151
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Muddle TWD, Colquhoun RJ, Magrini MA, Luera MJ, DeFreitas JM, Jenkins NDM. Effects of fatiguing, submaximal high- versus low-torque isometric exercise on motor unit recruitment and firing behavior. Physiol Rep 2018; 6:e13675. [PMID: 29673119 PMCID: PMC5907942 DOI: 10.14814/phy2.13675] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 03/02/2018] [Indexed: 12/04/2022] Open
Abstract
The purpose of this investigation was to evaluate the effects of repeated, high- (HT: 70% MVIC) versus low-torque (LT: 30% MVIC) isometric exercise performed to failure on motor unit (MU) recruitment and firing behavior of the vastus lateralis. Eighteen resistance-trained males (23.1 ± 3.8 years) completed familiarization, followed by separate experimental sessions in which they completed either HT or LT exercise to failure in random order. LT exercise resulted in a greater time to task failure and a more dramatic decline in the muscle's force capacity, but the total work completed was similar for HT and LT exercise. An examination of the firing trains from 4670 MUs recorded during exercise revealed that firing rates generally increased during HT and LT exercise, but were higher during HT than LT exercise. Furthermore, recruitment thresholds (RT) did not significantly change during HT exercise, whereas the RT of the smallest MUs increased and the RT for the moderate to large MUs decreased during LT exercise. Both HT and LT exercise resulted in the recruitment of additional higher threshold MUs in order to maintain torque production. However, throughout exercise, HT required the recruitment of larger MUs than did LT exercise. In a few cases, however, MUs were recruited by individuals during LT exercise that were similar in size and original (pre) RT to those detected during HT exercise. Thus, the ability to achieve full MU recruitment during LT exercise may be dependent on the subject. Consequently, our data emphasize the task and subject dependency of muscle fatigue.
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Affiliation(s)
- Tyler W. D. Muddle
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
| | - Ryan J. Colquhoun
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
| | - Mitchel A. Magrini
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
| | - Micheal J. Luera
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
| | - Jason M. DeFreitas
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
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152
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Contessa P, Letizi J, De Luca G, Kline JC. Contribution from motor unit firing adaptations and muscle coactivation during fatigue. J Neurophysiol 2018. [PMID: 29537913 DOI: 10.1152/jn.00766.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The control of motor unit firing behavior during fatigue is still debated in the literature. Most studies agree that the central nervous system increases the excitation to the motoneuron pool to compensate for decreased force contributions of individual motor units and sustain muscle force output during fatigue. However, some studies claim that motor units may decrease their firing rates despite increased excitation, contradicting the direct relationship between firing rates and excitation that governs the voluntary control of motor units. To investigate whether the control of motor units in fact changes with fatigue, we measured motor unit firing behavior during repeated contractions of the first dorsal interosseous (FDI) muscle while concurrently monitoring the activation of surrounding muscles, including the flexor carpi radialis, extensor carpi radialis, and pronator teres. Across all subjects, we observed an overall increase in FDI activation and motor unit firing rates by the end of the fatigue task. However, in some subjects we observed increases in FDI activation and motor unit firing rates only during the initial phase of the fatigue task, followed by subsequent decreases during the late phase of the fatigue task while the coactivation of surrounding muscles increased. These findings indicate that the strategy for sustaining force output may occasionally change, leading to increases in the relative activation of surrounding muscles while the excitation to the fatiguing muscle decreases. Importantly, irrespective of changes in the strategy for sustaining force output, the control properties regulating motor unit firing behavior remain unchanged during fatigue. NEW & NOTEWORTHY This work addresses sources of debate surrounding the manner in which motor unit firing behavior is controlled during fatigue. We found that decreases in the motor unit firing rates of the fatiguing muscle may occasionally be observed when the contribution of coactive muscles increases. Despite changes in the strategy employed to sustain the force output, the underlying control properties regulating motor unit firing behavior remain unchanged during muscle fatigue.
