Ankle Robotics for Error Augmentation After Stroke
The goal of this pilot clinical trial is to test whether training with a portable ankle robot improves ankle push-off and walking speed in adults with chronic stroke who have ankle weakness. The study will also evaluate whether the device is safe and practical to use during walking rehabilitation.
The main questions it aims to answer are:
Does training with the portable ankle robot improve paretic ankle propulsion during walking? Does training with the portable ankle robot improve walking speed at self-selected and fast walking speeds?
Participants will:
Complete 30 training sessions of treadmill and overground walking while wearing the portable ankle robot, 3 to 4 times per week over 8 to 9 weeks Complete walking and movement assessments before training, after 15 sessions, and after 30 sessions Walk at self-selected and fast speeds while researchers measure ankle propulsion, gait symmetry, and walking speed
Study Overview
Detailed Description
This is a single-arm pilot study evaluating robotic error augmentation of paretic ankle propulsion during gait training in adults with chronic stroke. Ten participants with chronic (>6 months) stroke and residual ankle weakness will complete 30 training sessions using the AMBLE portable ankle exoskeleton. Assessments are conducted at baseline, after 15 sessions, and after 30 sessions. The hypothesis is that 30 sessions of robot-assisted treadmill gait training enhances paretic ankle plantarflexion propulsive torque and gait symmetry.
Approximately half of stroke survivors are left with chronic mobility disability, typically involving ankle weakness that impairs walking and increases fall risk. Current care relies on ankle-foot orthoses, functional electrical stimulation, canes, and walkers, none of which address the underlying deficit in ankle motor control. Weakness of the paretic plantarflexors limits push-off during late stance, reducing forward propulsion and contributing to reduced walking speed and gait asymmetry.
The investigators previously developed the AMBLE, a lightweight portable ankle exoskeleton that uses impedance-based control with real-time gait event detection to deliver torque synchronized to specific phases of the gait cycle. Prior work by this group using laboratory-based and portable ankle robotics targeted dorsiflexion, demonstrating reduced foot drop and improved overground walking in both early and chronic stroke, and the present study extends an ongoing investigation of the device (NCT04594837). Paretic plantarflexion propulsion has not previously been targeted with the AMBLE. Recent engineering modifications enable graded resistance during the push-off phase of gait, permitting investigation of whether error augmentation applied to paretic ankle propulsion can enhance forward propulsion during walking.
Training sessions consists of two 10-minute bouts of treadmill walking at progressively increasing speed and one 10-minute bout of overground walking as able, with the robot donned on the paretic leg. Plantarflexion resistance is delivered through the ankle robot and calibrated individually, increased as tolerated up to the level just below the point at which hip circumduction or instability emerges. Resistance is applied after attainment of steady-state walking speed and intermittently removed at predetermined intervals to sample voluntary paretic ankle power. Treadmill speed is then progressed toward a target of 70-85% heart rate reserve and RPE 15-18, recorded every 3-5 minutes. Seated rest of 2-3 minutes is provided between bouts.
Visual feedback of ankle propulsion power is delivered through a tablet-based application on a faded schedule: continuously during weeks 1-2, for 1 minute every 5 minutes during weeks 3-4, for 1 minute at the end of each 10-minute bout during weeks 5-6, and as terminal summary feedback during seated rest in weeks 7-9.
Assessments include the 10-meter walk test at self-selected and fastest comfortable speeds; overground gait biomechanics using an instrumented walkway for spatiotemporal parameters and gait symmetry and two force plates for propulsive torque during push-off; and paretic and non-paretic ankle power normalized to body mass with kinetic symmetry, collected during unassisted walking with the device in evaluation mode. The Fugl-Meyer Assessment for the Lower Extremity is administered at baseline. Baseline and post-training measures will be compared using paired t-tests or nonparametric equivalents. Findings will provide preliminary effect estimates to inform the design of a larger trial.
