320

CLINICAL NOTE

Near-Normal Gait Pattern With Peroneal Electrical
Stimulation as a Neuroprosthesis in the Chronic Phase of
Stroke: A Case Report
Roos van Swigchem, PT, MSc, Vivian Weerdesteyn, PhD, Hanneke J. van Duijnhoven, MD,
Jasper den Boer, PT, PhD, Tjemme Beems, MD†, Alexander C. Geurts, MD, PhD
ABSTRACT. van Swigchem R, Weerdesteyn V, van Duijnhoven HJ, den Boer J, Beems T, Geurts AC. Near-normal gait
pattern with peroneal electrical stimulation as a neuroprosthesis in
the chronic phase of stroke: a case report. Arch Phys Med Rehabil
2011;92:320-4.
In recent years, the use of functional electrical stimulation
(FES) of the peroneal nerve has increased as an alternative for
an ankle-foot orthosis (AFO) to treat stroke-related drop foot.
We present a chronic stroke patient demonstrating an almost
normal gait pattern with peroneal FES as a neuroprosthesis. A
60-year-old survivor of a right hemisphere infarction 21
months ago, who regularly used a polypropylene AFO, was
provided with a surface-based peroneal FES device for severe
drop foot. In a second instance, he received an implanted FES
system because of skin problems with the surface stimulator.
With both FES devices, the patient achieved an adequate foot
elevation. Moreover, his hip and knee flexion angles during
walking increased to normal values and his ankle push-off
power increased. His gait pattern became almost symmetrical
and less variable than with the AFO. Furthermore, his ability to
avoid a sudden obstacle improved to normal values with FES.
Our patient showed benefits from peroneal FES beyond what
can be attributed to improved foot lift alone. With regard to the
potential working mechanisms underlying this response to
FES, biomechanical benefits related to improved ankle pushoff are suggested as the main mechanism.
Key Words: Electric stimulation; Peroneal nerve; Rehabilitation; Stroke; Walking.
© 2011 by the American Congress of Rehabilitation
Medicine
PATIENTS who suffer from a drop foot, an
IphaseNAFOSTROKE
is usually provided to lift the foot during the swing
and early stance phase of gait in order to prevent the toes
from touching the ground and to facilitate heel loading. As an
alternative treatment, FES of the peroneal nerve as a form of

From the Department of Rehabilitation, Radboud University Nijmegen Medical
Centre, Nijmegen Centre for Evidence Based Practice (van Swigchem, Weerdesteyn,
van Duijnhoven, den Boer, Geurts) and Department of Neurosurgery, Radboud
University Nijmegen Medical Centre (Beems); Sint Maartenskliniek Research, Development and Education (Weerdesteyn, Geurts); and TWIN Institute for Neuromodulation (Beems), Nijmegen, The Netherlands.
Supported by Ness Netherlands B.V. (now Bioness), Otto Bock, and Unu B.V. in
The Netherlands.
No commercial party having a direct financial interest in the results of the research
supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.
Reprint requests to Roos van Swigchem, PT, MSc, Dept of Rehabilitation, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The
Netherlands, e-mail: R.Swigchem@reval.umcn.nl.
†Deceased.
0003-9993/11/9202-00522$36.00/0
doi:10.1016/j.apmr.2010.10.038

