1. Acute intermittent hypoxia increases maximal motor unit discharge rates in people with chronic incomplete spinal cord injuryGregory E. P. Pearcey, Babak Afsharipour, Aleš Holobar, Milap S. Sandhu, William Zev Rymer, 2024, izvirni znanstveni članek Opis: Acute intermittent hypoxia (AIH) is an emerging technique for enhancing neuroplasticity and motor function in respiratory and limb musculature. Thus far, AIH-induced improvements in strength have been reported for upper and lower limb muscles after chronic incomplete cervical spinal cord injury (iSCI), but the underlying mechanisms have been elusive. We used high-density surface EMG (HDsEMG) to determine if motor unit discharge behaviour is altered after 15 × 60 s exposures to 9% inspired oxygen, interspersed with 21% inspired oxygen (AIH), compared to breathing only 21% air (SHAM). We recorded HDsEMG from the biceps and triceps brachii of seven individuals with iSCI during maximal elbow flexion and extension contractions, and motor unit spike trains were identified using convolutive blind source separation. After AIH, elbow flexion and extension torque increased by 54% and 59% from baseline (P = 0.003), respectively, whereas there was no change after SHAM. Across muscles, motor unit discharge rates increased by ∼4 pulses per second (P = 0.002) during maximal efforts, from before to after AIH. These results suggest that excitability and/or activation of spinal motoneurons is augmented after AIH, providing a mechanism to explain AIH-induced increases in voluntary strength. Pending validation, AIH may be helpful in conjunction with other therapies to enhance rehabilitation outcomes after incomplete spinal cord injury, due to these enhancements in motor unit function and strength.
Ključne besede: muscle strength, motoneuron function, motor unit
Objavljeno v DKUM: 02.08.2024; Ogledov: 73; Prenosov: 0 |
2. Motor unit identification in the M waves recorded by high-density electromyMiloš Kalc, Jakob Škarabot, Matjaž Divjak, Filip Urh, Matej Kramberger, Matjaž Vogrin, Aleš Holobar, 2023, izvirni znanstveni članek Ključne besede: M wave, high-density surface EMG, firing identification, motor unit
Objavljeno v DKUM: 13.06.2024; Ogledov: 144; Prenosov: 8
 Celotno besedilo (2,30 MB)
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3. Materials for HybridNeuro webinar titled "Validation of results: statistical models and MU identification accuracy"Aleš Holobar, Nina Murks, 2024, zaključena znanstvena zbirka raziskovalnih podatkov Opis: This dataset contains a collection of teaching materials that were used in the HybridNeuro project webinar titled "Validation of results: statistical models and MU identification accuracy". The webinar was presented by Aleš Holobar and covered the complexities of motor unit (MU) identification accuracy, regression analysis and Bayesian models. The primary aim of the webinar was to spark a robust discussion within the scientific community, particularly focusing on the application and implications of linear mixed models and Bayesian regression in the realm of MU identification. The teaching materials include Matlab and R source code for statistical analysis of the included data, as well as three examples of MU identification results in CSV format (from both synthetic and experimental HDEMG signals). The presentation slides in PDF format are also included. The dataset is approximately 9 MB in size.
Ključne besede: HybridNeuro, webinar, teaching materials, statistical models, regression analysis, motor unit identification, matlab, rstudio, statistics, surface high density electromyogram (HDEMG), tibialis anterior, dataset
Objavljeno v DKUM: 30.05.2024; Ogledov: 221; Prenosov: 15
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4. Simulated and experimental HDEMG signals of biceps brachii muscle for analysis of motor unit mergingAleš Holobar, Jakob Škarabot, Dario Farina, 2024, zaključena znanstvena zbirka raziskovalnih podatkov Opis: This dataset contains a collection of simulated and experimental surface HDEMG recordings of the biceps brachii muscle during the isometric elbow flexion. Simulated data contains 50 recordings: 5 subjects and 5 excitation levels, each with and without added noise. Experimental data contains 16 recordings: 2 subjects with 4 excitation levels and 2 repetitions of each level. Synthetic data was simulated using the cylindrical volume conductor model [1] and the motor unit recruitment and firing modulation model proposed in [2]. Each recording is 20 seconds in length with 90 HDEMG channels sampled at 2048 Hz and is stored as a 2D matrix of raw EMG values in Matlab’s MAT format. Experimental surface EMG data was recorded on two volunteers during isometric contractions at constant force level. Each recording is 25 seconds in length with 64 HDEMG channels sampled at 2048 Hz and is also stored as a 2D matrix of raw EMG values in Matlab’s MAT format. The dataset is approximately 1.5 GB in size.
