Clinical Investigation to Validate the Safety and Performance of Integrating Functional Electrical Stimulation Into the ABLE Exoskeleton

The primary objective of this study is to validate the safety and clinical performance of the ABLE Exoskeleton with integrated Functional Electrical Stimulation (ABLE FES) in individuals with neurological conditions that impair gait, including spinal cord injury, acquired brain injury, and multiple sclerosis.

The secondary objective is to collect preliminary data on the potential clinical and psychosocial benefits of combining robotic gait assistance with electrical stimulation.

Study Overview

• Status: Recruiting
• Conditions: Multiple Sclerosis; Spinal Cord Injury; Acquired Brain Injury (Including Stroke)
• Intervention / Treatment: Device: ABLE Exoskeleton with Functional Electrical Stimulation (ABLE FES)

Detailed Description

This is a pre-post, single-centre, quasi-experimental study with an estimated duration of 16 weeks. The study will be conducted at therapy2people GmbH (Vienna, Austria). A minimum of 15 participants (5 per subgroup: spinal cord injury, acquired brain injury, multiple sclerosis) will be recruited within a period of up to 8 weeks.

After providing informed consent, participants will undergo a screening visit to confirm eligibility based on predefined inclusion and exclusion criteria. At the latest, one week after screening, participants will complete a baseline assessment.

The intervention will consist of 8 gait training sessions with the ABLE Exoskeleton with Functional Electrical Stimulation integration(ABLE FES), performed twice per week over 4-5 weeks. Each session will last approximately 60 minutes and include donning/doffing, walking training, and safety/performance assessments. Electrode placement and stimulation parameters will be adapted to the participant's neurological condition.

Outcome measures will focus on device safety (adverse events, serious adverse events, withdrawals) and clinical performance (donning/doffing time, walking distance, number of steps, standing time, therapist assistance, gait parameters, and motor torque). Additional measures will include lower limb spasticity, pain, perceived exertion, user satisfaction, and tolerance to FES.

For safety monitoring during sessions involving functional electrical stimulation (FES) with the exoskeleton, vital signs including heart rate and blood pressure will be measured before, during, and after the intervention sessions.

At the latest, one week after the last training session, a post-training assessment will be conducted. Two weeks later, participants will return for a follow-up visit to record any adverse events since the end of training.

This study will provide valuable evidence on the safety, feasibility, and potential rehabilitation benefits of integrating functional electrical stimulation into a robotic exoskeleton for patients with neurological gait impairments.

• Study Type: Interventional
• Enrollment (Estimated): 15
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Peter Lackner, Dr.; Phone Number: +43 681 207 41241; Email: peter@tech2people.at

Study Locations

• Austria
  • State of Vienna
    • Vienna, State of Vienna, Austria, 1220
      • Recruiting
      • therapy2people GmbH
      • Contact: Philipp Bruchbacher; Phone Number: +43 681 20741241; Email: philipp@tech2people.at
      • Contact: Dennis Veit; Phone Number: +43 681 20741241; Email: dennis@tech2people.at

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• 18 to 80 years old
• Diagnosis of acquired brain injury, spinal cord injury (neurological level between C5 and L2, AIS B to AIS D), or multiple sclerosis
• Currently undergoing physiotherapy treatment, either as an inpatient or outpatient at the investigating center
• Ability to provide informed consent

Exclusion Criteria:

