Biofeedback to Increase Propulsion During Walking After Stroke
Phase: PHASE1
Conditions: Stroke
Sponsor: VA Office of Research and Development

 
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Study Title 
 
Biofeedback to Increase Propulsion during Walking after Stroke 
 
 
 
 
 
 
 
 
 
NCT# 
02667392 
 
 
 
 
 
 
 
Date 
8/08/19 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
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Protocol 
1. Project Title: Biofeedback to Increase Propulsion during Walking after Stroke 
2. Investigator(s):  Dorian Rose, PhD, PT 
 
 
 
 
Dave Clark, ScD 
3. Abstract: 
Background/Purpose: Approximately 15,000 Veterans are hospitalized for stroke each year. 
Impairments of motor control and the subsequent functional limitations in ambulation are the 
most common manifestations and regaining the ability to walk is the number one stated goal 
of Veteran stroke survivors. Forward propulsion of the body’s center of mass is a cardinal 
feature of gait that depends on the generation of appropriate anterior-posterior ground 
reaction forces. Decreased propulsive force generation by the paretic limb of stroke 
survivors has been identified through both simulation and cross-sectional studies as a major 
contributor to walking dysfunction. Extrinsic verbal feedback from a therapist is the standard 
approach used during gait retraining to improve propulsion generation. However, this key 
component of gait is not directly observable by therapists and patients are often unable to 
sense propulsion generation due to impaired intrinsic feedback, specifically deficits in 
somatosensation and proprioception, hindering recovery of paretic propulsion and 
compromising walking function. The objective of this study is to provide preliminary 
evidence that biofeedback as an adjuvant to therapists’ verbal feedback will improve 
propulsion and enhance walking function for Veterans post-stroke. 
Subjects: Thirty individuals > 6-months post-stroke will participate. Additional study criteria 
include: 1) Ambulation of household distances without physical assistance to advance or 
support the paretic leg; 2) Unilateral leg paresis confirmed by a score of < 32 on the Fugl-
Meyer Motor Assessment; 3) Step length asymmetry (paretic > non-paretic step length); 4) 
Ambulation without an assistive or orthotic device. 
Methods: Participants will be randomized to either an experimental group that will train with 
propulsion biofeedback from commercially available pressure-sensitive insole sensors 
(Biofeedback group; n=15) or a control group that will train with standard therapist-provided 
verbal feedback alone (Standard group; n=15). The 12 session (3X/week for 4 weeks) gait 
training intervention will be delivered by a physical therapist-led team. For participants in the 
Biofeedback group, prior to the first intervention session, the baseline amount of pressure 
exerted by the paretic forefoot during late stance will be determined. The insole area 
underlying the forefoot will then be calibrated to produce a tone when pressure exceeds 5% 
of this baseline pressure. This threshold will be progressively increased at regular intervals 
throughout the intervention period to ensure participants are training at their challenge-point 
to improve propulsion of the paretic limb.  An insole of similar thickness will be worn in the 
shoe of the non-paretic leg for symmetry and comfort but will not produce a tone during the 
intervention. Those in the Standard group will not wear insoles during intervention but will 
receive verbal feedback alone regarding propulsion of the paretic limb during gait training. 
Therapist-provided verbal feedback will be used to instruct participants on achieving and/or 
maintaining appropriate movement patterns that contribute to propulsion generation. For 

