Motor Unit Research Articles

Increased prevalence of mild myopathic changes in the post-COVID-19 duration

ABSTRACT Objective There are reports of peripheral nerve and muscle involvement during or after coronavirus disease 2019 (COVID-19), even following a mild infection. Here, we aimed to analyze the objective findings regarding peripheral nerve, neuromuscular junction, and muscle function using electrophysiology in patients with a previous COVID-19 infection. Methods All consecutive patients with a history of COVID-19 were questioned for post-COVID-19 duration-related neurological complaints via Composite Autonomic Symptom Score-31 (COMPASS-31), modified Toronto Neuropathy score (mTORONTO), and Fatigue Severity Scale (FSS). Patients were dichotomized into two groups based on their scores in the questionnaire. Group 1 (patients with high scores in any area of the questionnaire) and Group 2 (patients with normal scores in all sections of the questionnaire). In the second step, Group 1 was invited to a preplanned hospital visit for electrophysiological analysis, including nerve conduction studies, repetitive nerve stimulation, needle electromyography (EMG), quantitative motor unit potential analysis (qMUP), and single fiber EMG. We included 106 patients in the study. According to the questionnaire, 38 patients constituted Group 1, and 68 formed Group 2. Results Of the 38 patients, 14 accepted and underwent preplanned electrophysiological examinations. Needle EMG revealed small, short, polyphasic MUPs with early recruitment, and qMUP analysis demonstrated an increased percentage of polyphasic potentials in three patients. The examinations in other patients were unremarkable. Conclusions The high prevalence of complaints and objective myopathic findings in our cohort implicated the role of muscle involvement in the post-COVID-19 duration. Considering the socioeconomic and psychological burden of the post-COVID-19 duration among individuals and societies, a better understanding of the symptoms and myopathy is warranted.

Effects of fatigue on intra-muscle force-stabilizing synergies.

We applied the recently introduced concept of intra-muscle synergies in spaces of motor units (MUs) to quantify indices of such synergies in the tibialis anterior during ankle dorsiflexion force production tasks and their changes with fatigue. We hypothesized that MUs would be organized into robust groups (MU-modes), which would co-vary across trials to stabilize force magnitude, and the indices of such synergies would drop under fatigue. Healthy, young subjects (n = 14; 7 females) produced cyclical, isometric dorsiflexion forces while surface electromyography was used to identify action potentials of individual MUs. Principal component analysis was used to define MU-modes. The framework of the uncontrolled manifold (UCM) was used to analyze inter-cycle variance and compute the synergy index, ∆VZ. The tests were repeated after a non-fatiguing exercise (control) and fatiguing exercise. Across subjects, fatigue led, on average, to a 43% drop in maximal force and fewer identified MUs per subject (29.6±2.1 vs. 32.4±2.1). The first two MU-modes accounted for 81.2±0.08% of variance across conditions. Force-stabilizing synergies were present across all conditions and was diminished after fatiguing exercise (1.49±0.40), but not control exercise (1.76±0.75). Decreased stability after fatigue was caused by an increase in the amount of variance orthogonal to the UCM. These findings contrast with earlier studies of multi-effector synergies demonstrating increased synergy index under fatigue. We interpret the results as reflections of a drop in the gain of spinal reflex loops under fatigue. The findings corroborate an earlier hypothesis on the spinal nature of intra-muscle synergies.

Differential impact on motor unit characteristics across severities of adult spinal muscular atrophy.