Arch Phys Med Rehabil Vol 92, February 2011

neuroprosthesis is gradually becoming more feasible due to
advanced and commercially available systems. Peroneal FES
activates the muscles that dorsiflex and evert the ankle joint as
well as the toe extensors and may lead to significant improvement in the gait pattern1 and gait speed2,3 compared to walking
without aids. Although FES has several theoretical advantages
over an AFO and patients’ preferences often support the use of
FES, there is as yet no conclusive evidence for the superiority
of peroneal FES over an AFO with respect to walking abilities.4,5 The aim of the present report is to demonstrate the
potential superiority of peroneal FES over an AFO. To this end,
we present a stroke patient who was used to walking with a
polypropylene AFO and who showed functional benefits from
FES that went beyond what can be attributed to improved foot
elevation alone (open access videos on http://www.neurorehab.
nl/APMR_english.htm). Secondly, we aim to discuss the potential mechanisms underlying the observed functional improvements.
CASE DESCRIPTION
Patient and Methods
A 60-year-old farmer presented himself at the outpatient
clinic of our university hospital 21 months after a right hemispheric infarction. Characteristics of the participant are provided in table 1. The Motricity Index6 of his left lower limb
was 27% with a 0 score for the ankle dorsiflexors. The strength
of his calf muscles was scored Medical Research Council7
grade 4. Because of his ankle dorsiflexor paralysis, the patient
used an AFO, which was a custom made polypropylene
(2.5-mm thickness) posterior splint, trimmed behind the malleoli of the ankle. The AFO was rigid into plantar flexion, but
allowed about 15° of ankle dorsiflexion. The patient was hardly
able to walk without this AFO due to foot drag during the
swing phase of gait, which he was not able to compensate by
active hip and knee flexion. At baseline (t0), his gait ability
with AFO was assessed, after which he received a surfacebased peroneal FES device, the NESS L300.a The L300 stimulated the peroneal nerve and the anterior tibial muscle using 2
electrodes embedded into a lightweight orthosis placed just

List of Abbreviations
AFO
COV
FES
Vplfl
Tswingasym
Mplfl

ankle-foot orthosis
coefficient of variation
functional electrical stimulation
maximal ankle plantar flexion velocity (at
push-off)
asymmetry in swing time duration
between left and right limb
maximal ankle plantar flexion torque (at
push-off)

321

PERONEAL STIMULATION IN STROKE, van Swigchem
Table 1: Characteristics of the Participant at Baseline
Variable

Patient’s outcome

Age (y)
Time poststroke (mo)
Sex (male/female)
Body weight (kg)
Body height (m)
Hemisphere of stroke
Type of stroke
Modified Ashworth Score (0–5)*
Knee flexors/extensors*
Ankle plantar flexors/dorsiflexors*
Lower extremity Motricity Index (0–100) *
Ankle score (0–33)*
Lower extremity Fugl-Meyer Assessment
(0–34)*
Calf muscle strength (Medical Research
Council 0–5)*
Quantitative Vibration Threshold (0⫽no
sensation; 8⫽normal)*
First metatarsophalangeal joint*
Lateral malleolus*
Berg Balance Scale (0–56)
Passive range of motion at ankle
(degrees)*
Dorsiflexion (knee extended/flexed)/
Plantar flexion*
Varus/Valgus*

59
21
Male
101
1.78
Right
Infarction
0/0
0/0
27
0
6
4

⬍2
2
41

(0/10)/35
30/15

*Scores at the paretic body side.

below the knee (symmetrical bipolar 42mA current; pulse rate
30Hz; phase duration 200␮sec) during the swing phase and the
subsequent loading response. Stimulation onset and offset were
based on detection of heel-off and heel-on by an insole foot
switch that communicated wirelessly with the stimulator that
was attached to the orthosis. In the following 2 weeks, the

patient increased the use of FES up to 6 hours a day. Subsequently, the gait assessment was repeated with both the AFO
and FES (t1 [measurements after 2 wk]). In the third week, the
patient developed an allergic skin reaction to the electrodes,
which was dermatologically confirmed. Because no alternative
electrodes were available at that time, the patient had to terminate the use of the surface stimulator shortly after he had
started. One year later, this patient was the first person to be
implanted with the ActiGaitb peroneal stimulator in The Netherlands. With this system, the common peroneal nerve was
directly stimulated through 4 distinct electrode arrays embedded in a cuff, which was surgically placed around the nerve
about 4cm above the knee joint (asymmetrical bipolar 1.2mA
current; pulse rate 20Hz; phase duration 247, 236, 210, and
0␮sec for channel 1 to 4). The stimulation settings of the 4
channels were individually adjusted such that a balanced eversion and dorsiflexion were evoked during the swing phase and
early stance phase of gait. Stimulation onset was timed simultaneously with heel-off, and the offset of stimulation was timed
using a ramp-down period of 0.5 seconds following heel strike.
Heel contacts were detected by an insole foot switch that
communicated wirelessly with the control unit that was worn
on a waist belt. The control unit was hard-wired externally to
a transmitter coil (antenna), positioned on the skin over a
receiver and stimulator, which was implanted subcutaneously
on the lateral side of the proximal thigh. The stimulator was
hard-wired subcutaneously to the cuff electrode. After he had
used this system all day long for 6 months, a third gait assessment was conducted with his AFO and with the implanted
stimulator (t2 [measurement after 1.5 y]. In addition, in spite of
the difficulties the patient experienced when he walked without
an orthosis, the assessment of comfortable walking was also
performed without any device at this occasion.
During each gait assessment, 70 gait cycles of treadmill walking at a comfortable speed of 0.56m/s were analyzed. Flexionextension movements of the hip, knee, and ankle joints were
measured with goniometersc at a sample rate of 1000Hz, and
maximal flexion and extension joint angles during the step cycle

