Dual-channel functional electrical stimulation improvements in speed-based gait classifications
Clinical Interventions in Aging
Dual-channel functional electrical stimulation improvements in speed-based gait classifications
Shmuel Springer 1 2
Yocheved Laufer 2
Meni Becher 1 2
Jean-Jacques Vatine 0 3
0 Outpatient and Research Division, Reuth Medical Center , Tel Aviv
1 Clinical Department , Bioness Neuromodulation, Ra'anana
2 Department of Physical Therapy, Faculty of Social Welfare and Health Sciences, University of Haifa , Haifa
3 Department of Rehabilitation Medicine, Sackler Faculty of Medicine, Tel-Aviv University , Tel-Aviv , Israel
PowerdbyTCPDF(ww.tcpdf.org) Background: Functional electrical stimulation (FES) is becoming an accepted treatment method for enhancing gait performance in patients who present with gait difficulties resulting from hemiparesis. The purpose of this study was to test whether individuals with hemiparesis who have varied gait speeds, which place them in different functional categories, benefit to the same extent from the application of FES. Methods: Thirty-six subjects with chronic hemiparesis demonstrating foot-drop and deficits in knee and/or hip control were fitted with a dual-channel FES system activating the dorsiflexors and hamstring muscles. Gait was assessed during a 2-minute walk test with and without stimulation. A second assessment was conducted after 6 weeks of daily use. Analysis was performed with the subjects stratified into three functional ambulation classes according to their initial gait categories. Results: The dual-channel FES improved the gait velocity of all three subgroups. No minimal gait velocity was required in order to gain benefits from FES. For example, subjects with limited household ambulation capabilities improved their gait speed by 63.3% (from 0.30 ± 0.09 m/sec to 0.49 ± 0.20 m/sec; P , 0.01), while subjects with functional community ambulation capabilities improved their gait speed by 25.5% (from 0.90 ± 0.11 m/sec to 1.13 ± 0.22 m/sec; Conclusion: Dual-channel FES positively affects gait velocity in patients with chronic hemiparesis, regardless of their initial gait velocity. Furthermore, gait velocity gains may be large enough to change an individual's ambulation status to a higher functional category.
hemiparesis; functional electrical stimulation; gait velocity; ambulation
open access to scientific and medical research
Restoration of independent and functional ambulation is a major rehabilitation goal
for patients with hemiparesis. Although the majority of these patients achieve some
degree of independent gait, many do not reach a walking level that enables them to
perform activities of daily living.1,2 The inability to resume community level
ambulation is estimated to afflict at least 50% of individuals with hemiparesis, resulting in
diminished independence and quality of life.1,3 Furthermore, gait performance
following termination of conventional therapy is characterized by elevated energy cost, poor
endurance, and repeated falls with ensuing dire consequences.4
Gait speed is related to lower extremity strength and motor control,5 balance
and functional mobility,6 gait endurance,7 energy expenditure and disability.8 Gait
speed is considered to be a significant, sensitive, and reliable marker of hemiparetic
gait recovery.9 Improved gait velocity is associated with better function and quality
prolonged use of FES as an orthotic device, even by patients
with chronic hemiparesis, has been shown to have a
therapeutic effect, with some of the gains in gait performance
maintained even when FES is not activated.13–15
Traditionally, peroneal stimulation to ameliorate
footdrop, which entails the use of two electrodes located over the
common peroneal nerve and tibialis anterior muscle, is the
most commonly used form of FES.16 However, FES of the
dorsiflexors does not improve all gait deficits associated with
hemiparetic gait, because many patients with hemiparesis
also demonstrate other muscle control deficits, such as
insufficient knee and hip control. In recent years, multichannel
FES has been used to include additional muscle groups by
placing more than one pair of electrodes near motor points or
nerves targeted for activation. Thus, stimulation of different
combinations of muscle groups has been shown to improve
the gait speed of patients with hemiparesis.17,18 However,
to the best of our knowledge, none of the previous studies
examined whether the improvement in speed is dependent on
the initial gait speed deficits of the users. In particular, they
did not explore whether individuals with varied gait speeds,
which place them in different functional categories, benefit
to the same extent from application of FES.
In recent research, it was demonstrated that specific use
of multichannel stimulation, ie, dual-channel stimulation
applied to the ankle dorsiflexors during the swing phase
and to the hamstrings during the stance phase, improved
the temporal as well as kinematic characteristics of gait
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in patients with insufficient knee and ankle control.19,20
Following these studies, the objective of the current study
was to determine whether the impact of dual-channel FES
applied to these muscles is dependent on the individuals’
initial deficits in gait speed.
