Article

Foot drop is a common gait impairment after stroke. Functional
electrical stimulation (FES) of the ankle dorsiflexor muscles during the swing
phase of gait can help correct foot drop. Compared with constant-frequency trains
(CFTs), which typically are used during FES, novel stimulation patterns called
variable-frequency trains (VFTs) have been shown to enhance isometric and
nonisometric muscle performance. However, VFTs have never been used for FES
during gait. OBJECTIVE: The purpose of this study was to compare knee and ankle
kinematics during the swing phase of gait when FES was delivered to the ankle
dorsiflexor muscles using VFTs versus CFTs. DESIGN: A repeated-measures design
was used in this study. PARTICIPANTS: Thirteen individuals with hemiparesis
following stroke (9 men, 4 women; age=46-72 years) participated in the study.
METHODS: Participants completed 20- to 40-second bouts of walking at their
self-selected walking speeds. Three walking conditions were compared: walking
without FES, walking with dorsiflexor muscle FES using CFTs, and walking with
dorsiflexor FES using VFTs. RESULTS: Functional electrical stimulation using both
CFTs and VFTs improved ankle dorsiflexion angles during the swing phase of gait
compared with walking without FES (X+/-SE=-2.9 degrees +/- 1.2 degrees). Greater
ankle dorsiflexion in the swing phase was generated during walking with FES using
VFTs (X+/-SE=2.1 degrees +/- 1.5 degrees) versus CFTs (X+/-SE=0.3+/-1.3 degrees).
Surprisingly, dorsiflexor FES resulted in reduced knee flexion during the swing
phase and reduced ankle plantar flexion at toe-off. CONCLUSIONS: The findings
suggest that novel FES systems capable of delivering VFTs during gait can produce
enhanced correction of foot drop compared with traditional FES systems that
deliver CFTs. The results also suggest that the timing of delivery of FES during
gait is critical and merits further investigation.

Langue : ANGLAIS