To test the hypotheses that decomposition electromyography (dEMG) motor unit action potential (MUAP) amplitude and firing rate are altered in SMA; dEMG parameters are associated with strength and function; dEMG parameters are correlated with traditional electrophysiological assessments. Ambulatory and non-ambulatory adults with SMA on nusinersen and healthy controls were enrolled. MUAPs were decomposed from multielectrode surface recordings during 30-s maximum contraction of the abductor digiti minimi (ADM). Isometric strength, upper limb function, patient-reported function, and standard electrophysiologic measures of the ADM (compound muscle action potential [CMAP], single motor unit potential [SMUP], motor unit number estimation [MUNE]) were collected. dEMG MUAP amplitudes were higher in ambulatory versus control and non-ambulatory groups and were higher in controls versus non-ambulatory SMA. In contrast, dEMG firing rates were higher in ambulatory versus non-ambulatory and control groups but similar between non-ambulatory and control. dEMG parameters showed moderate to strong positive correlation with strength and function whereas CMAP and MUNE better correlated with function than strength. SMUP did not correlate with strength, function, or dEMG MUAP amplitude. dEMG parameters show overall good test-retest reliability. dEMG provided reliable, noninvasive measure of MUAP amplitude size and firing rate and revealed divergent patterns across disease severity in adults with SMA. Firing rate enhancement, as seen in milder SMA, may provide a therapeutic avenue for improving function in more severe SMA, where firing rates appear preserved. MUAP amplitude size and firing rate, quantified with dEMG, may be promising monitoring biomarker candidates for noninvasive assessment of SMA.

Detailed muscle state analysis method based on real-time wavelet analysis of surface myoelectric potential

Myoelectric refers to the use of electricity generated by muscles and is harnessed in the development of electrically powered prostheses, which are controlled by electromyographic (EMG) signals created in the residual musculature. Assistant professor Hidetoshi Nagai, Department of Artificial Intelligence, Kyushu Institute of Technology, Japan, is interested in surface myoelectric signals and is working on a project to develop technology that can advance their use. Nagai will capture motor unit activities using surface electromyography, which is easy to measure during exercise, and use this as the basis for more detailed muscle activity analysis. The methods Nagai has developed require no special equipment, other than the ability to sample at frequencies of several tens of kHz, and only require a single channel, which indicates the potential for more sophisticated analysis when multiple channels of information are present. It is also a simple and lightweight process that can be executed in real time. Conventional analysis and evaluation of muscle activity cannot be performed from the perspective of motor unit activity but Nagai has built on the basic premise that given that muscle activity is the sum of motor unit activities, the analysis of muscle activity should be based on the analysis of motor unit activity. He will analyse the surface EMG signal from the viewpoint of its component waveform the motor unit waveform so that muscle activity analysis can be performed as it should be.

Redox control of signalling responses to contractile activity and aging in skeletal muscle

During aging loss of skeletal muscle mass and function has a significant effect of an individual’s quality of life and ability to maintain independence. Both loss of muscle fibres and atrophy of the remaining fibres play a role in the muscle decline and this is associated with loss of motor units and a reduction in the number of motor neurons. Increased oxidative damage has long been claimed to be associated with aging and many studies have reported increased amounts of oxidative damage markers are found in tissues from old organisms. Reactive oxygen species (ROS) are recognised to play a major role in cell signalling and in muscle ROS generated during contractile play an important role in signalling adaptations to contractile activity. These ’redox-regulated’ pathways are beneficial adaptations which are attenuated during aging. This review will briefly cover what is currently known about the mechanisms underlying these muscle adaptations to exercise, how they are affected by aging and assess the importance of these pathways in age-related loss of skeletal muscle mass and function.

Spatial decomposition of ultrafast ultrasound images to identify motor unit activity – A comparative study with intramuscular and surface EMG

The smallest voluntarily controlled structure of the human body is the motor unit (MU), comprised of a motoneuron and its innervated fibres. MUs have been investigated in neurophysiology research and clinical applications, primarily using electromyographic (EMG) techniques. Nonetheless, EMG (both surface and intramuscular) has a limited detection volume. A recent alternative approach to detect MUs is ultrafast ultrasound (UUS) imaging. The possibility of identifying MU activity from UUS has been shown by blind source separation (BSS) of UUS images, using optimal separation spatial filters. However, this approach has yet to be fully compared with EMG techniques for a large population of unique MU spike trains. Here we identify individual MU activity in UUS images using the BSS method for 401 MU spike trains from eleven participants based on concurrent recordings of either surface or intramuscular EMG from forces up to 30% of the maximum voluntary contraction (MVC) force. We assessed the BSS method’s ability to identify MU spike trains from direct comparison with the EMG-derived spike trains as well as twitch areas and temporal profiles from comparison with the spike-triggered-averaged UUS images when using the EMG-derived spikes as triggers. We found a moderate rate of correctly identified spikes (53.0 ± 16.0%) with respect to the EMG-identified firings. However, the MU twitch areas and temporal profiles could still be identified accurately, including at 30% MVC force. These results suggest that the current BSS methods for UUS can accurately identify the location and average twitch of a large pool of MUs in UUS images, providing potential avenues for studying neuromechanics from a large cross-section of the muscle. On the other hand, more advanced methods are needed to address the convolutive and partly non-linear summation of velocities for recovering the full spike trains.