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Affiliation(s)
| | - John Letizi
- Delsys and Altec Inc. , Natick, Massachusetts
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153
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Colquhoun RJ, Magrini MA, Haun CT, Muddle TWD, Tomko PM, Luera MJ, Mackey CS, Vann CG, Martin JS, Young KC, DeFreitas JM, Roberts MD, Jenkins NDM. Muscle phenotype is related to motor unit behavior of the vastus lateralis during maximal isometric contractions. Physiol Rep 2018. [PMID: 29527830 PMCID: PMC5845862 DOI: 10.14814/phy2.13636] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Previous investigations have reported a relationship between skeletal muscle phenotype and motor unit (MU) firing parameters during submaximal contractions. The purpose of the current investigation, however, was to examine the relationships between motor unit firing behavior during a maximal voluntary contraction, Myosin Heavy Chain (MHC) isoform content, and various molecular neuromuscular targets of the vastus lateralis (VL) muscle in resistance-trained men. Ten resistance-trained males completed a trapezoidal ramp contraction up to 100% of their maximal voluntary isometric strength (MVIC). Surface electromyography was recorded from the VL using a multichannel electrode array and decomposed to examine the firing characteristics of individual MUs. A skeletal muscle biopsy of the VL was also collected from each subject. Regression analyses were performed to identify relationships between type II fiber area and the slopes and/or intercepts of the mean firing rate (FRMEAN ) versus recruitment threshold (RT), max firing rate (FRMAX ) versus RT, and RT versus MU action potential amplitude (MUAPPP ) relationships. There were significant inverse relationships between type II fiber area and the y-intercept of the FR versus RT relationship (P < 0.05). Additionally, strong relationships (r > 0.5) were found between type II fiber area and FRMEAN versus RT slope and RT versus MUAPPP slope and intercept. These data further support the hypothesis that skeletal muscle phenotype is related to MU behavior during isometric contraction. However, our data, in concert with previous investigations, may suggest that these relationships are influenced by the intensity of the contraction.
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Affiliation(s)
- Ryan J Colquhoun
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Mitchel A Magrini
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Cody T Haun
- Molecular and Applied Sciences Laboratory, Auburn University, Auburn, Alabama
| | - Tyler W D Muddle
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Patrick M Tomko
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Micheal J Luera
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Cameron S Mackey
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Christopher G Vann
- Molecular and Applied Sciences Laboratory, Auburn University, Auburn, Alabama
| | - Jeffrey S Martin
- Department of Cell Biology and Physiology, Edward Via College of Osteopathic Medicine - Auburn Campus, Auburn, Alabama
| | - Kaelin C Young
- Department of Cell Biology and Physiology, Edward Via College of Osteopathic Medicine - Auburn Campus, Auburn, Alabama
| | - Jason M DeFreitas
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Michael D Roberts
- Molecular and Applied Sciences Laboratory, Auburn University, Auburn, Alabama
| | - Nathaniel D M Jenkins
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
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154
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Sterczala AJ, Miller JD, Trevino MA, Dimmick HL, Herda TJ. Differences in the motor unit firing rates and amplitudes in relation to recruitment thresholds during submaximal contractions of the first dorsal interosseous between chronically resistance-trained and physically active men. Appl Physiol Nutr Metab 2018; 43:759-768. [PMID: 29481763 DOI: 10.1139/apnm-2017-0646] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous investigations report no changes in motor unit (MU) firing rates during submaximal contractions following resistance training. These investigations did not account for MU recruitment or examine firing rates as a function of recruitment threshold (REC). Therefore, MU recruitment and firing rates in chronically resistance-trained (RT) and physically active controls (CON) were examined. Surface electromyography signals were collected from the first dorsal interosseous during isometric muscle actions at 40% and 70% maximal voluntary contraction (MVC). For each MU, force at REC, mean firing rate (MFR) during the steady force, and MU action potential amplitude (MUAPAMP) were analyzed. For each individual and contraction, the MFRs were linearly regressed against REC, whereas, exponential models were applied to the MFR versus MUAPAMP and MUAPAMP versus REC relationships with the y-intercepts and slopes (linear) and A and B terms (exponential) calculated. For the 40% MVC, the RT had less negative slopes (p = 0.001) and lower y-intercepts (p = 0.006) of the MFR versus REC relationships and lower B terms (p = 0.011) of the MUAPAMP versus REC relationships. There were no differences in either relationship between groups for the 70% MVC. During the 40% MVC, the RT had a smaller range of MFRs and MUAPAMPS in comparison with the CON, likely because of reduced MU recruitment. The RT had lower MFRs and recruitment during the 40% MVC, which may indicate a leftward shift in the force-frequency relationship, and thus require less excitation to the motoneuron pool to match the same relative force.
