The Shoulder Horizontal Abduction Strength Test measures the maximum isometric force produced as the arm moves away from the body's midline in the transverse plane. Using the Anker, the assessment provides an objective measure of posterior shoulder strength in a repeatable testing position.
Horizontal abduction strength contributes to rowing movements, throwing preparation, swimming, climbing, posture and scapular control. Assessing this movement complements horizontal adduction testing and provides a broader profile of shoulder strength.
The primary muscles assessed include the posterior deltoid, middle trapezius, rhomboids and infraspinatus, with contribution from the teres minor depending on shoulder position.
When used with Measurz, the Anker records peak force and additional force-time metrics including force relative to body weight, impulse, torque, rate of force development, time to peak and fatigue index.
The assessment measures muscle force only and should always be interpreted alongside symptoms, mobility and functional performance.
The Shoulder Horizontal Abduction Strength Test is an isometric assessment where the client attempts to move the arm backwards in the transverse plane while maintaining a stable trunk and shoulder.
The test is commonly performed with the shoulder abducted to 90° and the elbow flexed to 90°, allowing consistent loading of the posterior shoulder musculature.
The fixed resistance of the Anker provides repeatable testing when positioning, anatomical landmarks and instructions remain unchanged.
Explain that the assessment measures how strongly they can move their arm backwards.
Record any:
shoulder pain
upper back pain
previous shoulder injury
previous surgery
neurological symptoms
stiffness
fatigue
Perform one or two familiarisation trials.
Position the client:
seated upright
trunk supported
feet flat on the floor
shoulder abducted to 90°
elbow flexed to 90°
forearm neutral
Maintain identical positioning during every reassessment.
Ensure:
scapula remains neutral
humerus remains level
elbow aligns with the shoulder
wrist remains relaxed
Position the Anker load cell against the posterior aspect of the distal humerus, approximately 5 cm proximal to the olecranon.
Avoid direct contact over the elbow joint.
Record the contact point for future testing.
Prevent movement of:
trunk
pelvis
opposite shoulder
scapular elevation
The effort should come from shoulder horizontal abduction rather than trunk extension or rotation.
Use consistent verbal cues.
"Push your arm backwards."
"Increase the pressure smoothly."
"Push as hard as you can."
"Hold."
"Keep breathing."
Use:
1–2 familiarisation trials
2–3 maximal trials
3–5 second contractions
30–60 seconds rest
Record the highest force or average of recorded trials.
trunk rotates
shoulder elevates
elbow changes position
load cell slips
pain limits effort
client starts before instructed
The assessment may be useful for:
baseline posterior shoulder assessment
side-to-side comparison
athlete profiling
monitoring progress
objective Measurz reporting
client education
Primary outcome:
Peak isometric shoulder horizontal abduction force.
Additional Measurz metrics 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 joint stability, movement quality or sporting performance.
Higher force values indicate greater posterior shoulder force production.
Lower values may reflect:
pain
fatigue
previous injury
reduced effort
inconsistent positioning
Interpret findings using:
baseline comparison
left versus right comparison
symptoms
functional demands
Published Anker-specific normative values are currently unavailable. Consistent testing procedures and repeated assessments are generally more valuable than external reference values.
Youth: Interpret relative to development.
Adults: Useful for baseline assessment.
Older adults: Consider daily upper-limb function.
Athletes: Particularly useful for throwing, swimming, rowing, climbing and racquet sports.
Clients with persistent symptoms: Interpret alongside symptoms and function.
Common errors include:
trunk extension
trunk rotation
shoulder elevation
inconsistent load cell placement
inconsistent cueing
Limitations include:
position-specific results
pain may reduce force
strength alone does not determine shoulder function
Useful for:
baseline assessment
monitoring progress
athlete profiling
Measurz reporting
client education
Maximal isometric shoulder horizontal abduction strength.
Posterior deltoid, middle trapezius, rhomboids and infraspinatus.
Yes.
Peak force.
No.
Measures maximal shoulder horizontal abduction strength.
Primarily assesses the posterior shoulder musculature.
Peak force is the primary outcome.
Consistent positioning improves repeatability.
Measurz provides additional force-time metrics.
Compare results with previous assessments and the opposite shoulder.
Bohannon, R. W. (1997). Archives of Physical Medicine and Rehabilitation, 78(1), 26–32.
Stark, T., et al. (2011). PM&R, 3(5), 472–479.
Mentiplay, B. F., et al. (2015). PLOS ONE, 10(10), e0140822.