Ključne besede: surface high density electromyogram (HDEMG), motor unit, spike train, motor unit merging, simulated data, experimental data, biceps brachii, dataset
Objavljeno v DKUM: 30.05.2024; Ogledov: 172; Prenosov: 5
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7. The dose–response relationship of quercetin on the motor unit firing patterns and contractile properties of muscle in men and womenKohei Watanabe, Shun Kunugi, Aleš Holobar, 2023, izvirni znanstveni članek Opis: Quercetin is one type of ergogenic aid and its effects on the neuromuscular system have recently attracted interest, but its dose-effect is not yet fully understood. The aim of this study was to examine the effect of different doses of quercetin ingestion on motor unit firing patterns and muscle contractile properties in humans. Thirteen young males and females conducted neuromuscular performance tests before (PRE) and 60 min after (POST) ingestions of 500 or 200 mg of quercetin glycosides (Qg500/Qg200, respectively) or placebo (PLA) on three different days. At PRE and POST, motor unit firing rates were calculated from high-density surface electromyography of the vastus lateralis muscle during 120-s isometric contraction of knee extension at 10% of maximal voluntary contraction. Electrically elicited forces in knee extensor muscles were also measured. After 60 s of voluntary contraction, motor unit firing rates, normalized by the exerted muscle force at POST, were significantly lower at POST than PRE with Qg500 and Qg200 (p < 0.05), but not with PLA (p > 0.05). Changes in motor unit firing rates normalized by the exerted force from PRE to POST were significantly greater with Qg500 than Qg200 at the end of contraction (p < 0.05). Under all three conditions, the electrically elicited force did not significantly change from PRE to POST (p > 0.05). These results suggest that both 500 and 200-mg quercetin ingestions alter motor unit firing patterns, and that quercetin’s effect is at least partially dose-dependent.
Ključne besede: ergogenic aids, nutritional supplementation, multichannel surface electromyography, motor unit identification, quercetin
Objavljeno v DKUM: 09.02.2024; Ogledov: 273; Prenosov: 16
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8. Motor unit characteristics after targeted muscle reinnervationTamás Kapelner, Ning Jiang, Aleš Holobar, Ivan Vujaklija, Aidan Roche, Dario Farina, Oskar Aszmann, 2016, izvirni znanstveni članek Opis: Targeted muscle reinnervation (TMR) is a surgical procedure used to redirect nerves originally controlling muscles of the amputated limb into remaining muscles above the amputation, to treat phantom limb pain and facilitate prosthetic control. While this procedure effectively establishes robust prosthetic control, there is little knowledge on the behavior and characteristics of the reinnervated motor units. In this study we compared the m. pectoralis of five TMR patients to nine able-bodied controls with respect to motor unit action potential (MUAP) characteristics. We recorded and decomposed high-density surface EMG signals into individual spike trains of motor unit action potentials. In the TMR patients the MUAP surface area normalized to the electrode grid surface (0.25 ± 0.17 and 0.81 ± 0.46, p < 0.001) and the MUAP duration (10.92 ± 3.89 ms and 14.03 ± 3.91 ms, p < 0.01) were smaller for the TMR group than for the controls. The mean MUAP amplitude (0.19 ± 0.11 mV and 0.14 ± 0.06 mV, p = 0.07) was not significantly different between the two groups. Finally, we observed that MUAP surface representation in TMR generally overlapped, and the surface occupied by motor units corresponding to only one motor task was on average smaller than 12% of the electrode surface. These results suggest that smaller MUAP surface areas in TMR patients do not necessarily facilitate prosthetic control due to a high degree of overlap between these areas, and a neural information—based control could lead to improved performance. Based on the results we also infer that the size of the motor units after reinnervation is influenced by the size of the innervating motor neuron.
