The study of motor unit behavior has been classically performed by selective recording systems muscle electrical activity (EMG signals) and decomposition algorithms able to discriminate between individual action potentials from multi-unit signals. In this study, we provide a general framework for the multi-channel intramuscular surface EMG signals extensively validate approach with experimental recordings.First, describe conditions under which assumptions convolutive blind separation model...

The aim of the study was to investigate relation between linear transformations motor unit discharge rates and muscle force. Intramuscular (wire electrodes) high‐density surface EMG (13 × 5 electrode grid) were recorded from abductor digiti minimi eight healthy men during 60 s contractions at 5%, 7.5% 10% maximal Spike trains a total 222 units identified recordings with decomposition algorithms. Principal component analysis smoothed indicated that one (first common component, FCC) described...

Key points Previous studies have indicated that several weeks of strength training is sufficient to elicit significant adaptations in the neural drive sent muscles. There are few data, however, on changes elicited by recruitment and rate coding motor units during voluntary contractions. We show for first time discharge characteristics tibialis anterior muscle tracked across intervention changed 4 with isometric The specific included increases unit rate, decreases recruitment‐threshold force...

We propose and validate a method for accurately identifying the activity of populations motor neurons during contractions at maximal rate force development in humans. The behaviour neuron pool rapid voluntary humans is presented. show with this approach that recruitment speed unit discharge largely explains individual ability generating contractions. results also indicate synaptic inputs received by before generated dictate human potential to generate rapidly. This first characterization...

Key points Despite the non‐linear property of individual motor neurons, pool neurons linearizes relation between their common synaptic input and neural drive to muscle, i.e. ensemble axonal action potentials reaching muscle from spinal cord. In frequency bandwidth relevant for force generation, neuron attenuates signals sent independently each transfers only signal components with a pure scaling. The effective tends exactly replicate, without phase distortion, increasing number active...

Key points Classic motor unit (MU) recording and analysis methods do not allow the same MUs to be tracked across different experimental sessions, therefore, there is limited evidence on adjustments in MU properties following training or during progression of neuromuscular disorders. We propose a new processing method track sessions (separated by weeks) using high‐density surface electromyography. The application proposed two experiments showed that individual can identified reliably...

The aim of this study was to compare the decomposition results obtained from high-density surface electromyography (EMG) and concurrently recorded intramuscular EMG. Surface EMG signals were with electrode grids tibialis anterior, biceps brachii, abductor digiti minimi muscles twelve healthy men during isometric contractions ranging between 5% 20% maximal force. Bipolar pairs wire electrodes. independently decomposed into motor unit spike trains. When averaged over all same contraction...

Research on pattern recognition for myoelectric control has usually focused a small number of electromyography (EMG) channels because better clinical acceptability and low computational load with respect to multi-channel EMG. However, recently, high density (HD) EMG technology substantially improved, also in practical usability, can thus be applied myocontrol. HD provides several closely spaced recordings multiple locations over the skin surface. This study considered use controlling upper...

Motoneurons receive synaptic inputs from tens of thousands connections that cause membrane potential to fluctuate continuously (synaptic noise), which introduces variability in discharge times action potentials. We hypothesized the influence noise on force steadiness during voluntary contractions is limited low muscle forces. The hypothesis was examined with an analytical description transduction motor unit spike trains into force, a computational model recruitment and rate coding,...

This study investigated the relative proportion of motor-unit action potentials that are uniquely represented in simulated and experimental surface electromyogram (EMG). Two hundred motor units were a cylindrical anatomical system. Action for each unit generated with model then compared those other units. Pairs considered indistinguishable not EMG, when difference mean energy pair was <5%. The conditions recording configurations had substantial influence on percentage could be identified...

The surface interference EMG signal provides some information on the neural drive to muscles. However, association between muscle and activation has long been debated with controversial indications due unavailability of motor unit population data. In this study, we clarify potential limitations analysis infer recruitment strategies an experimental investigation several concurrently active units associated features EMG. For purpose, recorded high-density signals during linearly increasing...