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Affiliation(s)
- Adam J Sterczala
- a Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66045, USA
| | - Jonathan D Miller
- a Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66045, USA
| | - Michael A Trevino
- b Department of Health Sciences, Armstrong State University, Savannah, GA 31419, USA
| | - Hannah L Dimmick
- a Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66045, USA
| | - Trent J Herda
- a Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66045, USA
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155
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Ren X, Zhang C, Li X, Yang G, Potter T, Zhang Y. Intramuscular EMG Decomposition Basing on Motor Unit Action Potentials Detection and Superposition Resolution. Front Neurol 2018; 9:2. [PMID: 29410646 PMCID: PMC5787143 DOI: 10.3389/fneur.2018.00002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 01/03/2018] [Indexed: 11/15/2022] Open
Abstract
A novel electromyography (EMG) signal decomposition framework is presented for the thorough and precise analysis of intramuscular EMG signals. This framework first detects all of the active motor unit action potentials (MUAPs) and assigns single MUAP segments to their corresponding motor units. MUAP waveforms that are found to be superimposed are then resolved into their constituent single MUAPs using a peel-off approach and similarly assigned. The method is composed of six stages of analytical procedures: preprocessing, segmentation, alignment and feature extraction, clustering and refinement, supervised classification, and superimposed waveform resolution. The performance of the proposed decomposition framework was evaluated using both synthetic EMG signals and real recordings obtained from healthy and stroke participants. The overall detection rate of MUAPs was 100% for both synthetic and real signals. The average accuracy for synthetic EMG signals was 87.23%. Average assignment accuracies of 88.63 and 94.45% were achieved for the real EMG signals obtained from healthy and stroke participants, respectively. Results demonstrated the ability of the developed framework to decompose intramuscular EMG signals with improved accuracy and efficiency, which we believe will greatly benefit the clinical utility of EMG for the diagnosis and rehabilitation of motor impairments in stroke patients.
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Affiliation(s)
- Xiaomei Ren
- School of Electrical Engineering and Information, Sichuan University, Chengdu, China
| | - Chuan Zhang
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States.,Guangdong Provincial Work Injury Rehabilitation Hospital, Guangzhou, China
| | - Xuhong Li
- The Third Xiangya Hospital, Central South University, Changsha, China
| | - Gang Yang
- School of Electrical Engineering and Information, Sichuan University, Chengdu, China
| | - Thomas Potter
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Yingchun Zhang
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States.,Guangdong Provincial Work Injury Rehabilitation Hospital, Guangzhou, China
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156
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Tieland M, Trouwborst I, Clark BC. Skeletal muscle performance and ageing. J Cachexia Sarcopenia Muscle 2018; 9:3-19. [PMID: 29151281 PMCID: PMC5803609 DOI: 10.1002/jcsm.12238] [Citation(s) in RCA: 441] [Impact Index Per Article: 73.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 07/20/2017] [Accepted: 08/05/2017] [Indexed: 02/06/2023] Open
Abstract
The world population is ageing rapidly. As society ages, the incidence of physical limitations is dramatically increasing, which reduces the quality of life and increases healthcare expenditures. In western society, ~30% of the population over 55 years is confronted with moderate or severe physical limitations. These physical limitations increase the risk of falls, institutionalization, co-morbidity, and premature death. An important cause of physical limitations is the age-related loss of skeletal muscle mass, also referred to as sarcopenia. Emerging evidence, however, clearly shows that the decline in skeletal muscle mass is not the sole contributor to the decline in physical performance. For instance, the loss of muscle strength is also a strong contributor to reduced physical performance in the elderly. In addition, there is ample data to suggest that motor coordination, excitation-contraction coupling, skeletal integrity, and other factors related to the nervous, muscular, and skeletal systems are critically important for physical performance in the elderly. To better understand the loss of skeletal muscle performance with ageing, we aim to provide a broad overview on the underlying mechanisms associated with elderly skeletal muscle performance. We start with a system level discussion and continue with a discussion on the influence of lifestyle, biological, and psychosocial factors on elderly skeletal muscle performance. Developing a broad understanding of the many factors affecting elderly skeletal muscle performance has major implications for scientists, clinicians, and health professionals who are developing therapeutic interventions aiming to enhance muscle function and/or prevent mobility and physical limitations and, as such, support healthy ageing.