Table 2: Results of the Gait Assessments
t0

t1

t2

Variable

AFO

AFO

Surface FES

AFO

Implanted FES

NO

Referent

Hip flexion (deg)
Hip extension (deg)
Knee flexion (deg)
Knee extension (deg)
Ankle dorsiflexion (deg)
Ankle plantar flexion (deg)
Mplfl (Nm/kg)
Vplfl (°/s)
COVhip (%)
COVknee (%)
COVankle (%)
Tswing asym (%)
OA success (%)
Gait speed (m/s)

23.2⫾1.5
0.5⫾1.6
45.6⫾5.9
1.8⫾0.9
9.2⫾1.3
⫺7.9⫾0.9
ND
76.5⫾15.0
16.0
37.1
33.6
42.0
17.0
0.99⫾0.13

17.9⫾1.5
⫺7.7⫾3.6
45.9⫾5.5
4.2⫾0.6
6.8⫾1.8
⫺8.0⫾1.4
ND
88.7⫾14.1
26.8
37.6
34.3
38.6
0.0
1.06⫾0.06

24.2⫾1.5
⫺8.1⫾1.5
66.3⫾1.6
2.7⫾0.7
9.5⫾0.8
⫺17.1⫾2.7
ND
135.0⫾28.0
15.4
23.2
29.4
14.8
68.0
1.07⫾0.04

20.5⫾3.2
8.9⫾5.2
27.6⫾2.4
6.3⫾4.6
3.2⫾2.1
⫺13.2⫾2.7
0.93⫾0.06
31.1⫾10.1
22.5
65.0
48.1
35.9
7.0
1.01⫾0.09

24.5⫾1.3
⫺9.3⫾1.5
56.8⫾1.2
4.4⫾0.6
10.8⫾1.0
⫺16.6⫾0.8
1.50⫾0.02
181.0⫾34.2
14.6
18.5
26.3
18.1
90.0
1.00⫾0.17

21.8⫾2.1
6.3⫾5.0
25.9⫾9.5
5.9⫾1.4
1.0⫾4.1
⫺26.9⫾4.0
1.15⫾0.21
117.4⫾46.0
27.1
71.7
37.6
60.1
ND
0.41⫾0.02

18.6⫾5.412
⫺11.3⫾7.812
61.8⫾7.012
1.7⫾3.212
8.6⫾3.612
⫺17.6⫾4.712
1.54⫾0.2312
136⫾53*12
88
88
218
⫺0.1⫾11.39
89.7⫾5.810
1.36⫾0.2113

NOTE. Results are displayed as mean ⫾ (within subject) SD at the paretic body side or as otherwise noted. Referent data are retrieved from
literature8-10,12,13 and displayed as mean ⫾ (between subjects) SD.
Abbreviations: COVankle, coefficient of variation for the ankle; COVhip, coefficient of variation for the hip; COVknee, coefficient of variation for
the knee; deg, degrees; gait speed, 10-m comfortable walking speed; Mplfl, maximal ankle plantar flexion torque (at push-off); ND, no data; NO,
no orthosis; OA success, obstacle avoidance success score; Tswing asym, asymmetry in swing time between left and right leg; Vplfl, maximal
ankle plantar flexion velocity within 200ms before toe-off.
*Referent SD of Vplfl was estimated from the figure of Winter.12

