Impact of electrode geometry on force generation during functional electrical stimulation

AbstractThe goal of functional electrical stimulation is to restore lost movements by excitation of motor axons inner-vating the target muscle. For optimal electrode placement and geometry the distribution and spatial orientation of the desired motor axons has to be known. In this study, the response of motor axons with different orientations to electrical stimulation was simulated. Three electrode geometries with the same area were used. The simulated axon activation was compared to experimental force measurements and showed good agreements. It is now assumed that optimal electrode geometry does strongly depend on motor axon orientation, which can vary from one subject to the other. Lack of knowledge about the dominant motor axon orientation makes the use of square, round or multi-pad electrodes favorable.

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A flexible standalone system with integrated sensor feedback for multi-pad electrode FES of the hand

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2016-0087 ◽

2016 ◽

Vol 2 (1) ◽

pp. 391-394 ◽

Cited By ~ 1

Author(s):

Jan C. Loitz ◽

Aljoscha Reinert ◽

Ann-Kristin Neumann ◽

Fanny Quandt ◽

Dietmar Schroeder ◽

...

Keyword(s):

Electrical Stimulation ◽

Muscle Fatigue ◽

Functional Electrical Stimulation ◽

Electrode Placement ◽

Treatment Efficiency ◽

Integrated Sensor ◽

Correct Placement ◽

Cord Injury ◽

Early Occurrence ◽

Stimulation Electrode

AbstractFunctional electrical stimulation aims to help patients suffering from stroke or spinal cord injury to supplement lost motor function. Effective functional electrical stimulation requires precise placement of the stimulation electrode. Finding the correct placement, however, can be difficult and time consuming. Another common problem with functional electrical stimulation is early occurrence of muscle fatigue upon repetitive stimulation, limiting treatment efficiency. Both, precise electrode placement as well as the reduction of muscle fatigue can be achieved using multi-pad electrodes. Here we present a new standalone device for multi-pad functional electrical stimulation. The device is easy to use and designed to help patients recovering from stroke to train and perform opening of the hand.

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Decreased excitability of motor axons contributes substantially to contraction fatigability during neuromuscular electrical stimulation

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2020-0366 ◽

2020 ◽

Author(s):

Minh John Luu ◽

Kelvin E. Jones ◽

David F. Collins

Keyword(s):

Electrical Stimulation ◽

Time Course ◽

Tibialis Anterior Muscle ◽

Neuromuscular Electrical Stimulation ◽

Motor Units ◽

Drop Out ◽

Motor Axon ◽

Dependent Manner ◽

Motor Axons ◽

Axonal Excitability

The present study was designed to: 1) determine the time course of changes in motor axon excitability during and after neuromuscular electrical stimulation (NMES), and 2) characterise the relationship between contraction fatigability, NMES frequency, and changes at the axon, neuromuscular junction, and muscle. Eight neurologically-intact participants attended three sessions. NMES was delivered over the common peroneal nerve at 20, 40, or 60 Hz for 8 min (0.3 s “on”, 0.7 s “off”). Threshold tracking was used to measure changes in axonal excitability. Supramaximal stimuli were used to assess neuromuscular transmission and force-generating capacity of the tibialis anterior muscle. Torque decreased 49 and 62% during 8 min of 40 and 60 Hz NMES, respectively. Maximal twitch torque decreased only during 60 Hz NMES. Motor axon excitability decreased by 14, 27, and 35% during 20, 40, and 60 Hz NMES, respectively. Excitability recovered to baseline immediately (20 Hz), 2 min (40 Hz), and 4 min (60 Hz) following NMES. Overall, decreases in axonal excitability best predicted how torque declined over 8 min of NMES. During NMES, motor axons become less excitable and motor units “drop out” of the contraction, contributing substantially to contraction fatigability and its dependence on NMES frequency. NOVELTY BULLETS • The excitability of motor axons decreased during neuromuscular electrical stimulation (NMES) in a frequency-dependent manner. • As excitability decreased, axons failed to reach threshold and motor units dropped out of the contraction. • Overall, decreased excitability best predicted how torque declined and thus is a key contributor to fatigability during NMES.

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Personalized protocol and scoring scale for functional electrical stimulation of the hand: A pilot feasibility study

Technology and Health Care ◽

10.3233/thc-213016 ◽

2021 ◽

pp. 1-13

Author(s):

Jessica K. Camacho-Zavala ◽

Ana L. Perez-Medina ◽

Jorge A. Mercado-Gutierrez ◽

Mario I. Gutierrez ◽

Josefina Gutierrez-Martinez ◽

...

Keyword(s):

Electrical Stimulation ◽

Feasibility Study ◽

Functional Electrical Stimulation ◽

Precision Grip ◽

Parameter Selection ◽

Hand Movements ◽

Electrode Placement ◽

Upper Limb Rehabilitation ◽

Electrode Positioning ◽

Pilot Feasibility Study

BACKGROUND: Complex personalized Functional Electrical Stimulation (FES) protocols for calibrating parameters and electrode positioning have been proposed, most being time-consuming or technically cumbersome for clinical settings. Therefore, there is a need for new personalized FES protocols that generate comfortable, functional hand movements, while being feasible for clinical translation. OBJECTIVE: To develop a personalized FES protocol, comprising electrode placement and parameter selection, to generate hand opening (HO), power grasp (PW) and precision grip (PG) movements, and compare in a pilot feasibility study its performance to a non-personalized protocol based on standard FES guidelines. METHODS: Two FES protocols, one personalized (P1) and one non-personalized (P2), were used to produce hand movements in twenty-three healthy participants. FES-induced movements were assessed with a new scoring scale which comprises items for selectivity, functionality, and comfort. RESULTS: Higher FES-HSS scores were obtained with P1 for all movements: HO (p= 0.00013), PW (p= 0.00007), PG (p= 0.00460). Electrode placement time was significantly shorter for P2 (p= 0.00003). Comfort scores were similar for both protocols. CONCLUSIONS: The personalized protocol for electrode placement and parameter selection enabled functional FES-induced hand movements and presented advantages over a non-personalized protocol. This protocol warrants further investigation to confirm its suitability for developing upper-limb rehabilitation interventions with clinical translational potential.

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