Functional electrical stimulation (FES) is limited by the rapid onset of muscle fatigue caused by localized nerve excitation repeatedly activating only a subset of motor units. The purpose of this study was to investigate reducing fatigue by sequentially changing, pulse by pulse, the area of stimulation using multiple surface electrodes that cover the same area as one electrode during conventional stimulation. Paralyzed triceps surae muscles of an individual with complete spinal cord injury were stimulated, via the tibial nerve, through four active electrodes using spatially distributed sequential stimulation (SDSS) that was delivered by sending a stimulation pulse to each electrode one after another with 90° phase shift between successive electrodes. For comparison, single electrode stimulation was delivered through one active electrode. For both modes of stimulation, the resultant frequency to the muscle as a whole was 40 Hz. Isometric ankle torque was measured during fatiguing stimulations lasting 2 min. Each mode of stimulation was delivered a total of six times over 12 separate days. Three fatigue measures were used for comparison: fatigue index (final torque normalized to maximum torque), fatigue time (time for torque to drop by 3 dB), and torque-time integral (over the entire trial). The measures were all higher during SDSS (P < 0.001), by 234, 280, and 171%, respectively. The results are an encouraging first step toward addressing muscle fatigue, which is one of the greatest problems for FES.

PurposeA critical limitation with transcutaneous neuromuscular electrical stimulation is the rapid onset of muscle fatigue. We have previously demonstrated that spatially distributed sequential stimulation (SDSS) shows a drastically greater fatigue-reducing ability compared to a single active electrode stimulation (SES). The purposes of this study were to investigate (1) the fatigue-reducing ability of SDSS in more detail focusing on the muscle contractile properties and (2) the mechanism of this effect using array-arranged electromyogram (EMG).MethodsSDSS was delivered through four active electrodes applied to the plantarflexors, sending a stimulation pulse to each electrode one after another with 90° phase shift between successive electrodes. In the first experiment, the amount of exerted ankle torque and the muscle contractile properties were investigated during a 3 min fatiguing stimulation. In the second experiment, muscle twitch potentials with SDSS and SES stimulation electrode setups were compared using the array-arranged EMG.ResultsThe results demonstrated negligible torque decay during SDSS in contrast to considerable torque decay during SES. Moreover, small changes in the muscle contractile properties during the fatiguing stimulation using SDSS were observed, while slowing of muscle contraction and relaxation was observed during SES. Further, the amplitude of the M-waves at each muscle portion was dependent on the location of the stimulation electrodes during SDSS.ConclusionWe conclude that SDSS is more effective in reducing muscle fatigue compared to SES, and the reason is that different sets of muscle fibers are activated alternatively by different electrodes.

Our study has revealed improvements in fatigue tolerance during transcutaneous neuromuscular electrical stimulation using SDSS, a stimulation strategy that alternates activation of subcompartments of muscles. The SDSS protocol can provide greater stimulation times with less decrement in mechanical output compared with the conventional protocol.

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Rick Hansen InstituteBackground/objective: Predicting clinical and economic variables that impact upon inpatient rehabilitation length of stay (LOS) is controversial, yet significantly influences resource allocation required for optimal outcomes. Our aim was to identify patient-related factors evident at admission to a spinal cord injury (SCI) rehabilitation unit likely to extend LOS. We sought to describe the impact of relevant demographic, impairment, and medical complexity variables at rehabilitation admission on rehabilitation LOS among adult Canadians with traumatic SCI admitted for inpatient rehabilitation. Methods/Overview: Data were obtained via chart abstraction from Rick Hansen SCI Registry sites. Variables included subject's rehabilitation onset days, LOS, age at injury, sex, International Standards for Neurological Classification for Spinal Cord Injury (ISNCSCI) impairment (Neurological Level of Injury (NLI), ASIA Impairment Scale (AIS)), and medical complexity including prior ventilation (VENT), PEG tube (PEG) or indwelling bladder catheter (IBC) at acute discharge, Pain Interference Scale Score (PISS) > 15 and functional ability using ISNCSCI lower extremity motor scores (LEMS) ≤20/50 at rehabilitation admission. For univariate analyses, the dependent variable was LOS, with VENT, PEG, IBC, LEMS, and PISS as independent variables. Multivariate linear regression analyses used log LOS as the dependent variable with AIS, VENT, IBC, and LEMS as independent variables. Results: Adult men and women (n = 827, 82% male), mean (SD) age of 45 (18)