Arch Phys Med Rehabil Vol 92, February 2011

322

PERONEAL STIMULATION IN STROKE, van Swigchem

Fig 1. Time-normalized joint angles (from heel strike to heel strike) of the measurements at t1 (with the AFO and surface-based FES) and at
t2 (with the AFO, implanted FES, and no orthosis). Note: Movement variability (see variability band) of hip and knee decreased with FES.
Broken line, unaffected joint; solid line, affected joint; gray area, variability (2 times SD); Asterisks (*) at the affected and unaffected joint
angles indicate toe-off.

were determined. The COV for the hip (COVhip), knee (COVknee),
and ankle (COVankle) joint angles, and maximal ankle plantar
flexion velocity (Vplfl) were computed after low-pass filtering
(6Hz; zero lag, 4th order Butterworth filter) of the joint angle
signals. The COV was calculated as the root mean square of the
SD at each time interval divided by the mean magnitude of joint
angle over the stride.8 Vplfl was determined from the differentiated
ankle angle signal as the maximum value within 200ms before toe
off. With a 6-camera 3-dimensional motion analysis systemd, foot
marker data were collected at a sample rate of 100Hz to determine
heel strike and toe off. The asymmetry in swing time between left
and right limb (Tswingasym) was defined as:

关共Tswing-left ⫺ Tswing-right兲 ⁄ max共Tswing-left, Tswing-right兲兴 * 1009
where Tswing-left stands for swing time (from toe off to heel
strike) of the left (paretic) leg and Tswing-right stands for swing
time of the right (nonparetic) leg. Subsequently, to assess
advanced gait skills, the ability to avoid sudden obstacles
during walking was tested on a treadmill. Thirty obstacles were
dropped in front of the paretic foot during each test (for
detailed description of the methods see Weerdesteyn et al10,11).
Avoidance success rates were determined as the proportion of
trials without foot contact to the obstacle. Without any device,
walking ability was too poor to perform the obstacle avoidance
trials. Finally, comfortable gait speed was measured during overground walking on a 10-m walkway, both with FES and AFO.
In addition, at t2, ground reaction forces were measured for 1
step with each leg during 3 overground trials by means of 2 force
Arch Phys Med Rehabil Vol 92, February 2011

platese positioned in the middle of the walkway. Kinematic data
were recorded from 16 reflective markers, which were placed on
the lower limbs according to the lower-body model (Vicond).
These data were analyzed using the PlugInGait model in Vicon
Workstationd to obtain the joint torques of the lower limb.
RESULTS
The outcomes of the gait assessments are summarized in table
2. With surface-based FES (t1), maximal hip and knee flexion
angles during the gait cycle increased by 6.3° and 20.4°, respectively, compared with the AFO, while maximal hip and knee
extension angles were similar. COVhip and COVknee decreased by
11.4% and 14.4%, respectively. Vplfl increased by 46.3°/s with
FES compared to AFO. Finally, movement symmetry increased
with FES, as indicated by a 23.8% decrease in Tswingasym.
At t2, the gait pattern with AFO had deteriorated compared to
t0 and t1, as indicated most clearly by decreased stance phase hip
extension and swing phase knee flexion and increased movement
variability. With implanted FES, similar improvements as with
surface-based FES were observed for hip and knee flexion angles,
COVhip and COVknee, Tswingasym, and for Vplfl. Walking ability
without any device was measured, although only 10 gait cycles on
the treadmill could be performed. The movement pattern was
characterized by large variability and asymmetry, but could not be
compared with previous assessments because measurements without a device were lacking at those instants.
The increased joint excursions and decreased joint motion
variability with FES are illustrated in figure 1. In addition, this

PERONEAL STIMULATION IN STROKE, van Swigchem

Fig 2. Plantar flexion torque at the affected ankle, averaged over 3
trials in each of the conditions. Abbreviation: NO, no orthosis.

