Development of Sensory Augmentation Methods to Improve Post-stroke Gait Stability
Phase: EARLY_PHASE1
Conditions: Stroke
Sponsor: VA Office of Research and Development

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Official title: Development of sensory augmentation methods to improve post-stroke gait 
stability 
 
 
NCT number: NCT03988400 
 
Document date: 3/3/20 
 

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PROTOCOL TITLE: 
Development of sensory augmentation methods to improve post-stroke gait stability 
 
PRINCIPAL INVESTIGATOR: 
Jesse Dean 
 
 
1.0 
Objectives / Specific Aims 
The objective of this project is to develop and test a method of providing real-time 
augmentation of hip proprioceptive feedback during post-stroke walking. Our central 
hypothesis is that augmented proprioception will increase the mechanics-dependent 
modulation of step width, an important gait stabilization strategy. The first aim of this 
study is to identify the physiological mechanism underlying the beneficial effects of 
sensory augmentation on step-by-step gait stabilization. Here, we will differentiate 
between the potential mechanisms of altered perception and cutaneous cueing. The second 
aim is to determine whether personalizing sensory augmentation methods to individual 
participants produces greater beneficial effects on post-stroke gait stability. Here, we will 
identify the optimal combination of vibration pattern and location for each participant, and 
test whether this personalized stimulation is superior to standard methods. The third aim is 
to establish the safety, feasibility, and efficacy of a rehabilitation intervention centered on 
repeated exposure to sensory augmentation during gait. This will be accomplished through 
a small-scale clinical trial.   
 
2.0 
Background 
Chronic stroke survivors often experience gait instability, which can reduce quality of life 
through an increased fall-risk and fear of falling [1-5]. Unfortunately, recent clinical trials 
focused on strengthening and balance [6], multifactorial fall prevention [7], and locomotor 
training [8] have all failed to substantially impact this important problem, likely because 
they were not targeted to the specific mechanisms underlying post-stroke instability. To 
overcome this obstacle, we must design interventions based on a mechanistic 
understanding of gait instability, which can ultimately be accessed by patients outside of 
cutting-edge research laboratories   
As it is unlikely that a single intervention will “cure” post-stroke gait instability, our long-
term goal is to develop a toolbox of interventions, from which clinicians can select the 
most appropriate option for individual patients. Toward this goal, this study will 
investigate the real-time augmentation of hip proprioceptive feedback during post-stroke 
walking. Essentially, sensory stimulation will augment perceived movement errors, a direct 
extension of methods promoting useful gait adaptation by mechanically augmenting 
movement errors [9-10].   
This proposal is based on our prior work revealing a sensorimotor strategy of sensing the 
body’s mechanical state using hip proprioceptive feedback [11] and actively adjusting foot 
placement in response [12]. This strategy is often disrupted in chronic stroke survivors 
with poor balance [13]. Our ongoing work indicates that deficits in this stabilization 
strategy can be improved through mechanical error-augmentation. Here, we will test 

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whether sensory error-augmentation has similar beneficial effects, while investigating the 
underlying mechanism and determining whether sensory augmentation should be 
personalized to individual patients. 
 
3.0 
Intervention to be studied 
In this study, Aims 1 and 2 do not involve an intervention, instead including cross-
sectional mechanistic experiments. Aim 3 will test the safety, feasibility, and efficacy of a 
novel intervention involving low-intensity vibration applied over the bilateral hip abductor 
muscles of chronic stroke survivors during walking. This Aim will take the form of an 
early-stage, small-scale (n=44 participants) randomized controlled clinical trial.  
The precise intervention to be studied is novel, as the vibration amplitude applied during 
walking will be directly controlled by the user’s walking mechanics, allowing us to 
augment the sensory information available to users. However, the method and form of the 
vibration itself is not novel. Many prior studies have used vibrating motors (as in the 
present study) to deliver the same type of mechanical vibration to clinical populations 
during the performance of functional movement tasks (e.g. reaching, standing, walking) 
[14-17]. We ourselves have published work investigating the effects of mechanical 
vibration [11, 18-19], and have an IRB-approved project that involves these methods 
(Pro00046775).  
No medication is involved in the intervention, and FDA approval will not be required for 
the use of our vibrating tactors, which deliver minimal mechanical energy to users – 
instead simply evoking a sensory response.  
The rationale for the intervention is to use non-invasive methods (vibration) to improve the 
sensory accuracy of chronic stroke survivors. This low-risk method could have the 
potential to produce large improvements in patient functional mobility. While we have 
observed no adverse events in the use of these methods, and no such adverse events have 
been reported in the literature due to the use of these methods, one of the goals of this 
project will be to definitively establish the safety of this intervention.  
For the intervention, the control group will receive vibration applied over the bilateral hip 
abductors, just as the experimental group. However, the vibration will not be linked to the 
user’s mechanics, instead being randomly delivered – a method that has been used 
previously [11].  
 