Tomato Fruit Quality as Affected by Ergonomic Conditions While Manually Harvested

The harvest phase plays an important role in the whole process of production of tomato fruit. Therefore, it is necessary to ensure a technological process that will not damage biological materials. The harvest phase plays an important role in the whole process. Many growers use special machines for harvesting, but there are fruits and vegetables that should be harvested manually to avoid damaging the surface or parenchyma tissue of the harvested objects. In addition to maintaining the quality of biological materials, work comfort, and ergonomic conditions for pickers should be ensured because inadequate working conditions do not encourage employees to undertake manual work in horticulture. Therefore, there have been shortages of workers on Polish plantations in the past year. Based on manual tomato harvesting, the authors conducted a matched qualitative research study on biological materials and work ergonomics. For this purpose, the Grip System was used to investigate tomato quality by assessing the impact of picking hand pressure (in three different picker’s body positions) on the harvested objects. Simultaneously, for the picker’s ergonomic analysis, a non-invasive surface electromyography method was used to precisely measure changes in muscle motor unit action in the picker’s wrist and lumbar spine while in three characteristic picker’s positions. The tests found that the poorest body position was when the body was deeply inclined and simultaneously twisted. No significant effect was shown of the body position of the tomato picker on the deterioration of the picked fruit quality. However, body positions significantly affect the level of physical load and work comfort.

A comparison of techniques for verifying the accuracy of precision decomposition-derived relationships between motor unit firing rates and recruitment thresholds from surface EMG signals.

Approaches for validating motor unit firing times following surface electromyographic (EMG) signal decomposition with the precision decomposition III (PDIII) algorithm have not been agreed upon. Two approaches have been common: (1) "reconstruct-and-test" and (2) spike-triggered averaging (STA). We sought to compare motor unit results following the application of these approaches. Surface EMG signals were recorded from the vastus lateralis of 13 young males performing trapezoidal, isometric knee extensions at 50% and 80% of maximum voluntary contraction (MVC) force. The PDIII algorithm was used to quantify motor unit firing rates. Motor units were excluded using eight combinations of the reconstruct-and-test approach with accuracy thresholds of 0, 90, 91, and 92% with and without STA. The mean firing rate versus recruitment threshold relationship was minimally affected by STA. At 80% MVC, slopes acquired at the 0% accuracy threshold were significantly greater (i.e., less negative) than when 91% (p = .010) and 92% (p = .030) accuracy thresholds were applied. The application of STA has minimal influence on surface EMG signal decomposition results. Stringent reconstruct-and-test accuracy thresholds influence motor unit-derived relationships at high forces, perhaps explained through the increased presence of large motor unit action potentials. Investigators using the PDIII algorithm can expect negligible changes in motor unit-derived linear regression relationships with the application of secondary validation procedures.

Safety and Efficacy of DT-DEC01 Therapy in Duchenne Muscular Dystrophy Patients: A 12 - Month Follow-Up Study After Systemic Intraosseous Administration