Study Type
Enrollment (Estimated)
Phase
- Not Applicable
Contacts and Locations
Study Locations
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Maryland
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Baltimore, Maryland, United States, 21201
- Allied Health Research Building
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Baltimore, Maryland, United States, 21042
- Allied Health Research Building
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Participation Criteria
Eligibility Criteria
Ages Eligible for Study
- Adult
- Older Adult
Accepts Healthy Volunteers
Description
Inclusion Criteria:
- Chronic stroke, more than 6 months post-stroke
- Clinical evidence of hemiparetic gait
- Ankle dorsiflexion and plantarflexion strength on the affected side graded 1/5 (trace contraction) to 4/5 (reduced strength) on manual muscle testing
- Able to independently complete the 10-Meter Walk Test at a walking speed less than 1.0 m/s, with or without an assistive device
Exclusion Criteria:
- Self-reported unstable angina, myocardial infarction within the past 3 months, congestive heart failure (NYHA Class II), or hemodynamically significant valvular disease
- Self-reported hypertension that is a contraindication to routine physical therapy (greater than 160/100 mmHg on two assessments)
- Self-reported hospitalization within the past 3 months for severe medical illness
- Self-reported symptomatic peripheral arterial occlusive disease
- Self-reported orthopedic conditions or chronic pain that significantly alter gait function
- Self-reported pulmonary or renal failure
- Self-reported active cancer
- Self-reported history of a non-stroke neuromuscular disorder restricting gait
- Aphasia or cognitive functioning that confounds participation, defined as unable to follow two-step commands or by judgment of the evaluating therapist
- Self-reported history of cerebellar stroke or observable cerebellar signs
- Self-reported botulinum toxin prescribed for the lower extremities within the previous 3 months
Study Plan
How is the study designed?
Design Details
- Primary Purpose: Treatment
- Allocation: N/A
- Interventional Model: Single Group Assignment
- Masking: None (Open Label)
Arms and Interventions
Participant Group / Arm |
Intervention / Treatment |
|---|---|
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Experimental: AMBLE Robotic Gait Training
Participants with chronic stroke will receive a 30-session gait training program using the AMBLE portable robotic ankle exoskeleton.
Training will include treadmill and overground walking with individualized robotic resistance to improve ankle plantarflexion during push-off.
Robotic assistance will be adjusted throughout the intervention based on participant performance and tolerance to promote active motor recovery and improve walking function.
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The AMBLE is a portable robotic ankle exoskeleton designed to provide individualized assistance and/or resistance during gait training.
The device uses adaptive impedance-based control and real-time gait detection to provide dorsiflexion assistance during swing and plantarflexion assistance or resistance during push-off based on participant performance.
It is used during treadmill and overground walking to promote recovery of ankle motor control and walking function.
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What is the study measuring?
Primary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
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Peak ankle plantarflexion propulsive torque during walking
Time Frame: Baseline (prior to intervention), 5 weeks after intervention initiation (following approximately 15 sessions), and 10 weeks after intervention initiation (following approximately 30 sessions)
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Peak ankle plantarflexion propulsive torque will be measured using force plates during overground walking to quantify propulsion generated by the paretic limb during the push-off phase of gait.
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Baseline (prior to intervention), 5 weeks after intervention initiation (following approximately 15 sessions), and 10 weeks after intervention initiation (following approximately 30 sessions)
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Secondary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
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Self-selected walking speed
Time Frame: Baseline (prior to intervention), 5 weeks after intervention initiation (following approximately 15 training sessions), and 10 weeks after intervention initiation (following approximately 30 training sessions)
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Self-selected walking speed will be assessed using the 10-Meter Walk Test and reported in meters per second.