 
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both groups, the therapist will choose from a standardized bank of gait activities, suitable to 
each participant’s ability level. The goal for total walking time for each session will be 50 
minutes: 5, 10-minute bouts with a 2-minute rest between each bout. 
Outcome Measures: Paretic limb propulsion is our primary outcome measure. Secondary 
measures include the Six Minute Walk Test, Functional Gait Assessment, Fall Self-Efficacy, 
temporal-distance gait measures and gait kinematics, and lower extremity strength 
measures, all of which will be measured pre- and post-intervention.  
Data Analysis Plan: Descriptive statistics will be provided for all outcome measures. To 
identify the effect of the intervention, differences between the pre- and post-training 
assessment within each group (i.e. change scores) will be calculated. To test our 
hypotheses, we will apply independent sample t-tests to the change scores of the 
Biofeedback and Standard group. Hypothesis testing will be conducted at a two-sided p < 
0.05 level.  
4.  Background: 
Improved walking ability is considered one of the most important outcomes of stroke 
rehabilitation1 with walking speed a widely used measure of recovery2 and surrogate for 
functional walking ability.3 Forward propulsion of the body center of mass (COM) is a 
cardinal feature of normal, efficient adult gait that depends on the generation of 
appropriate anterior-posterior ground reaction forces (AP GRFs). Decreased propulsive 
force generation by the paretic limb of stroke survivors during walking has been identified 
through both simulation and cross-sectional studies as a major contributor to walking 
dysfunction.4-7 Bowden et. al., 8 demonstrated that propulsion symmetry during walking is 
able to differentiate individuals post-stroke as limited community versus community 
ambulators and that those who achieve clinically meaningful improvements in walking 
speed also improve propulsion symmetry. With this direct link between paretic propulsive 
ability and poststroke walking performance, it is important to develop rehabilitation 
interventions that target paretic propulsion. 
The primary contributor to the propulsive impulse in healthy controls is activity of the 
ankle plantarflexors.9, 10 Similarly, in individuals post-stroke, coordinated activity of the 
plantarflexor muscles in late stance and preswing positively correlated with paretic 
propulsive impulse.11 From work in our own lab, Clark and colleagues, in their 
investigation of modular organization of muscle activity post-stroke revealed that deficits 
in independent modulation of the quadriceps and plantarflexors resulted in decreased 
propulsion of the paretic compared to the nonparetic leg.12 Peterson and colleagues6 
further determined that hip extension angle was a significant predictor and positively 
correlated with propulsive impulse of the paretic leg. Given that activity of the ankle 
plantarflexors and hip extension angle are primary contributors to paretic propulsion,6 
Awad and colleagues implemented a gait rehabilitation intervention consisting of 
Functional Electrical Stimulation (FES) to the ankle plantarflexors (to increase muscle 
activation) while participants ambulated at their maximum speed (to facilitate greater hip 
extension) on a treadmill with overhead body-weight support 13 Post-intervention, 
improvements in paretic propulsion were observed, demonstrating the responsiveness of 
this impairment to rehabilitation. However, the modalities used to achieve this 
improvement, FES and a treadmill with a body-weight support system, are resources not 

 
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available to many rehabilitation clinics. Additionally, this intervention strategy required 2-3 
rehabilitation personnel to implement.  More frequently in stroke rehabilitation when these 
resources are not available, therapists provide verbal feedback to encourage a patient 
(with right hemiparesis for example) to “take a large step” (with the left leg to increase hip 
extension of the paretic, right leg) or “push through to the floor” (with the right foot to 
increase plantarflexor activation). This type of feedback, with attention focused on the 
patient’s movement, defined as “internal-focus feedback” may not be sufficient as patients 
post-stroke often lack intrinsic feedback mechanisms (i.e. decreased proprioception, 
decreased somatosenation) to translate these verbal commands into desired movements.  
Furthermore, the therapist is unable to objectively determine the magnitude propulsion 
force generated by the patient.  Therefore, this pilot study will test the use of biofeedback 
(external-focus feedback) as an adjuvant to therapist-provided (internal-focus) feedback 
to determine if this relatively simple and cost-effective intervention strategy will serve to 
increase paretic propulsion during gait.   
Provision of feedback is a widely known requisite for motor learning to occur.14 Physical 
rehabilitation following stroke primarily consists of re-learning motor skills that have been 
impaired or lost secondary to CNS damage. Intrinsic feedback mechanisms (i.e. 
proprioception, somatosensation), are crucial to motor skill learning in healthy adults, but 
are either impaired or absent post-stroke.  Therefore, extrinsic feedback from a therapist 
or from technology becomes a crucial alternative feedback source in rehabilitation. 
 