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Affiliation(s)
- Michael Tieland
- Faculty of Sports and NutritionAmsterdam University of Applied SciencesDr. Meurerlaan 81067 SMAmsterdamthe Netherlands
| | - Inez Trouwborst
- Faculty of Sports and NutritionAmsterdam University of Applied SciencesDr. Meurerlaan 81067 SMAmsterdamthe Netherlands
| | - Brian C. Clark
- Ohio Musculoskeletal and Neurological Institute (OMNI)Ohio University250 Irvine HallAthensOH 45701USA
- Department of Biomedical SciencesOhio UniversityAthensOH 45701USA
- Department of Geriatric MedicineOhio UniversityAthensOH 45701USA
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157
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Kapelner T, Negro F, Aszmann OC, Farina D. Decoding Motor Unit Activity From Forearm Muscles: Perspectives for Myoelectric Control. IEEE Trans Neural Syst Rehabil Eng 2018; 26:244-251. [DOI: 10.1109/tnsre.2017.2766360] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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158
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The effects of local forearm muscle cooling on motor unit properties. Eur J Appl Physiol 2017; 118:401-410. [DOI: 10.1007/s00421-017-3782-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 12/03/2017] [Indexed: 10/18/2022]
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159
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Hight RE, Beck TW, Bemben DA, Black CD. Adaptations in antagonist co-activation: Role in the repeated-bout effect. PLoS One 2017; 12:e0189323. [PMID: 29216288 PMCID: PMC5720767 DOI: 10.1371/journal.pone.0189323] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 11/22/2017] [Indexed: 11/23/2022] Open
Abstract
Eccentric exercise results in an adaptation which attenuates muscle damage from subsequent exercise—termed the “repeated-bout effect (RBE).” Purpose: Study examined antagonist co-activation and motor-unit recruitment strategy, assessed via dEMG, concomitant to the RBE. Methods: Nine participants performed 5 sub-maximal isometric trapezoid (ramp-up, hold, ramp-down) contractions at force levels corresponding to 50% and 80% of maximal isometric strength (MVC). Surface EMG signals of the biceps brachii were decomposed into individual motor-unit action potential trains. The relationship between mean firing rate (MFR) of each motor-unit and its recruitment threshold (RT) was examined using linear regression. Eccentric exercise was then performed until biceps brachii MVC had decreased by ~40%. Surface EMG of the biceps and triceps were collected during eccentric exercise. MVC, range-of-motion (ROM), and delayed onset muscle soreness (DOMS) were measured 24-hours, 72-hours, and 1-week following eccentric exercise. Three weeks later all procedures were repeated. Results: Changes in MVC (-32±14% vs -25±10%; p = 0.034), ROM (-11% vs 6%; p = 0.01), and DOMS (31.0±19mm vs 19±12mm; p = 0.015) were attenuated following the second bout of exercise. Triceps EMG was reduced (16.8±9.5% vs. 12.6±7.2%; p = 0.03) during the second bout of eccentric exercise. The slope (-0.60±0.13 vs -0.70±0.18; p = 0.029) and y-intercept (46.5±8.3 vs 53.3±8.8; p = 0.020) of the MFR vs. RT relationship was altered during contractions at 80% of MVC prior to the second bout of eccentric exercise. No changes were observed at 50% of MVC. Conclusion: A reduction in antagonist co-activation during the second bout of eccentric exercise suggests less total force was required to move an identical external load. This finding is supported by the increased negative slope coefficient and an increased y-intercept of the linear relationship between RT and MFR.
