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

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.

Torque, Current, and Discomfort During 3 Types of Neuromuscular Electrical Stimulation of Tibialis Anterior.

BACKGROUND: The benefits of neuromuscular electrical stimulation (NMES) for rehabilitation depend on the capacity to generate functionally relevant torque with minimal fatigability and discomfort. Traditionally, NMES is delivered either over a muscle belly (mNMES) or a nerve trunk (nNMES). Recently, a technique that minimizes contraction fatigability by alternating pulses between the mNMES and nNMES sites, termed "interleaved" NMES (iNMES), was developed. However, discomfort and the ability to generate large torque during iNMES have not been explored adequately. OBJECTIVE: The study objective was to compare discomfort and maximal torque between mNMES, nNMES, and iNMES. METHODS: Stimulation trains (12 pulses at 40 Hz) were delivered to produce dorsiflexion torque using mNMES, nNMES, and iNMES. Discomfort was assessed using a visual analogue scale for contractions that generated 5-30% of a maximal voluntary isometric contraction (MVIC), and for the maximal tolerable torque. RESULTS: Discomfort scores were not different between NMES types when torque was ≤20% MVIC. At 30% MVIC, mNMES produced more discomfort than nNMES and iNMES. nNMES produced the most torque (65% MVIC), followed by iNMES (49% MVIC) and mNMES (33% MVIC); in these trials, mNMES produced more discomfort than nNMES, but not iNMES. LIMITATIONS: The present results may be limited to individuals with no history of neuromusculoskeletal impairment. CONCLUSIONS: In terms of discomfort, there were no differences between mNMES, nNMES, or iNMES for contractions between 5-20% MVIC. However, mNMES produced more discomfort than nNMES and iNMES for contractions of 30% MVIC, while for larger contractions, mNMES only produced more discomfort than nNMES. The advantages and disadvantages of each NMES type should be considered prior to implementation in rehabilitation programs.

Rehabilitation Interventions to modify endocrine-metabolic disease risk in Individuals with chronic Spinal cord injury living in the Community (RIISC): A systematic review and scoping perspective.

CONTEXT: Endocrine-metabolic disease (EMD) risk following spinal cord injury (SCI) is associated with significant multi-morbidity (i.e. fracture, diabetes, heart disease), mortality, and economic burden. It is unclear to what extent rehabilitation interventions can modify EMD risk and improve health status in community-dwelling adults with chronic SCI. OBJECTIVES: To characterize rehabilitation interventions and summarize evidence on their efficacy/effectiveness to modify precursors to EMD risk in community-dwelling adults with chronic SCI. METHODS: Systematic searches of MEDLINE PubMed, EMBASE Ovid, CINAHL, CDSR, and PsychInfo were completed. All randomized, quasi-experimental, and prospective controlled trials comparing rehabilitation/therapeutic interventions with control/placebo interventions in adults with chronic SCI were eligible. Two authors independently selected studies and abstracted data. Mean differences of change from baseline were reported for EMD risk outcomes. The GRADE approach was used to rate the quality of evidence. RESULTS: Of 489 articles identified, 16 articles (11 studies; n=396) were eligible for inclusion. No studies assessed the effects of rehabilitation interventions on incident fragility fractures, heart disease, and/or diabetes. Individual studies reported that exercise and/or nutrition interventions could improve anthropometric indices, body composition/adiposity, and biomarkers. However, there were also reports of non-statistically significant between-group differences. CONCLUSIONS: There was very low-quality evidence that rehabilitation interventions can improve precursors to EMD risk in community-dwelling adults with chronic SCI. The small number of studies, imprecise estimates, and inconsistency across studies limited our ability to make conclusions. A high-quality longitudinal intervention trial is needed to inform community-based rehabilitation strategies for EMD risk after chronic SCI.

Fatigue reduction during aggregated and distributed sequential stimulation.

INTRODUCTION: Transcutaneous neuromuscular electrical stimulation (NMES) can generate muscle contractions for rehabilitation and exercise. However, NMES-evoked contractions are limited by fatigue when they are delivered "conventionally" (CONV) using a single active electrode. Researchers have developed "sequential" (SEQ) stimulation, involving rotation of pulses between multiple "aggregated" (AGGR-SEQ) or "distributed" (DISTR-SEQ) active electrodes, to reduce fatigue (torque-decline) by reducing motor unit discharge rates. The primary objective was to compare fatigue-related outcomes, "potentiation," "variability," and "efficiency" between CONV, AGGR-SEQ, and DISTR-SEQ stimulation of knee extensors in healthy participants. METHODS: Torque and current were recorded during testing with fatiguing trains using each NMES type under isometric and isokinetic (180°/s) conditions. RESULTS: Compared with CONV stimulation, SEQ techniques reduced fatigue-related outcomes, increased potentiation, did not affect variability, and reduced efficiency. CONCLUSIONS: SEQ techniques hold promise for reducing fatigue during NMES-based rehabilitation and exercise; however, optimization is required to improve efficiency. Muscle Nerve 56: 271-281, 2017.