Since the human central nervous system controls muscle contraction through inputs to spinal motoneurons, oscillations recorded on primary motor cortex during voluntary movements are correlated with electrical activity produced surface of muscles. We show theoretical derivations and experimental recordings that cortical input is transmitted partly in a linear way population motoneurons. The results demonstrate effective spread projections motoneuron pool allow an efficient control force output.

Key points The spinal alpha motoneuron is the only cell in human CNS whose discharge can be routinely recorded humans. We have reengineered motor unit collection and decomposition approaches, originally developed humans, to measure neural drive muscle estimate force generation vivo cat model. Experimental, computational, predictive approaches are used demonstrate validity of this approach across a wide range modes activate pool. utility shown through ability track individual units trials,...

Oscillatory common inputs of cortical or peripheral origin can be identified from the motor neuron output with coherence analysis. Linear transmission is possible despite non-linearity because same input sent commonly to several neurons. Because linear transmission, components neurons investigated surface EMG, for example by EEG-EMG EMG-EMG coherence. In these studies, there an open debate on utility and appropriateness EMG rectification. The present study addresses this issue using...

Surface electromyographic (EMG) signal amplitude is typically used to compare the neural drive muscles. We experimentally investigated this association by studying motor unit (MU) behavior and action potentials in vastus medialis (VM) lateralis (VL) Eighteen participants performed isometric knee extensions at four target torques [10, 30, 50, 70% of maximum torque (MVC)] while high-density EMG signals were recorded from VM VL. The absolute was greater for than VL ( P &lt; 0.001), whereas...

Key points Motor neurons in a pool receive both common and independent synaptic inputs, although the proportion role of their input is debated. Classic correlation techniques between motor unit spike trains do not measure absolute have limitations as result non‐linearity neurons. We propose method that for first time allows an accurate quantification low frequency (&lt;5 Hz) to humans. applied proposed three human muscles determined experimentally they similar large amount (&gt;60%) input,...

α-Motor neurons receive synaptic inputs from spinal and supraspinal centers that comprise components either common to the motor neuron pool or independent. The input shared by neurons—common input—determines force control. aim of study was investigate changes in strength delivered with fatigue, two conditions underlie an increase net excitatory drive neurons. High-density surface electromyogram (EMG) signals were recorded tibialis anterior muscle during contractions at 20, 50, 75% maximal...

Intramuscular electrodes developed over the past 80 years can record concurrent activity of only a few motor units active during muscle contraction. We designed, produced and tested novel multi-channel intramuscular wire electrode that allows in vivo recordings substantially greater number than with conventional methods. The has been extensively deep superficial human muscles. performed tests indicate applicability proposed technology variety conditions. represents an important opens new...

Purpose Using a novel technique of high-density surface EMG decomposition and motor unit (MU) tracking, we compared changes in the properties vastus medialis lateralis MU after endurance (END) high-intensity interval training (HIIT). Methods Sixteen men were assigned to END or HIIT group (n = 8 each) performed six sessions for 14 d. Each session consisted 8–12 × 60-s intervals at 100% peak power output separated by 75 s recovery (HIIT) 90–120 min continuous cycling ~65% V˙O2peak (END). Pre-...

Current myoelectric control algorithms for active prostheses map time- and frequency-domain features of the interference EMG signal into prosthesis commands. With this approach, only a fraction available information content is used resulting fails to satisfy majority users. In study, we predict joint angles three degrees freedom wrist from motor unit discharge timings identified by decomposition high-density surface EMG. We recorded kinematics signals six able-bodied individuals one patient...

A new method of estimating synaptic drive to multiple, simultaneously recorded motor units provides evidence that the portion depolarizing from persistent inward currents contributes self-sustained firing is similar across motoneurons different sizes.