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Affiliation(s)
- Robert E. Hight
- Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma, United States of America
| | - Travis W. Beck
- Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma, United States of America
| | - Debra A. Bemben
- Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma, United States of America
| | - Christopher D. Black
- Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma, United States of America
- * E-mail:
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160
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McManus L, Hu X, Rymer WZ, Suresh NL, Lowery MM. Motor Unit Activity during Fatiguing Isometric Muscle Contraction in Hemispheric Stroke Survivors. Front Hum Neurosci 2017; 11:569. [PMID: 29225574 PMCID: PMC5705653 DOI: 10.3389/fnhum.2017.00569] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 11/09/2017] [Indexed: 12/03/2022] Open
Abstract
Enhanced muscle weakness is commonly experienced following stroke and may be accompanied by increased susceptibility to fatigue. To examine the contributions of central and peripheral factors to isometric muscle fatigue in stroke survivors, this study investigates changes in motor unit (MU) mean firing rate, and action potential duration during, and directly following, a sustained submaximal fatiguing contraction at 30% maximum voluntary contraction (MVC). A series of short contractions of the first dorsal interosseous muscle were performed pre- and post-fatigue at 20% MVC, and again following a 10-min recovery period, by 12 chronic stroke survivors. Individual MU firing times were extracted using surface EMG decomposition and used to obtain the spike-triggered average MU action potential waveforms. During the sustained fatiguing contraction, the mean rate of change in firing rate across all detected MUs was greater on the affected side (-0.02 ± 0.03 Hz/s) than on the less-affected side (-0.004 ± 0.003 Hz/s, p = 0.045). The change in firing rate immediately post-fatigue was also greater on the affected side than less-affected side (-13.5 ± 20 and 0.1 ± 19%, p = 0.04). Mean MU firing rates increased following the recovery period on the less-affected side when compared to the affected side (19.3 ± 17 and 0.5 ± 20%, respectively, p = 0.03). MU action potential duration increased post-fatigue on both sides (10.3 ± 1.2 to 11.2 ± 1.3 ms on the affected side and 9.9 ± 1.7 to 11.2 ± 1.9 ms on the less-affected side, p = 0.001 and p = 0.02, respectively), and changes in action potential duration tended to be smaller in subjects with greater impairment (p = 0.04). This study presents evidence of both central and peripheral fatigue at the MU level during isometric fatiguing contraction for the first time in stroke survivors. Together, these preliminary observations indicate that the response to an isometric fatiguing contraction differs between the affected and less-affected side post-stroke, and may suggest that central mechanisms observed here as changes in firing rate are the dominant processes leading to task failure on the affected side.
