1,475 results match your criteria Motor Unit Recruitment in EMG


Effect of milk fat globule membrane supplementation on motor unit adaptation following resistance training in older adults.

Physiol Rep 2020 Jun;8(12):e14491

Department of Human Nutrition, School of Life Studies, Sugiyama Jogakuen University, Nagoya, Japan.

This study aimed to investigate the effect of milk fat globule membrane (MFGM) supplementation on motor unit adaptation following resistance training in older adults. Twenty-five older males and females took MFGM (n = 12) or a placebo (PLA; n = 12) while performing 8 weeks of isometric knee extension training. During the training, the motor unit firing pattern during submaximal contractions, muscle thickness, and maximal muscle strength of knee extensor muscles were measured every 2 weeks. Read More

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http://dx.doi.org/10.14814/phy2.14491DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7322501PMC

Quantitative electromyography: Normative data in paraspinal muscles.

Muscle Nerve 2020 Jun 12. Epub 2020 Jun 12.

Dep. of Clinical Neurophysiology, Rigshospitalet, University of Copenhagen.

Introduction: Quantitative electromyography of paraspinal muscle is a valuable diagnostic tool, but normative data are lacking.

Methods: EMG was obtained in 65 healthy subjects (49% men, 51% women) aged 21-82 years at C7, Th10, and L5 segments bilaterally. The incidence of spontaneous activity; motor unit potential (MUP) amplitudes, durations, and the incidence of polyphasic potentials; and the recruitment pattern at maximal voluntary contraction (MVC) were evaluated. Read More

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http://dx.doi.org/10.1002/mus.27000DOI Listing

Muscle fiber conduction velocity in the vastus lateralis and medialis muscles of soccer players after ACL reconstruction.

Scand J Med Sci Sports 2020 Jun 9. Epub 2020 Jun 9.

Department of Movement, Human and Health Sciences, University of Rome "Foro Italico", Rome, Italy.

The neural factors underlying the persistency of quadriceps weakness after anterior cruciate ligament reconstruction (ACLR) have been only partially explained. This study examined muscle fiber conduction velocity (MFCV) as an indirect parameter of motor unit recruitment strategies in the vastus lateralis (VL) and medialis (VM) muscles of soccer players with ACLR. High-density surface electromyography (HDsEMG) was acquired from VL and VM in nine soccer players (22. Read More

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http://dx.doi.org/10.1111/sms.13748DOI Listing

Greater Short-Time Recovery of Peripheral Fatigue After Short- Compared With Long-Duration Time Trial.

Front Physiol 2020 14;11:399. Epub 2020 May 14.

Division of Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, Cape Town, South Africa.

The kinetics of recovery from neuromuscular fatigue resulting from exercise time trials (TTs) of different durations are not well-known. The aim of this study was to determine if TTs of three different durations would result in different short-term recovery in maximal voluntary contraction (MVC) and evoked peak forces. Twelve trained subjects performed repetitive concentric right knee extensions on an isokinetic dynamometer self-paced to last 3, 10, and 40 min (TTs). Read More

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http://dx.doi.org/10.3389/fphys.2020.00399DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240104PMC

Estimation of self-sustained activity produced by persistent inward currents using firing rate profiles of multiple motor units in humans.

J Neurophysiol 2020 Jul 27;124(1):63-85. Epub 2020 May 27.

Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.

Persistent inward calcium and sodium currents () activated during motoneuron recruitment help synaptic inputs maintain self-sustained firing until derecruitment. Here, we estimate the contribution of the to self-sustained firing in human motoneurons of varying recruitment threshold by measuring the difference in synaptic input needed to maintain minimal firing once the is fully activated compared with the larger synaptic input required to initiate firing before full activation. Synaptic input to ≈20 dorsiflexor motoneurons simultaneously recorded during ramp contractions was estimated from firing profiles of motor units decomposed from high-density surface electromyography (EMG). Read More

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http://dx.doi.org/10.1152/jn.00194.2020DOI Listing

Mind-Muscle Connection: Limited Effect of Verbal Instructions on Muscle Activity in a Seated Row Exercise.

Percept Mot Skills 2020 May 25:31512520926369. Epub 2020 May 25.

School of Physical Education and Sport of Ribeirao Preto, University of Sao Paulo.

Verbal instruction increases electromyographic (EMG) activity in the first three repetitions of an exercise, but its effect on an entire exercise set until failure is unknown. Once there are changes in motor unit recruitment due to fatigue, the effect of verbal instructions can change during different intervals of a set. This study analyzed whether verbal instruction emphasized the contraction of back muscles (i. Read More

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http://dx.doi.org/10.1177/0031512520926369DOI Listing

Muscle activation during leg-press exercise with or without eccentric overload.

Eur J Appl Physiol 2020 Jul 23;120(7):1651-1656. Epub 2020 May 23.

Institute of Physiology, Department of Biomedical Sciences, University of Padua, Padua, Italy.

Purpose: This study sought to investigate the electromyographic activity of the vastus lateralis (VL) muscle during concentric-eccentric exercise using a new concept leg press machine enabling a preset overloading in the eccentric phase.