Materials and methods
Design and participants
Data in this study were derived from a parent study which
evaluated the effects of daily peroneal and thigh (hamstring
or quadriceps) muscle FES on the temporal aspects of gait
performance in individuals with hemiparesis.19 The findings
of the parent study suggested that dual-channel application
of FES improves the temporal characteristics of gait better
than single-channel FES in this group of patients. The study
was approved by the institutional review board of the Reuth
Medical Center, Israel. All subjects signed an informed
The present analysis included only subjects who were at
least 6 months post-diagnosis and who had the dual-channel
FES applied to the peroneal and hamstring muscles (and not
to the quadriceps, as in the parent study). Peroneal
stimulation was intended to ameliorate foot-drop, and hamstring
stimulation was applied to assist with hip and knee control
(ie, to reduce knee hyperextension and/or improve hip
Thirty-six subjects with chronic hemiparesis were
included in the analysis. Subjects were recruited from
outpatient clinics at rehabilitation centers in the central region
of Israel. Inclusion criteria were: diagnosis of an upper
motor neuron lesion; hamstring strength less than 4/5, as
determined by manual muscle testing; foot-drop, ie, toe
drag during walking; lower limb spasticity ranked at 0–3
according to the modified Ashworth scale; ability to walk
independently or with an assistance device (eg, a cane or
walker) or spot guarding for at least 10 m; ability to follow
multiple-step directions, with a score greater than 21 on the
Mini Mental State Examination;21 and sufficient response to
electrical stimulation, ie, visible muscle contractions of each
designated muscle, as tested in a seated position. Exclusion
criteria were a cardiac pacemaker, a skin lesion at the site of
the stimulation electrodes, severe neglect (Star cancellation
test , 30), or major depression.
Dual-channel FES system
The dual-channel FES system used in this study (NESS
L300Plus Bioness, Valencia, CA, USA) consisted of lower
leg and thigh cuffs, a gait sensor, and a control unit that
communicates by radiofrequency signals (Figure 1). The
lower leg and thigh cuffs were designed to enable accurate
and repeatable placement. Each cuff integrates two electrodes
and a stimulation unit. The electrodes of the lower leg cuff
were located over the common peroneal nerve and the tibialis
anterior muscle. The electrodes of the thigh cuff were
positioned over the hamstring muscles. The gait sensor detects the
force under the foot using a force-sensitive resistor. It uses a
dynamic gait tracking algorithm to detect whether the foot
is on the ground or in the air and transmits radio signals
to synchronize stimulation according to the timing of gait
events. A miniature control unit enables the user to activate
the system and receive information regarding its status.
A hand-held computer is used by a clinician during the fitting
process to set the stimulation parameters (eg, intensity, pulse
frequency) and timing of the stimulation.
The peroneal stimulation (symmetrical biphasic, phase
duration 200 µsec, pulse rate 30 Hz) was configured to the
swing phase so as to ameliorate foot-drop, while the
hamstring stimulation (symmetrical biphasic, phase duration
300 µsec, pulse rate 40 Hz) was delivered from mid stance
to initial swing in order to assist with knee and hip control.
gait velocity evaluation
Gait velocity was assessed at baseline and after 6 weeks of
conditioning by a qualified physical therapist as follows:
immediately after fitting the dual-channel FES system and
adjusting the electrode placement and stimulation parameters,
each patient underwent gait evaluations with and without
FES. This initial assessment (T1) was followed by a 6-week
adaptation period during which participants increased their
daily use of the system according to a fixed protocol, so that
by the end of the fourth week, all subjects were able to use
the system for the entire day. A second assessment (T2) was
conducted after this 6-week period. Under each walking
condition (ie, with and without FES) in both assessments,
gait velocity was measured during a 2-minute walk test.
Under each 2-minute walk test condition, the subjects were
instructed to walk as far as they could, at their self-selected
normal walking speed, back and forth along a 50 m hallway,
turning around each time they reached the end of the
walkway. Average gait speed was determined by dividing the
distance covered in 2 minutes by 120 seconds.