Duchenne Muscular Dystrophy (DMD) is a progressive and fatal muscle-wasting disease with no known cure. We previously reported the preliminary safety and efficacy up to six months after the administration of DT-DEC01, a novel Dystrophin Expressing Chimeric (DEC) cell therapy created by fusion of myoblasts of DMD patient and the normal donor. In this 12-month follow-up study, we report on the safety and functional outcomes of three DMD patients after the systemic intraosseous administration of DT-DEC01. The safety of DT-DEC01 was confirmed by the absence of Adverse Events (AE) and Severe Adverse Events (SAE) up to 21 months after intraosseous DT-DEC01 administration. The lack of presence of anti-HLA antibodies and Donors Specific Antibodies (DSA) further confirmed DT-DEC01 therapy safety. Functional assessments in ambulatory patients revealed improvements in 6-Minute Walk Test (6MWT) and timed functions of North Star Ambulatory Assessment (NSAA). Additionally, improvements in PUL2.0 test and grip strength correlated with increased Motor Unit Potentials (MUP) duration recorded by Electromyography (EMG) in both ambulatory and non-ambulatory patients. DT-DEC01 systemic effect was confirmed by improved cardiac and pulmonary parameters and daily activity recordings. This follow-up study confirmed the safety and preliminary efficacy of DT-DEC01 therapy in DMD-affected patients up to 12 months after intraosseous administration. DT-DEC01 introduces a novel concept of personalized myoblast-based cellular therapy that is irrespective of the mutation type, does not require immunosuppression or the use of viral vectors, and carries no risk of off target mutations. This establishes DT-DEC01 as a promising and universally effective treatment option for all DMD patients.Graphical

MR Neurography and Quantitative Muscle MRI of Parsonage Turner Syndrome Involving the Long Thoracic Nerve.

Parsonage-Turner syndrome (PTS) is characterized by severe, acute upper extremity pain and subsequent paresis and most commonly involves the long thoracic nerve (LTN). While MR neurography (MRN) can detect LTN hourglass-like constrictions (HGCs), quantitative muscle MRI (qMRI) can quantify serratus anterior muscle (SAM) neurogenic changes. 1) To characterize qMRI findings in LTN-involved PTS. 2) To investigate associations between qMRI and clinical assessments of HGCs/electromyography (EMG). Prospective. 30 PTS subjects (25 M/5 F, mean/range age = 39/15-67 years) with LTN involvement who underwent bilateral chest wall qMRI and unilateral brachial plexus MRN. 3.0 Tesla/multiecho spin-echo T2-mapping, diffusion-weighted echo-planar-imaging, multiecho gradient echo. qMRI was performed to obtain T2, muscle diameter fat fraction (FF), and cross-sectional area of the SAM. Clinical reports of MRN and EMG were obtained; from MRN, the number of HGCs; from EMG, SAM measurements of motor unit recruitment levels, fibrillations, and positive sharp waves. qMRI/MRN were performed within 90 days of EMG. EMG was performed on average 185 days from symptom onset (all ≥2 weeks from symptom onset) and 5 days preceding MRI. Paired t-tests were used to compare qMRI measures in the affected SAM versus the contralateral, unaffected side (P < 0.05 deemed statistically significant). Kendall's tau was used to determine associations between qMRI against HGCs and EMG. Relative to the unaffected SAM, the affected SAM had increased T2 (50.42 ± 6.62 vs. 39.09 ± 4.23 msec) and FF (8.45 ± 9.69 vs. 4.03% ± 1.97%), and decreased muscle diameter (74.26 ± 21.54 vs. 88.73 ± 17.61 μm) and cross-sectional area (9.21 ± 3.75 vs. 16.77 ± 6.40 mm2). There were weak to negligible associations (tau = -0.229 to <0.001, P = 0.054-1.00) between individual qMRI biomarkers and clinical assessments of HGCs and EMG. qMRI changes in the SAM were observed in subjects with PTS involving the LTN. 2 TECHNICAL EFFICACY: Stage 1.