figure shows that with FES the joint angles at the paretic side
closely resembled those at the nonparetic side, whereas with
the AFO the joint excursions showed substantial differences
between the lower limbs with a time shift in the start of the
swing phase. These results demonstrate that with FES, the
movement pattern became more symmetrical, and that particularly, the ranges of motion at the ankle, knee, and hip were
almost normalized.12
Kinetic data were only obtained at t2. Profiles of ankle
torques with FES, AFO, and without device are provided in
figure 2. Consistent with the data for Vplfl, maximal ankle
plantar flexion torques at push-off (Mplfl) were larger with FES
than with AFO or without device (1.50, 0.93, and 1.15Nm/kg,
respectively) (table 2).
The obstacle avoidance success scores were better with
surface-based and implanted FES (68% and 90% success,
respectively) than with the AFO (0%–17%) (see table 2). In
contrast, the comfortable walking speed did not differ between
AFO and FES (1.04m/s with both devices).
DISCUSSION
In our patient, knee and hip movements almost normalized
when he walked with FES, which was reflected by increased
knee and hip flexion angles, decreased knee and hip motion
variability, and increased movement symmetry (see table 2).
Remarkably, the active ankle push-off benefited from FES. In
addition, the ability to avoid sudden obstacles during walking
improved with FES. These results indicate that peroneal FES
not only elevates the foot, but may improve the entire gait
pattern after stroke, even when walking is affected by severe
hemiparesis.
In order to evaluate whether this potential of peroneal FES
has been addressed previously, a literature search was conducted. Gait speed appeared to be used most frequently as an
outcome measure. However, gait speed does not provide information about the quality of the walking pattern. Indeed, our
patient had an almost normal gait speed,13 yet a very asymmetric and inefficient gait pattern at baseline (see t0 in table 2).
The effects of peroneal FES on knee and hip motion angles
during gait have only been reported in 2 preexperimental
studies14,15 showing inconclusive results. Hence, the possibility

323

of more extended effects of FES on the hemiparetic walking
pattern has received little attention. Some mechanisms have
been suggested that might explain the extended effects of FES
that we observed. First, peroneal FES might reduce lower-limb
spasticity.16,17 However, in our patient, this mechanism is not
likely because the modified Ashworth scores at baseline (see
table 1) indicated no signs of spasticity. Particularly in spinal
cord injured patients, it has been observed that peroneal FES
may facilitate the lower-limb flexion reflex.18 In our patient,
maximal knee and hip flexion increased with FES (see table 2),
which might indeed be indicative of such flexion reflex facilitation. An additional observation in our patient might support
this notion. When he was sitting on a chair, he was not able to
flex his paretic hip to lift his leg from the ground, whereas with
FES he was able to do so. On the other hand, the movement
sequence for swing initiation, as observed in all conditions, was
similar to the sequence in normal gait and started with knee
flexion, followed by hip flexion, and finally ankle dorsiflexion.12 When the flexion reflex would have been triggered in a
stationary position, the onset of hip, knee, and ankle movements would have typically occurred simultaneously, which
renders this possibility less likely. Nevertheless, because we
did not record muscle activations and because gait is influenced
by passive mechanical constraints as well, preservation of the
normal movement sequence does not preclude the possibility of
a facilitated flexion reflex. Another mechanism that has been
mentioned in the literature is that, in contrast to most AFOs,
FES allows the use of residual active ankle plantar flexion at
push-off.19 Such increased plantar flexion power increases
knee flexion during preswing and, thus, facilitates the swing
phase of gait.20 Indeed, the increased Vplfl (see table 2) indicated that with FES our patient had faster plantar flexion
movements at push-off. The increase in Mplfl at t2 showed that
with FES, the ankle plantar flexion torques increased to normal
values (see table 2), which confirms that the increased ankle
plantar flexion velocity reflected an active propulsion. However, the precise mechanism underlying the improved ankle
push-off with FES in our patient is not clear. It might be related
to less dependency on a compensatory movement strategy that
he had developed to overcome impaired swing phase initiation.
Both with the AFO and without a device, he showed excessive
hip exorotation during the stance phase, which may have
enabled him to use the inertia of the trunk to initiate the
subsequent swing of the leg (see videos on http://www.neurorehab.
nl/APMR_english.htm). This increased hip exorotation might
explain the decreased hip extension and ankle dorsiflexion
during the stance phase as observed with and without AFO at
t2 (see table 2). With FES, there was improved hip extension
(without exorotation) and increased ankle dorsiflexion during
the stance phase, which may have contributed to an increase in
push-off ankle torque due to more passive stretch of the calf
muscle. The larger ankle plantar flexion velocity may have
further added to the increased push-off power with FES.
With respect to the functional benefits related to FES in our
patient, we expected him to have better walking abilities with
peroneal FES on regular, but even more so, on irregular terrain.
The large improvement in obstacle avoidance success rates
confirmed that his advanced gait skill had indeed substantially
improved with FES. Such improvements might also have led to
safer ambulation during daily life. Indeed, our patient reported
to fall about once a week with his AFO, whereas he reported no
more falls with FES. With FES, he experienced an improvement of balance and went out for a walk, which he was
reluctant to do with his AFO. With respect to comfortable
walking speed, we observed no difference between AFO and
FES, whereas previous work on the L300 and the ActiGait
Arch Phys Med Rehabil Vol 92, February 2011