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Affiliation(s)
- Lara McManus
- Neuromuscular Systems Lab, School of Electrical and Electronic Engineering, University College Dublin, Belfield, Ireland
| | - Xiaogang Hu
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, United States
| | - William Z Rymer
- Shirley Ryan AbilityLab, Chicago, IL, United States.,Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, United States
| | - Nina L Suresh
- Shirley Ryan AbilityLab, Chicago, IL, United States.,Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, United States
| | - Madeleine M Lowery
- Neuromuscular Systems Lab, School of Electrical and Electronic Engineering, University College Dublin, Belfield, Ireland
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161
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Chen YC, Lin LL, Lin YT, Hu CL, Hwang IS. Variations in Static Force Control and Motor Unit Behavior with Error Amplification Feedback in the Elderly. Front Hum Neurosci 2017; 11:538. [PMID: 29167637 PMCID: PMC5682334 DOI: 10.3389/fnhum.2017.00538] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/23/2017] [Indexed: 11/13/2022] Open
Abstract
Error amplification (EA) feedback is a promising approach to advance visuomotor skill. As error detection and visuomotor processing at short time scales decline with age, this study examined whether older adults could benefit from EA feedback that included higher-frequency information to guide a force-tracking task. Fourteen young and 14 older adults performed low-level static isometric force-tracking with visual guidance of typical visual feedback and EA feedback containing augmented high-frequency errors. Stabilogram diffusion analysis was used to characterize force fluctuation dynamics. Also, the discharge behaviors of motor units and pooled motor unit coherence were assessed following the decomposition of multi-channel surface electromyography (EMG). EA produced different behavioral and neurophysiological impacts on young and older adults. Older adults exhibited inferior task accuracy with EA feedback than with typical visual feedback, but not young adults. Although stabilogram diffusion analysis revealed that EA led to a significant decrease in critical time points for both groups, EA potentiated the critical point of force fluctuations [Formula: see text], short-term effective diffusion coefficients (Ds), and short-term exponent scaling only for the older adults. Moreover, in older adults, EA added to the size of discharge variability of motor units and discharge regularity of cumulative discharge rate, but suppressed the pooled motor unit coherence in the 13-35 Hz band. Virtual EA alters the strategic balance between open-loop and closed-loop controls for force-tracking. Contrary to expectations, the prevailing use of closed-loop control with EA that contained high-frequency error information enhanced the motor unit discharge variability and undermined the force steadiness in the older group, concerning declines in physiological complexity in the neurobehavioral system and the common drive to the motoneuronal pool against force destabilization.
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Affiliation(s)
- Yi-Ching Chen
- Department of Physical Therapy, College of Medical Science and Technology, Chung Shan Medical University, Taichung City, Taiwan.,Physical Therapy Room, Chung Shan Medical University Hospital, Taichung City, Taiwan
| | - Linda L Lin
- Institute of Physical Education, Health and Leisure Studies, National Cheng Kung University, Tainan City, Taiwan
| | - Yen-Ting Lin
- Physical Education Office, Asian University, Taichung City, Taiwan
| | - Chia-Ling Hu
- Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
| | - Ing-Shiou Hwang
- Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan City, Taiwan.,Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
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162
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Origins of Common Neural Inputs to Different Compartments of the Extensor Digitorum Communis Muscle. Sci Rep 2017; 7:13960. [PMID: 29066852 PMCID: PMC5654835 DOI: 10.1038/s41598-017-14555-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 10/12/2017] [Indexed: 11/25/2022] Open
Abstract
The extensor digitorum communis (EDC) is a multi-compartment muscle that allows dexterous extension of the four digits. However, the level of common input shared across different compartments of this muscle is not well understood. We seek to systematically characterize the common and independent neural input, originated from different levels of the central nervous system, to the different compartments. A motor unit (MU) coherence analysis was used to capture the different sources of common and independent input, by quantifying the coherence of MU discharge between different compartments. The MU activities were obtained from decomposition of surface electromyogram recordings. Our results showed that the MU coherence across different muscle compartments accounted for only a small proportion (<20%) of the total input in the alpha (5–12 Hz) and beta (15–30 Hz) bands, but was a major driver (>60%) in the delta (1–4 Hz) band. Additionally, cross-compartment coherence between the middle and ring-little fingers tended to be higher as compared with other finger combinations. Overall, the common input shared across different fingers are found to be at low to moderate levels, in comparison with the total input, which allows dexterous control of individual digits with some degree of coordinated control of multiple digits.
