Reliability and minimal detectable change of stiffness and other mechanical properties of the ankle joint in standing and walking.
Luis H Cubillos, Elliott J Rouse, Thomas E Augenstein and 3 others
PMID 37988887WHAT IT FOUND
Ankle stiffness and viscosity measured via perturbation show good-to-excellent reliability in healthy adults during both standing and walking.
Standing measurements had lower error margins, making them quicker and more stable, while walking offers functional insight but requires strict foot placement.
Key findings
01Stiffness and viscosity parameters demonstrated good to excellent test-retest reliability in both standing and walking conditions.
02The minimal detectable change for stiffness was 53-65% of the mean, and for viscosity was 20-55%, with standing generally showing lower error than walking.
03Inertia measurements during walking were unreliable when the robot's inertia was removed, but stiffness and viscosity remained robust.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only healthy young adults, so reliability and minimal detectable change may differ significantly in patient populations with spasticity or gait disorders. The measurement device is a specialized lab-based robotic platform, which limits immediate clinical application outside research settings. Only the dominant leg and dorsiflexion direction were tested, so results may not generalize to the non-dominant leg or plantarflexion. Inertia measurements were unreliable during walking when the robot's mass was excluded, limiting the utility of that specific parameter in gait analysis.
Declared interests
The authors declared no conflicts of interest. The study was supported by the National Institutes of Health and the University of Michigan.
The easy way to misread this
Do not assume these reliability values apply to patients with neurological conditions like stroke. The study only tested healthy adults, and the authors explicitly state that further testing in clinical populations is needed before this method can be used as a standard assessment tool.