A novel 3D bilayer hydrogel tri-culture system for studying functional motor units

BackgroundA motor unit (MU) is formed by a single alpha motor neuron (MN) and the muscle fibers it innervates. The MU is essential for all voluntary movements. Functional deficits in the MU result in neuromuscular disorders (NMDs). The pathological mechanisms underlying most NMDs remain poorly understood, in part due to the lack of in vitro models that can comprehensively recapitulate multistage intercellular interactions and physiological function of the MU.ResultsWe have designed a novel three-dimensional (3D) bilayer hydrogel tri-culture system where architecturally organized MUs can form in vitro. A sequential co-culture procedure using the three cell types of a MU, MN, myoblast, and Schwann cell was designed to construct a co-differentiating tri-culture on a bilayer hydrogel matrix. We utilized a µ-molded hydrogel with an additional Matrigel layer to form the bilayer hydrogel device. The µ-molded hydrogel layer provides the topological cues for myoblast differentiation. The Matrigel layer, with embedded Schwann cells, not only separates the MNs from myoblasts but also provides a proper micro-environment for MU development. The completed model shows key MU features including an organized MU structure, myelinated nerves, aligned myotubes innervated on clustered neuromuscular junctions (NMJs), MN-driven myotube contractions, and increases in cytosolic Ca2+ upon stimulation.ConclusionsThis organized and functional in vitro MU model provides an opportunity to study pathological events involved in NMDs and peripheral neuropathies, and can serve as a platform for physiological and pharmacological studies such as modeling and drug screening. Technically, the rational of this 3D bilayer hydrogel co-culture system exploits multiple distinct properties of hydrogels, facilitating effective and efficient co-culturing of diverse cell types for tissue engineering.

Sensorimotor integration is affected by acute whole-body vibration: a coherence study.

Introduction: Several whole-body vibration (WBV) effects on performance have been related to potential changes in the neural drive, motor unit firing rate, and sensorimotor integration. In the present paper, motor unit coherence analysis was performed to detect the source of neural modulation based on the frequency domain. Methods: Thirteen men [25 ± 2.1years; Body Mass Index (BMI) = 23.9 ± 1.3kgm2; maximal voluntary force (MVF): 324.36 ± 41.26N] performed sustained contractions of the Tibialis Anterior (TA) at 10%MVF before and after acute WBV. The vibrating stimulus was applied barefoot through a platform to target the TA. High-Density surface Electromyography (HDsEMG) was used to record the myoelectrical activity of TA to evaluate coherence from motor unit cumulative spike-trains (CSTs). Results: Mean coherence showed a significant decrease in the alpha and low-beta bandwidths (alpha: from 0.143 ± 0.129 to 0.132 ± 0.129, p = 0.035; low-beta: from 0.117 ± 0.039 to 0.086 ± 0.03, p = 0.0001), whereas no significant changes were found in the other ones (p > 0.05). The discharge rate (DR) and the Force Covariance (CovF%) were not significantly affected by acute WBV exposure (p > 0.05). Discussion: According to the significant effects found in alpha and low-beta bandwidths, which reflect sensorimotor integration parameters, accompanied by no differences in the DR and CovF%, the present results underlined that possible neural mechanisms at the base of the previously reported performance enhancements following acute WBV are likely based on sensorimotor integration rather than direct neural drive modulation.

Identification of a Novel ARSA Gene Mutation Through High-Throughput Molecular Diagnosis Method in Two Girls with Late Infantile Metachromatic Leukodystrophy.

Metachromatic leukodystrophy (MLD) is a rare leukoencephalopathy caused by pathogenic mutations in the ARSA gene. It manifests as severe motor symptoms, mental problems, and sometimes, seizures. We aimed to investigate the phenotypic manifestations and genetic causes of MLD in an Iranian family. We present the case of a 3-year-old girl who presented with hypotonia, muscular atrophy, and seizures. Neurological and neuromuscular examinations were performed to evaluate clinical characteristics. Whole exome sequencing (WES) was used to detect disease-causing variants. In silico analysis was performed to predict the pathogenicity of this variant. GROMACS software was utilized for molecular dynamic simulation (MDS). Neurological studies revealed marked slowing of motor conduction velocities and an increased motor unit action potential duration. Brain MRI scan revealed white matter abnormalities. By applying WES, we identified a novel homozygous missense variant (NM_000487.6, c.938G > C, p.R313P) in ARSA. Direct sequencing identified this homozygous variant in her asymptomatic younger sister, whereas both parents carried a heterozygous variant. This mutation has not been reported in genetic databases or in literature. In silico analysis predicted that any variation in this DNA position would cause disease, as it is highly conserved. The c.938G > C variant was classified as a pathogenic variant according to ACMG/AMP guidelines. MDS analysis indicated that c.938G > C had a significant impact on both the structure and stabilization of ARSA, ultimately resulting in impaired protein function. The identification of this variant expands the spectrum of ARSA gene mutations associated with MLD and highlights the importance of genetic testing for the diagnosis of MLD.

