Closed-Loop Asynchronous Neuromuscular Electrical Stimulation Prolongs Functional Movements in the Lower Body

Area of Science:

• Rehabilitation Engineering
• Biomedical Engineering
• Neuroscience

Background:

• Neuromuscular electrical stimulation (NMES) aids rehabilitation and functional movement but is limited by muscle fatigue.
• Asynchronous stimulation, switching between channels, can mitigate NMES-induced fatigue.
• Implementing asynchronous stimulation requires managing complex switching dynamics and varied muscle responses.

Purpose of the Study:

• To develop and validate a closed-loop controller for asynchronous NMES.
• To assess the controller's ability to maintain limb trajectory tracking during asynchronous stimulation.
• To compare asynchronous stimulation with conventional single-channel stimulation.

Main Methods:

• Development of a closed-loop controller for multi-channel asynchronous NMES.
• Implementation of the controller on able-bodied individuals performing knee-shank complex movements.
• Testing asynchronous stimulation against single-channel conventional stimulation.

Main Results:

• The closed-loop controller achieved asymptotic tracking of desired limb trajectories.
• Asynchronous stimulation significantly extended the duration of functional movement performance under feedback control.
• The controller effectively managed channel switching for sustained functional tasks.

Conclusions:

• Closed-loop asynchronous NMES is a viable strategy to reduce muscle fatigue.
• This approach enhances the potential for sustained functional movements in rehabilitation and assistive technologies.
• The developed controller shows promise for improving the efficacy of NMES-based interventions.