Comparing Spatially Distributed and Single Electrode Stimulation on Individuals with Spinal Cord Injury

Abstract

It is still a challenge to delay the onset of fatigue on muscle contraction induced by Functional Electrical Stimulation (FES). We explored the use of two stimulation methods with the same total area, single electrode stimulation (SES), and spatially distributed electrical stimulation (SDSS) during isometric knee extension with spinal cord injured (SCI) volunteers. We applied stimulation on the left and right quadriceps of two SCI participants with both methods and recorded isometric force and evoked electromyography (eEMG). We calculated the force-time integral (FTI) and eEMG-time integral (eTI) for each stimulation series and used a linear regression as a measure of decay ratio. Moreover, we also estimated the contribution from each channel from eEMG.

User-Centered Design and Spatially-Distributed Sequential Electrical Stimulation in Cycling for Individuals with Paraplegia

“…The strategy was feasible due to the internal circuit responsible for generating the biphasic pulses being based on an H-bridge and none of the channels being simultaneously activated during the experiments. This setup is similar to [17] and [18].…”

“…A single method, i.e., SES or SDSS, was applied in each session. The choice of FES parameters was based on studies where SDSS was applied on different tasks, such as [19] and our previous work [17]. Pulses with an amplitude of 100 mA were applied, and the pulse width was used as the modulation parameter.…”

“…In addition to the influence of SDSS matrix topology/placement and the type of muscle fiber in the overall performance of the asynchronous stimulation, another reason for the limited improvement in SDSS-based FES cycling may lie in the exercise itself. Indeed, the literature cited so far compares SES and SDSS in the context of isometric [19,21,22,13,34,35,26,36,37,38,39,40,24,25,41,17] and isokinetic exercises [19,22,23,39,24,25]. Studies comparing SES and SDSS in isometric protocols have reported the more substantial gains in favor of SDSS when compared with isokinetic exercises.…”

“…One approach to mitigate this limitation is to spread the stimulation intensity into smaller spatially distributed electrodes, or spatially distributed sequential stimulation (SDSS) [15]. SDSS has been recently investigated in reducing fatigue compared to SES in spinal cord injury individuals (SCI) in isometric leg extension [16], [17] and also in dynamic knee extension task simulating FES Cycling [18]. In this paper,…”