist the whole leg.”
“Tell me if you feel pain, cramping, tingling or anything unusual.”
Use 1–2 practice trials, then record 2–3 maximal trials. A common contraction duration is 3–5 seconds. Rest for 30–60 seconds between trials, or longer if symptoms, fatigue or cramping occur.
Record whether the final score is the best trial or the average of recorded trials. Use the same method at retest.
Repeat or mark a trial as invalid if:
The hip rotates
The knee moves
The lower leg lifts or twists
The device slips
The strap or anchor moves
The client plantarflexes or dorsiflexes instead of inverting
Toe gripping dominates the effort
Pain limits the contraction
The professional cannot hold the device steady
Record medial ankle pain, arch discomfort, tendon-region symptoms, cramping, paraesthesia, confidence, apprehension and symptom response after testing. Do not repeatedly test through high pain or worsening symptoms.
For retesting, match the same position, device placement, instructions, contraction duration, rest period, scoring method and symptom recording.
The Ankle Inversion Strength Test is used to quantify inversion force output in a repeatable setup. It may be useful for:
Baseline ankle strength assessment
Side-to-side comparison
Monitoring change over time
Strength profiling for running and change-of-direction sports
Assessing medial ankle force capacity
Comparing inversion with eversion strength
Supporting balance and lower-limb control reasoning
Workplace context where walking, uneven surfaces or ladder use are relevant
Fitness and performance progress tracking
Client education
The test primarily measures isometric ankle inversion force output in the chosen setup. It reflects the client’s ability to produce force in an inward-turning direction at the ankle and foot.
It does not diagnose tendon pathology, ankle instability, nerve involvement, balance capacity, foot posture or readiness for sport or work. It also does not fully measure dynamic control during cutting, landing, running or uneven-ground walking.
A higher score may suggest greater inversion force output in that specific test setup. A lower score may suggest reduced inversion force output, but the reason should be interpreted carefully.
Lower force may reflect pain, apprehension, poor familiarisation, fatigue, guarding, inconsistent device placement, poor stabilisation, medial ankle sensitivity, reduced confidence or compensation.
One result should not be interpreted in isolation. Interpretation is strongest when the same setup is repeated over time and reviewed alongside symptoms, confidence, movement quality, eversion strength, dorsiflexion strength, calf capacity, ankle ROM, balance, hopping, cutting or work-specific tasks.
Important influences include:
Pain
Apprehension
Poor familiarisation
Fatigue
Guarding
Poor stabilisation
Hip rotation compensation
Toe gripping
Different device placement
Different strap angle
Different knee or ankle position
Foot posture
Breath holding
Client confidence
Professional strength if using handheld resistance
Published Muscle Meter-specific ankle inversion norms are limited. Because of this, reference values should be used as context only and not as direct targets unless the protocol is closely matched.
More user-friendly comparison data include:
In people with chronic ankle instability, published handheld dynamometry inversion values have been reported around 157.2–187.5 N. In practical terms, this is roughly similar to about 16–19 kg of force.
In healthy participants, other handheld dynamometry inversion values have been reported around 19.5–22.0 kg, which is approximately 191–216 N.
One healthy-control comparison value for inversion was reported around 127.5 N, or roughly 13 kg of force.
These values vary because the studies used different positions, devices and stabilisation methods. A seated Muscle Meter result should not be directly compared with a side-lying, supine or belt-stabilised HHD result as if they are the same test.
For side-to-side comparison, a difference of around 10% or more is often worth reviewing more closely in strength testing, especially if it matches symptoms, previous injury, poor confidence or a functional difference. This is not a strict pass/fail cut-off.
Comparing inversion with eversion can also be useful. Large differences between directions may provide context, especially when paired with balance, hopping, change-of-direction or sport/work tasks.
If you calculate force as a percentage of body weight in Measurz, use it mainly for the client’s own baseline, side-to-side comparison and retesting. Published bodyweight-percentage norms for this exact Muscle Meter inversion setup are not currently strong enough to use as universal targets.
These values are best used as comparison data. They can help provide context, but they should not be used as diagnostic, clearance or pass/fail cut-offs.
Use this order:
Compare with the client’s own baseline.
Compare right and left sides when relevant.
Compare inversion and eversion where relevant.
Consider symptoms during and after testing.
Consider confidence and effort quality.
Review whether compensations were present.
Compare with related strength, mobility or performance tests.
Relate the result to the client’s sport, work, exercise or daily-life demands.
Retest under the same conditions to monitor change.
Do not use reference values as pass/fail criteria.
Peak force
Use for maximum inversion force output, baseline strength, side-to-side comparison, inversion-to-eversion comparison, progress tracking and comparing force across retests. Look for best score or average score, consistent setup, side-to-side difference, change from baseline, pain response and compensation during maximal effort.
Force as percentage of body weight
Use only when calculated directly from test force and body weight. Look for changes over time and differences between sides, but do not treat it as a universal target unless the comparison data use the same method.
Rate of force development
Use when rapid ankle control is relevant, such as cutting, landing, agility, change-of-direction or reactive balance tasks. Look for early force production and whether RFD changes while peak force stays similar.
Time to peak
Use to understand whether force is produced quickly or gradually. Look for delayed peak force, faster time to peak across retests, and whether a slower time reflects caution, pain, poor cueing or an actual performance difference.
Impulse
Use only if a defined sustained force window is intentionally tested. Look for whether the client can sustain force briefly and whether impulse improves while peak force stays similar.
Fatigue index
Use only if repeated or sustained inversion efforts are part of the protocol. Look for drop-off across repeated trials, symptom-related fatigue and whether fatigue improves across a training block.
Youth clients
Consider growth, maturation, coordination, training age, attention and familiarisation. Clear instructions and practice trials are important.
