Development of Walk Assist Device to Improve Community Ambulation
Phase: NA
Conditions: Stroke
Sponsor: Shirley Ryan AbilityLab

Protocol:  Development of Walk Assist Device to Improve Community Ambulation 
PI – Arun Jayaraman PT, PhD 
Department of Physical Medicine & Rehabilitation 
Northwestern University 
Rehabilitation Institute of Chicago 
345 E. Superior 
Chicago, IL 60611 
Ph: (312) 238-6875 
Fax: (312) 238-2081 
ajayaraman@northwestern.edu 
 
Version Date:  
4/16/10 
 
 

Study Number # NUSTU00022438 
 
I. Overview 
We will assess a walk assist device (WAD) which assists flexion and extension at the hip joint 
to assist community walking/ambulation.  Prototype model of this device has been developed by 
Honda Motor Corporation ®, Japan.  This device: 1) will be simple to use in the clinical setting; 
2) will be easily adjustable to alter the requirement of each subject; and, 3) will be able to quantify 
the amount of assistance required to facilitate normal community walking patterns. With the use 
of this device we will evaluate adaptations in walking performance following both over ground 
and body weight supported treadmill walking (BWSTT) in individuals with stroke. This 
information will help us identify the impact of an automated walking assistance device on lower 
extremity muscle activity, motor performance (kinematics), and corticospinal excitability after 
chronic neurological injury.   
The assessment of WAD will be undertaken to determine the optimal use of the device tested 
on the treadmill and over ground in individuals with chronic motor unilateral stroke.  
Testing procedures and informed consent procedures are described below. 
II. Subject Population 
Subject sample size of 12 stroke subjects will be sufficient to detect a significant difference, 
however considering attrition 15 subjects will be recruited. For the objective measures, power 
analysis yielded a sample size of 12 will be sufficient to detect a significant difference, however 
considering attrition 15 subjects will be recruited.  
Subjects will be chosen to participate in this study, drawn from the Rehabilitation Institute of 
Chicago Research Registry. 

Study Number # NUSTU00022438 
Specific inclusion for participation of subjects includes: 
a. Stroke subjects with a history of unilateral, supratentorial, ischemic or hemorrhage stroke 
will be recruited, with lesion location confirmed by radiographic findings. 
b. All subjects who score > 10 on the Lower Extremity Motor Score (LEMS) developed 
previously to measure strength in SCI. For the LEMS criteria, preliminary data indicate 
that subjects with LEMS < 10 in the chronic stages do not recover walking. 
c.  All subjects will be required to walk > 10 m over ground without physical assistance at 
self-selected walking speeds ≤ 0.8 m/s using assistive devices and bracing below the knee 
as needed. A criterion of 0.8 m/s is utilized to target participants with limited or minimal 
ambulation in the community.  Subjects will be further stratified into those who walk < 0.4 
m/s and > 0.4 m/s, identified as household vs. limited community ambulators, respectively. 
d. Range of motion (ankle: -10 to 30 deg, knee: 0 to 90 deg, hip: -10 to 40 deg) consistent 
with gait; 
e. Medically stable with medical clearance to participate (absence of concurrent illness, 
including unhealed decubiti, infection, cardiopulmonary disease, osteoporosis, active 
heterotrophic ossification or peripheral nerve damage in the lower limbs, history of 
traumatic head injury); 
f. Able to tolerate 30 minutes of upright (standing) position without orthostasis (decrease in 
blood pressure by 20 mmHg systolic and 10 mmHg diastolic; minimized with ambulatory 
population); 
g. Must not be undergoing concurrent physical therapy to eliminate effects of additional 
interventions; 

Study Number # NUSTU00022438 
h. Patients prescribed medications for spasticity will not be excluded from participation but 
will be asked to maintain current levels of medication or inform the researcher if changes 
are necessary. 
Specific exclusion for participation of subjects includes: 
a. Women of childbearing potential will not be excluded, although women who are pregnant 
will be excluded due to potential forces at trunk from BWS or pelvic assistance;  
b. Significant cardiorespiratory or metabolic disease that may limit exercise participation. 
c. Weights limit > 250 lbs (limit of most counter-weight safety systems). 
d.  History of previous orthopedic or neurological conditions which may impair walking.   
e. Exclusion for TMS: pacemaker, metal implants in the head region, history of epilepsy or 
seizures, skull fractures or skull deficits, concussion within the last 6 months, unexplained 
recurring headaches, medications that lower seizure threshold, and pregnancy. 
f. Subjects with scores < 23 on the Mini Mental Status Exam will be excluded. 
III. Evaluation of motor and walking performance using walk assist device 
A. Clinical Assessment of motor and walking performance 
 
For evaluation purposes and measures of walking progression, reliable and valid measures will 
be utilized to assess: a) lower extremity voluntary control; b); degree of walking independence; 
and, c) walking speed, endurance and temporal-spatial parameters.  
 Assessment of strength, spastic motor behaviors and functional ambulation will be performed 
by a licensed physical therapist at the initial evaluation and during walking protocols.  
Assessment includes: 
 Lower Extremity Motor Scores: to determine strength in the lower extremities 

Study Number # NUSTU00022438 
  Functional Independence Measure (FIM): extent of disability and societal limitations linked 
with functional limitations of ambulation. 
 10m walk: gait speed 
 6min walk: gait speed and distance 
 GaitMat II (Equitest, Chalfont, PA): to detect temporal-spatial gait patterns. 
 