How best to augment the patient’s own impaired feedback mechanisms is a critical factor 
for rehabilitation scientists to determine in the development of efficacious rehabilitation 
practices. A recent systematic review15 found that augmenting feedback through the use of 
biofeedback was superior to therapist feedback in terms of performance of lower limb 
activities in the short term, with the effect being maintained beyond the intervention, 
indicating that learning had occurred. These previous results in training muscle activity, joint 
position and limb position provides the impetus of this pilot study to examine the use of 
biofeedback in the acquisition of paretic limb propulsion during gait.  
A systematic review on the use of biofeedback  across a variety of lower limb activities 
following stroke determined that biofeedback with an external-focus was superior to 
therapist-generated feedback.15 In this pilot study specialized shoe insoles that generate 
an audible tone when a prescribed threshold of loading on the forefoot during late stance 
is achieved (external-focus feedback) will be tested as an adjuvant to therapist-provided 
feedback. We hypothesize individuals who receive biofeedback intervention as an 
adjuvant to therapist-provided feedback will demonstrate improved paretic limb propulsion 
compared to those who receive therapist-provided feedback alone.    
As achievement of walking independence, not necessarily the reduction in impairment, is 
often the standard for successful rehabilitation16 and consequently the focus of 
rehabilitation services,17 there exists a high prevalence of inefficient walking strategies 
among persons with chronic stroke.18 Although a restitution-based versus compensation-
based approach to rehabilitation implicitly seems most prudent, there is a current need to 
demonstrate the link between restoration of impairments and functional gains. Awad and 

 
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colleagues19 recently demonstrated that improvement in propulsion of the paretic leg, 
following a 12-week locomotor training program, predicted improvement in distance 
walked, providing support for rehabilitation practice based in restitution of impairments. 
Aim 2 of this proposal will compare the effect of our two interventions on functional gait 
ability as determined by long-distance walking ability, dynamic balance and self-efficacy. 
5. Specific Aims: 
 
Specific Aim #1: Compare the effect of two interventions for improving paretic limb 
propulsion in individuals with impaired, asymmetric gait post-stroke:  standard therapist-
provided verbal feedback (“verbal feedback group”) versus standard therapist-provided 
verbal feedback plus propulsion biofeedback (“biofeedback group”). 
Hypothesis #1: Improvement in paretic propulsion during natural gait (i.e., tested without 
feedback) will be greater for the biofeedback group than for the verbal feedback group. 
 
Specific Aim #2: Compare the effect of two interventions for improving functional mobility in 
individuals with impaired, asymmetric gait post-stroke: standard therapist-provided verbal 
feedback (“verbal feedback group”) versus standard therapist-provided verbal feedback plus 
propulsion biofeedback (“biofeedback group”). 
Hypothesis #2: Improvement in functional mobility will be greater for the biofeedback group 
than for the verbal feedback group, as measured by the Six-Minute Walk Test, Functional 
Gait Assessment and Modified Falls Self Efficacy Scale. 
6. Research Plan: 
This will be a prospective, single-blind, RCT enrolling individuals at 6-months post-stroke. 
Consent for participation and enrollment will occur in two parts: 1) Screening Consent and 
2) Intervention Consent. Part 1, Screening Consent, consists of physical screening to 
determine study eligibility. 
 Participants who meet all inclusion/exclusion criteria will be enrolled and randomized to 
either the experimental (Biofeedback) or control (Verbal Feedback) group.  Individual 
treatment allocations will be in sealed envelopes which will be opened only on enrollment 
of the next eligible participant. 
Priority for participation in this study will be given to volunteers who are Veterans.  To 
optimize our capability to recruit Veterans we will conduct our rehabilitation intervention at 
the Malcom Randall VA Medical Center in Gainesville FL.  
Recruitment. Potential participants will be recruited from the Database (IRB# 457-1999) of 
the VA Brain Rehabilitation and Research Center (BRRC), a VA RR&D Center of 
Excellence. The database contains over 400 individuals with diagnosis of stroke who 
have been screened by a neurologist and interdisciplinary team to gather preliminary 
information about medical, motor and cognitive status. All individuals in the database 
have signed informed consent and agreed to be contacted for research participation.  