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163
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Petersen E, Buchner H, Eger M, Rostalski P. Convolutive blind source separation of surface EMG measurements of the respiratory muscles. ACTA ACUST UNITED AC 2017; 62:171-181. [PMID: 28076295 DOI: 10.1515/bmt-2016-0092] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 11/28/2016] [Indexed: 11/15/2022]
Abstract
Electromyography (EMG) has long been used for the assessment of muscle function and activity and has recently been applied to the control of medical ventilation. For this application, the EMG signal is usually recorded invasively by means of electrodes on a nasogastric tube which is placed inside the esophagus in order to minimize noise and crosstalk from other muscles. Replacing these invasive measurements with an EMG signal obtained non-invasively on the body surface is difficult and requires techniques for signal separation in order to reconstruct the contributions of the individual respiratory muscles. In the case of muscles with small cross-sectional areas, or with muscles at large distances from the recording site, solutions to this problem have been proposed previously. The respiratory muscles, however, are large and distributed widely over the upper body volume. In this article, we describe an algorithm for convolutive blind source separation (BSS) that performs well even for large, distributed muscles such as the respiratory muscles, while using only a small number of electrodes. The algorithm is derived as a special case of the TRINICON general framework for BSS. To provide evidence that it shows potential for separating inspiratory, expiratory, and cardiac activities in practical applications, a joint numerical simulation of EMG and ECG activities was performed, and separation success was evaluated in a variety of noise settings. The results are promising.
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Affiliation(s)
- Eike Petersen
- Institute for Electrical Engineering in Medicine, University of Lübeck
| | - Herbert Buchner
- University of Cambridge, Department of Engineering, Cambridge
| | | | - Philipp Rostalski
- Institute for Electrical Engineering in Medicine, University of Lübeck
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164
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Stock MS, Mota JA. Shifts in the relationship between motor unit recruitment thresholds versus derecruitment thresholds during fatigue. Med Eng Phys 2017; 50:35-42. [PMID: 28918955 DOI: 10.1016/j.medengphy.2017.08.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 08/13/2017] [Accepted: 08/28/2017] [Indexed: 11/29/2022]
Abstract
Muscle fatigue is associated with diminished twitch force amplitude. We examined changes in the motor unit recruitment versus derecruitment threshold relationship during fatigue. Nine men (mean age = 26 years) performed repeated isometric contractions at 50% maximal voluntary contraction (MVC) knee extensor force until exhaustion. Surface electromyographic signals were detected from the vastus lateralis, and were decomposed into their constituent motor unit action potential trains. Motor unit recruitment and derecruitment thresholds and firing rates at recruitment and derecruitment were evaluated at the beginning, middle, and end of the protocol. On average, 15 motor units were studied per contraction. For the initial contraction, three subjects showed greater recruitment thresholds than derecruitment thresholds for all motor units. Five subjects showed greater recruitment thresholds than derecruitment thresholds for only low-threshold motor units at the beginning, with a mean cross-over of 31.6% MVC. As the muscle fatigued, many motor units were derecruited at progressively higher forces. In turn, decreased slopes and increased y-intercepts were observed. These shifts were complemented by increased firing rates at derecruitment relative to recruitment. As the vastus lateralis fatigued, the central nervous system's compensatory adjustments resulted in a shift of the regression line of the recruitment versus derecruitment threshold relationship.
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Affiliation(s)
- Matt S Stock
- Applied Physiology Laboratory, Doctor of Physical Therapy Program, Department of Health Professions, University of Central Florida, Health and Public Affairs Bldg I, Room 258, 4364 Scorpius Street, Orlando, FL, USA.