324

PERONEAL STIMULATION IN STROKE, van Swigchem

systems reported increased speeds (34%1 and 19%21, respectively) for walking with FES in the long term compared with
walking without FES at baseline. The difference with the
present study can most likely be attributed to the almost
normal initial walking speed of our patient, which probably
prevented any FES-induced improvement. Previous studies
did not evaluate the effects of the L300 or ActiGait on the
quality of the gait pattern in terms of kinematics.
In order to convincingly demonstrate the potential superiority of FES over an AFO in our patient, the finding of a
deterioration of gait with the AFO at t2 needs to be further
clarified. In the year that the patient waited for implantation, he
retired from his profession and reduced his activity level. At a
gait assessment 2 weeks before implantation, the gait pattern
already showed deteriorations similar to those observed at t2,
with absent hip extension, decreased knee flexion angles, and
increased movement variability. This indicated that the deterioration of gait at t2 was not related to the 6 months of FES use,
but was most likely due to the decrease in physical activity
before the implantation of FES. Whether a similar deterioration
was also present in his gait pattern without any device could
not be evaluated because of the lack of walking assessments
without any device at t0 and t1.
CONCLUSIONS
The presented case study shows that peroneal FES may have
important effects on the entire hemiparetic gait pattern beyond
what can be attributed to improved foot lift alone. The effects
of FES on knee and hip motion angles as well as on gait
symmetry, gait variability, and obstacle avoidance skills call
for further research including these outcome measures and the
most commonly used walking speed. Furthermore, fundamental studies are needed on the neural and biomechanical mechanisms that may underlie the observed extended effects of
peroneal FES.4 Finally, because the extended effects of FES in
our patient may not be generalized to other patients, future
research should try to identify the subject characteristics that
are predictive of such a beneficial response in patients with
hemiparesis due to stroke.
References
1. Hausdorff JM, Ring H. Effects of a new radio frequencycontrolled neuroprosthesis on gait symmetry and rhythmicity in
patients with chronic hemiparesis. Am J Phys Med Rehabil 2008;
87:4-13.
2. Kottink AI, Hermens HJ, Nene AV, et al. A randomized controlled trial of an implantable 2-channel peroneal nerve stimulator
on walking speed and activity in poststroke hemiplegia. Arch Phys
Med Rehabil 2007;88:971-8.
3. Kottink AI, Oostendorp LJ, Buurke JH, Nene AV, Hermens HJ,
IJzerman MJ. The orthotic effect of functional electrical stimulation on the improvement of walking in stroke patients with a
dropped foot: a systematic review. Artif Organs 2004;28:577-86.
4. IJzerman MJ, Renzenbrink GJ, Geurts AC. Neuromuscular stimulation after stroke: from technology to clinical deployment. Expert Rev Neurother 2009;9:541-52.
5. van Swigchem R, Vloothuis J, den Boer J, Weerdesteyn V, Geurts
AC. Is transcutaneous peroneal stimulation beneficial to patients
with chronic stroke using an ankle-foot orthosis? A withinsubjects study of patients’ satisfaction, walking speed and physical activity level. J Rehabil Med 2010;42:117-21.