4.0 
Study Endpoints 
For the intervention in Aim 3, our outcome measure of safety will be the proportion of 
participants who experience an adverse event potentially related to the intervention (e.g. 
skin irritation; falls) or any serious adverse event (e.g. hospitalization; death). Our primary 
measures of feasibility will be participant adherence (percentage of training sessions 
attended) and drop-out (non-attendance of final assessment session). We will also track the 
total walking time across training sessions (of a maximum possible 312 minutes). Our 
primary measure of efficacy will be changes in ρdisp, a metric that quantifies the extent to 
which participants effectively stabilize their gait by adjusting their step width to account 
for pelvis dynamics [20]. Our secondary measures of efficacy will be the common clinical 
measures of Functional Gait Assessment score, Activities-specific Balance Confidence 
score, overground gait speed, and fear of falling.  

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5.0 
Inclusion and Exclusion Criteria/ Study Population 
Participants will be recruited from an MUSC database containing the contact information 
of stroke survivors who have agreed to be contacted for research participation 
(Pro00037803). Initial screening will be performed by study staff through a phone call to 
confirm basic participant characteristics (e.g. timing of stroke) and interest in research 
participation. The ability of potential participants to meet the more detailed inclusion and 
exclusion criteria will subsequently be determined in person. 
Inclusion Criteria  
• Age ≥ 21 years 
• Experience of a stroke ≥ 6 months prior to participation 
• Gait speed of at least 0.2 m/s 
• Ability to walk on a treadmill without a cane or walker 
• Provision of informed consent 
Exclusion Criteria 
• Evidence of cerebellar damage 
• Resting blood pressure higher than 220/110 mm Hg 
• History of unstable cardiac arrhythmias, hypertrophic cardiomyopathy, severe 
aortic stenosis, angina or dyspnea at rest or during activities of daily living 
• Preexisting neurological disorders or dementia 
• Legal blindness or severe visual impairment 
• History of DVT or pulmonary embolism within 6 months 
• Uncontrolled diabetes with recent weight loss, diabetic coma, or frequent 
insulin reactions 
• Orthopedic injuries or conditions (e.g. joint replacements) in the lower 
extremities with the potential to alter the gait pattern 
• Recent (within last 6 months) Botox injections in the hip musculature 
We plan to include a diverse participant population, paralleling the general demographic 
characteristics of the Charleston area. This will be accomplished using the database 
referenced above, which currently contains contact information for over 800 individuals. 
We will not exclude any sex/gender or racial/ethnic group. This study will not involve any 
special classes of subjects, including fetuses, neonates, pregnant women, children, 
prisoners, institutionalized individuals, or other vulnerable populations. Children will not 
be included because this study focuses on individuals who have experienced a stroke. This 
is rare among children, and would be expected to involve a quite different mechanism or 
pattern of recovery. 
 
6.0 
Number of Subjects 
A total of 120 chronic stroke survivors will be accrued, all locally. 
 

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7.0 
Setting 
All research will be performed in the MUSC College of Health Professions Research 
Building at 77 President St. Charleston, South Carolina. 
8.0 
Recruitment Methods 
This study will recruit from the Registry for Stroke Recovery (RESTORE-Pro#00037803, 
IRB approved 9/6/14), which is a research tool sponsored by the National Institutes of 
Health (NIH) Center of Biomedical Research Excellence (COBRE) in Stroke Recovery 
with subjects consented for future contact to support stroke recovery research conducted at 
MUSC.  RESTORE staff will query the registry for potential subjects and provide the 
Principal Investigator (PI) with the contact information of subjects who meet their criteria.  
The PI or research staff will contact subjects to further screen for potential enrollment.   
Additionally, we have developed a study flyer that will be shared through the COBRE and 
distributed through stroke support groups attended by study personnel. 
 