Methods: Ten young males familiar with resistive exercise were recruited for this study. Tests were performed on a Leg-press Biostrength® (Technogym S. Read More

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http://dx.doi.org/10.1007/s00421-020-04394-6DOI Listing

A Comparison of Motor Unit Control Strategies between Two Different Isometric Tasks.

Int J Environ Res Public Health 2020 Apr 18;17(8). Epub 2020 Apr 18.

Department of Health, Exercise Science, and Recreation Management, The University of Mississippi, Oxford, MS 38677, USA.

Background: This study examined the motor unit (MU) control strategies for non-fatiguing isometric elbow flexion tasks at 40% and 70% maximal voluntary isometric contraction.

Methods: Nineteen healthy individuals performed two submaximal tasks with similar torque levels: contracting against an immovable object (force task), and maintaining the elbow joint angle against an external load (position task). Surface electromyographic (EMG) signals were collected from the agonist and antagonist muscles. Read More

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http://dx.doi.org/10.3390/ijerph17082799DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7215511PMC

Lower Extremity Biomechanics During a Drop-Vertical Jump and Muscle Strength in Women With Patellofemoral Pain.

J Athl Train 2020 Jun;55(6):615-622

Exercise and Sport Injury Laboratory, University of Virginia, Charlottesville.

Context: Patellofemoral pain (PFP) is one of the most prevalent knee conditions observed in women. Current research suggests that individuals with PFP have altered muscle activity, kinematics, and kinetics during functional tasks. However, few authors have examined differences in lower extremity biomechanics in this population during the drop-vertical jump (DVJ). Read More

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http://dx.doi.org/10.4085/1062-6050-476-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7319735PMC

Acute physiological responses to combined blood flow restriction and low-level laser.

Eur J Appl Physiol 2020 Jun 22;120(6):1437-1447. Epub 2020 Apr 22.

Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan City, 70101, Taiwan.

Purpose: Blood flow restriction (BFR) is an innovation in fitness to train muscles with low loads at low oxygen levels. Low-level laser therapy (LLLT) is a bio-energetic approach to alleviate muscle fatigue during resistance training. This study investigated the immediate effect of LLLT pre-conditioning on BFR that accelerates muscle fatigue due to ischemia. Read More

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http://dx.doi.org/10.1007/s00421-020-04378-6DOI Listing

Fine-wire recordings of flexor hallucis brevis motor units up to maximal voluntary contraction reveal a flexible, nonrigid mechanism for force control.

J Neurophysiol 2020 May 8;123(5):1766-1774. Epub 2020 Apr 8.

The University of Queensland, School of Human Movement and Nutrition Sciences, Brisbane, Queensland, Australia.

Our current knowledge on the neurophysiological properties of intrinsic foot muscles is limited, especially at high forces. This study therefore aimed to investigate the discharge characteristics of single motor units in an intrinsic foot muscle, namely flexor hallucis brevis, during voluntary contractions up to 100% of maximal voluntary contraction. We measured the recruitment threshold and discharge rate of flexor hallucis brevis motor units using indwelling fine-wire electrodes. Read More

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http://dx.doi.org/10.1152/jn.00023.2020DOI Listing

Sex-related differences in motor unit firing rates and action potential amplitudes of the first dorsal interosseous during high-, but not low-intensity contractions.

Exp Brain Res 2020 May 30;238(5):1133-1144. Epub 2020 Mar 30.

Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, 1301 Sunnyside Ave, Room 101BE, Lawrence, KS, 66045, USA.

Despite ample evidence that females are weaker and possess smaller muscle cross-sectional areas (CSAs) compared to males, it remains unclear if there are sex-related differences in the properties of motor units (MU). Eleven males (age 22 ± 3 years) and 12 females (age 21 ± 1 years) performed isometric trapezoid muscle actions at 10% and 70% of maximal voluntary contraction (MVC). Surface electromyography signals were recorded and decomposed into MU action potential (AP) waveforms and firing instances. Read More

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http://dx.doi.org/10.1007/s00221-020-05759-1DOI Listing

Divergent response of low- versus high-threshold motor units to experimental muscle pain.

J Physiol 2020 Jun 29;598(11):2093-2108. Epub 2020 Apr 29.

Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, UK.

Key Points: The neural strategies behind the control of force during muscle pain are not well understood as previous research has been limited in assessing pain responses only during low-force contractions. Here we compared, for the first time, the behaviour of motor units recruited at low and high forces in response to pain. The results showed that motor units activated at low forces were inhibited while those recruited at higher forces increased their activity in response to pain. Read More

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http://dx.doi.org/10.1113/JP279225DOI Listing

Contraction level, but not force direction or wrist position, affects the spatial distribution of motor unit recruitment in the biceps brachii muscle.

Eur J Appl Physiol 2020 Apr 19;120(4):853-860. Epub 2020 Feb 19.

Laboratory for Engineering of the Neuromuscular System (LISiN), Department of Electronic and Telecommunications, Politecnico di Torino, Turin, Italy.