B. Objective measure of motor and walking performance 
 
Evaluation of the changes in walking performance with the use of the proposed WAD will be 
assessed using computerized gait analysis during independent stepping on an instrumented 
treadmill and during over ground walking.  Specific outcome measures include: a) extent of lower 
extremity loading and ground reaction forces during independent treadmill stepping; c) peak 
treadmill speed at minimal body weight support; c) lower extremity kinematics during stepping, 
including peak hip, knee, and ankle joint kinematics during walking, and temporal-spatial gait 
parameters, and, d) timing of lower extremity EMG activity during treadmill stepping. In addition, 
metabolic costs will be determined.  Metabolic costs will be collected using a portable metabolic 
system (K4b2, CosMed USA, Inc., Chicago).  Metabolic measures will be obtained in sitting for 
5 minutes prior to walking.  Metabolic measures will be taken during un-assisted walking and 
device assisted walking for comparison.  Subjects will return to their metabolic baseline between 
the walking trials.  Metabolic measures will always be measured at sub-maximal levels and will 
be stopped 75% of target heart rates. Written approval from subject’s physician will be obtained 
before allowing subjects to participate in sub-maximal graded treadmill test. Non-approval from 
physician will exclude the subject’s participation only in the sub-maximal graded treadmill test; 
however they will be allowed to participate in the other tests involved in the study. Gait analysis 

Study Number # NUSTU00022438 
will be performed with use of a motion analysis system (Motion Analysis Corp, Santa Rosa, CA), 
which includes eight strategically positioned charge-coupled device video cameras (VC491; 
Oxford Metrics), a minicomputer (PDP 11/73; Digital Equipment, Maynard, Massachusetts), and 
software for the collection and analysis of the data. Twenty-one, 1-inch diameter spherical 
reflective markers will be placed over pre-determined anatomical landmarks on the trunk and 
extremities. The patient will walk on a treadmill with embedded bilateral force plates, and the 
position coordinates for the markers on both sides of the body will be recorded simultaneously at 
120 Hz using phase-locked cameras. The recording technique and the software allow for the three-
dimensional reconstruction of the motion of all of the major joints of the upper and lower 
extremities. All of the patients will wear comfortable shoes, and each will walk at pre-determined 
(0.5 km/hr increments) and maximal speed.  A harness attached to the suspension system will be 
used for all patients to prevent the patient from falling. Data will be collected at least three times 
for 30 sec at various speeds. In cases of visual occlusion of reflective markers during walking with 
assistance and/or devices, gait kinematics at the knee and hip will be detected by 
electrogoniometers placed bilaterally (Biometrics, Ltd, UK).   The electrical activity of the TA, 
SOL, MG, VL, RF, and MH will be recorded bilaterally with a 32-channel dynamic EMG 
telemetry system (Noraxon Inc., Scottsdale, AZ), with surface electrodes sampling at 960 Hz. 
Force-plates (OR6; AMTI, Newton, Massachusetts) that are embedded in the treadmill will sample 
the ground-reaction forces at 960 Hz.  
 
 
 
 

Study Number # NUSTU00022438 
C. Objective measure of corticospinal excitability during walking: 
Transcranial magnetic stimulation (TMS) will be performed while walking with and without the 
WAD. TMS is a safe, non-invasive, painless method of brain stimulation that has been widely used 
to study the physiology of the representations of muscles in the motor cortex in healthy and 
neurologically disordered individuals. Very short duration (< 1 ms) magnetic pulses are applied 
via an insulated wire coil placed on the intact scalp overlaying the motor cortical. Each pulse 
induces a motor evoked potential (MEP) in a target muscle that can be readily monitored by 
recording EMG from the muscle. Magnetic stimuli will be delivered from a Magstim 200 unit via 
a Magstim double cone coil (Magstim Company, Boston MA). Self adhesive disposable electrodes 
(Suretrace) with an inter-electrode distance of 2 cm will be applied over the muscle bellies of the 
quadriceps, hamstrings, ankle dorsiflexors and ankle plantar flexors in the lower extremities.  A 
ground electrode will be applied over the patella. Standard skin preparation techniques (light 
abrasion and cleansing with alcohol) will be completed prior to application of the electrodes. EMG 
recordings will be amplified (Octopus AMT-8; Bortec Biomedical, Calgary, Alberta), band-pass 
filtered (10-1000 Hz), and sampled at 5000 Hz. Electromyographic (EMG) activity will be 
collected from all muscles bilaterally. TMS will be delivered with the stimulating coil positioned 
over the vertex at intensities ranging from 70 – 140% of “walking threshold”. This threshold is a 
better estimate of excitability than conventional thresholding because during walking, EMG burst 
patterns and EMG amplitude differ between subjects, and walking threshold is typically lower than 
tonic contraction threshold, and much lower than rest threshold. Walking threshold is the stimulus 
intensity that results in MEPs just visible as time locked waveforms emerging out of background 
EMG. Pre-burst onset MEPs will also be recorded at an intensity that results in a MEP of ~ 500 
V. This measure is important because we expect when the WAD is providing assistance, the 