The 2-minute walk test has been shown to correlate well
with the longer 6-minute and 12-minute walk tests,22 and was
selected to minimize fatigue effects. This commonly used
gait performance test is highly reliable and frequently used
to evaluate gait performance in individuals with hemiparesis
Descriptive statistics (mean ± standard deviation) were used
to differentiate between three subgroups according to their
initial gait velocity, as determined at T1 without stimulation:
subgroup A (limited household ambulation); subgroup B
(limited community ambulation); and subgroup C (functional
community ambulation). A 3 × 2 × 2 (group ×
condition × time) repeated-measures analyses of variance was
performed in order to examine the effect of FES versus no
stimulation and time on gait velocity in each subgroup. A
separate 2 × 2 (condition × time) analysis of variance was
also performed in order to examine the effect of FES and time
on the entire group. Analyses of variances were followed by
preplanned comparisons based on adjusted Tukey-Kramer
tests. Significance was determined at P , 0.05. The analysis
was conducted using SAS version 9.1 (SAS Institute, Cary,
Data on subject characteristics are summarized in Table 1. Of the
36 subjects, 15 subjects were classified as subgroup A (limited
household ambulation), 15 subjects as subgroup B
(limited community ambulation), and only six as subgroup C
(functional community ambulation). Table 2 presents all gait
velocity results with and without FES at T1 and T2 by subgroup
as well as for all subjects combined. Gait velocity results for
all three subgroups (A–C) are also presented in Graph 1.
The two-way analysis of variance examining the effect
of stimulation condition and time on the entire group
(2 × 2 analysis) indicated significant effects for condition
(P , 0.0001) and time (P , 0.0001), as well as a significant
Graph 1 Effect of functional electrical stimulation on gait velocity in the three subgroups of ambulation categories.
interaction effect for condition × time (P = 0.02). The
three-way analysis of variance examining the effect of FES
and time on each subgroup separately (3 × 2 × 2 analysis)
indicated significant effects for group, time, and condition
(P , 0.0001). An interaction effect was also found for
group × condition × time (P = 0.04). Preplanned comparisons
based on adjusted Tukey-Kramer tests were used to
investigate the four fundamental effects of FES as delineated (also
shown in Table 3).
The orthotic effect refers to the change in gait speed during
ambulation while using the FES device, as compared with
ambulation without stimulation. Two comparisons were made
in order to reflect the orthotic effect over the trial period:
orthotic effect at T1 (ie, FES at T1 versus no stimulation at T1)
and orthotic effect at T2 (ie, FES at T2 versus no stimulation
at T2). The orthotic effect at T1 was found to be significant
in all three subgroups, as well as in the entire group analysis.
For example, in subgroup A, gait speed with FES increased by
33.3% from 0.30 ± 0.09 m/sec to 0.40 ± 0.14 m/sec (P , 0.01).
In the entire group, gait speed increased at T1 by 18.5% from
0.54 ± 0.24 m/sec to 0.63 ± 0.27 m/sec (P , 0.001).
After 6 weeks of using the FES system (T2), the orthotic
effect was found to be signif icant in the entire group
(P , 0.001), as well as in subgroups A and B (P = 0.0003
and P , 0.0001, respectively), but not in subgroup C among
the functional community ambulators.
The therapeutic effect, which refers to the carryover impact
of FES, was measured by comparing the gait speed without
stimulation at T1 with the gait speed in the same condition
at T2. Although higher gait speeds were measured at T2 in
all three subgroups, none of the changes reached significance.
However, the entire group analysis did demonstrate a
significant therapeutic effect (P = 0.001).
The habituation effect illustrates the conditioning of the user
to the FES device. It compares the baseline gait speed with
FES at T1 with walking using the system after a 6-week
adaptation period at T2. The habituation effect was found to
be significant in the entire group (P , 0.001), as well as in
subgroups A and B (P = 0.02 and P , 0.0002, respectively),
but not in subgroup C. The adaptation period increased gait
speed with FES in subgroup A, subgroup B, and the entire
group by 22.5%, 20%, and 17%, respectively.
Overall FES effect
The overall FES effect summarizes the inclusive FES impact
by comparing the baseline gait speed without stimulation at
T1 with the gait speed with stimulation at T2. This outcome
was found to be significant in all three subgroups, as well as
in the entire group analysis. The subgroup with the largest
improvement was that of the limited household ambulators
(subgroup A), which improved by 63.3% from 0.30 ± 0.09 m/
sec to 0.49 ± 0.20 m/sec (P , 0.01).
This study investigated the effect of dual-channel FES,
applied to the hamstrings and dorsiflexors muscles, on gait
speed of patients with chronic hemiparesis with varied gait
abilities. Our goal was to examine the effect of FES on
gait velocity in patients differing in their initial ambulatory
capabilities, as determined by three functional ambulation
categories. The results showed that dual-channel FES had
a positive effect on gait velocity in all three subgroups. In
addition, no minimal gait velocity was required in order to
gain benefits from FES. The household ambulators, who
were characterized by very low gait speed and probably had
more severe neurological deficits, enhanced their walking
speed as well.
