Physiology of Muscle Activation and Force Generation

Enoka, Roger R.M.; Duchateau, Jacques

doi:10.1002/9781119082934.ch01

Cited by 7 publications

(4 citation statements)

References 106 publications

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“…We extracted the average discharge rate of each identified motor neuron as well as the coefficient of variation of the estimated inter-spike intervals. The estimated motor neuron discharge rates were within the physiological range of 5-25 Hz [52,53] at both force levels (12.23 ± 1.58 Hz and 12.90 ± 2.14 Hz at 15% and 30% MVC, respectively) (figure 2(e)), being significantly higher at 30% than at 15% MVC (F 1, 8 = 12.879, p = 0.007, one-way repeated measures ANOVA), in agreement with motor neuron's rate coding in force production [54]. The coefficient of variation of the estimated inter spike intervals was 23.51 ± 3.63% and 24.47 ± 4.01%, for 15% and 30% MVC, respectively (figure 2(e)), which is within known physiological values [40].…”

Section: Physiological Analysissupporting

confidence: 70%

Far-field electric potentials provide access to the output from the spinal cord from wrist-mounted sensors

et al. 2022

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Objective. Neural interfaces need to become more unobtrusive and socially acceptable to appeal to general consumers outside rehabilitation settings. Approach. We developed a non-invasive neural interface that provides access to spinal motor neuron activities from the wrist, which is the preferred location for a wearable. The interface decodes far-field potentials present at the tendon endings of the forearm muscles using blind source separation. First, we evaluated the reliability of the interface to detect motor neuron firings based on far-field potentials, and thereafter we used the decoded motor neuron activity for the prediction of finger contractions in offline and real-time conditions. Main results. The results showed that motor neuron activity decoded from the far-field potentials at the wrist accurately predicted individual and combined finger commands and therefore allowed for highly accurate real-time task classification. Significance. These findings demonstrate the feasibility of a non-invasive, neural interface at the wrist for precise real-time control based on the output of the spinal cord.

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Section: Physiological Analysissupporting

confidence: 70%

Far-field electric potentials provide access to the output from the spinal cord from wrist-mounted sensors

et al. 2022

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“…In this study, we proposed a new method for the estimation of the twitch forces of groups of motor units in vivo during voluntary isometric contractions. The STA technique has been proposed several decades ago for estimating the twitch force of individual motor units (Goldberg and Derfler, 1977;Stein et al, 1972), and it is still the only available method to estimate the contractile properties of the muscle units (Enoka and Duchateau, 2016) from voluntary contractions. Several studies have underlined the limitations of this technique that are mostly related with the fusion of the twitch forces (Negro et al, 2014;C K Thomas et al, 1990) and motor unit synchronization (Taylor et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Robust estimation of average twitch contraction forces of populations of motor units in humans

Negro

Orizio

2017

Journal of Electromyography and Kinesiology

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The characteristics of motor unit force twitch profiles provide important information for the understanding of the muscle force generation. The twitch force is commonly estimated with the spike-triggered averaging technique, which, despite the many limitations, has been important for clarifying central issues in force generation. In this study, we propose a new technique for the estimation of the average twitch profile of populations of motor units with uniform contractile properties. The method encompasses a model-based deconvolution of the force signal using the identified discharge times of a population of motor units. The proposed technique was validated using simulations and tested on signals recorded during voluntary activation. The results of the simulations showed that the proposed method provides accurate estimates (relative error <25%) of the main parameters of the average twitch force when the number of identified motor units is between 5% and 15% of the total number of active motor units. It is discussed that current detection and decomposition methods of multi-channel surface EMG signals allow decoding this relative sample of the active motor unit pool. However, even when this condition is not met, our results show that the estimates provided by the new method are anyway always superior to those obtained by the spike triggered average approach, especially for high motor unit synchronization levels and when a relatively small number of triggers is available. In conclusion, we present a new method that overcome the main limitations of the spike-triggered average for the study of contractile properties of individual motor units. The method provides a new reliable tool for the investigation of the determinants of muscle force.

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“…Surface electromyography (sEMG) is a method that uses electrodes placed on the surface of the skin to record muscle activity [ 1 , 2 ]. These signals are valuable in a variety of applications, including diagnosis of neuromuscular diseases and evaluations of muscle function [ 3 , 4 , 5 ].…”

Section: Introductionmentioning

confidence: 99%

Assessment of Dry Epidermal Electrodes for Long-Term Electromyography Measurements

Yamagami

Peters

Milovanovic

et al. 2018

Sensors

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Commercially available electrodes can only provide quality surface electromyography (sEMG) measurements for a limited duration due to user discomfort and signal degradation, but in many applications, collecting sEMG data for a full day or longer is desirable to enhance clinical care. Few studies for long-term sEMG have assessed signal quality of electrodes using clinically relevant tests. The goal of this research was to evaluate flexible, gold-based epidermal sensor system (ESS) electrodes for long-term sEMG recordings. We collected sEMG and impedance data from eight subjects from ESS and standard clinical electrodes on upper extremity muscles during maximum voluntary isometric contraction tests, dynamic range of motion tests, the Jebsen Taylor Hand Function Test, and the Box & Block Test. Four additional subjects were recruited to test the stability of ESS signals over four days. Signals from the ESS and traditional electrodes were strongly correlated across tasks. Measures of signal quality, such as signal-to-noise ratio and signal-to-motion ratio, were also similar for both electrodes. Over the four-day trial, no significant decrease in signal quality was observed in the ESS electrodes, suggesting that thin, flexible electrodes may provide a robust tool that does not inhibit movement or irritate the skin for long-term measurements of muscle activity in rehabilitation and other applications.

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Physiology of Muscle Activation and Force Generation

Cited by 7 publications

References 106 publications

Far-field electric potentials provide access to the output from the spinal cord from wrist-mounted sensors

Far-field electric potentials provide access to the output from the spinal cord from wrist-mounted sensors

Robust estimation of average twitch contraction forces of populations of motor units in humans

Assessment of Dry Epidermal Electrodes for Long-Term Electromyography Measurements

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