9.0 
Consent Process 
Informed consent will be obtained from participants prior to participation, using a VA 
Informed Consent form approved by the MUSC IRB. Participants will first be informed of 
the purpose of the experiments and possible risks. A member of the study staff will then 
review the Informed Consent form with the potential participant, ensuring they are given 
adequate time to review the document. The potential participant will be asked if they have 
any questions about the study, and asked if they agree to participate. The Informed 
Consent form will be signed by the participant. Copies of the signed forms will be given to 
the participant. The consent process will take place in a private room in the MUSC College 
of Health Professions Building. There will be no set period between informing the 
prospective participant and obtaining the consent. Participants will be reminded that they 
may end their participation in the study at any point.    
 
10.0 Study Design / Methods 
A total of 120 chronic stroke survivors will be recruited for an initial Screening session to 
determine eligibility for enrollment in the subsequent Aims. From this initial session, 40 
stroke survivors will be recruited for Aim 1, and a separate 40 stroke survivors will be 
recruited for Aim 2. From these 80 participants in Aims 1 and 2, a total of 44 will be 
recruited for Aim 3. Aim 1 involves a single-session experiment, Aim 2 involves two 
experimental sessions, while Aim 3 involves an intervention with a total of 10-11 sessions. 
Participants will be enrolled in this study for a period of a year, allowing time to complete 
all potential sessions.  
In the initial Screening session, participants will walk on an instrumented treadmill for 2-
minutes. We will calculate ρdisp (a measure of the typical gait stabilization strategy) using 
LED markers and inertial measurement units placed over participants’ legs and pelvis. If 
ρdisp is less than 0.56 (well below control norms), participants will qualify to progress to 
the subsequent Aims. During the Screening session, we will also quantify the secondary 

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measures of: Functional Gait Assessment; Activities-specific Balance Confidence scale, 
Fugl-Meyer Lower Extremity Motor Function subscale; Fugl-Meyer Lower Extremity 
Sensation subscale; self-selected and fastest-comfortable overground gait speed; fear of 
falling; fall history. All of these secondary measures are commonly used in clinical 
practice.   
In Aim 1, participants will complete a single-session experiment. We will quantify the 
cutaneous detection threshold for vibration delivered over the bilateral hip abductors. We 
will also calculate the lateral sway evoked by vibration of each leg, quantified as the shift 
in center of pressure while standing on a force plate. Participants will then perform a series 
of treadmill walking trials. In some of these trials, vibration will be applied to the hip 
abductors or lateral trunk, while we quantify ρdisp. 
In Aim 2, participants will complete two experimental sessions. In the first session, 
participants will perform a series of treadmill walking trials, across which we will vary the 
pattern and location of vibration applied over the bilateral hip abductors. We will identify 
the combination of pattern and location that produces the largest increase in ρdisp for each 
participant. In the second session, participants will again perform a series of treadmill 
walking trials, across which we will compare the personalized stimulation (optimal pattern 
and location for this individual) with the standard pattern of stimulation used in prior work. 
In Aim 3, participants will complete 10-11 experimental sessions. The first and last session 
will consist of pre and post assessments, in which we will quantify ρdisp, Functional Gait 
Assessment score, Activities-specific Balance Confidence score, overground self-selected 
and fastest-comfortable walking speeds, and fear of falling. If Aim 2 reveals that 
personalized stimulation is superior to standard stimulation, the second session will be 
used to identify the optimal combination of stimulation pattern and location for each 
participant. Otherwise, this session will not be performed. The remaining sessions will be 
training sessions, in which participants will perform a series of walking trials at their self-
selected speed. In some trials, hip abductor vibration will be applied on a step-by-step 
basis. In the Augmented group, this vibration will be scaled to augment sensory feedback 
providing information about the mechanical state of the pelvis. In the Control group, the 
magnitude of this vibration will be randomized, providing no additional information.  
To reduce the risk of participants falling, participants will wear a harness attached to an 
overhead rail during all treadmill and overground walking trials. This harness will not 
support body weight, but would prevent participants from falling in the case of a loss of 
balance. The vibrating tactor and adhesive used to secure the tactor and LED markers to 
the skin may produce the risk of minor skin irritation. We will reduce this risk by asking 
participants if they have had any previous experience of skin irritation in reaction to 
specific gel or tape types, and by checking the participants’ skin after each experiment.  
 