Ključne besede: target muscle reinnervation, motor unit, controlling muscles
Objavljeno v DKUM: 19.06.2017; Ogledov: 1639; Prenosov: 390
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9. UVEDBA METODOLOGIJE DMAIC V PODJETJU ISKRA MEHANIZMI D.O.O.Borut Kavčič, 2016, diplomsko delo/naloga Opis: Vsaka proizvodna enota, ki danes želi uresničevati zahteve po cenovni konkurenčnosti in biti hkrati kapitalsko donosna, mora poskrbeti za nenehno odpravljanje vsakršnih izgub v proizvodnji.
V diplomskem delu je obravnavano reševanje problema povečanega izmeta v realnem okolju proizvodne motorjev DMU. Izmet je lahko posledica različnih vzrokov, zato so v teoretičnem delu naloge predstavljene ugotovitve s področja učinkovitosti proizvodnih procesov in vitke proizvodnje. Opisan je tudi pristop šest sigma in metodologija DMAIC, s katero smo problem reševali.
Diplomsko delo temelji na projektnem pristopu uvajanja metodologije DMAIC v proizvodnjo z namenom zmanjšanja izmeta. V praktičnem delu naloge so predstavljeni posamezni koraki te metodologije, ki so od definiranja problema, opisa začetnega stanja ter izvedenih meritev in analiz pripeljali projektni tim do rešitev, implementacije le teh in obenem zagotovili ohranjanje pridobljenih rezultatov implementiranih izboljšav.
Projektni pristop in metodologija DMAIC sta se izkazala kot učinkovit način za odpravo določenih izgub v proizvodnji in dvig delovne kulture zaposlenih, ki je temelj nadaljnjih nenehnih izboljšav.
Ključne besede: prenova procesov, metodologija DMAIC, učinkovito vzdrževanje, DMU (Drum Motor Unit), mali projekt
Objavljeno v DKUM: 04.10.2016; Ogledov: 1826; Prenosov: 59
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10. Real-time motor unit identification from high-density surface EMGVojko Glaser, Aleš Holobar, Damjan Zazula, 2013, izvirni znanstveni članek Opis: This study addresses online decomposition of high-density surface electromyograms (EMG) in real-time. The proposed method is based on previouslypublished Convolution Kernel Compensation (CKC) technique and sharesthe same decomposition paradigm, i.e. compensation of motor unit action potentials and direct identification of motor unit (MU) discharges. In contrast to previously published version of CKC, which operates in batch mode and requires ~ 10 s of EMG signal, the real-time implementation begins with batch processing of ~ 3 s of the EMG signal in the initialization stage and continues on with iterative updating of the estimators of MU discharges as blocks of new EMG samples become available. Its detailed comparison to previously validated batch version of CKC and asymptotically Bayesian optimal Linear Minimum Mean Square Error (LMMSE) estimator demonstrates high agreementin identified MU discharges among all three techniques. In the case of synthetic surface EMG with 20 dB signal-to-noise ratio, MU discharges were identified with average sensitivity of 98 %. In the case of experimental EMG, real-time CKC fully converged after initial 5 s of EMG recordings and real-time and batch CKC agreed on 90 % of MU discharges, on average. The real-time CKC identified slightly fewer MUs than its batch version (experimental EMG, 4 MUs versus 5 MUs identified by batch CKC, on average), but required only 0.6 s of processing time on regular personal computer for each second of multichannel surface EMG.
Ključne besede: discharge pattern, high-density EMG, surface EMG, motor unit, real time decomposition
Objavljeno v DKUM: 25.05.2015; Ogledov: 1639; Prenosov: 0 |
