The Shoulder Internal Rotation Strength Test measures the maximum isometric force produced during shoulder internal rotation with the shoulder positioned at 0° of abduction. Using the Anker, the assessment provides an objective and repeatable measure of internal rotator strength in a standardised position.
Internal rotation strength is essential for pushing movements, lifting, climbing, swimming, throwing acceleration and many activities of daily living. It also contributes to dynamic glenohumeral stability by helping maintain humeral head position during upper-limb movement.
The primary muscles assessed include the subscapularis, pectoralis major, latissimus dorsi, teres major and anterior deltoid.
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, shoulder mobility and functional performance.
The Shoulder Internal Rotation Strength Test is an isometric assessment where the client attempts to rotate the forearm towards the body while the elbow remains flexed to 90° and the upper arm stays against the trunk.
Testing with the shoulder at 0° abduction places the rotator cuff in a neutral position and provides a practical assessment of internal rotator strength without placing the shoulder in more demanding overhead positions.
The fixed resistance of the Anker allows repeatable testing when the same client position, anatomical landmarks and instructions are maintained.
Explain that the assessment measures how strongly they can rotate their forearm towards their stomach without moving the elbow away from the body.
Record any:
shoulder pain
neck pain
previous shoulder injury
previous surgery
neurological symptoms
stiffness
fatigue
Complete one or two familiarisation contractions before maximal testing.
Position the client:
seated upright
feet flat on the floor
trunk supported
shoulder adducted against the side of the body
elbow flexed to 90°
forearm in neutral rotation
A towel may be placed between the arm and trunk to help maintain a consistent shoulder position throughout testing.
Maintain the same setup during every reassessment.
Ensure:
the humerus remains against the trunk
the elbow stays flexed to 90°
the forearm begins in neutral
the wrist remains relaxed
Position the Anker load cell against the volar (anterior) aspect of the distal forearm, approximately 3–5 cm proximal to the radial and ulnar styloid processes.
Avoid placing the load cell directly over the wrist joint.
Record the contact point to improve repeatability during future testing.
Prevent movement of:
trunk
shoulder girdle
scapula
elbow
The movement should occur only as an isometric shoulder internal rotation effort.
Use consistent verbal cues.
"Rotate your forearm towards your body."
"Increase the pressure smoothly."
"Push as hard as you can."
"Hold."
"Keep breathing."
Repeat the same instructions during every reassessment.
Use:
1–2 familiarisation trials
2–3 maximal trials
3–5 second contractions
30–60 seconds rest between trials
Record either:
highest force value, or
average of recorded trials
Maintain the same scoring method during future testing.
the elbow lifts away from the trunk
the trunk rotates
the shoulder elevates
the forearm changes position
the load cell slips
pain limits maximal effort
the client starts before instructed
The assessment may be useful for:
baseline shoulder strength assessment
side-to-side comparison
monitoring strength over time
athlete performance profiling
objective reporting using Measurz
monitoring response to exercise
client education
The assessment should support broader clinical reasoning and should not be used as a stand-alone diagnostic or return-to-sport assessment.
The primary outcome is peak isometric shoulder internal rotation 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:
rotator cuff integrity
shoulder joint stability
movement quality
shoulder mobility
throwing mechanics
readiness for sport or work
Higher force values generally indicate greater shoulder internal rotation strength.
Lower force values may reflect:
pain
fatigue
previous injury
reduced confidence
poor familiarisation
inconsistent positioning
movement compensation
Interpret results by considering:
previous assessment results
left versus right differences
symptoms during testing
movement compensations
occupational, sporting or daily-life demands
Published Anker-specific normative values are currently unavailable.
Shoulder internal rotation strength has demonstrated excellent reliability using handheld and fixed dynamometry when shoulder position, elbow position and lever arm are standardised. Because testing protocols differ between devices, the client's own baseline and repeated assessments performed using the same setup are generally more meaningful than comparison with published force values.
A side-to-side difference of approximately 10% or greater may warrant further investigation, particularly when accompanied by symptoms, previous injury or reduced functional performance.
Youth
Interpret findings relative to growth, coordination and sporting participation.
Adults
Useful for baseline assessment and monitoring strength over time.
Older adults
Interpret alongside upper-limb function, lifting ability and activities of daily living.
Athletes
Particularly useful for throwing sports, swimming, racquet sports, combat sports and strength athletes.
Clients with persistent symptoms
Interpret alongside pain, confidence and functional capacity rather than muscle strength alone.
Common errors include:
elbow lifting away from the trunk
shoulder abduction during the effort
trunk rotation
shoulder elevation
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 shoulder function
published Anker-specific normative values remain limited
The assessment may be useful for:
establishing baseline shoulder strength
monitoring progress over time
comparing left and right limbs
athlete performance profiling
objective reporting using Measurz
educating clients using measurable outcomes
It measures maximal isometric shoulder internal rotation strength with the shoulder positioned at 0° abduction.
Testing at 0° shoulder abduction provides a comfortable and repeatable position while minimising unnecessary shoulder loading.
Peak force is the primary outcome measure.
Yes. Bilateral testing allows meaningful side-to-side comparison.
No. It measures muscle force only and should always be interpreted alongside symptoms and other assessment findings.
Measures maximal isometric shoulder internal rotation strength.
Performed with the shoulder adducted and the elbow flexed to 90°.
Primarily assesses the subscapularis and larger shoulder internal rotators.
Peak force is the primary routine outcome measure.
Consistent positioning and forearm contact point improve repeatability.
Baseline comparison and repeated testing are generally more valuable than broad population norms.
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.
