Active proportional electromyogram controlled functional electrical stimulation system

Scientific Reports, 2020 · DOI: https://doi.org/10.1038/s41598-020-77664-0 · Published: December 4, 2020

Assistive Technology Neurorehabilitation

Simple Explanation

The study introduces an active functional electrical stimulation (FES) system which uses voluntary electromyogram (EMG) to proportionally control the intensity of FES. This aims to improve motor neurorehabilitation by engaging the user actively. The main challenge is electrical artefact contamination of the voluntary EMG during FES application. The presented system resolves this in real-time using an adaptive filtering technique, without requiring special hardware or blanking windows. The Active FES system was tested on fifteen patients with tetraplegia, demonstrating that FES intensity modulated by the system was proportional to intentional movement, suggesting it may be useful for neurorehabilitation and assistive technology.

Study Duration

Not specified

Participants

15 patients with tetraplegia

Evidence Level

Pilot study

Key Findings

1
The Active FES system effectively extracts voluntary EMG from muscles under FES using an adaptive filtering technique, outperforming the classic comb filtering method.
2
The extracted EMG signal with the Active FES system is coherent with its noise-free version, indicating that the extracted signal is sufficiently similar to the real voluntary EMG.
3
The Active FES system can proportionally modulate the intensity of FES in accordance with a user’s intentional movement, which can be used as a proportional EMG-FES system.

Research Summary

The study introduces a novel Active FES system that utilizes an adaptive filtering technique to extract voluntary EMG from muscles during FES, addressing the challenge of electrical artefact contamination. The Active FES system demonstrated its ability to proportionally modulate FES intensity based on intentional movement in patients with tetraplegia, suggesting its potential for neurorehabilitation and assistive technology. The system's software-based solution eliminates the need for special hardware or blanking windows, enabling full bandwidth EMG acquisition and providing a reliable method for proportional EMG-controlled FES.

Practical Implications

Neurorehabilitation potential

The Active FES system may promote active engagement and corticospinal changes, making it useful for neurorehabilitation of functional movement following neurological disorders.

Assistive technology application

The Active FES system has the potential to serve as an assistive device, particularly for patients with limited hand function, following further development.

Research opportunities

The Active FES system can be used for further research, including studying the effect of stimulation parameters on muscle activities, assessment of reflexes during FES, and real-time control models.

Study Limitations

1
The study acknowledges the need to reduce the delay introduced by the filters in the Active FES system.
2
The study mentions the need to increase the number of channels in a computationally efficient manner.
3
The study suggests the need for further tests to determine the performance of the method during activities of daily living.

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