Purpose: Different motor units (MUs) in the biceps brachii (BB) muscle have been shown to be preferentially recruited during either elbow flexion or supination. Whether these different units reside within different regions is an open issue. In this study, we tested wheter MUs recruited during submaximal isometric tasks of elbow flexion and supination for two contraction levels and with the wrist fixed at two different angles are spatially localized in different BB portions. Read More

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http://dx.doi.org/10.1007/s00421-020-04324-6DOI Listing

Quantifying muscle coactivation in individuals with incomplete spinal cord injury using wavelets.

Clin Biomech (Bristol, Avon) 2020 Mar 7;73:101-107. Epub 2020 Jan 7.

Department of Physical Therapy and Human Movement Sciences, Northwestern University, 645 N Michigan Avenue, Chicago, IL, USA.

Background: Individuals with incomplete spinal cord injury often have decreased gait function and coactivation of antagonistic muscle pairs. Common ways of quantifying coactivation using electromyographic signals do not consider frequency information in the signal. As electromyographic signals from different motor unit types have different frequency components and muscle fiber type can change in individuals with spinal cord injury, it may be beneficial to consider frequency components. Read More

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http://dx.doi.org/10.1016/j.clinbiomech.2020.01.001DOI Listing

Burst-modulated wide-pulse neuromuscular electrical stimulation enhances H-reflex recruitment in rats.

Muscle Nerve 2020 04 3;61(4):535-541. Epub 2020 Feb 3.

Key Laboratory of Biorheological Science and Technology of Ministry of Education, Chongqing University, Chongqing, China.

Introduction: In this study we investigated whether burst-modulated wide-pulse neuromuscular electrical stimulation (NMES) can improve the H-reflex and activation efficiency of sensory fibers.

Methods: NMES-induced electromyography (EMG) was recorded from hindpaw plantar muscles in 11 anesthetized rats. A burst-modulated wide pulse (mWP) with three carrier frequencies (2 kHz, 5 kHz, and 10 kHz) and a continuous wide-pulse (WP) were delivered to the tibial nerve of each rat. Read More

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http://dx.doi.org/10.1002/mus.26812DOI Listing

Modulation of reciprocal inhibition at the wrist as a neurophysiological correlate of tremor suppression: a pilot healthy subject study.

Conf Proc IEEE Eng Med Biol Soc 2019 07;2019:6267-6272

It has been shown that Ia afferents inhibit muscle activity of the ipsilateral antagonist, a mechanism known as reciprocal inhibition. Stimulation of these afferents may be explored for the therapeutic reduction of pathological tremor (Essential Tremor or due Parkinson's Disease, for example). However, only a few studies have investigated reciprocal inhibition of wrist flexor / extensor motor control. Read More

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http://dx.doi.org/10.1109/EMBC.2019.8857018DOI Listing

Properties of Motor Units of Elbow and Ankle Muscles Decomposed Using High-Density Surface EMG.

Conf Proc IEEE Eng Med Biol Soc 2019 07;2019:3874-3878

Analyses of motor unit activity provide a window to the neural control of motor output. In recent years, considerable advancements in surface EMG decomposition methods have allowed for the discrimination of dozens of individual motor units across a range of muscle forces. While these non-invasive methods show great potential as an emerging technology, they have difficulty discriminating a representative sample of the motor pool. Read More

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http://dx.doi.org/10.1109/EMBC.2019.8857475DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6986378PMC

Differential Modulation of Motor Unit Properties from the Separate Components of the Triceps Surae in Humans.

Neuroscience 2020 01 7;428:192-198. Epub 2020 Jan 7.

School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada.

The triceps surae is comprised of the soleus, and medial (MG) and lateral (LG) gastrocnemii. Modulation of triceps surae motor units (MUs) is context- and muscle-dependent, yet it is unknown how the disparate components of the triceps surae work together to achieve the common goal of high-intensity voluntary isometric plantar flexion torque gradation. Thus, the purpose was to assess the interrelationships between MU recruitment thresholds (MURTs) and MU discharge rates (MUDRs) among these three muscles during contractions from low to high intensities. Read More

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http://dx.doi.org/10.1016/j.neuroscience.2019.12.023DOI Listing
January 2020

The effects of local forearm heating and cooling on motor unit properties during submaximal contractions.

Exp Physiol 2020 Jan 8. Epub 2020 Jan 8.

Department of Kinesiology, Brock University, St Catharines, Ontario, Canada.

New Findings: What is the central question of this study? How do temperature manipulations affect motor unit (MU) properties during submaximal contractions to the same relative percentage of maximal force? What is the main finding and its importance? MU recruitment patterns are affected by temperature manipulations at the forearm. However, the relationship between MU potential amplitude and recruitment threshold indicates no change to the order or recruitment. Additionally, the MU potential amplitude and firing rate relationship was affected by temperature, suggesting that smaller MUs are more affected by temperature changes than larger MUs. Read More

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http://dx.doi.org/10.1113/EP088256DOI Listing
January 2020

Genioglossus motor unit activity in supine and upright postures in obstructive sleep apnea.