 
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Inclusion criteria: 1) Diagnosis of stroke, 2) > 6 months < 10 years post-stroke onset, 3) 
Medically stable, 4) 18-85 years of age, 5) Impaired lower extremity sensation confirmed 
by a score of < 12 on the Fugl-Meyer Sensory Assessment or  <  50% correct on 
monofilament testing on the plantar surface of the foot,20 6) Community-dwelling, 7) Step 
length asymmetry (paretic step length > non-paretic step length); this asymmetry has 
been determined to be correlated with minimal propulsive force of the paretic leg4, 8) 
Unilateral lower extremity paresis confirmed by a score of < 32 on the Fugl-Meyer Motor 
Assessment,20 9) Able to ambulate without an orthotic device, 10) Able to ambulate 
without an assistive device, 11) Ambulation of household distances without physical 
assistance to advance or support paretic lower extremity.   
Exclusion criteria: 1) Presence of a neurological condition other than stroke, 2) Pain upon 
ambulation, 3) Receiving physical therapy services for mobility and/or gait, 4) Severe 
arthritis or orthopedic problems that limit passive ranges of motion (knee flexion 
contracture of  -10°, knee flexion ROM < 90°, hip flexion contracture > 25°, and ankle 
plantar flexion contracture  > 15°). 
 
Inclusion and Exclusion criteria will initially be determined by medical record review.  If 
following the medical record review a potential participant remains eligible, they will be 
scheduled for an in-person screen to determine if they meet the criteria listed below.  
Potential participants will sign the screening Informed Consent Form and then the 
following screening assessments will be administered:  
 
1. Lower Extremity Fugl-Meyer Motor Assessment: The participant’s ability to move 
their paretic lower limb will be assessed in the supine, sitting and standing 
position. 
2. Lower Extremity Fugl-Meyer Sensory Assessment: The participant’s ability to 
sense light touch and movement of their paretic lower limb will be assessed  in 
the supine and sitting position. 
3. Observational Gait Assessment: Participant will walk a distance of 14 meters, 
two times at their self-selected walking pace. The physical therapist assessor will 
observe participant’s gait for asymmetry. 
4. Range of Motion:  Range of Motion of the hips, knees and ankles of both lower 
limbs will be assessed. This assessment will take place in the supine and sitting 
positions. 
5. Monofilament Testing: A monofilament will be touched to the sole of the 
participant’s paretic foot and they will be queried if they can feel the 
monofilament. 
Participants who meet eligibility criteria following the screening assessment will be 
invited to sign Part 2 Consent, the Intervention Informed Consent Form. Intervention 
Informed Consent allows for baseline testing and study participation.  
 
Procedure.  Thirty individuals will be randomized to either the Verbal Feedback Group 
(n=15) or the Biofeedback Group (n=15) group. Participants in the Biofeedback Group 

