Does Gait Assistance Modulate Reflex Excitability in Those with Spasticity? A Preliminary Study.

Area of Science:

• Neuroscience
• Rehabilitation Engineering
• Biomechanics

Background:

• Stiff-knee gait (SKG) is a common post-stroke mobility impairment characterized by reduced knee flexion during the swing phase.
• This impairment increases fall risk and necessitates compensatory movements, leading to adverse biomechanical effects.
• Assistive technologies like functional electrical stimulation (FES) and exoskeletons aim to mitigate muscle weakness in SKG, but may inadvertently affect spinal reflex excitability.

Purpose of the Study:

• To investigate the impact of two FES modalities (plantarflexor and knee flexor assistance) on rectus femoris (RF) reflex excitability in individuals with post-stroke SKG.
• To determine if FES effects on reflex excitability differ between rest and during gait.

Main Methods:

• Six individuals with post-stroke SKG participated in the study.
• The study assessed RF reflex excitability at rest and during gait under two FES conditions: plantarflexor assistance and knee flexor assistance.

Main Results:

• At rest, plantarflexor FES facilitated RF reflex excitability, whereas knee flexor FES induced a slight inhibition.
• During gait, FES-induced changes in reflex excitability were observed in some individuals but were less consistent than at rest.

Conclusions:

• Functional electrical stimulation (FES) can modulate reflex excitability in individuals with stiff-knee gait.
• The effect of FES on reflex excitability is context-dependent, varying between rest and gait, and between different FES modalities.