Effects of emphasized plantarflexion stop and heel lift height on the plantarflexion resistive torque in healthy young adults wearing ankle foot orthoses.
Mikio Fujimoto, Shota Suzuki, Minori Masuda and 1 others
Moving the AFO's plantarflexion stop toward dorsiflexion and adding a heel lift both increase the torque the brace absorbs at heel strike, and the two effects compound.
The ankle joint hardware must be reinforced when both settings are increased.
Key findings
1Both plantarflexion stop angle and heel-lift height significantly increased the first peak PFRT (partial η² = 0.94 and 0.85 respectively), with a synergistic interaction (partial η² = 0.24). All simple main effects were significant (p = 0.000).
2The second peak PFRT was primarily influenced by plantarflexion stop angle, while the effect of heel-lift height was limited.
3No significant effects of plantarflexion stop angle, heel-lift height, or their interaction were found on cadence, stride length, or walking speed.
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What it does not show
All participants were healthy young adults with no gait abnormality; the values do not reflect what happens in a patient with spastic hemiplegia, ankle or knee contractures, or impaired tibialis anterior function, all of which would change the torque the AFO must absorb. The AFO ankle joint position could not be individually adjusted for each participant; three standard sizes were used, so some mismatch between the joint axis and the anatomical axis was unavoidable. Only a rigid metal-rod stop was tested. AFOs with springs, oil dampers, or controlled plantarflexion will produce different PFRT values. No electromyography was recorded, so the contribution of tibialis anterior eccentric activity (which would reduce the first peak in a healthy person but be absent in a hemiplegic patient) could not be assessed. Participants were told the study focused on PFRT and may have consciously maintained a consistent gait pattern, potentially masking real effects on cadence and stride. Gait screening was by visual assessment only, without objective gait analysis, so subtle abnormalities may have been missed.
Declared interests
Partially supported by the Research Foundation for Rehabilitation Medicine, Koshigaya, Japan. The funding body had no role in study design, conduct, data analysis, interpretation, or manuscript preparation. The authors declare no conflicts of interest.
The easy way to misread this
Do not read the PFRT values measured here as what a patient with hemiplegia will experience in their AFO. The study used healthy young adults with intact tibialis anterior function and no contractures; in a spastic hemiplegic patient the absent or reduced eccentric muscle control and altered joint geometry would produce different torques, and the rigid-stop design tested here is not representative of spring- or damper-based AFOs commonly prescribed in practice.
Summarised by AI from the full paper, without a clinician reviewing it. Check it against the source before it changes what you do. Read it on PubMed →