Innovative Closed-loop Functional Electrical Stimulation Control System for Augmenting Post-stroke Gait

This study will compare the performance of a novel data-driven model-predictive controller (MPC) based functional electrical stimulation (FES) system versus a conventional FES system for footdrop correction during treadmill and overground walking tasks in people post-stroke.

Study Overview

• Status: Not yet recruiting
• Conditions: Post-stroke Hemiparesis
• Intervention / Treatment: Device: Model-Predictive Controller (MPC) Functional Electrical Stimulation (FES); Device: Conventional Functional Electrical Stimulation (FES)

Detailed Description

Functional electrical stimulation (FES) is a common rehabilitation tool that incorporates electrical stimulation timed with a functional task to augment paretic muscle function in people with neuro-pathologies such as stroke and spinal cord injury. The rigor of previous research has established the safety, as well as both neuro-prosthetic and therapeutic effects of FES systems for standing, walking, and grasping. Stroke is the leading cause of disability, and footdrop is a highly prevalent post-stroke gait deficit, leading to insufficient ankle dorsiflexion during the swing phase of gait, and contributing to reduced mobility. FES systems that correct footdrop to improve gait function and reduce fall risk are gaining popularity, with commercial systems such as enhancing translation potential. Despite their promising functional value, accessibility, and positive neuroplasticity effects, current FES systems have some fundamental limitations, which limit their clinical prescription.

The goal of this project is to overcome two major limitations and technical gaps in FES: rapid onset of muscle fatigue during FES and lack of sophisticated closed-loop control of FES intensity. Most existing FES systems do not automatically modulate stimulation intensity in response to muscle fatigue, and may overstimulate the muscles if fixed (open-loop) stimulation or a pure feedback-based stimulation strategy is used to control FES intensity. To address this limitation, the researchers aim to develop and clinically test FES for improving stroke gait using data-driven FES control systems.

Footdrop is a highly prevalent post-stroke gait deficit, leading to insufficient ankle dorsiflexion during the swing phase of gait, and reducing functional mobility. FES, which is an external application of stimulation to generate muscle contractions during a functional motor task, can achieve muscle force demands during standing and walking, and help persons with stroke and spinal cord injury recover mobility. FES for the correction of footdrop is one of the most popular gait applications of FES, which has been shown to improve mobility and reduce falls.

Although FES has positive effects on walking function, elicits active muscle contractions, and enhances corticomotor excitability, FES is not used as commonly as passive orthotics. Most current FES systems incorporate motion sensors to control the timing of FES during the gait cycle (paretic leg swing phase). However, none of these systems provide automatic closed-loop control of FES intensity, so that optimal stimulation can be delivered for each step, preventing over-stimulation, reducing fatigue, and maintaining optimal muscle performance for a greater number of steps. Additionally, rapid onset of muscle fatigue during FES is caused by synchronous, non-selective, repeated recruitment of largely fatigable muscle fibers.

The researchers will implement an innovative model-predictive controller (MPC) combined with real-time ultrasound-based feedback to deliver optimal FES intensities and minimize fatigue.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Trisha Kesar, PT, PhD; Phone Number: (404) 712-5803; Email: trisha.m.kesar@emory.edu

Study Locations

• United States
  • Georgia
    • Atlanta, Georgia, United States, 30322
      • Emory Rehabilitation Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• >6 months since stroke
• cortical or subcortical stroke
• able to walk 10-meters with or without an assistive device
• sufficient cardiovascular health and ankle stability to walk on treadmill without ankle orthosis
• passive ankle range of motion to benefit from dorsiflexor FES assistance
• resting heart rate 40-100 bpm

Exclusion Criteria:

• cerebellar signs
• score >1 on question 1b (does not know the current month and age) and >0 on question 1c (can not blink eyes and squeeze hands) on NIH Stroke Scale
• inability to communicate with investigators
• neglect/hemianopia
• unexplained dizziness in past 6 months
• sensory loss in paretic leg
• musculoskeletal or medical conditions limiting walking
• neurologic diagnoses other than stroke