The National Institutes of Health has emphasized the need
for research in order to assess the effectiveness of
rehabilitation interventions for subjects post stroke.24 The present study
contributes to this goal by demonstrating that FES can be a
useful intervention for a wide variety of patients following
stroke. Furthermore, the study was conducted in subjects
with chronic hemiparesis who were, on average, 6.3 years out
from diagnosis. The performance of individuals with chronic
hemiparesis is generally expected to either remain steady or
to deteriorate over time.25 Thus, it seems unlikely that these
results would have been achieved without the use of FES.
The overall FES effect, namely the contribution of FES
following the adaptation period, was found to be significant
and larger than 0.1 m/sec in all three subgroups, as well as in
the entire group analysis. Previous research findings indicate
that even small improvements in gait speed are sufficient to
detect real clinical changes in disabled elderly individuals.23 For
example, based on a data set that included 100 individuals post
stroke, Perera et al26 estimated a change of 0.04–0.06 m/sec
in gait speed to be a small meaningful change. In older adults
without specific impairments, as well as in adults after a hip
fracture, a change in gait velocity of 0.1 m/sec has been
determined as a minimal clinically important difference.27
The magnitude of the increase in gait velocity with FES
(overall FES effect) in subgroups A and B was large enough
to change an individual’s ambulation status from limited
household ambulation to limited community ambulation and
from limited community ambulation to functional community
ambulation. This is of particular significance, because it has
been demonstrated that gait velocity gains which result in
a transition to a higher ambulation category are associated
with better function and quality of life.10
.rvdoepww ll.syeuon suggest that such studies are warranted.
the subjects in the two slower subgroups continued to
improve their performance with FES, as demonstrated by
the significant habituation effect, those in the fastest
subgroup (subgroup C) showed a more immediate FES effect.
One possible explanation for this difference is that patients who
can walk relatively fast and are functional community
ambulators may require a longer period of use (ie, .6 weeks) of the
FES in order to demonstrate a habituation effect.28 Moreover,
lack of a significant effect in the subgroup of the functional
community ambulators may be related to its small size, which
may also explain the lack of an orthotic effect in this subgroup
at T2. Thus, the differences in improvement with FES over
time between the subgroups cannot be addressed adequately
with the current data. To understand these differences fully,
longer longitudinal studies with a larger sample should be
planned. The promising results of the present investigation
The carryover effect to gait without the application of
FES was found to be significant only in the entire group
analysis. Although not all previous studies of FES have
demonstrated carryover effects,29–31 there is a growing body
of evidence indicating that FES may have therapeutic effects
which persist beyond the period of stimulation.28,32 A possible
explanation for these results may be related to the relatively
small size of the subgroups, such that the therapeutic effect
becomes evident only in the entire group analysis. In addition,
positive carryover effects may necessitate longer periods of
FES and need to be investigated further.
The present study has several limitations, including
the protocol duration of 6 weeks and the relatively small
sample size, especially in the subgroup of functional
community ambulators. The initial mean gait velocity in the
present sample (0.54 ± 0.24 m/sec) is consistent with other
studies involving subjects with chronic hemiparesis.33,34 It
can thus be assumed that the gait velocity distribution in
our study is also representative of the population of patients
with chronic hemiparesis who have deficits in knee and
ankle control, because not many patients with these
limitations are expected to obtain a baseline velocity greater
than 0.8 m/sec. Further investigations should be undertaken
to confirm our study results in larger samples and with
longer durations of use. Finally, our results demonstrated
gait velocity gains with FES that are associated with better
function and quality of life. However, the study did not
include specific measures of function and social
participation. Thus, future research using appropriate outcome
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Although all three subgroups improved their gait speed
measures for function and social participation in addition
with FES, the improvement pattern was not similar. While
to gait speed are warranted.
The study indicates that dual-channel FES positively affects
gait velocity in patients with chronic hemiparesis, regardless
of their initial status in terms of gait performance.
Furthermore, the gains in gait velocity are apparently of a magnitude
that may have functional implications for an individual’s
degree of independent ambulation, enabling individuals who
were initially home-bound to acquire limited community
ambulation capabilities, and those who had limited
community ambulation capabilities to reach the level of functional
community ambulation. Because this study included a
relatively small sample size, future studies should be carried out
in order to confirm the current results.
SS and MB are employed by Bioness Neuromodulation,
the manufacturer of the L300Plus. Other authors have no
conflicts of interest to declare.
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Clinical Interventions in Aging is an international, peer-reviewed journal
focusing on evidence-based reports on the value or lack thereof of
treatments intended to prevent or delay the onset of maladaptive correlates
of aging in human beings. This journal is indexed on PubMed Central,
MedLine, the American Chemical Society’s ‘Chemical Abstracts
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