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Baseline (prior to intervention), 5 weeks after intervention initiation (following approximately 15 training sessions), and 10 weeks after intervention initiation (following approximately 30 training sessions)
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Fast walking speed
Time Frame: Baseline (prior to intervention), 5 weeks after intervention initiation (following approximately 15 training sessions), and 10 weeks after intervention initiation (following approximately 30 training sessions)
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Maximum comfortable walking speed will be assessed using the 10-Meter Walk Test and reported in meters per second.
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Baseline (prior to intervention), 5 weeks after intervention initiation (following approximately 15 training sessions), and 10 weeks after intervention initiation (following approximately 30 training sessions)
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Step Length Symmetry Ratio During Overground Walking Measured by Instrumented Walkway
Time Frame: Baseline (prior to intervention), 5 weeks after intervention initiation (following approximately 15 training sessions), and 10 weeks after intervention initiation (following approximately 30 training sessions)
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Step length symmetry ratio computed as paretic step length divided by non-paretic step length from spatiotemporal data collected during overground walking on a GAITRite instrumented walkway.
A ratio of 1.0 indicates perfect symmetry between limbs; values below 1.0 indicate shorter paretic steps and values above 1.0 indicate longer paretic steps.
Values are averaged across [N] walkway passes at self-selected walking speed at each assessment timepoint.
Unit of Measure: ratio
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Baseline (prior to intervention), 5 weeks after intervention initiation (following approximately 15 training sessions), and 10 weeks after intervention initiation (following approximately 30 training sessions)
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Collaborators and Investigators
Collaborators
Investigators
- Principal Investigator: Kelly Westlake, PhD, PT, University of Maryland, Baltimore
Publications and helpful links
General Publications
- Forrester LW, Roy A, Krywonis A, Kehs G, Krebs HI, Macko RF. Modular ankle robotics training in early subacute stroke: a randomized controlled pilot study. Neurorehabil Neural Repair. 2014 Sep;28(7):678-87. doi: 10.1177/1545968314521004. Epub 2014 Feb 10.
- Forrester LW, Roy A, Krebs HI, Macko RF. Ankle training with a robotic device improves hemiparetic gait after a stroke. Neurorehabil Neural Repair. 2011 May;25(4):369-77. doi: 10.1177/1545968310388291. Epub 2010 Nov 29.
- Macko RF, Ivey FM, Forrester LW, Hanley D, Sorkin JD, Katzel LI, Silver KH, Goldberg AP. Treadmill exercise rehabilitation improves ambulatory function and cardiovascular fitness in patients with chronic stroke: a randomized, controlled trial. Stroke. 2005 Oct;36(10):2206-11. doi: 10.1161/01.STR.0000181076.91805.89. Epub 2005 Sep 8.
- Macko RF, Ivey FM, Forrester LW. Task-oriented aerobic exercise in chronic hemiparetic stroke: training protocols and treatment effects. Top Stroke Rehabil. 2005 Winter;12(1):45-57. doi: 10.1310/PJQN-KAN9-TTVY-HYQH.
- Westlake KP, Dudek K, Roy A, Henderson CE, Hornby TG. The Concept of Shaping Applied to Locomotor Interventions: Clinical and Robotic Strategies to Facilitate and Progress Variable Stepping Training at Higher Intensities. Neurorehabil Neural Repair. 2026 Jun 15:15459683261454948. doi: 10.1177/15459683261454948. Online ahead of print.
Study record dates
Study Major Dates
Study Start (Actual)
Primary Completion (Estimated)
Study Completion (Estimated)
Study Registration Dates
First Submitted
First Submitted That Met QC Criteria
First Posted (Actual)
Study Record Updates
Last Update Posted (Actual)
Last Update Submitted That Met QC Criteria
Last Verified
More Information
Terms related to this study
Keywords
Other Study ID Numbers
- HP-00108406
Plan for Individual participant data (IPD)
Plan to Share Individual Participant Data (IPD)?
Drug and device information, study documents
Studies a U.S. FDA-regulated drug product
Studies a U.S. FDA-regulated device product
product manufactured in and exported from the U.S.
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