Study Number # NUSTU00022438 
EMG burst amplitude may change, making it difficult to interpret changes in MEP amplitude 
assessed during the EMG burst. Subjects will be walking on a treadmill when magnetic stimulation 
is delivered. An optical motion switch will detect when a limb is in mid-swing and sends a pulse 
to software that in turn delays a TMS trigger pulse to coincide with a chosen cycle phase. Motor 
cortex excitability changes during walking will be examined by calculating the mean amplitude of 
10 MEPs recorded from each muscle with and without WAD. A harness will be placed around the 
subject’s pelvis and lower torso. The harness is attached to a rope and pulley system that is capable 
of supporting the subject’s entire body weight in the upright position. A physical therapist (PT) 
will be in attendance at all times. Use of the harness and handrails, and the PT in attendance, will 
ensure that the subject is comfortable and secure at all times. Subjects will be provided with 
sufficient breaks between walking to avoid fatigue.  
 
 
IV. Using the Walk Assist Device (WAD) 
As part of the testing in this study, subjects will be asked to participate in body weight supported 
treadmill walking and/or over ground walking with the help of the WAD.  All testing procedures 
will be with a licensed physical therapist or physical therapist assistant as described below. 
Device Assisted Walking: The walk assist device (WAD) consists of a waist frame, rechargeable 
lithium ion batteries, hip actuators / motors, angle sensor and thigh frame. The WAD gently assists 
both forward and backward movements at a person’s hip joints in a very smooth way with the 
electrical actuators. The electrical actuators are equipped with angular sensors to monitor walking 
speed, velocity, and the degrees of the forward and backward movement of the hip joints. Using 
the information from the sensors, the WAD gently assists the person towards normal walking 
patterns. However, most subjects are unaware of this manipulation because the assistive torque is 

Study Number # NUSTU00022438 
small. The WAD stops functioning when the subject stops walking and will in no way control 
walking or movement of the subject causing tripping or falling. The total weight of the WAS is 
approximately six pounds. All subjects will receive a thorough explanation of the structure and 
function of the WAD before the experiment to eliminate any concerns. Individual fitting of the 
WAD will be performed by the persons who developed the WAD to avoid any kind of discomfort 
to the subjects. The WAD also helps in conserving the subject’s energy consumption during 
walking as the device utilizes the subject’s inertia and gravity to assist walking. The WAD has 
been successfully used to assist walking in the elderly population and reduce energy consumption 
during walking in healthy controls.1, 2 
 

Study Number # NUSTU00022438 
IV. Statistical Analysis 
Paired comparisons of electromyographic, kinematic, kinetics, strength and metabolic data will be 
made within subjects between groups (un-assisted stepping, device-assisted stepping) using 
standard parametric (t-test, ANOVA) comparisons. Changes in clinical performance will be 
assessed using primarily ordinal measures, with statistical comparisons made using non-
parametric tests.  Correlation (Pearson or Spearman) will be made between clinical/functional 
assessments and kinematics/kinetics observed during device-assisted walking. 
 
 
V. References 
1. Effects of an automated stride assistance system on walking parameters and muscular glucose 
metabolism in elderly adults. Shimada H, Suzuki T, Kimura Y, Hirata T, Sugiura M, Endo Y, 
Yasuhara K, Shimada K, Kikuchi K, Oda K, Ishii K, Ishiwata K. Br J Sports Med. 2008 
Nov;42(11):622-9. Epub 2008 Feb 28. 
2. The use of positron emission tomography and [18F]fluorodeoxyglucose for functional imaging 
of muscular activity during exercise with a stride assistance system.Shimada H, Kimura Y, 
Suzuki T, Hirata T, Sugiura M, Endo Y, Yasuhara K, Shimada K, Kikuchi K, Hashimoto M, 
Ishikawa M, Oda K, Ishii K, Ishiwata K. IEEE Trans Neural Syst Rehabil Eng. 2007 
Sep;15(3):442-8.