Excellent Reliability for an Instrumented Test of Ankle Plantarflexion Force.
Moez Glaied, Rodney Whiteley
PMID 39906052WHAT IT FOUND
A new seated plantarflexion strength test showed excellent reliability in 61 healthy adults.
Scores need to change by 118N to be considered real. This provides a consistent baseline for monitoring lower-limb rehab and performance in sports.
Key findings
01The test demonstrated excellent test-retest reliability with an ICC of 0.976.
02The minimal detectable change for the force measure was 118N, equivalent to 0.148 bodyweights.
03There was no systematic bias between the initial test and the retest.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The sample was a convenience group of healthy adults, so results may not apply to injured or clinical populations. Only 20% of participants were women, so caution is needed when applying these reliability values to female patients. The test measures total plantarflexion force, not soleus strength specifically, as other calf muscles also contribute to the movement. Thigh and knee angles were standardized by position but not recorded numerically, which could affect reproducibility in other settings.
Declared interests
The authors developed the custom testing device but declared no financial links or conflicts of interest. The device is not for sale, and instructions for building it are provided.
The easy way to misread this
Do not interpret this test as measuring soleus muscle strength in isolation. The force generated includes contributions from all plantarflexor muscles, so a change in score reflects overall calf function rather than soleus-specific capacity.