Sleep 2020 Jun;43(6)

Neuroscience Research Australia, Randwick, NSW, Australia.

This study investigated whether a change in posture affected the activity of the upper-airway dilator muscle genioglossus in participants with and without obstructive sleep apnea (OSA). During wakefulness, a monopolar needle electrode was used to record single motor unit activity in genioglossus in supine and upright positions to alter the gravitational load that causes narrowing of the upper airway. Activity from 472 motor units was recorded during quiet breathing in 17 males, nine of whom had OSA. Read More

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http://dx.doi.org/10.1093/sleep/zsz316DOI Listing

Eight weeks of resistance training increases strength, muscle cross-sectional area and motor unit size, but does not alter firing rates in the vastus lateralis.

Eur J Appl Physiol 2020 Jan 12;120(1):281-294. Epub 2019 Dec 12.

Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, 1301 Sunnyside Ave., Room 101BE, Lawrence, KS, 66045, USA.

Purpose: Previous investigations analyzing resistance training's influence on motor unit (MU) firing rates have yielded mixed results. These mixed results may be clarified by concurrently measuring changes in MU size. Thus, this study analyzed whether post-training strength gains were due to increases in MU firing rates and/or sizes as measured indirectly via action potential amplitudes. Read More

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http://dx.doi.org/10.1007/s00421-019-04273-9DOI Listing
January 2020

Differential Diagnosis Of Multiple-System Atrophy With Parkinson's Disease By External Anal- And Urethral-Sphincter Electromyography.

Neuropsychiatr Dis Treat 2019 5;15:3061-3067. Epub 2019 Nov 5.

Department of Neurology, Sixth Medical Center of Chinese PLA General Hospital, Beijing, 100048, People's Republic of China.

Background: The differential diagnosis of Parkinson's disease (PD) with multiple-system atrophy (MSA) is difficult because of their similarity in symptoms and signs. The objective of this study was to investigate the value of external anal-sphincter electromyography (EAS-EMG) and urethral-sphincter electromyography (US-EMG) in differentiating MSA from PD.

Methods: A total of 201 patients, - 101 MSA and 100 PD - were recruited in this study. Read More

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http://dx.doi.org/10.2147/NDT.S218073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6842278PMC
November 2019
2.154 Impact Factor

Impact of parameter selection on estimates of motoneuron excitability using paired motor unit analysis.

J Neural Eng 2020 02 18;17(1):016063. Epub 2020 Feb 18.

Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, United States of America. Department of Biomedical Engineering, Northwestern University, Chicago, IL, United States of America.

Objective: Noninvasive estimation of motoneuron excitability in human motoneurons is achieved through a paired motor unit analysis (ΔF) that quantifies hysteresis in the instantaneous firing rates at motor unit recruitment and de-recruitment. The ΔF technique provides insight into the magnitude of neuromodulatory synaptic input and persistent inward currents (PICs). While the ΔF technique is commonly used for estimating motoneuron excitability during voluntary contractions, computational parameters used for the technique vary across studies. Read More

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http://dx.doi.org/10.1088/1741-2552/ab5edaDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7295184PMC
February 2020

Muscle cross-sectional area and motor unit properties of the medial gastrocnemius and vastus lateralis in normal weight and overfat children.

Exp Physiol 2020 Feb 9;105(2):335-346. Epub 2020 Jan 9.

Neuromechanics Laboratory, University of Kansas, Lawrence, KS, USA.

New Findings: What is the central question of this study? Are differences in muscle size and motor unit properties between normal weight and overfat children muscle specific? What is the main finding and its importance? Muscle cross-sectional area and motor unit action potential amplitudes and firing rates were similar between overfat and normal weight children for both the medial gastrocnemius and vastus lateralis muscles. There was no evidence that the chronic mechanical overload provided by the greater body mass resulted in significant hypertrophy of contractile tissue or motor units that would be used during lower-to-moderate intensity activities.

Abstract: This study examined the possible differences in muscle cross-sectional area (mCSA), motor unit action potential amplitudes (MUAP ) and interspike intervals (ISIs) of the firing instances of the medial gastrocnemius (MG) and vastus lateralis (VL) between normal weight (NW) and overfat (OF) children aged 7-10 years. Read More

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http://dx.doi.org/10.1113/EP088181DOI Listing
February 2020

High-density electromyographic assessment of stretch reflex activity during drop jumps from varying drop heights.

J Electromyogr Kinesiol 2020 Feb 12;50:102375. Epub 2019 Nov 12.

Department of Biomechanics in Sports, Technical University Munich, Germany; Human Movement Science, Bundeswehr University Munich, Germany.

This study investigated how drop heights and their associated drop jump performance relate to stretch reflex modulations. Eleven male subjects performed ten drop jumps from each of three individually predetermined drop heights. These were the drop height resulting in maximal performance (OPT), as well as 10 cm below (LOW) and above (HIGH) maximal performance. Read More

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http://dx.doi.org/10.1016/j.jelekin.2019.102375DOI Listing
February 2020

Main branch of ACN-to-RLN for management of laryngospasm due to unilateral vocal cord paralysis.