 
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will wear a commercially available pressure-sensitive insole (Pedar, Novel Electronics, 
Inc.) in the shoe on the paretic lower extremity. Prior to the first intervention session, 
participants in the Biofeedback Group will walk wearing the pressure-sensitive in-soles 
to determine the baseline amount of pressure exerted by the paretic forefoot during late 
stance as the limb transitions to the pre-swing position. The insole area underlying the 
participant’s forefoot will be calibrated to produce a tone when pressure exceeds 5% of 
baseline. This threshold will be progressively increased at regular intervals throughout 
the intervention period to ensure participants are gait training at their challenge-point.  
An insole of similar thickness will be worn in the shoe of the non-paretic leg for 
symmetry and comfort but will not produce a tone. Participants in the Verbal Feedback 
Group will not wear insoles during intervention. 
Intervention. Intervention (12, 60-minute sessions, 3X/week for four weeks) will occur in 
an outpatient research setting. Participants will be supervised by a licensed physical 
therapist and wear a gait belt during all activities. The therapist will choose from a 
standardized bank of gait activities, suitable to each participant’s ability level, such as: 
1) walking along a straight indoor path, 2) negotiating obstacles, 3) walking up and 
down inclined surfaces, and 4) walking in a distracting environment. These varied 
environments will be utilized to assure participants continued engagement in the 
intervention. The goal for total walking time for each session will be 50 minutes: 5, 10-
minute bouts with a 2-minute rest between bouts. This is the typical length and intensity 
of outpatient rehabilitation sessions for ambulatory patients discharged from inpatient 
rehabilitation. 
Biofeedback Group: Biofeedback (external-focus feedback) will be provided as an 
adjuvant to therapist-provided feedback during the intervention. Therapist feedback is 
described in the “Verbal Feedback Group” section below. Participants will be instructed 
that a tone will sound when they “push off with their (paretic) leg to swing it forward” 
when the participant-specific pre-programmed threshold is exceeded.  
Verbal Feedback Group: Therapist-provided internal-focus feedback (“directed towards 
components of body movement”21) will be used to instruct participants on achieving 
and/or maintaining appropriate movement patterns that contribute to propulsion 
generation.  Feedback will be customized for each participant, but will generally focus 
on 1) shifting body weight onto the paretic side during stance 2) rolling over the front of 
the foot during late stance, 3) walking with symmetrical step length on both sides, 4) 
pushing off with the paretic leg when stepping forward.  If participants are performing 
any/all of these movements well, feedback will be used to acknowledge and encourage 
continuation of the appropriate movements. 
 
Outcome Measures.  Assessments will take place pre- and post-intervention and 
conducted by a licensed physical therapist, blinded to group assignment.  
 
The primary outcome for Specific Aim #1 will be Paretic Limb Propulsion (PLP). 
 
Paretic Limb Propulsion (PLP). The propulsive impulse will be derived from the time 
integral of the positive A-P GRF for each leg.5 Participants will walk along a 10 meter 
pathway equipped with embedded force platforms (Advanced Medical Technology, 
Inc.). The force plates are flush with the floor and are not an obstacle or tripping hazard.   

 
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GRFs will be measured throughout the stance phase for both legs. The A-P GRF 
component, normalized to body weight will be used to derive PLP. 
 
Secondary outcome measures will be collected and assessed to more explicitly describe 
participants’ gait. We will conduct exploratory analyses on these measures to guide 
formulation of future studies’ aims and hypotheses in this line of research. Additional 
outcome measures will include:  
 
1) Hip, knee and ankle angle data from the LE’s will be acquired using a modified Helen 
Hayes marker set with rigid clusters on the pelvis and each thigh, shank and foot 
segments and recording the movement of these markers at 100 Hz using a 12 camera 
motion capture system (Vicon Motion Capture Systems, Oxford, UK). Data will be 
processed using Visual 3D (C-Motion, Inc., Germantown, MD). We are particularly 
interested in hip extension angle during late stance given its known contribution to 
forward propulsion.6  
 
2) Spatial-temporal gait variables of stride time, stride length, step time, step length, step 
width and gait speed will be captured while walking across a GAITRite instrumented 
walkway (CIR Systems Inc, Havertown, PA),  
 
3) Surface EMG will be recorded from the soleus (SO) and medial gastrocnemius (MG) of 
both legs because of their known contribution to forward propulsion.10 
 
The primary outcome for Specific Aim #2 will be long-distance walking function as 
measured by the Six-Minute Walk Test (6MWT).22  
 
Six Minute Walk Test:  reflects a person’s ability to maintain a moderate amount of exertion 
over a period of time. It has been identified as an excellent measure of poststroke walking 
capacity and community ambulation23, 24 as well as indicative of community reintegration 
post-stroke.25  Participants will walk for a total of six minutes at their comfortable walking 
speed and the total distance walked will be recorded. Participants will be guarded by 
research personnel and will be permitted to stand and rest or sit and rest during the six 
minute time-frame as needed.  
 