Concordance between needle electromyography and manual muscle test findings for muscles with motor grades 0 and 1.

When it is difficult to determine whether a muscle is grade 0 or 1, manual muscle test (MMT) accuracy can be further improved by using needle electromyography (EMG) as a supplementary and confirmatory examination tool. To evaluate concordance between needle EMG and MMT findings for key muscles with motor grades 0 and 1 on the International Standards of Neurological Classification of Spinal Cord Injury (ISNCSCI) examination, and to potentially improve the prognosis for grade 0 muscles with proven muscle activity based on needle EMG findings. A retrospective analysis. Inpatient tertiary rehabilitation facility. Not applicable. One hundred seven patients with spinal cord injury (SCI) admitted for rehabilitation (n = 1218 key muscles, grades 0 or 1). Inter-rater reliability between MMTs and needle EMG was analyzed using Cohen's kappa coefficient (κ). A Mantel Haenszel linear-by-linear association chi-square testwas used to determine whether the presence of motor unit action potentials (MUAPs) in muscles graded 0 on the initial MMT at admission was associated with MMT grades at discharge and readmission. Moderate-to-substantial agreement between needle EMG and MMT findings was observed (κ = 0.671, p < .01). Concerning key upper and lower extremity muscles, moderate and substantial agreement was identified, respectively. The lowest agreement was noted for C6 muscles. During follow up, 68.8% of muscles with proven MUAPs showed improved motor grades. At initial assessment, distinguishing between motor grades 0 and 1 is imperative because motor grade 1 muscles are more likely to have a better prognosis for improvement. Moderate-to-substantial agreement was observed between MMT and needle EMG findings. The MMT is a reliable method of muscle grading, yet needle EMG may be of value in certain clinical situations to evaluate for the presence of MUAPs when evaluating motor function.

Adsorbate motors for unidirectional translation and transport.

Artificial molecular motors are designed to transform external energy into useful work in the form of unidirectional motion1. They have been studied mainly in solution2-4, but also on solid surfaces5,6, which provide fixed reference points, allowing for tracking of their movement. However, these molecules require sophisticated design and synthesis, because the motor function must be imprinted into the chemical structure, and show reduced functionality on surfaces compared with in solution5-8. DNA walkers9,10,on the other hand, impart high directionality as they include the surface as part of the motor function, but they require chemical surface patterning and sequential solvent modification for motor activation. Here we show how efficient motors can operate at much smaller length scales on a homogeneous metal surface without any liquid. This is realized by combining a surface with a simple molecule, which, by itself, does not contain any motor unit. The motion, which is tracked at the single-molecule level, is triggered by intramolecular proton transfer with a corresponding modulation of the potential energy surface. Each molecule moves with 100 percent unidirectionality along an atomically defined straight line. Proof of the motor performing meaningful work is shown by controlled transport of single carbon monoxide molecules. This simplistic concept could form the basis for the controlled bottom-up assembly of nanostructures at the atomic scale.

Larger and Denser: An Optimal Design for Surface Grids of EMG Electrodes to Identify Greater and More Representative Samples of Motor Units.