11.0 Data Management  
For Aim 1, our first analysis will be correlation-based, testing whether metrics of altered 
perception or cutaneous cueing are associated with the beneficial effects of sensory 
augmentation. For each participant, we will quantify four independent variables: cutaneous 
detection threshold (paretic and non-paretic legs); lateral sway distance evoked by hip 
abductor vibration (paretic and non-paretic legs). We will also quantify the effect of 
sensory augmentation during gait as the mean change in paretic ρdisp between the Normal 
and Vibrated Abductors trials (∆ ρdisp). We will test whether each of the four independent 

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variables is significantly associated with ∆ ρdisp, using an alpha value of 0.0125 to account 
for multiple comparisons. Our second analysis will involve a repeated measures 
experimental design – directly testing whether vibration designed solely to provide 
cutaneous cues (Vibrated Trunk condition) has a smaller beneficial effect than vibration 
designed to elicit both cutaneous cues and an altered perception of pelvis mechanics 
(Vibrated Abductors condition). For this analysis, we will use a repeated measures 
ANOVA to compare mean paretic ρdisp values during the Normal, Vibrated Abductors, and 
Vibrated Trunk trials. 
For Aim 2, our primary statistical analysis will compare the average increase in paretic 
ρdisp values during Standard Augmentation and Personalized Augmentation conditions 
(relative to Normal). We will use a paired t-test to compare these ∆ ρdisp values. 
Secondarily, we will use a repeated measures ANOVA to test for group-wide effects of 
vibration pattern and location, based on data from the first session.  
For Aim 3, our primary statistical analysis will use an independent t-test to determine 
whether the change in paretic ρdisp differs significantly between the Augmented and 
Control groups. 
Power analyses were performed for each Aim. For Aim 1, the proposed sample size (n=40) 
was selected to be able to detect a moderate correlation (r=0.5) between our input variables 
and ∆ ρdisp. Aim 2 was powered to detect a moderate effect size (Cohen’s d = 0.5) between 
Standard and Personalized sensory augmentation methods. For our Aim 3 intervention, we 
estimate an effect size of 1.0 based on our prior results. It should be noted that we expect 
this effect to increase with the repeated exposure to sensory augmentation proposed here. 
With an effect size of 1.0 and an alpha value of 0.05, we will need 17 participants per 
group for 0.80 power. We propose 22 participants per group to account for 20% dropout. 
Steps will be taken to minimize the risk of loss of confidentiality. All data will be stored on 
a password-protected computer and password-protected secure server that is backed-up 
nightly.  
The RESTORE registry (Pro#00037803), from which this study will recruit subjects, also 
serves as a data analysis tool by which interdisciplinary teams may share data across 
projects and provide MUSC’s stroke recovery research community with a more complete 
registry with key stroke elements. Some subjects may have participated or will participate 
in other stroke related research studies at MUSC. Sharing data from this and other stroke 
research studies with RESTORE will allow for more targeted recruitment efforts in the 
future and could reduce the burden placed on subjects by reducing the duplicative efforts 
of collecting common data and physical function assessments requested by multiple studies 
and storing them in one centralized and secure location.   
Subjects are informed in the consent process if they enroll into the RESTORE registry, 
their data from this study will be shared. Subjects will be asked to sign a HIPAA 
authorization stating their health information may be disclosed to MUSC investigators 
requiring their data for their research projects upon approval by an Institutional Review 
Board.   
 