Secondary Outcomes for Specific Aim #2 are:  
 
Functional Gait Assessment (FGA),26 a 10-item clinical gait and balance test during 
which participants perform the following activities: walk at normal speeds, at fast and 
slow speeds, with vertical and horizontal head turns, with eyes closed, over obstacles, 
in tandem, backward and while ascending and descending stairs. The FGA is a superior 
test of dynamic balance to other oft-used clinical performance tests such as the 
Performance-Oriented Mobility Assessment, the Berg Balance Scale, and the Dynamic 
Gait Index all of which have reported ceiling effects in community-living older adults.27 
Excellent test-retest28 and intra- and inter-rater reliability29 has been established 
patients post-stroke. Additionally, a FGA cut-off score of 22/30 to classify those who are 
at increased risk for falls has been established.26 Although fall-incidence is beyond the 
scope of this current pilot study we hypothesize that increased contribution of the 

 
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paretic leg to forward propulsion would lead to improved dynamic balance and more 
stable gait, decreasing fall incidence. 
Modified Falls Efficacy Scale (MFES)30 is a 14-item questionnaire based on the Falls 
Efficacy Scale (FES),31 modified for people with chronic stroke. It includes the 10 items 
from the FES plus 4 items considered complex for people with stroke and is designed to 
measure self-perceived fear of falling during task performance. Significant differences in 
MFES scores between patients in a Falls and Balance Clinic and healthy older adults (p 
< 0.05) attests to the scales’ validity.30 Long-distance walking ability, dynamic balance 
during complex gait and falls self-efficacy will inform us regarding if restitution of paretic 
limb propulsion during gait translates into improvements in function and improved 
quality of life. These results will inform the next study in this line of research. 
Lower Extremity Strength Testing: Muscle strength of both limbs will be assessed 
utilizing a hand-held dynamometer32. The dynamometer is placed between the hand of 
the assessor and the participant’s limb, similar to a manual muscle test, with the 
advantage of the dynamometer providing a quantified measurement of force. 
Participants will be instructed to contract their muscle and move their limb against the 
dynamometer. Muscle strength will be recorded. 
Videorecording. For participants who signed the video recording consent, we will 
periodically videorecord training sessions. This will allow the intervention therapists to 
view the participant’s training and strategize on how to progress the intervention. 
Videorecordings will also provide the therapists feedback on how they can best assist 
the participant. Assessment sessions will also be periodically recorded. This will provide 
assessment therapists feedback on their implementation of the assessments. 
Videorecordings may also be used in scientific presentations. Participants will be 
informed when videotaping is occurring. 
7. Possible Discomforts and Risks: 
The risks undertaken in the walking therapy programs of the study are no greater than 
those in everyday physical therapy clinics where persons who have had a stroke are 
challenged daily to exercise, train, practice and improve beyond their current abilities. 
Safety in therapy is mandatory. Research personnel will walk beside participants during 
all aspects of the exercise intervention and all aspects of the assessment that assess 
gait. Participants may experience some fatigue while being tested or during the therapy 
sessions. Should they become tired, they will be allowed to rest. Participants may 
experience temporary muscle soreness as they increase the use of their trunk and limbs 
during the walking intervention. There is a risk of falling during walking activities, but 
guarding by research personnel will minimize the risk. Stroke patients, including those in 
this study, are at risk for another stroke, coronary heart disease related event and 
cardiac related death, regardless of intervention. 
8. Possible Benefits: 
Subjects participating in this study may see improvements in their walking speed, 
balance, and/or the amount of walking that they are able to do. They may become more 
confident in their balance and walking ability.    

 
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9. Conflict of Interest: 
There are no conflicts of interest apparent for any of the investigators. 
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