• Significant osteoporosis that may increase the risk of fracture
• Unresolved fractures in the pelvis or limbs, or a history of fragility fractures in the lower limbs within the past 2 years
• Spinal instability (or use of spinal orthoses, unless medically approved)
• Deterioration >3 points of the total in the motor score of the International Standards for the Neurological Classification of Spinal Cord Injury (ISNCSCI) in the last 4 weeks. Loss of sensation and/or motor activity above the level of injury detected that has not been evaluated by a doctor.
• Severe spasticity: Level 4 on the Modified Ashworth Scale
• Orthostatic hypotension: Inability to tolerate at least 10 minutes in an upright position
• Uncontrolled autonomic dysreflexia
• Medical instability
• Unstable cardiovascular condition, hemodynamic instability, untreated hypertension (SBP > 140 mmHg, DBP > 90 mmHg), deep vein thrombosis (DVT), or uncontrolled autonomic dysreflexia
• Severe comorbidities, including any condition deemed inappropriate by the investigator for using the ABLE Exoskeleton or for completing the study
• Pressure ulcers Grade I or higher (as defined by the European Pressure Ulcer Advisory Panel - EPUAP) in areas that will be in contact with the device
• Anthropometric measurements incompatible with the ABLE Exoskeleton, specifically height outside the 1.5-1.9 m range or weight exceeding 100 kg
• Anatomical constraints (such as leg length differences, users unable to position themselves inside the device) that are incompatible with the device
• Range of motion restrictions preventing normal gait or sit-to-stand transitions, including: Ankle: ability to achieve at least neutral (0°) position; Knee: ability to extend to at least -10°; Hip: bilateral hip flexion of at least 100° and extension of at least 0°
• Heterotopic ossification
• Pregnant or breastfeeding women
• Cognitive impairment that results in the inability to follow simple instructions, particularly psychological or cognitive problems that do not allow a participant to follow study procedures
• Requires assisted ventilation.
• Scoliosis >40-50º Cobb angle.
• Presence of pacemakers, defibrillators, or other non-compatible electronic implants.
• Open wounds, infections, or active irritation at the electrode placement sites.
• Severe dermatological conditions in the stimulation area.
• Uncontrolled active epilepsy.
• Malignant tumors in the area of application.
• Severe loss of sensation in the areas where electrodes are to be placed.
• Medical conditions where electrical stimulation is contraindicated by physician recommendation.
• Inability to communicate pain, discomfort, or adverse reactions during stimulation.
• Venous thrombosis, thrombophlebitis, or severe arterial obstruction.
• Chronic venous insufficiency with significant varicosities.
• Hemophilia.
• Ongoing infectious process or fever.
• Presence of metallic implants in the flow area between the electrodes

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Gait training with ABLE Exoskeleton + Functional Electrical Stimulation (ABLE FES); Participants will undergo 8 rehabilitation sessions over 4-5 weeks using the ABLE Exoskeleton with Functional Electrical Stimulation integration (ABLE FES). Each session will last approximately 60 minutes and include donning/doffing, gait training, and functional assessments. Electrode placement and stimulation parameters will be adapted to the participant's pathology (spinal cord injury, acquired brain injury, or multiple sclerosis). Participants will also complete baseline, post-training, and follow-up assessments.