Arch Phys Med Rehabil Vol 92, February 2011

6. Demeurisse G, Demol O, Robaye E. Motor evaluation in vascular
hemiplegia. Eur Neurol 1980;19:382-9.
7. Medical Research Council. Aids to examination of the peripheral
nervous sytem. Memorandum no.45. London: Her Majesty’s Stationary Office; 1976.
8. Winter DA, Patla AE, Frank JS, Walt SE. Biomechanical walking
pattern changes in the fit and healthy elderly. Phys Ther 1990;70:
340-7.
9. Chen G, Patten C, Kothari DH, Zajac FE. Gait differences between individuals with post-stroke hemiparesis and non-disabled
controls at matched speeds. Gait Posture 2005;22:51-6.
10. Weerdesteyn V, Nienhuis B, Geurts AC, Duysens J. Age-related
deficits in early response characteristics of obstacle avoidance
under time pressure. J Gerontol A Biol Sci Med Sci 2007;62:
1042-7.
11. Weerdesteyn V, Schillings AM, van Galen GP, Duysens J. Distraction affects the performance of obstacle avoidance during
walking. J Mot Behav 2003;35:53-63.
12. Winter DA. The biomechanics and motor control of human gait:
normal, elderly and pathological. 2nd ed. Waterloo: Univ of
Waterloo Pr; 1991.
13. Bohannon RW. Comfortable and maximum walking speed of
adults aged 20-79 years: reference values and determinants. Age
Ageing 1997;26:15-9.
14. Takebe K, Basmajian JV. Gait analysis in stroke patients to assess
treatments of foot-drop. Arch Phys Med Rehabil 1976;57:305-10.
15. Voigt M, Sinkjaer T. Kinematic and kinetic analysis of the walking pattern in hemiplegic patients with foot-drop using a peroneal
nerve stimulator. Clin Biomech (Bristol, Avon) 2000;15:340-51.
16. Burridge J, Taylor P, Hagan S, Wood DE, Swain I. The effect of
common peroneal nerve stimulation on quadriceps spasticity in
hemiplegia. Physiotherapy 1997;83:82-9.
17. Veltink PH, Ladouceur M, Sinkjaer T. Inhibition of the triceps
surae stretch reflex by stimulation of the deep peroneal nerve in
persons with spastic stroke. Arch Phys Med Rehabil 2000;81:
1016-24.
18. Stefancic M, Kralj A, Turk R, Bajd T, Benko H, Sega J. Neurophysiological background of the use of functional electrical stimulation in paraplegia. Electromyogr Clin Neurophysiol 1986;26:
423-35.
19. Ring H, Treger I, Gruendlinger L, Hausdorff JM. Neuroprosthesis
for footdrop compared with an ankle-foot orthosis: effects on
postural control during walking. J Stroke Cerebrovasc Dis 2009;
18:41-7.
20. Goldberg SR, Anderson FC, Pandy MG, Delp SL. Muscles that
influence knee flexion velocity in double support: implications for
stiff-knee gait. J Biomech 2004;37:1189-96.
21. Burridge JH, Haugland M, Larsen B, et al. Phase II trial to
evaluate the ActiGait implanted drop-foot stimulator in established hemiplegia. J Rehabil Med 2007;39:212-8.
Suppliers
a. Bioness Inc, 25103 Rye Canyon Loop, Valencia, CA 91355.
b. Neurodan A/S, Sofiendalsvej 85, DK-9200 Aalborg SV, Denmark.
c. Biometrics SG150 and SG110/A; Biometrics Ltd, PO Box 340,
Ladysmith VA 22501.
d. Vicon, 14 Minns Business Park, West Way, Oxford, OX2 0JB, UK.
e. Advanced Mechanical Technology Inc, 176 Waltham St, Watertown, MA 02472.