The spinal motor neurons are the only neural cells whose individual activity can be noninvasively identified. This is usually done using grids of surface electromyographic (EMG) electrodes and source separation algorithms; an approach called EMG decomposition. In this study, we combined computational and experimental analyses to assess how the design parameters of grids of electrodes influence the number and the properties of the identified motor units. We first computed the percentage of motor units that could be theoretically discriminated within a pool of 200 simulated motor units when decomposing EMG signals recorded with grids of various sizes and interelectrode distances (IEDs). Increasing the density, the number of electrodes, and the size of the grids, increased the number of motor units that our decomposition algorithm could theoretically discriminate, i.e., up to 83.5% of the simulated pool (range across conditions: 30.5-83.5%). We then identified motor units from experimental EMG signals recorded in six participants with grids of various sizes (range: 2-36 cm2) and IED (range: 4-16 mm). The configuration with the largest number of electrodes and the shortest IED maximized the number of identified motor units (56 ± 14; range: 39-79) and the percentage of early recruited motor units within these samples (29 ± 14%). Finally, the number of identified motor units further increased with a prototyped grid of 256 electrodes and an IED of 2 mm. Taken together, our results showed that larger and denser surface grids of electrodes allow to identify a more representative pool of motor units than currently reported in experimental studies.

Structural and pathophysiological muscle changes up to one year after post-stroke hemiplegia: a systematic review.

Muscle changes after stroke cannot be explained solely on the basis of corticospinal bundle damage. Muscle-specific changes contribute to limited functional recovery but have been poorly characterized. We conducted a systematic review of muscular changes occurring at the histological, neuromuscular and functional levels during the first year after the onset of post-stroke hemiplegia. A literature search was performed on PubMed, Embase and CINHAL databases up to November 2022 using a keyword combination comprising cerebral stroke, hemiplegic, atrophy, muscle structure, paresis, skeletal muscle fiber type, motor unit, oxidative stress, strength, motor control. Twenty-seven trial reports were included in the review, out of 12,798 articles screened. Structural modifications described on the paretic side include atrophy, transformation of type II fibers into type I fibers, decrease in fiber diameter and apparent myofilament disorganization from the first week post-stroke up to the fourth month. Reported biochemical changes comprise the abnormal presence of lipid droplets and glycogen granules in the subsarcolemmal region during the first month post-stroke. At the neurophysiological level, studies indicate an early decrease in the number and activity of motor units, correlated with the degree of motor impairment. All these modifications were present to a lesser degree on the non-paretic side. Although only sparse data concerning the subacute stage are available, these changes seem to appear during the first two weeks post-stroke and continue up to the third or fourth month. Considering these early pathophysiological changes on both the paretic and non-paretic sides, it seems crucial to promptly stimulate central and also peripheral muscular activation after stroke through specific rehabilitation programs focused on the maintenance of muscle capacities associated with neurological recovery or plasticity.

Poster (Technology Innovation) ID 1984794

Background Cervical spinal cord injury (SCI) can cause significant impairment and disability with an impact on individuals’ quality of life and independence. Surface electromyography (SEMG) is a sensitive and non-invasive technique to measure muscle activity and has demonstrated great potential in capturing the impact from SCI. The mechanisms of SCI damage on SEMG signal characteristics are multi-faceted and difficult to study in vivo. Objective Use validated computational models to characterize changes in SEMG signal after SCI and identify SEMG features that are sensitive and specific to the impact from different aspects of SCI. Method Starting from existing computational models for motor neuron pool organization and for motor unit action potential generation for healthy neuromuscular systems, we set up scenarios to model alterations in upper motor neurons, lower motor neurons, and the number of muscle fibers within each motor unit after SCI. After simulating SEMG signals from each scenario, we extracted time and frequency domain features and investigated the impact of SCI disruptions on SEMG features using the Pearson correlation between a feature and the extent of a given disruption. Findings Commonly used amplitude-based SEMG features cannot differentiate between injury scenarios. A broader set of features provides greater specificity to the type of damage present. Conclusion We demonstrated a novel approach to mechanistically relate SEMG features to different types of neuromuscular alterations after SCI. This work contributes to a deeper understanding and exploitation of SEMG in clinical applications, which will ultimately improve patient outcomes after SCI.

Effects Of Obesity On Motor Unit Properties For A Non-weight Bearing Muscle

Effects Of Obesity On Motor Unit Properties For A Non-weight Bearing Muscle

Test Re-test Reliability Of Motor Unit Action Potential Relationships During Isokinetic Knee Extension

Test Re-test Reliability Of Motor Unit Action Potential Relationships During Isokinetic Knee Extension