An interventional study of Fatigue-Feedback FES Control Strategy and Standard FES Control Strategy in Muscle Fatigue, Functional Electrical Stimulation and Neuromuscular Rehabilitation, sponsored by National Council of Scientific and Technical Research, Argentina. Recruiting at 1 site in Argentina. Open to participants aged 18 Years to 60 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-14.
Sponsored by National Council of Scientific and Technical Research, Argentina · Not applicable, Interventional, and Basic science
This study evaluates two different control strategies for a rehabilitation device that combines recumbent leg-cycling with functional electrical stimulation (FES) of the quadriceps muscle. The device assists pedaling using a motor and electrical stimulation, and is intended for use after knee surgery (such as ACL reconstruction) or in other lower-limb rehabilitation. During muscle stimulation, fatigue can develop, which reduces the force produced by the stimulated muscle. This study compares a standard control strategy with a new strategy that adjusts stimulation based on the muscle's fatigue level, measured in real time. Healthy adult volunteers will complete two sessions on a recumbent stationary bicycle, 2 to 7 days apart. Each session lasts about 60 minutes and includes periods of pedaling with electrical stimulation, as well as isometric wall squats to induce muscle fatigue. Muscle activity, pedal force, and pedal position will be recorded throughout. The goal is to determine which control strategy produces more mechanical work from the leg muscles and better tracks the desired pedaling pattern, especially as fatigue develops.
The study uses a custom-instrumented recumbent stationary bicycle equipped with a brushless DC motor coupled to the pedal axis, load cells to measure pedal force, a Hall-effect sensor to measure pedal angular position, and a functional electrical stimulation (FES) system targeting the quadriceps femoris of the dominant leg. Surface electromyography (sEMG) is recorded using a 16-channel wireless system to estimate muscle fatigue in real time.
The study uses a randomized crossover design. Each participant completes both control strategies (with and without fatigue feedback) in randomized order across two separate sessions, 2 to 7 days apart, under similar physical and time-of-day conditions. Each session includes: a calibration phase (free pedaling without stimulation, followed by stimulation threshold testing); a first FES-assisted pedaling block; an isometric fatigue-induction phase (five wall squats); and a second FES-assisted pedaling block.
The primary outcome is the mechanical work performed during pedaling while under stimulation, measured in joules. Secondary outcomes include pedal force, muscle electrical activity (EMG RMS), muscle fatigue (estimated from pedal force variation and M-wave median frequency shift), and cadence-tracking error. The study is being conducted at the Biomechanics Laboratory, Facultad de Ingeniería, Universidad Nacional de Entre Ríos (Oro Verde, Entre Ríos, Argentina).
National Council of Scientific and Technical Research, Argentina is the lead sponsor of 18 studies on the registry; 4 are open to participants now.
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Participants perform recumbent cycling with FES assistance using the fatigue-feedback control strategy in the first session, followed by the standard control strategy in the second session, 2 to 7 days later. Session order of strategies is randomized across participants.
Device: Fatigue-Feedback FES Control Strategy · Device: Standard FES Control Strategy
Participants perform recumbent cycling with FES assistance using the standard control strategy in the first session, followed by the fatigue-feedback control strategy in the second session, 2 to 7 days later. Session order of strategies is randomized across participants.
Device: Fatigue-Feedback FES Control Strategy · Device: Standard FES Control Strategy
A closed-loop control strategy for the FES-assisted recumbent cycling device that explicitly incorporates real-time estimation of muscle fatigue (based on pedal force variation and M-wave median frequency) into the calculation of motor and electrical stimulation control signals.
A closed-loop control strategy for the FES-assisted recumbent cycling device based on a previously published approach, without explicit real-time incorporation of muscle fatigue estimation into the control signal calculation.
Mechanical work performed during FES-assisted pedaling
Mechanical work performed by the stimulated lower limb during FES-assisted pedaling, in joules. Computed from pedal force (load cells) and pedal angular position, integrated over the stimulated regions of the pedaling cycle. Measured during the FES pedaling blocks before and after the isometric fatigue-induction phase, and compared between control strategies within each participant.
Time frame: Day 1 (Session 1) and Day 3 to Day 8 (Session 2)
Pedal force
Force applied to the pedals, in newtons, recorded with compression load cells mounted on the pedal platforms during the FES pedaling blocks before and after the isometric fatigue-induction phase.
Time frame: Day 1 (Session 1) and Day 3 to Day 8 (Session 2)
Muscle electrical activity (EMG RMS)
Muscle electrical activity quantified as the root mean square (RMS) value computed from the surface electromyography signal of the stimulated and contralateral muscles.
Time frame: Day 1 (Session 1) and Day 3 to Day 8 (Session 2)
Muscle fatigue
Muscle fatigue estimated from the variation in pedal force and from the shift in median frequency of the M-wave obtained from the surface electromyography signal.
Time frame: Day 1 (Session 1) and Day 3 to Day 8 (Session 2), before and after the isometric fatigue-induction phase
Cadence tracking error
Error between the target pedaling cadence reference and the cadence actually achieved during FES-assisted pedaling.
Time frame: Day 1 (Session 1) and Day 3 to Day 8 (Session 2)
Plan to share: No
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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National Council of Scientific and Technical Research, Argentina