12.0 Provisions to Monitor the Data to Ensure the Safety of Subjects 
A Data Safety Monitoring Board (DSMB) will oversee the experiments in Aim 3 (a small-
scale randomized controlled trial). This board will consist of a neurologist, a statistician, 

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and an experienced rehabilitation researcher (all with no direct ties to this study). On a 
quarterly basis, the DSMB will review the status of the study. The role of the DSMB will 
be to: 
• 
Protect the safety of study participants 
• 
Review the research protocol, informed consent documents, amendments, and 
plans for data safety and monitoring 
• 
Evaluate the progress of the trial, including periodic assessments of data quality 
and timeliness, recruitment, accrual, and retention, participant risk vs. benefit, and 
other factors that may potentially affect study outcome 
• 
Review study performance, make recommendations and assist in the resolution of 
problems reported by the Principal Investigator 
• 
Report to the IRB on the safety and progress of the trial 
• 
Ensure the confidentiality of the study data and the results of the monitoring 
• 
Advise the IRB and the study investigators as to whether the protocol should 
continue as scheduled or undergo a modification due to a finding from the 
monitoring process 
Any adverse events will be recorded, monitored, and promptly reported to the IRB, 
following policy HRPP 4.7. Our exclusion criteria will minimize the risk of enrolling 
participants with severe cardiovascular risk. Scheduled rest breaks will be provided 
between trials during experimental testing, as well as whenever requested. Minimization of 
risk of adverse events will be accomplished by monitoring vital signs during trials in which 
subjects are performing potentially demanding exercise. Collected data and any events 
potentially affecting participant safety will be reviewed by the principal investigator after 
each data collection session.  
 
13.0 Withdrawal of Subjects 
Participants will be withdrawn from the study without their consent if study staff determine 
that the participants are at risk of negative health events (e.g. large increase in blood 
pressure from the initial screening assessment; consistent inability to maintain balance 
while walking on the treadmill). If a participant voluntarily withdraws from the study, their 
results will not be included in our data analysis, as our intervention sample size accounts 
for 20% dropout. 
 
14.0 Risks to Subjects 
 
Potential risks for participation in this study are low.  
 
Participants will perform standing and walking trials, in which there is the risk of a loss of 
balance. To mitigate this risk, in these trials participants will wear a safety harness attached 
to an overhead rail. The harness is designed to eliminate the consequences of falling as the 
device “catches” the subject should they trip or stumble. Additionally, in all walking trials, 
an investigator will be near the participant to provide assistance in the event of a loss of 
balance. There is also the risk of minor muscle soreness due to the exercise of walking. 

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This risk will be mitigated by walking only at speeds that are comfortable for each 
participant, and allowing rest breaks if participants ever indicate they are fatigued. 
 
General post-stroke function will be assessed using several commonly-used clinical tests. 
There is a risk of a loss of balance during the Functional Gait Assessment, in which 
individuals perform various functional gait tasks. We will mitigate this risk by having a 
physical therapist always next to participants, as is common in a clinical context. The other 
clinical tests either involve verbal questions or are of minimal physical risk.  
 
In some treadmill walking trials, vibrating tactor motors will apply sensory stimuli to 
participants’ hip muscles. This stimulation will deliver minimal mechanical energy to 
participants, as the vibration amplitude will be less than 2 mm. Extensive prior 
experiments have used these devices, without reports of adverse events. However, there is 
the risk of the vibration producing skin redness and minor irritation. After every session, 
we will check the skin for irritation, which should resolve within 24 hours. 
 
All research studies have the risk of loss of participant confidentiality. Our Data 
Management Plan (see above) will minimize this risk.  
 
15.0 Potential Benefits to Subjects or Others 
The research conducted in the Aim 3 intervention has the potential to improve the gait 
stability of chronic stroke participants, which may have beneficial effects on functional 
mobility and quality of life. Promising effects would justify larger-scale studies able to 
benefit a larger number of individuals. As the risks to participants are minimal (no more 
than a moderate period of exercise), we believe the risks are reasonable in relation to the 
anticipated benefits.   
 
16.0 Sharing of Results with Subjects 
Results will be in the form of research data, and will not be shared with participants or 
others. 
 
17.0 Devices 
This study will involve the use of tactors (Engineering Acoustics, Inc.), which are small 
vibrating motors designed to cause the sensation of pressure or movement. These tactors 
are non-invasive and will not be distributed to participants, but will only be used during 
research procedures in the laboratory setting over the course of this study.  
 
 
 
 
 
 

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