The Hip Internal Rotation Strength Test measures the maximum isometric force produced during hip internal rotation with the hip positioned in neutral (0° hip flexion). Performed using the Anker, the assessment provides an objective measure of hip internal rotator strength in a standardised and repeatable position.

Assessing hip rotation strength in neutral complements testing performed at 90° of hip flexion, as muscle contribution and force production vary with hip position. The assessment may assist with baseline strength profiling, side-to-side comparison and monitoring changes over time.

The primary muscles contributing to hip internal rotation include the anterior fibres of gluteus medius, anterior gluteus minimus and tensor fasciae latae, while several adductor muscles provide secondary assistance depending on hip position.

When used with Measurz, the Anker records peak force and can calculate 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 muscle strength only and should always be interpreted alongside symptoms, movement quality and functional performance.

What Is the Hip Internal Rotation Strength Test?

The Hip Internal Rotation Strength Test is an isometric assessment performed with the hip in a neutral position (0° flexion). The client attempts to rotate the leg inward by pushing the lower leg against the Anker while maintaining a stable pelvis and trunk.

Unlike testing at 90° hip flexion, assessing internal rotation in neutral places the hip musculature in a different mechanical position and may provide additional information about hip strength across functional positions.

The Anker's fixed resistance and four independent load cells allow the assessment to be reproduced consistently when the same setup is used during every testing session.

Step-by-Step Protocol

1. Prepare the client

Explain that the assessment measures how strongly they can rotate their leg inward without allowing the hip or trunk to move.

Record any:

• hip pain
• groin pain
• buttock pain
• lower back pain
• recent injury
• previous surgery
• neurological symptoms
• fatigue

Perform one or two submaximal practice contractions before maximal testing.

2. Position the client

Position the client in long sitting or supine, depending on the Anker configuration.

Maintain:

• hips in neutral (0° flexion)
• knees fully extended unless the protocol specifies otherwise
• pelvis level
• trunk supported
• lower limbs aligned with the pelvis
• feet pointing towards the ceiling

The same position should be reproduced during every reassessment.

3. Position the testing limb

Ensure:

• the patella faces directly upwards
• the femur remains in neutral rotation before testing
• the tibia remains aligned with the femur
• the ankle remains relaxed

Position the Anker load cell against the lateral aspect of the distal tibia, approximately 2–3 cm superior to the lateral malleolus.

Avoid contact directly over the lateral malleolus or fibular head.

Record the contact point to ensure identical positioning during future assessments.

4. Stabilise the client

Prevent movement of:

• pelvis
• lumbar spine
• opposite limb
• trunk

The movement should be generated by the hip only.

5. Testing instructions

Use consistent verbal instructions.

"Push your leg outwards."

"Build the pressure gradually."

"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 contraction
• 30–60 seconds recovery between trials

Record either:

• the highest value, or
• the average of the recorded trials

Use the same scoring method during every reassessment.

7. Repeat the trial if

• the pelvis rotates
• the lumbar spine moves
• the opposite leg assists
• the testing leg lifts
• the load cell slips
• pain limits maximal effort
• the client begins before instructed

Why It Is Used

The Hip Internal Rotation Strength Test may be useful for:

• establishing baseline hip strength
• comparing left and right limbs
• monitoring changes following injury or reduced loading
• lower-limb strength profiling
• athlete performance assessment
• monitoring exercise progress
• objective reporting using Measurz
• educating clients about measurable change

The assessment should contribute to a broader assessment process and should not be used in isolation.

What It Measures

The primary outcome is peak isometric hip internal rotation force with the hip positioned in neutral.

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:

• hip joint mobility
• structural pathology
• balance
• movement quality
• running mechanics
• readiness to return to sport

Understanding the Result, Reference Values and What to Look For

Higher force values generally indicate greater hip internal rotation strength in the tested position.

Lower force values may reflect:

• pain
• reduced confidence
• fatigue
• previous injury
• poor familiarisation
• inconsistent positioning
• movement compensation

When interpreting results:

• compare with previous assessments
• compare left and right limbs
• consider symptoms during testing
• observe compensatory movement
• relate findings to the client's functional goals

Published Anker-specific normative values are currently unavailable.

Research has consistently demonstrated excellent reliability for hip strength assessment using fixed and handheld dynamometry when standardised protocols are followed. Healthy adults generally demonstrate less than a 10% side-to-side difference in hip rotational strength, although acceptable variation depends on the individual's sporting background, previous injury and testing methodology.

Comparing results with the client's own baseline and using consistent testing procedures is generally more valuable than comparing absolute force values between different dynamometry systems.

Assessing Different Client Populations

Youth

Provide additional familiarisation trials and interpret findings relative to growth, maturation and activity level.

Adults

Useful for baseline assessment and long-term monitoring.

Older adults

Interpret alongside mobility, balance, transfers and daily function.

Athletes

Useful for assessing rotational hip strength as part of a comprehensive lower-limb performance profile.

Clients with persistent symptoms

Interpret results alongside pain, confidence and movement quality rather than strength alone.

Common Errors and Limitations

Common errors include:

• pelvis rotating
• lumbar extension
• opposite leg assisting
• inconsistent load cell placement
• inconsistent starting position
• excessive trunk movement
• inconsistent verbal cueing

Limitations include:

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

Practical Applications

The assessment may be useful for:

• establishing baseline hip strength
• monitoring progress over time
• comparing left and right limbs
• lower-limb performance profiling
• objective reporting using Measurz
• educating clients using measurable outcomes

FAQs

What does the Hip Internal Rotation Strength Test measure?

It measures maximal isometric hip internal rotation strength with the hip positioned in neutral (0° flexion).

Why test at both 0° and 90° hip flexion?

Hip muscle contribution changes with hip position. Assessing both positions may provide a more comprehensive understanding of hip rotational strength.

Which metric should be used routinely?

Peak force is the primary outcome measure for routine assessment.

Should both hips be tested?

Yes. Bilateral testing provides meaningful side-to-side comparison and assists with progress monitoring.

Can this assessment diagnose hip pathology?

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

Key Takeaways

• Measures maximal isometric hip internal rotation strength with the hip in neutral.
• Complements hip rotation testing performed at 90° of hip flexion.
• Peak force is the primary outcome measure.
• Standardised positioning improves repeatability.
• Measurz provides additional force-time metrics.
• Baseline comparison and consistent retesting are generally more valuable than published reference values.

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.

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.

Thorborg, K., Bandholm, T., Schick, M., Jensen, J., & Hölmich, P. (2013). Hip strength assessment using handheld dynamometry is reliable in athletes. Scandinavian Journal of Medicine & Science in Sports, 23(3), e181–e189.