Functional electrical stimulation of ankle plantarflexor and dorsiflexor muscles: effects on poststroke gait

Abstract

Background and purpose: Functional electrical stimulation (FES) is a popular poststroke gait rehabilitation intervention. Although stroke causes multijoint gait deficits, FES is commonly used only for the correction of swing-phase foot drop. Ankle plantarflexor muscles play an important role during gait. The aim of the current study was to test the immediate effects of delivering FES to both ankle plantarflexors and dorsiflexors on poststroke gait.

Methods: Gait analysis was performed as subjects (N=13) with chronic poststroke hemiparesis walked at their self-selected walking speeds during walking with and without FES.

Results: Compared with delivering FES to only the ankle dorsiflexor muscles during the swing phase, delivering FES to both the paretic ankle plantarflexors during terminal stance and dorsiflexors during the swing phase provided the advantage of greater swing-phase knee flexion, greater ankle plantarflexion angle at toe-off, and greater forward propulsion. Although FES of both the dorsiflexor and plantarflexor muscles improved swing-phase ankle dorsiflexion compared with noFES, the improvement was less than that observed by stimulating the dorsiflexors alone, suggesting the need to further optimize stimulation parameters and timing for the dorsiflexor muscles during gait.

Conclusions: In contrast to the typical FES approach of stimulating ankle dorsiflexor muscles only during the swing phase, delivering FES to both the plantarflexor and dorsiflexor muscles can help to correct poststroke gait deficits at multiple joints (ankle and knee) during both the swing and stance phases of gait. Our study shows the feasibility and advantages of stimulating the ankle plantarflexors during FES for poststroke gait.

Figures

Figure 1

(A) Foot switch and vertical ground reaction force (GRF) data from the paretic and non-paretic leg of one subject. There was considerable variability in the relative timing of the events shown in this figure across subjects. Vertical GRFs were used to identify swing and stance phases of gait. Footswitch signals were used to trigger FES during gait. During each gait cycle, dorsiflexor FES was started at paretic foot-off and terminated at paretic initial contact. Plantarflexor FES was started at paretic heel-off (Arrow 1) for Logic 1 and at non-paretic initial contact (Arrow 2) for Logic 2; and terminated at paretic foot-off. (B) Stimulation train patterns used for FES. VFTs consisting of a three-pulse 200-Hz burst at the start of a 30-Hz CFT were used in this study. Traditionally-used CFTs are shown for comparison.

Figure 2

(A) Antero-posterior GRF during the gait cycle for one representative subject. (B) and (C) Means (N=11) and standard errors for (B) peak AGRF and (C) % paretic propulsion during paretic stance. Walking conditions presented are noFES, DF, and PDF. * Significant difference from noFES (p 0.05). † Significant difference from DF (p≤0.05).

Figure 3

(A) Sagittal plane knee angles during the gait cycle for one representative subject. (B) Means (N=12) and standard errors for peak swing phase knee flexion angles during noFES, DF, and PDF. * Significant difference from noFES (p≤0.05). ‡ Significant difference from DF (p≤0.05).

Figure 4

(A) Sagittal plane ankle angles during the gait cycle for one representative subject. Means (N=12 subjects) and standard errors for ankle angles at paretic toe-off (B) and peak swing phase ankle dorsiflexion (C) during noFES, DF, and PDF. * Significant difference from noFES (p≤0.05). ‡ Significant difference from DF (p≤0.05). Negative angles represent plantarflexion.