Laryngoscope 2019 Nov 29. Epub 2019 Nov 29.

Department of Otolaryngology-Head & Neck Surgery, Changhai Hospital, The Second Military Medical University, Shanghai, the People's Republic of China.

Objectives/hypothesis: This study explored the feasibility and efficiency of main branch of ansa cervicalis nerve (ACN)-to-recurrent laryngeal nerve (RLN) anastomosis for management of paroxysmal laryngospasm due to unilateral vocal cord paralysis (UVCP).

Methods: Thirteen patients who underwent main branch of ACN-to-RLN anastomosis for management of paroxysmal laryngospasm due to UVCP were enrolled in the present study. Multidimensional assessments, including videostroboscopy, voice assessment, and laryngeal electromyography (LEMG), were performed preoperatively and postoperatively. Read More

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http://dx.doi.org/10.1002/lary.28426DOI Listing
November 2019
2.032 Impact Factor

force-length and activation dynamics of two distal rat hindlimb muscles in relation to gait and grade.

J Exp Biol 2019 12 18;222(Pt 24). Epub 2019 Dec 18.

Concord Field Station, Department of Organismic and Evolutionary Biology, Harvard University, Bedford 01730, MA, USA.

Muscle function changes to meet the varying mechanical demands of locomotion across different gait and grade conditions. A muscle's work output is determined by time-varying patterns of neuromuscular activation, muscle force and muscle length change, but how these patterns change under different conditions in small animals is not well defined. Here, we report the first integrated force-length and activation patterns in rats, a commonly used small animal model, to evaluate the dynamics of two distal hindlimb muscles (medial gastrocnemius and plantaris) across a range of gait (walk, trot and gallop) and grade (level and incline) conditions. Read More

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http://dx.doi.org/10.1242/jeb.205559DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6955210PMC
December 2019

Pelvic floor muscle activity patterns in women with and without stress urinary incontinence while running.

Ann Phys Rehabil Med 2019 Nov 13. Epub 2019 Nov 13.

Division of Physiotherapy, Department of Health Professions, Bern University of Applied Sciences, Bern, Switzerland.

Background: High-impact activities are often related to urine leakage in women, so deeper insight into continence mechanisms of pelvic floor muscles (PFMs) while running is needed. Therefore, simultaneous information about the intensity of PFM muscle activity and fibre recruitment behavior at each time point of the gait cycle can help in understanding PFM activity patterns.

Objective: We aimed to analyse spectral changes of the pre- and post-initial contact phase during running at 3 different speeds and to compare women with stress urinary continence (SUI) to those without SUI by using a wavelet approach. Read More

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http://dx.doi.org/10.1016/j.rehab.2019.09.013DOI Listing
November 2019

Modular motor control of the sound limb in gait of people with trans-femoral amputation.

J Neuroeng Rehabil 2019 11 6;16(1):132. Epub 2019 Nov 6.

Department of Engineering, University Roma TRE, Roma, Italy.

Background: The above-knee amputation of a lower limb is a severe impairment that affects significantly the ability to walk; considering this, a complex adaptation strategy at the neuromuscular level is needed in order to be able to move safely with a prosthetic knee. In literature, it has been demonstrated that muscle activity during walking can be described via the activation of a small set of muscle synergies. The analysis of the composition and the time activation profiles of such synergies have been found to be a valid tool for the description of the motor control schemes in pathological subjects. Read More

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http://dx.doi.org/10.1186/s12984-019-0616-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6836453PMC
November 2019
1 Read

Intraoperative Responses May Predict Chronic Performance of Composite Flat Interface Nerve Electrodes on Human Femoral Nerves.

IEEE Trans Neural Syst Rehabil Eng 2019 12 4;27(12):2317-2327. Epub 2019 Nov 4.

Peripheral nerve cuff electrodes (NCEs) in motor system neuroprostheses can generate strong muscle contractions and enhance surgical efficiency by accessing multiple muscles from a single proximal location. Predicting chronic performance of high contact density NCEs based on intraoperative observations would facilitate implantation at locations that maximize selective recruitment, immediate connection of optimal contacts to implanted pulse generators (IPGs) with limited output channels, and initiation of postoperative rehabilitation as soon as possible after surgery. However, the stability of NCE intraoperative recruitment to predict chronic performance has not been documented. Read More

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http://dx.doi.org/10.1109/TNSRE.2019.2951079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6938031PMC
December 2019

Strength Training Increases Conduction Velocity of High-Threshold Motor Units.

Med Sci Sports Exerc 2020 Apr;52(4):955-967

Department of Movement, Human and Health Sciences, University of Rome "Foro Italico", Rome, ITALY.

Purpose: Motor unit conduction velocity (MUCV) represents the propagation velocity of action potentials along the muscle fibers innervated by individual motor neurons and indirectly reflects the electrophysiological properties of the sarcolemma. In this study, we investigated the effect of a 4-wk strength training intervention on the peripheral properties (MUCV and motor unit action potential amplitude, RMSMU) of populations of longitudinally tracked motor units (MU).

Methods: The adjustments exhibited by 12 individuals who participated in the training (INT) were compared with 12 controls (CON). Read More

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http://dx.doi.org/10.1249/MSS.0000000000002196DOI Listing

Orofacial sensorimotor behaviour in unilateral chewing: A comparative analysis in asymptomatic population.

Physiol Behav 2019 12 18;212:112718. Epub 2019 Oct 18.

Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Spain; Motion in Brains Research Group, Institute of Neuroscience and Sciences of the Movement (INCIMOV), Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Spain.

The main aim of the present study was to evaluate the presence of differences in motor, somatosensory and laterality recognise variables between individuals with unilateral chewing (UC) versus bilateral chewing (BC). A cross-sectional study with a nonprobabilistic sample was conducted. Seventy asymptomatic individuals were grouped as UC or BC to assess differences in motor, somatosensory, and laterality recognise variables. Read More

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http://dx.doi.org/10.1016/j.physbeh.2019.112718DOI Listing
December 2019

Impact of stimulation frequency on neuromuscular fatigue.

Eur J Appl Physiol 2019 Dec 11;119(11-12):2609-2616. Epub 2019 Oct 11.

INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, 21000, Dijon, France.

Purpose: The aim of the present study was to examine the frequency effects (20 Hz and 100 Hz) on neuromuscular fatigue using stimulation parameters favoring an indirect motor unit recruitment through the afferent pathway.

Methods: Nineteen subjects were divided into two groups: 20 Hz (n = 10) and 100 Hz (n = 9). The electrical stimulation session consisted of 25 stimulation trains (20 s ON/20 s OFF, pulse width: 1 ms) applied over the tibial nerve and delivered at an intensity evoking 10% maximal voluntary isometric contraction (MVIC). Read More

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http://dx.doi.org/10.1007/s00421-019-04239-xDOI Listing
December 2019

Modulation of corticospinal output during goal-directed actions: Evidence for a contingent coding hypothesis.

Neuropsychologia 2019 11 30;134:107205. Epub 2019 Sep 30.

Department of Psychology, University of Torino, Torino, 10123, Italy; C'MoN, Cognition, Motion and Neuroscience Unit, Fondazione Istituto Italiano di Tecnologia, Genova, 16152, Italy. Electronic address:

Seeing a person perform an action activates the observer's motor system. The present study aimed at investigating the temporal relationship between execution and observation of goal-directed actions. One possibility is that the corticospinal excitability (CSE) follows the dynamic evolution of the pattern of muscle activity in the executed action. Read More

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http://dx.doi.org/10.1016/j.neuropsychologia.2019.107205DOI Listing
November 2019
4 Reads

Understanding the Consequences of Repetitive Subconcussive Head Impacts in Sport: Brain Changes and Dampened Motor Control Are Seen After Boxing Practice.

Front Hum Neurosci 2019 10;13:294. Epub 2019 Sep 10.

Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, United Kingdom.

Objectives: The potential effects of exposure to repetitive subconcussive head impacts through routine participation in sport are not understood. To investigate the effects of repetitive subconcussive head impacts we studied boxers following customary training (sparring) using transcranial magnetic stimulation (TMS), decomposition electromyographic (EMG) and tests of memory.

Methods: Twenty amateur boxers performed three 3-min sparring bouts. Read More

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http://dx.doi.org/10.3389/fnhum.2019.00294DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746992PMC
September 2019
1 Read

Estimates of persistent inward current in human motor neurons during postural sway.

J Neurophysiol 2019 11 18;122(5):2095-2110. Epub 2019 Sep 18.

Wilfrid Laurier University, Waterloo, Ontario, Canada.

Persistent inward current (PIC) plays a critical role in setting the gain of spinal motor neurons. In humans, most estimates of PIC are made from plantarflexor or dorsiflexor motor units in a seated position. This seated and static posture negates the task-dependent nature of the monoaminergic drive and afferent inhibition that modulate PIC activation. Read More

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http://dx.doi.org/10.1152/jn.00254.2019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6879958PMC
November 2019
1 Read

Evidence of bilinearity in the relationship between rate of neuromuscular excitation and rate of force development.

J Electromyogr Kinesiol 2019 Dec 11;49:102355. Epub 2019 Sep 11.

Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA.

The purpose was to examine the relationship between the rate of neural excitation (rate of rise in the electromyogram, EMG) and the rate of isometric force development (RFD) to determine whether surface EMG measures can detect nonlinearity that is expected due to underlying motor unit discharge behavior and the summation of progressively larger motor unit potentials throughout recruitment. Due to interest in obtaining a change point, a bilinear model was hypothesized to provide the best fit of the EMG-RFD relationship compared to a linear model, exponential model and log-transformed data. 21 young adult participants performed isometric dorsiflexion contractions to 40% of their maximal voluntary contraction (MVC) force. Read More

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http://dx.doi.org/10.1016/j.jelekin.2019.102355DOI Listing
December 2019
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Absence of hyperexcitability of spinal motoneurons in patients with amyotrophic lateral sclerosis.

J Physiol 2019 11 26;597(22):5445-5467. Epub 2019 Oct 26.

Sorbonne Université, Inserm, CNRS, Laboratoire d'Imagerie Biomédicale, LIB, Paris, France.

Key Points: •Amyotrophic lateral sclerosis (ALS) motoneurons become hypoexcitable with disease progression in experimental models, raising questions about the neural hyperexcitability supported by clinical observations. •A variant of the ∆F method, based on motor unit discharge frequency modulations during recruitment and derecruitment, has been developed to investigate the motoneuron capacity to self-sustained discharge in patients. •The modulation of motor unit firing rate during ramp contraction and vibration-induced recruitment are modified in ALS, suggesting lower motoneuron capacity to self-sustained discharge, which is a sign of hypoexcitability. Read More

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http://dx.doi.org/10.1113/JP278117DOI Listing
November 2019
1 Read

Direct Electrical Stimulation of Premotor Areas: Different Effects on Hand Muscle Activity during Object Manipulation.

Cereb Cortex 2020 01;30(1):391-405

Laboratory of Motor Control, Department of Medical Biotechnologies and Translational Medicine, Università degli Studi di Milano, Humanitas Reasearch Hospital, IRCCS, Milano, Italy.

Dorsal and ventral premotor (dPM and vPM) areas are crucial in control of hand muscles during object manipulation, although their respective role in humans is still debated. In patients undergoing awake surgery for brain tumors, we studied the effect of direct electrical stimulation (DES) of the premotor cortex on the execution of a hand manipulation task (HMt). A quantitative analysis of the activity of extrinsic and intrinsic hand muscles recorded during and in absence of DES was performed. Read More

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http://dx.doi.org/10.1093/cercor/bhz139DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7029688PMC
January 2020
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Is the motor unit mean firing rate versus recruitment threshold relationship linear?

Physiol Meas 2019 09 30;40(9):095002. Epub 2019 Sep 30.

Neuromuscular Plasticity Laboratory, School of Kinesiology and Physical Therapy, University of Central Florida, 12354 Research Parkway, Orlando, FL, 32826, United States of America.

Advances in surface electromyographic (EMG) signal decomposition allow researchers to analyze data for 20-50 motor units per contraction. To simplify interpretation, some investigators rely on group mean analysis of the mean firing rate versus recruitment threshold relationship, but it is unclear if this association is linear.

Objective: To determine whether this relationship is strongest when analyzed via linear, quadratic, or cubic regression. Read More

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http://dx.doi.org/10.1088/1361-6579/ab4025DOI Listing
September 2019
2 Reads

Anatomically accurate model of EMG during index finger flexion and abduction derived from diffusion tensor imaging.

PLoS Comput Biol 2019 08 29;15(8):e1007267. Epub 2019 Aug 29.

School of Electrical and Electronic Engineering, University College Dublin, Belfield, Dublin, Ireland.

This study presents a modelling framework in which information on muscle fiber direction and orientation during contraction is derived from diffusion tensor imaging (DTI) and incorporated in a computational model of the surface electromyographic (EMG) signal. The proposed model makes use of the principle of reciprocity to simultaneously calculate the electric potentials produced at the recording electrode by charges distributed along an arbitrary number of muscle fibers within the muscle, allowing for a computationally efficient evaluation of extracellular motor unit action potentials. The approach is applied to the complex architecture of the first dorsal interosseous (FDI) muscle of the hand to simulate EMG during index finger flexion and abduction. Read More

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http://dx.doi.org/10.1371/journal.pcbi.1007267DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6738720PMC
August 2019
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Reorganization of Masseter and Temporalis Muscle Single Motor Unit Activity During Experimental Masseter Muscle Pain.

J Oral Facial Pain Headache 2020 27;34(1):40–52. Epub 2019 Aug 27.

Aims: To test the hypothesis that experimental noxious stimulation of the right masseter muscle results in a reorganization of motor unit activity within the right temporalis and right masseter muscles during jaw closing tasks.

Methods: A total of 20 healthy participants received hypertonic saline (5% sodium chloride) infusion into the right masseter muscle, and pain intensity was maintained at 40-60/100 mm on a visual analog scale. Standardized isometric biting tasks were performed with an intraoral force transducer while single motor units (SMUs) were recorded from the right masseter and temporalis muscles. Read More

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http://dx.doi.org/10.11607/ofph.2426DOI Listing
January 2020

Prognostic value of needle electromyography in traumatic brachial plexus injury.

Muscle Nerve 2019 11 4;60(5):595-597. Epub 2019 Sep 4.

Department of Physical Medicine and Rehabilitation, University of Washington, Seattle, Washington.

Introduction: In this study we aimed to determine whether needle electromyographic assessment of voluntary motor unit recruitment in traumatic brachial plexus injuries could predict spontaneous motor recovery.

Methods: A retrospective study was performed on patients with brachial plexus injury affecting deltoid, supraspinatus/infraspinatus, and biceps brachii. The outcome measure was strength on manual muscle testing at least 1 year after injury. Read More

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http://dx.doi.org/10.1002/mus.26684DOI Listing
November 2019
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Clinical spectrums and outcomes of necrotizing autoimmune myopathy versus other idiopathic inflammatory myopathies: a multicenter case-control study.

Clin Rheumatol 2019 Dec 24;38(12):3459-3469. Epub 2019 Aug 24.

Division of Rheumatology, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkoknoi, Bangkok, 10700, Thailand.

Objective: To investigate the clinical characteristics, laboratory features, and treatment outcomes of Thai patients compared between those with necrotizing autoimmune myopathy (NAM) and those with other idiopathic inflammatory myopathies (IIMs) or non-NAM.

Methods: This multicenter case-control study included patients aged ≥ 18 years who were diagnosed with IIMs by muscle pathology, and who had relevant clinical and laboratory data, including muscle enzymes, from at least 3 follow-up visits during a 1-year period. Baseline clinical and laboratory data were recorded. Read More

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http://dx.doi.org/10.1007/s10067-019-04756-2DOI Listing
December 2019
4 Reads
1.774 Impact Factor

Discharge properties of human diaphragm motor units with ageing.

J Physiol 2019 10 1;597(20):5079-5092. Epub 2019 Sep 1.

Neuroscience Research Australia, University of New South Wales, NSW, Australia.

Key Points: Ageing is associated with changes in the respiratory system including in the lungs, rib cage and muscles. Neural drive to the diaphragm, the principal inspiratory muscle, has been reported to increase during quiet breathing with ageing. We demonstrated that low-threshold motor units of the human diaphragm recruited during quiet breathing have similar discharge frequencies across age groups and shorter discharge times in older age. Read More

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http://dx.doi.org/10.1113/JP278498DOI Listing
October 2019
1 Read

Effects of forward tilted seating and foot-support on postural adjustments in children with spastic cerebral palsy: An EMG-study.

Eur J Paediatr Neurol 2019 Sep 1;23(5):723-732. Epub 2019 Aug 1.

University of Groningen, University Medical Center Groningen, Department of Paediatrics - Division of Developmental Neurology, Groningen, the Netherlands. Electronic address:

Objective: To evaluate the effect of 15° forward (FW) seat inclination and foot-support in children with cerebral palsy (CP) on postural adjustments during reaching.

Design: Observational study repeated-measures design; step two of two-step-project.

Setting: Laboratory unit within University Hospital and two special education schools. Read More

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http://dx.doi.org/10.1016/j.ejpn.2019.07.001DOI Listing
September 2019
2 Reads

The effect of rate of torque development on motor unit recruitment and firing rates during isometric voluntary trapezoidal contractions.

Exp Brain Res 2019 Oct 8;237(10):2653-2664. Epub 2019 Aug 8.

Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, 1301 Sunnyside Ave, Room 101BE, Lawrence, KS, 66045, USA.

It is common practice to examine motor unit (MU) activity according to mean firing rate (MFR) and action potential amplitude (MUAP) vs. recruitment threshold (RT) relationships during isometric trapezoidal contractions. However, it is unknown whether the rate of torque development during the linearly increasing torque phase affects the activity of MUs during such contractions. Read More

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http://dx.doi.org/10.1007/s00221-019-05612-0DOI Listing
October 2019
2 Reads

Motor unit discharge rate and the estimated synaptic input to the vasti muscles is higher in open compared with closed kinetic chain exercise.

J Appl Physiol (1985) 2019 10 1;127(4):950-958. Epub 2019 Aug 1.

Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom.

Conflicting results have been reported on whether closed kinetic chain exercises (such as a leg press) may induce more balanced activation of vastus medialis (VM) and lateralis (VL) muscles compared with open kinetic chain exercise (such as pure knee extension). This study aimed to 1) compare between-vasti motor unit activity and 2) analyze the combined motor unit behavior from both muscles between open and closed kinetic chain exercises. Thirteen participants (four women, mean ± SD age: 27 ± 5 yr) performed isometric knee extension and leg press at 10, 30, 50, 70% of the maximum voluntary torque. Read More

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http://dx.doi.org/10.1152/japplphysiol.00310.2019DOI Listing
October 2019
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Two novel mutations in TTN of a patient with congenital myopathy: A case report.

Mol Genet Genomic Med 2019 08 22;7(8):e866. Epub 2019 Jul 22.

Department of Rehabilitation Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.

Background: Early-onset myopathies show a wide spectrum of phenotypes and are composed of various types of inherited neuromuscular diseases, making it difficult to diagnose. TTN mutation-related myopathy is a known cause of early-onset myopathy. Since a next-generation sequencing (NGS) has enabled sequencing of the vast amount of DNA, TTN, which is the longest coding sequence of any human gene, mutations can now be revealed. Read More

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http://dx.doi.org/10.1002/mgg3.866DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6687639PMC
August 2019
5 Reads