Device: ABLE Exoskeleton with Functional Electrical Stimulation (ABLE FES); A robotic lower-limb exoskeleton integrated with functional electrical stimulation (ABLE FES) used for gait rehabilitation training.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number and type of device-related Adverse Events	To assess safety, the number of Severe Adverse Events (SAE), Adverse Events (AE), and withdrawals related to the device will be recorded and classified by type and severity throughout the study period.	From baseline to follow-up (up to 2 weeks after end of intervention)
Time taken to don/doff the device	The time taken to don and doff the ABLE Exoskeleton with FES will be measured during each gait training session. Donning time will start from the moment the participant is ready to transfer into the device until all straps and clips are tightened. Doffing time will start from the moment the participant begins removing the device until it is fully removed. Time will be reported in minutes and seconds.	Up to 5 weeks (8 sessions)
Number of steps walked	In each gait training session, the number of steps taken with the device (step count) will be automatically measured and recorded by the device.	Up to 5 weeks (8 sessions)
Distance walked	In each gait training session, the distance walked with the device will be automatically measured and recorded by the device and reported in meters.	Up to 5 weeks (8 sessions)
Time spent upright and time spent walking	In each gait training session, the time spent upright and the time spent walking with the device will be automatically measured and recorded by the device and reported in minutes.	Up to 5 weeks (8 sessions)
Number of therapists assisting the session	In each gait training session, the number of therapists assisting the participant during the session will be recorded.	Up to 5 weeks (8 sessions)
Assistive device used	In each gait training session, the assistive device used (walker, crutches, cane, second therapist, etc) will be recorded.	Up to 5 weeks (8 sessions)
Step Length	Step length (in cm) will be automatically measured and recorded during each gait training session by the device.	Up to 5 weeks (8 sessions)
Step Symmetry	Step symmetry (in %) will be automatically measured and recorded during each gait training session by the device.	Up to 5 weeks (8 sessions)
Center of mass displacement (cm)	In each gait training session, the center of mass displacement (cm) will be automatically measured and registered by the device	Up to 5 weeks (8 sessions)
Motor torque (Nm)	In each gait training session, the motor torque (Nm) will be automatically measured and registered by the device	Up to 5 weeks (8 sessions)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
FES tolerance	Tolerance to Functional Electrical Stimulation (FES) will be assessed using a custom single-item ordinal scale developed by the research team during each training session. Scores range from 0 to 4, where 0 = no perception (no sensation felt), 1-3 represent increasing levels of perceived stimulation, and 4 = painful (uncomfortable or painful stimulus). This scale is descriptive; higher scores indicate greater perceived stimulation intensity, with the highest score reflecting an uncomfortable or painful stimulus.	During each training session (up to 5 weeks, 8 sessions)
Clinical observation	Clinical observations will be assessed using a structured questionnaire developed by the research team, consisting of 4 yes/no items completed during each session.	During each training session (up to 5 weeks, 8 sessions)
Quebec User Evaluation of Satisfaction with assistive Technology (QUEST 2.0) score	The Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST 2.0) is a 12-item outcome measure that assesses user satisfaction with two components (Device and Services) using a 5-point scale ranging from 1 (not satisfied) to 5 (very satisfied). Only the 8 items referred to the device will be evaluated from participants and the whole 12 items from the therapists to measure user satisfaction with the ABLE Exoskeleton after the training program experience	Post-training (up to 6 weeks)
Borg Rating of Perceived Exertion	The Borg Rating of Perceived Exertion (RPE) scale (0-10) will be used to evaluate perceived physical effort before and after each training session. Scores range from 0 (no exertion) to 10 (maximal exertion), with higher scores indicating greater perceived effort.	From baseline to post-training (up to 6 weeks)
Location and level of pain	The location and level of pain using the numeric rating scale (NRS) will be assessed. Each value is scored on a 0 to 10 scale, where 0 represents no pain and 10 represents the worst pain imaginable.	From baseline to post-training (up to 6 weeks)
Lower limb spasticity	The Modified Ashworth Scale (MAS) will be used to measure lower limb spasticity. Scores range from 0 (no increase in muscle tone) to 4 (rigid).	At baseline and post-training (up to 6 weeks)
Minimum tolerated assistance in Functional Test	Exoskeleton assistance level (%) tolerated by the patient for at least 5 minutes, when progressively reducing assistance levels during a 30-minute walk with the exoskeleton and without FES.	At baseline, each training session (4-5 weeks) and post-training (up to 6 weeks)

Collaborators and Investigators

• Sponsor: ABLE Human Motion S.L.
• Collaborators: therapy2people GmbH

Study record dates

Study Major Dates

• Study Start (Actual): April 20, 2026
• Primary Completion (Estimated): August 12, 2026
• Study Completion (Estimated): August 12, 2026

Study Registration Dates

• First Submitted: April 16, 2026
• First Submitted That Met QC Criteria: April 22, 2026
• First Posted (Actual): April 24, 2026

Study Record Updates

• Last Update Posted (Actual): April 24, 2026
• Last Update Submitted That Met QC Criteria: April 22, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Multiple Sclerosis; Spinal Cord Injury; Gait training; Functional Electrical Stimulation (FES); Acquired Brain Injury; Robotic exoskeleton; Lower-limb exoskeleton; Wearable exoskeleton; Hybrid exoskeleton-FES system
• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Wounds and Injuries; Autoimmune Diseases; Immune System Diseases; Demyelinating Autoimmune Diseases, CNS; Autoimmune Diseases of the Nervous System; Demyelinating Diseases; Craniocerebral Trauma; Trauma, Nervous System; Spinal Cord Diseases; Multiple Sclerosis; Brain Injuries; Spinal Cord Injuries
• Other Study ID Numbers: ABLEexoFES

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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