Adults and general fitness clients
Use the test for baseline strength, side-to-side comparison and progress tracking. Compare results with balance, calf strength, ankle mobility and general exercise goals.
Older adults
Consider balance, transfers, daily tasks, walking confidence, uneven surfaces, fatigue, rest periods and function. Lower force may provide useful context but should not be interpreted without function.
Athletes and sport clients
Consider cutting, pivoting, landing, sprinting, jumping and change-of-direction demands. Peak force alone does not equal sport performance.
Workplace and manual task clients
Consider uneven ground, ladders, carrying, prolonged standing, stairs, bracing and footwear demands. Do not use one score to clear work duties.
Clients returning after injury
Use the test to monitor force output, confidence and symptom response. Strength alone should not confirm readiness.
Clients with pain or persistent symptoms
Pain, fear, guarding, fatigue, apprehension and confidence may reduce force. Record symptom response carefully and compare with related tests.
Higher body mass clients
Absolute force and force relative to body mass may both be useful. Interpret results in relation to goals, symptoms and functional demands.
Repeatability improves when the same setup is used each time. Record and standardise:
Same test position
Same device attachment
Same device placement
Same strap setup, if used
Same anchor height and distance, if straps are used
Same strap angle, if straps are used
Same knee and ankle position
Same stabilisation
Same instructions
Same contraction duration
Same rest period
Same scoring method
Same symptom and compensation recording
Belt-stabilised handheld dynamometry for ankle inversion and eversion has shown reliable results in healthy adults, but values can differ depending on position. Handheld dynamometry values can also vary depending on whether the device is held manually or stabilised with a belt. This means internal consistency is more useful than comparing results from different protocols.
Common errors include:
Device placement changing between trials
Foot twisting instead of controlled inversion
Hip rotation compensation
Knee movement
Toe gripping
Plantarflexion or dorsiflexion substitution
Poor lower-leg stabilisation
Strap or anchor movement
Breath holding
Testing through high pain
Comparing sitting, supine and side-lying results as if identical
Treating the score as a diagnosis
Limitations include:
Testing is setup-dependent
Manual resistance may be limited by professional strength
Strap setup requires careful anchor control
Muscle Meter-specific universal norms may be limited
Published inversion norms are less complete than dorsiflexion and plantarflexion norms
Pain, fear or guarding can reduce force output
Peak force does not measure endurance or movement quality
Strong symmetry does not automatically indicate readiness for sport or work
The Ankle Inversion Strength Test may be useful for:
Baseline assessment
Side-to-side comparison
Inversion-to-eversion comparison
Strength profiling
Monitoring response to exercise or intervention
Reviewing medial ankle force capacity
Supporting balance and agility assessment reasoning
Client education
Comparing with related ankle, calf and foot tests
If force is low on both sides, consider assessing ankle ROM, foot strength, calf capacity, balance, gait, confidence and general lower-limb strength.
If one side or direction is much lower, compare with symptoms, injury history, eversion strength, ankle mobility, balance, hopping and change-of-direction tasks.
If pain limits the result, record symptom location and review whether device placement, ankle position or effort level needs modification.
If force is good but function is limited, compare with dynamic tasks such as single-leg balance, hopping, cutting, step-downs, walking tolerance or sport-specific demands.
If the client is improving, keep the same test setup and monitor whether force, symptoms, confidence and function improve together.
Position: Seated, hip and knee flexed, ankle near neutral
Start position: Foot relaxed, ankle close to neutral
Joint or trunk angle: Record knee and ankle position
Trials: 1–2 practice trials, then 2–3 recorded trials
Contraction duration: 3–5 seconds
Rest: 30–60 seconds between efforts
Metric: Peak force, plus percentage of body weight only if directly calculated
Attachment or device setup: Muscle Meter against medial forefoot near first metatarsal region, or strap-stabilised if used
Final score: Best trial or average of trials
Key retesting requirement: Same position, device placement, instructions, contraction duration, rest and scoring method
It measures isometric ankle inversion force output in a specific test setup.
It can be if you calculate it directly from test force and body weight. Use it for internal comparison rather than as a universal target.
Published universal Muscle Meter norms for this exact protocol appear limited. Baseline, side-to-side comparison, inversion-to-eversion comparison and repeated testing are usually more useful.
Published comparison values include inversion forces around 157.2–187.5 N, 191–216 N, and 127.5 N from different handheld dynamometry examples. These are not direct Muscle Meter targets unless the protocol is closely matched.
No. It can measure force output, but it does not diagnose a condition or explain symptoms on its own.
Yes, inversion-to-eversion comparison can be useful, but interpretation should include symptoms, history, setup quality and functional findings.
Different device placement, ankle angle, hip rotation, toe gripping, poor stabilisation, pain and inconsistent instructions can affect results.
Record side, position, device placement, peak force, percentage of body weight if directly calculated, symptoms, compensations, confidence, scoring method and related findings.
The Ankle Inversion Strength Test measures isometric inversion force output.
Peak force is usually the main routine Muscle Meter metric.
Published examples include approximately 157.2–187.5 N, 191–216 N, and 127.5 N, but protocols vary.
Percentage of body weight should only be used when calculated directly from force and body weight.
Baseline comparison, side-to-side comparison and inversion-to-eversion comparison are usually more useful than broad norms.
Reference values provide context, not diagnostic or clearance cut-offs.
Measurz should capture setup, symptoms, bodyweight-normalised values where directly calculated, compensations and retesting conditions.
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. https://doi.org/10.1371/journal.pone.0140822
Spink, M. J., Fotoohabadi, M. R., Menz, H. B., & Lord, S. R. (2010). Foot and ankle strength assessment using hand-held dynamometry: Reliability and age-related differences. Gerontology, 56(6), 525–532. https://doi.org/10.1159/000264655
