A Generic Sequential Stimulation Adapter for Reducing Muscle Fatigue during Functional Electrical Stimulation

Abstract

Background: Clinical applications of conventional functional electrical stimulation (FES) administered via a single electrode are limited by rapid onset neuromuscular fatigue. “Sequential” (SEQ) stimulation, involving the rotation of pulses between multiple active electrodes, has been shown to reduce fatigue compared to conventional FES. However, there has been limited adoption of SEQ in research and clinical settings. Methods: The SEQ adapter is a small, battery-powered device that transforms the output of any commercially available electrical stimulator into SEQ stimulation. We examined the output of the adaptor across a range of clinically relevant stimulation pulse parameters to verify the signal integrity preservation ability of the SEQ adapter. Pulse frequency, amplitude, and duration were varied across discrete states between 4 and 200 Hz, 10 and100 mA, and 50 and 2000 μs, respectively. Results: A total of 420 trials were conducted, with 80 stimulation pulses per trial. The SEQ adapter demonstrated excellent preservation of signal integrity, matching the pulse characteristics of the originating stimulator within 1% error. The SEQ adapter operates as expected at pulse frequencies up to 160 Hz, failing at a frequency of 200 Hz. Conclusion: The SEQ adapter represents an effective and low-cost solution to increase the utilization of SEQ in existing rehabilitation paradigms.

Toward a wearable monitor of local muscle fatigue during electrical muscle stimulation using tissue Doppler imaging

“…Further, without adequate rest to recover from fatigue, overworked muscles are at risk for injury and lead to muscle soreness and pain (Dugan and Frontera, 2000 ). Attempts to mitigate EMS-induced muscle fatigue often involve spatially distributing the stimulation (Sayenko et al, 2014 ; Buckmire et al, 2018 ; Ye et al, 2021 ) and modifying the stimulation parameters (e.g., timing and waveforms) (Graham et al, 2006 ; Shimada et al, 2006 ). However, these open-loop approaches do not attempt to evaluate or characterize the induced muscle fatigue throughout the stimulation protocol.…”