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: MPC FES Followed by Conventional FES; Post-stroke participants participating in both treadmill and overground walking trials with the novel model-predictive controller (MPC) functional electrical stimulation (FES) system first and with a conventional functional electrical stimulation (FES) system second.	Device: Model-Predictive Controller (MPC) Functional Electrical Stimulation (FES); The model-predictive controller (MPC) determines the timing and intensity of electrical stimulation delivered for FES. MPC combined with real-time ultrasound-based feedback delivers optimal FES intensities and minimizes fatigue. FES is delivered to the ankle dorsiflexor muscles using a commercially available FDA-approved electrical stimulator.; Device: Conventional Functional Electrical Stimulation (FES); For functional electrical stimulation, surface electrodes are placed on the paretic leg on skin overlying the tibialis anterior (TA) muscle, with intensity pre-set to elicit dorsiflexion to neutral against gravity. FES will be delivered to the ankle dorsiflexor muscles using a commercially available FDA-approved electrical stimulator.
Experimental: Conventional FES Followed by MPC FES; Post-stroke participants participating in both treadmill and overground walking trials with a conventional functional electrical stimulation (FES) system first and the novel model-predictive controller (MPC) functional electrical stimulation (FES) system second.	Device: Model-Predictive Controller (MPC) Functional Electrical Stimulation (FES); The model-predictive controller (MPC) determines the timing and intensity of electrical stimulation delivered for FES. MPC combined with real-time ultrasound-based feedback delivers optimal FES intensities and minimizes fatigue. FES is delivered to the ankle dorsiflexor muscles using a commercially available FDA-approved electrical stimulator.; Device: Conventional Functional Electrical Stimulation (FES); For functional electrical stimulation, surface electrodes are placed on the paretic leg on skin overlying the tibialis anterior (TA) muscle, with intensity pre-set to elicit dorsiflexion to neutral against gravity. FES will be delivered to the ankle dorsiflexor muscles using a commercially available FDA-approved electrical stimulator.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Adverse Events	Safety is assessed as the number of adverse events experienced by study participants.	Day 1
Count of Risks	Safety is assessed as the count of risks, including falling, discomfort, pain, skin problems, fatigue, and soreness.	Day 1
Participant Perception of Comfort	Participant perception of comfort is measured on an 10-point Likert scale ranging from 1 to 10, where 10 is the most comfortable.	Day 1
Participant Perception of Acceptability	Participant perception of acceptability is measured on an 10-point Likert scale ranging from 1 to 10, where 10 is the most acceptable.	Day 1
Percent of Gait Cycles with Footdrop Correction	Feasibility of the FES control system is assessed as the percentage of gait cycles with footdrop correction. The FES control system is considered effective if greater than 80% of gait cycles have footdrop correction.	Day 1
Number of Participants Completing Gait Bouts	Feasibility of the FES control system is assessed as the number of participants who are able to complete gait bouts with the MPC FES system. The FES control system is considered effective if greater than 80% of participants are able to complete gait bouts.	Day 1

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Peak Ankle Dorsiflexion Angle During Swing	Gait biomechanics performance is assessed as the peak ankle dorsiflexion angle during swing. The normal range for peak ankle dorsiflexion is 0 to 5 degrees.	Day 1
Overground Walking Distance	Gait performance is assessed as overground walking distance traveled, in meters, during a 6-minute walk test.	Day 1
FES Intensity	FES system performance is assessed as FES intensity. FES intensity is measured during a treadmill walking bout. Intensity is measured by milliamps (mA) or millivolts (mV).	Day 1

Collaborators and Investigators

• Sponsor: Emory University
• Collaborators: Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
• Investigators: Principal Investigator: Trisha Kesar, PT, PhD, Emory University

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): August 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: September 17, 2025
• First Submitted That Met QC Criteria: September 17, 2025
• First Posted (Actual): September 24, 2025

Study Record Updates

• Last Update Posted (Actual): March 25, 2026
• Last Update Submitted That Met QC Criteria: March 23, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: post-stroke gait
• Other Study ID Numbers: STUDY00010102; 1R21HD116484 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data for primary dependent variables that underlie the results reported in publications from this study (such as text, tables, appendices) will be made available for sharing with other researchers.
• IPD Sharing Time Frame: Data will be made available for sharing beginning 9 months and for 2 years after publication of the manuscript presenting the study primary results.
• IPD Sharing Access Criteria: Data will be made available for sharing with researchers who provide a methodologically sound proposal to achieve the aims proposed by the requestor. Proposed purposes for using the shared data include replication studies, meta-analyses or systematic reviews, and other special requests. Researchers wanting to use data from this study should direct their requests to tkesar@emory.edu. To gain access, data requestors will need to sign a data access agreement.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes