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Cherni Y, Hammami M, Jelid MC, Aloui G, Suzuki K, Shephard RJ, Chelly MS. Neuromuscular Adaptations and Enhancement of Physical Performance in Female Basketball Players After 8 Weeks of Plyometric Training. Front Physiol 2021; 11:588787. [PMID: 33584327 PMCID: PMC7873906 DOI: 10.3389/fphys.2020.588787] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 12/31/2020] [Indexed: 11/26/2022] Open
Abstract
The aim of this study was to examine the effects of an 8-week in-season plyometric training (PT) program on the physical performance and neuromuscular adaptations of female basketball players. Twenty-seven elite female basketball players (aged 21.0 ± 2.6 years) were assigned between an experimental group (n = 15) who substituted a part of their usual training with biweekly PT, and a control group (n = 12) who maintained their standard basketball training. Analyses of variance and co-variance assessed changes in 10, 20, and 30 m sprint times, ability to change direction (T-test) and jumping ability [squat jump (SJ) and countermovement jump (CMJ)] with electromyographic assessment of the vastus lateralis, vastus medialis, and rectus femoris muscles during jumping and meassurement of the isokinetic strength of the knee muscles. After 8 weeks of the plyometric program the experimental group enhanced change of direction performance (Δ = −3.90%, d = 0.67) and showed a greater thigh cross sectional area (Δ = 9.89%, d = 0.95) relative to controls. Neural adaptations included significant improvements of EMG parameters for the vastus medialis muscle during Squat Jumping (Δ = 109.3%, d = 0.59). However, trends to improvements of sprinting times and jumping performances did not reach statistical significance. In addition, there were no gains in the peak torque and the average power of the quadriceps and hamstring muscles at either slow or moderate test speeds. We conclude that 8-weeks of PT (72–126 jumps) was insufficient to improve many of the variables associated with basketball performance in our subject-group. Further studies of female basketball players, extending the program period and increasing the intensity and speed of jumps are recommended in the search for more significant results.
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Affiliation(s)
- Yosser Cherni
- Research Unit (UR17JS01) "Sport Performance, Health & Society", Higher Institute of Sport and Physical Education of Ksar Saîd, University of "La Manouba", Tunis, Tunisia.,Higher Institute of Sport and Physical Education of Ksar Said, University of "La Manouba", Tunis, Tunisia
| | - Mehrez Hammami
- Research Unit (UR17JS01) "Sport Performance, Health & Society", Higher Institute of Sport and Physical Education of Ksar Saîd, University of "La Manouba", Tunis, Tunisia.,Higher Institute of Sport and Physical Education of Ksar Said, University of "La Manouba", Tunis, Tunisia
| | - Mohamed Chedly Jelid
- Research Unit (UR17JS01) "Sport Performance, Health & Society", Higher Institute of Sport and Physical Education of Ksar Saîd, University of "La Manouba", Tunis, Tunisia.,Higher Institute of Sport and Physical Education of Ksar Said, University of "La Manouba", Tunis, Tunisia
| | - Ghaith Aloui
- Research Unit (UR17JS01) "Sport Performance, Health & Society", Higher Institute of Sport and Physical Education of Ksar Saîd, University of "La Manouba", Tunis, Tunisia
| | | | - Roy J Shephard
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON, Canada
| | - Mohamed Souhaiel Chelly
- Research Unit (UR17JS01) "Sport Performance, Health & Society", Higher Institute of Sport and Physical Education of Ksar Saîd, University of "La Manouba", Tunis, Tunisia.,Higher Institute of Sport and Physical Education of Ksar Said, University of "La Manouba", Tunis, Tunisia
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Martinez-Valdes E, Negro F, Laine CM, Falla D, Mayer F, Farina D. Tracking motor units longitudinally across experimental sessions with high-density surface electromyography. J Physiol 2017; 595:1479-1496. [PMID: 28032343 PMCID: PMC5330923 DOI: 10.1113/jp273662] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 11/15/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Classic motor unit (MU) recording and analysis methods do not allow the same MUs to be tracked across different experimental sessions, and therefore, there is limited experimental evidence on the adjustments in MU properties following training or during the progression of neuromuscular disorders. We propose a new processing method to track the same MUs across experimental sessions (separated by weeks) by using high-density surface electromyography. The application of the proposed method in two experiments showed that individual MUs can be identified reliably in measurements separated by weeks and that changes in properties of the tracked MUs across experimental sessions can be identified with high sensitivity. These results indicate that the behaviour and properties of the same MUs can be monitored across multiple testing sessions. The proposed method opens new possibilities in the understanding of adjustments in motor unit properties due to training interventions or the progression of pathologies. ABSTRACT A new method is proposed for tracking individual motor units (MUs) across multiple experimental sessions on different days. The technique is based on a novel decomposition approach for high-density surface electromyography and was tested with two experimental studies for reliability and sensitivity. Experiment I (reliability): ten participants performed isometric knee extensions at 10, 30, 50 and 70% of their maximum voluntary contraction (MVC) force in three sessions, each separated by 1 week. Experiment II (sensitivity): seven participants performed 2 weeks of endurance training (cycling) and were tested pre-post intervention during isometric knee extensions at 10 and 30% MVC. The reliability (Experiment I) and sensitivity (Experiment II) of the measured MU properties were compared for the MUs tracked across sessions, with respect to all MUs identified in each session. In Experiment I, on average 38.3% and 40.1% of the identified MUs could be tracked across two sessions (1 and 2 weeks apart), for the vastus medialis and vastus lateralis, respectively. Moreover, the properties of the tracked MUs were more reliable across sessions than those of the full set of identified MUs (intra-class correlation coefficients ranged between 0.63-0.99 and 0.39-0.95, respectively). In Experiment II, ∼40% of the MUs could be tracked before and after the training intervention and training-induced changes in MU conduction velocity had an effect size of 2.1 (tracked MUs) and 1.5 (group of all identified motor units). These results show the possibility of monitoring MU properties longitudinally to document the effect of interventions or the progression of neuromuscular disorders.
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Affiliation(s)
- E Martinez-Valdes
- Department of Sports Medicine and Sports Orthopaedics, University of Potsdam, Potsdam, Germany
| | - F Negro
- Institute of Neurorehabilitation Systems, Bernstein Focus Neurotechnology Göttingen (BFNT), Bernstein Centre for Computational Neuroscience (BCCN), University Medical Center Göttingen, Georg-August University, Göttingen, Germany.,Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
| | - C M Laine
- Institute of Neurorehabilitation Systems, Bernstein Focus Neurotechnology Göttingen (BFNT), Bernstein Centre for Computational Neuroscience (BCCN), University Medical Center Göttingen, Georg-August University, Göttingen, Germany
| | - D Falla
- 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
| | - F Mayer
- Department of Sports Medicine and Sports Orthopaedics, University of Potsdam, Potsdam, Germany
| | - D Farina
- Institute of Neurorehabilitation Systems, Bernstein Focus Neurotechnology Göttingen (BFNT), Bernstein Centre for Computational Neuroscience (BCCN), University Medical Center Göttingen, Georg-August University, Göttingen, Germany.,Department of Bioengineering, Imperial College London, Royal School of Mines, London, UK
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Roman-Liu D. Comparison of concepts in easy-to-use methods for MSD risk assessment. APPLIED ERGONOMICS 2014; 45:420-427. [PMID: 23849897 DOI: 10.1016/j.apergo.2013.05.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 05/20/2013] [Accepted: 05/24/2013] [Indexed: 06/02/2023]
Abstract
This article presents a comparative analysis of easy-to-use methods for assessing musculoskeletal load and the risk for developing musculoskeletal disorders. In all such methods, assessment of load consists in defining input data, the procedure and the system of assessment. This article shows what assessment steps the methods have in common; it also shows how those methods differ in each step. In addition, the methods are grouped according to their characteristic features. The conclusion is that the concepts of assessing risk in different methods can be used to develop solutions leading to a comprehensive method appropriate for all work tasks and all parts of the body. However, studies are necessary to verify the accepted premises and to introduce some standardization that would make consolidation possible.
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Affiliation(s)
- Danuta Roman-Liu
- Department of Ergonomics, Central Institute for Labour Protection - National Research Institute (CIOP-PIB), ul. Czerniakowska 16, 00-701 Warsaw, Poland.
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Volume conductor models in surface electromyography: Applications to signal interpretation and algorithm test. Comput Biol Med 2013; 43:953-61. [DOI: 10.1016/j.compbiomed.2013.03.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 03/12/2013] [Accepted: 03/14/2013] [Indexed: 11/20/2022]
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Estimation of impulse response between electromyogram signals for use in conduction delay distribution estimation. Med Biol Eng Comput 2013; 51:757-68. [PMID: 23385331 DOI: 10.1007/s11517-013-1042-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 01/22/2013] [Indexed: 10/27/2022]
Abstract
The time delay between two surface electromyograms (EMGs) acquired along the conduction path is used to estimate mean action potential conduction velocity. Modeling the linear impulse response between "upstream" and "downstream" EMG signals permits an estimate of the distribution of velocities, providing more information. In this work, we analyzed EMG from bipolar electrodes placed on the tibialis anterior of 36 subjects, using an inter-electrode distance of 10 mm. Regularized least squares was used to fit the coefficients of a finite impulse response model. We trained the model on one recording, then tested on two others. The optimum correlation between the model-predicted and actual EMG averaged 0.70. We also compared estimation of the mean conduction delay from the peak time of the impulse response to the "gold standard" peak time of the cross-correlation between the upstream and downstream EMG signals. Optimal models differed from the gold standard by 0.02 ms, on average. Model performance was influenced by the regularization parameters. The impulse responses, however, incorrectly contained substantive power at very low time delays, causing delay distribution estimates to exhibit high probabilities at very short conduction delays. Unrealistic distribution estimates resulted. Larger inter-electrode spacing may be required to alleviate this limitation.
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Gallina A, Ritzel CH, Merletti R, Vieira TMM. Do surface electromyograms provide physiological estimates of conduction velocity from the medial gastrocnemius muscle? J Electromyogr Kinesiol 2012; 23:319-25. [PMID: 23265664 DOI: 10.1016/j.jelekin.2012.11.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 11/09/2012] [Accepted: 11/11/2012] [Indexed: 11/18/2022] Open
Abstract
Muscle fiber conduction velocity (CV) is commonly estimated from surface electromyograms (EMGs) collected with electrodes parallel to muscle fibers. If electrodes and muscle fibers are not located in parallel planes, CV estimates are biased towards values far over the physiological range. In virtue of their pinnate architecture, the fibers of muscles such as the gastrocnemius are hardly aligned in planes parallel to surface electrodes. Therefore, in this study we investigate whether physiological CV estimates can be obtained from the gastrocnemius muscle. Specifically, with a large grid of 16×8 electrodes we map CV estimates over the whole gastrocnemius muscle while eleven subjects exerted isometric plantar flexions at three different force levels. CV was estimated for couples of single differential EMGs and estimate locations (i.e., channels) were classified as physiological and non-physiological, depending on whether CV estimates were within the physiological range (3-6ms(-1)) or not. Physiological CV values could be estimated from a markedly small muscle region for eight participants; channels providing physiological CV estimates corresponded to about 5% of the total number of channels. As expected, physiological and non-physiological channels were clustered in distinct regions. CV estimates within the physiological range were obtained for the most distal gastrocnemius portion (ANOVA, P<0.001), where occurrences of propagating potentials were often verified through visual analysis. For the first time, this study shows that CV might be reliably assessed from surface EMGs collected from the most distal gastrocnemius region.
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Affiliation(s)
- Alessio Gallina
- Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Politecnico di Torino, Italy
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Esposito F, Limonta E, Cè E. Time course of stretching-induced changes in mechanomyogram and force characteristics. J Electromyogr Kinesiol 2012; 21:795-802. [PMID: 21856170 DOI: 10.1016/j.jelekin.2011.07.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 05/11/2011] [Accepted: 07/18/2011] [Indexed: 11/26/2022] Open
Abstract
To evaluate the time-course of stretching-induced changes in mechanical properties of the muscle-tendon unit (MTU), 11 participants (age 22±1 yr; body mass 77±5 kg; stature 1.78±0.05 m; mean±SD) underwent tetanic electrical stimulations of the medial gastrocnemius muscle before and after (up to 2h) stretching administration. During contractions, surface electromyogram (EMG), mechanomyogram (MMG) and force were recorded simultaneously. From MMG, peak-to-peak (p-p) and root mean square (RMS) were calculated during the on-phase and plateau phase of tetanic contraction, respectively. After stretching: (i) no differences were found in EMG parameters; (ii) MMG p-p and slope decreased (-16% and -10%, respectively; P<0.05) and remained depressed for the entire recovery period; (iii) MMG RMS increased (+20%; P<0.05), returning to pre-stretching values within 15 min; and (iv) peak force (pF), with its first (dF/dt) and second (d(2)F/dt(2)) derivative, decreased significantly by 32%, 35% and 54%, respectively, and remained depressed for the entire recovery period. The lack of MMG p-p and pF recovery could be ascribable to a reduced muscle force generating capacity due to persisting changes in viscoelastic characteristics of series elastic components. The early return of MMG RMS to pre-stretching values suggests that changes in viscoelastic parallel components recovered after few minutes.
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Affiliation(s)
- Fabio Esposito
- Department of Sport, Nutrition and Health Sciences, Division of Human Physiology, University of Milan, Milan, Italy.
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Esposito F, Limonta E, Cè E. Passive stretching effects on electromechanical delay and time course of recovery in human skeletal muscle: new insights from an electromyographic and mechanomyographic combined approach. Eur J Appl Physiol 2010; 111:485-95. [DOI: 10.1007/s00421-010-1659-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2010] [Indexed: 10/19/2022]
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Esposito F, Cè E, Rampichini S, Veicsteinas A. Acute passive stretching in a previously fatigued muscle: Electrical and mechanical response during tetanic stimulation. J Sports Sci 2009; 27:1347-57. [DOI: 10.1080/02640410903165093] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Coza A, von Tscharner V, Nigg B. Activity mapping of lower leg muscles using a circumferential electrode array. FOOTWEAR SCIENCE 2009. [DOI: 10.1080/19424280903535421] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Tank FF, Silva GTD, Oliveira CGD, Garcia MAC. Influência da distância intereletrodos e da cadência de movimento no domínio da frequência do sinal de EMG de superfície. REV BRAS MED ESPORTE 2009. [DOI: 10.1590/s1517-86922009000500008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A eletromiografia de superfície (sEMG), apesar de amplamente utilizada em investigações biomecânicas, ainda apresenta inúmeros questionamentos sobre a influência das distâncias intereletrodos (DIE) na morfologia do sinal, principalmente em contrações isotônicas. Logo, muitos dos trabalhos desenvolvidos ainda se limitam ao âmbito do laboratório de pesquisa, onde é possível estabelecer maior controle nos protocolos de registro e análise, o que não é comumente observado na prática clínico-desportiva. Dessa forma, o objetivo do estudo foi examinar os efeitos de dois protocolos de colocação de eletrodos e a realização de contrações isotônicas no domínio da frequência do sinal de sEMG. Quinze sujeitos do sexo masculino (idade: 22,8 ± 3,5 anos), todos destros, realizaram contrações dinâmicas do bíceps braquial direito com carga estimada em 20% da contração voluntária máxima em três diferentes cadências (30, 45, 60bpm). Os sinais de sEMG foram registrados por meio de dois canais, cujas DIEs foram de 4,2 e 13cm, respectivamente. A avaliação dos sinais de sEMG foi baseada na frequência mediana do espectro de potencial do sinal, calculado via transformada rápida de Fourier. A DIE e a cadência foram definidas como fatores (ANOVA two-way; α = 0,05). Não foram observadas diferenças estatísticas e qualquer interação entre ambos os fatores nas três cadências (P > 0,05). Sugere-se que, independentemente da distância utilizada entre os eletrodos, uma investigação no domínio da frequência do sinal de sEMG em tarefas dinâmicas seja evitada, mesmo a partir de DIEs reduzidas, como é sugerido pela literatura, dado que variações no torque e no comprimento muscular podem corromper o sinal e, portanto, sua interpretação.
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Cè E, Paracchino E, Esposito F. Electrical and mechanical response of skeletal muscle to electrical stimulation after acute passive stretching in humans: A combined electromyographic and mechanomyographic approach. J Sports Sci 2008; 26:1567-77. [DOI: 10.1080/02640410802277429] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Mesin L. Simulation of Surface EMG Signals for a Multilayer Volume Conductor With a Superficial Bone or Blood Vessel. IEEE Trans Biomed Eng 2008; 55:1647-57. [DOI: 10.1109/tbme.2008.919104] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hedayatpour N, Arendt-Nielsen L, Farina D. Motor unit conduction velocity during sustained contraction of the vastus medialis muscle. Exp Brain Res 2007; 180:509-16. [PMID: 17287989 DOI: 10.1007/s00221-007-0877-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Accepted: 01/10/2007] [Indexed: 10/23/2022]
Abstract
The aim of the study was to analyze motor unit conduction velocity at varying force of the vastus medialis muscle during sustained contraction. Surface (8-electrode array) and intramuscular (two wire electrodes) EMG signals were recorded from the distal part of the dominant vastus medialis muscle of ten healthy male subjects. The subjects sat on a chair with the knee 90 degrees flexed and performed seven 180-s long contractions at forces in the range 2.5-30% of the maximal voluntary contraction force. For each force level, the discharge patterns of the newly recruited motor units with respect to the previous force level were identified from the intramuscular recordings and used as trigger for averaging the surface EMG signals. Motor unit conduction velocity was estimated from the averaged surface EMG. Average discharge rate at which motor units were analyzed was the same for each force level (mean +/- SD, 8.3 +/- 0.8 pulses per second). Motor unit conduction velocity at the beginning of the contraction and its rate of change over time increased with force (P < 0.05). Conduction velocity at the beginning of the contraction estimated from the interference surface EMG (4.44 +/- 0.66 m/s) and from single motor units (4.75 +/- 0.56 m/s) were positively correlated (R (2) = 0.46; P < 0.0001) but significantly different (P < 0.05). The results indicate that single motor unit conduction velocity and its rate of change during sustained contraction, assessed at a fixed discharge rate, depend on force level.
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Affiliation(s)
- Nosratollah Hedayatpour
- Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7 D-3, 9220 Aalborg, Denmark
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Drost G, Stegeman DF, van Engelen BGM, Zwarts MJ. Clinical applications of high-density surface EMG: A systematic review. J Electromyogr Kinesiol 2006; 16:586-602. [PMID: 17085302 DOI: 10.1016/j.jelekin.2006.09.005] [Citation(s) in RCA: 189] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
High density-surface EMG (HD-sEMG) is a non-invasive technique to measure electrical muscle activity with multiple (more than two) closely spaced electrodes overlying a restricted area of the skin. Besides temporal activity HD-sEMG also allows spatial EMG activity to be recorded, thus expanding the possibilities to detect new muscle characteristics. Especially muscle fiber conduction velocity (MFCV) measurements and the evaluation of single motor unit (MU) characteristics come into view. This systematic review of the literature evaluates the clinical applications of HD-sEMG. Although beyond the scope of the present review, the search yielded a large number of "non-clinical" papers demonstrating that a considerable amount of work has been done and that significant technical progress has been made concerning the feasibility and optimization of HD-sEMG techniques. Twenty-nine clinical studies and four reviews of clinical applications of HD-sEMG were considered. The clinical studies concerned muscle fatigue, motor neuron diseases (MND), neuropathies, myopathies (mainly in patients with channelopathies), spontaneous muscle activity and MU firing rates. In principle, HD-sEMG allows pathological changes at the MU level to be detected, especially changes in neurogenic disorders and channelopathies. We additionally discuss several bioengineering aspects and future clinical applications of the technique and provide recommendations for further development and implementation of HD-sEMG as a clinical diagnostic tool.
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Affiliation(s)
- Gea Drost
- Department of Clinical Neurophysiology, Institute of Neurology, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
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Mesin L. Simulation of Surface EMG Signals for a Multilayer Volume Conductor With Triangular Model of the Muscle Tissue. IEEE Trans Biomed Eng 2006; 53:2177-84. [PMID: 17073322 DOI: 10.1109/tbme.2006.879469] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This study analytically describes surface electromyogram (sEMG) signals generated by a model of a triangular muscle, i.e., a muscle with fibers arranged in a fan shape. Examples of triangular muscles in the human body are the deltoid, the pectoralis major, the trapezius, the adductor pollicis. A model of triangular muscle is proposed. It is a sector of a cylindrical volume conductor (with the fibers directed along the radial coordinate) bounded at the muscle/fat interface. The muscle conductivity tensor reflects the fan anisotropy. Edge effects have been neglected. A solution of the nonspace invariant problem for a triangular muscle is provided in the Fourier domain. An approximate analytical solution for a two plane layer volume conductor model is obtained by introducing a homogeneous layer (modeling the fat) over the triangular muscle. The results are implemented in a complete sEMG generation model (including the finite length of the fibers), simulating single fiber action potentials. The model is not space invariant due to the changes of the volume conductor along the direction of action potential propagation. Thus the detected potentials at the skin surface change shape as they propagate. This determines problems in the extraction and interpretation of parameters. As a representative example of application of the simulation model, the influence of the inhomogeneity of the volume conductor in conduction velocity (CV) estimation is addressed (for two channels; maximum likelihood and reference point methods). Different fiber depths, electrode placements and small misalignments of the detection system with respect to the fiber have been simulated. The error in CV estimation is large when the depth of the fiber increases, when the detection system is not aligned with the fiber and close to the innervation point and to the tendons.
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Affiliation(s)
- Luca Mesin
- Laboratory for Neuromuscular System Engineering (LISiN), Dipartimento di Elettronica, Politecnico di Torino, Italy.
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Mesin L, Farina D. An analytical model for surface EMG generation in volume conductors with smooth conductivity variations. IEEE Trans Biomed Eng 2006; 53:773-9. [PMID: 16686399 DOI: 10.1109/tbme.2006.872825] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A nonspace invariant model of volume conductor for surface electromyography (EMG) signal generation is analytically investigated. The volume conductor comprises planar layers representing the muscle and subcutaneous tissues. The muscle tissue is homogeneous and anisotropic while the subcutaneous layer is inhomogeneous and isotropic. The inhomogeneity is modeled as a smooth variation in conductivity along the muscle fiber direction. This may reflect a practical situation of tissues with different conductivity properties in different locations or of transitions between tissues with different properties. The problem is studied with the regular perturbation theory, through a series expansion of the electric potential. This leads to a set of Poisson's problems, for which the source term in an equation and the boundary conditions are determined by the solution of the previous equations. This set of problems can be solved iteratively. The solution is obtained in the two-dimensional Fourier domain, with spatial angular frequencies corresponding to the longitudinal and perpendicular direction with respect to the muscle fibers, in planes parallel to the detection surface. The series expansion is truncated for the practical implementation. Representative simulations are presented. The proposed model constitutes a new approach for surface EMG signal simulation with applications related to the validation of methods for information extraction from this signal.
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Affiliation(s)
- Luca Mesin
- Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Dipartimento di Elettronica, Politecnico di Torino, 10129 Torino, Italy
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Mesin L, Joubert M, Hanekom T, Merletti R, Farina D. A Finite Element Model for Describing the Effect of Muscle Shortening on Surface EMG. IEEE Trans Biomed Eng 2006; 53:593-600. [PMID: 16602565 DOI: 10.1109/tbme.2006.870256] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A finite-element model for the generation of single fiber action potentials in a muscle undergoing various degrees of fiber shortening is developed. The muscle is assumed fusiform with muscle fibers following a curvilinear path described by a Gaussian function. Different degrees of fiber shortening are simulated by changing the parameters of the fiber path and maintaining the volume of the muscle constant. The conductivity tensor is adapted to the muscle fiber orientation. In each point of the volume conductor, the conductivity of the muscle tissue in the direction of the fiber is larger than that in the transversal direction. Thus, the conductivity tensor changes point-by-point with fiber shortening, adapting to the fiber paths. An analytical derivation of the conductivity tensor is provided. The volume conductor is then studied with a finite-element approach using the analytically derived conductivity tensor. Representative simulations of single fiber action potentials with the muscle at different degrees of shortening are presented. It is shown that the geometrical changes in the muscle, which imply changes in the conductivity tensor, determine important variations in action potential shape, thus affecting its amplitude and frequency content. The model provides a new tool for interpreting surface EMG signal features with changes in muscle geometry, as it happens during dynamic contractions.
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Affiliation(s)
- Luca Mesin
- Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Dipartimento di Elettronica, Politecnico di Torino, 10129 Torino, Italy
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