| | - Jacob A Mota
- Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, NC, USA
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165
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Lei Y, Suresh NL, Rymer WZ, Hu X. Organization of the motor-unit pool for different directions of isometric contraction of the first dorsal interosseous muscle. Muscle Nerve 2017; 57:E85-E93. [PMID: 28877550 DOI: 10.1002/mus.25963] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/02/2017] [Indexed: 11/08/2022]
Abstract
INTRODUCTION Muscle force generation involves recruitment and firing rate modulation of motor units (MUs). The control of MUs in producing multidirectional forces remains unclear. METHODS We studied MU recruitment and firing properties, recorded from the first dorsal interosseous muscle, for 3 different directions of contraction: abduction; abduction/flexion combination; and flexion. RESULTS MUs were recruited systematically at higher threshold force during flexion. Larger MUs were recruited and firing rates of MUs were lower during abduction. There was an orderly recruitment of MUs according to MU size regardless of contraction direction, obeying the "size principle." Firing rates of earlier-recruited MUs were consistently higher than later-recruited MUs, affirming the "onion-skin" property. DISCUSSION Our findings suggest that the size principle and onion-skin organization together provide a general description of MU recruitment patterns and firing properties. The directional alternations of MU control properties likely reflect changes in neural drive to the muscle. Muscle Nerve 57: E85-E93, 2018.
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Affiliation(s)
- Yuming Lei
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami, 1095 NW 14th Terrace #48, Miami, Florida 33136, USA
| | - Nina L Suresh
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois, USA
| | - William Z Rymer
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois, USA
| | - Xiaogang Hu
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, USA
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166
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Khurram OU, Sieck GC, Mantilla CB. Compensatory effects following unilateral diaphragm paralysis. Respir Physiol Neurobiol 2017; 246:39-46. [PMID: 28790008 DOI: 10.1016/j.resp.2017.07.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 07/11/2017] [Accepted: 07/11/2017] [Indexed: 11/18/2022]
Abstract
Injury to nerves innervating respiratory muscles such as the diaphragm muscle results in significant respiratory compromise. Electromyography (EMG) and transdiaphragmatic pressure (Pdi) measurements reflect diaphragm activation and force generation. Immediately after unilateral diaphragm denervation (DNV), ventilatory behaviors can be accomplished without impairment, but Pdi generated during higher force non-ventilatory behaviors is significantly decreased. We hypothesized that 1) the initial reduction in Pdi during higher force behaviors after DNV is ameliorated after 14 days, and 2) changes in Pdi over time after DNV are associated with concordant changes in contralateral diaphragm EMG activity and ventilatory parameters. In adult male rats, the reduced Pdi during occlusion (∼40% immediately after DNV) was ameliorated to ∼20% reduction after 14 days. Contralateral diaphragm EMG activity did not significantly change immediately or 14days after DNV compared to the pre-injury baseline for any motor behavior. Taken together, these results suggest that over time after DNV compensatory changes in inspiratory related muscle activation may partially restore the ability to generate Pdi during higher force behaviors.
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Affiliation(s)
- Obaid U Khurram
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States
| | - Gary C Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States; Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN 55905, United States
| | - Carlos B Mantilla
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States; Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN 55905, United States.
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167
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Sterczala AJ, Herda TJ, Miller JD, Ciccone AB, Trevino MA. Age-related differences in the motor unit action potential size in relation to recruitment threshold. Clin Physiol Funct Imaging 2017; 38:610-616. [PMID: 28737276 DOI: 10.1111/cpf.12453] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 06/15/2017] [Indexed: 11/27/2022]
Abstract
Motor unit action potential size (MUAPsize ) versus recruitment threshold (RT) relationship analysis provides a non-invasive measure of motor unit (MU) hypertrophy; however, this method's ability to identify MU atrophy is unknown. This investigation sought to determine if MUAPsize versus RT relationship slope (APslope ) comparison could identify evidence of MU atrophy in older individuals. Surface electromyography signals were recorded from the first dorsal interosseous (FDI) of fourteen young (YG, age = 22·29 ± 2·79 years) and ten older (OG, 61·0 ± 2·0 years) subjects during a 50% maximal voluntary contraction (MVC) isometric trapezoidal muscle action. The signals were decomposed to yield a MUAPsize and RT for each MU. For each subject, the MUs recruited between 10% and 50% MVC were linearly regressed as a function of RT to calculate an individual APslope . FDI cross-sectional area (CSA) and echo intensity (EI) were quantified via ultrasonography. The mean APslope was lower for OG (0·033 ± 0·010 mV %MVC-1 ) than YG (0·056 ± 0·019 mV %MVC-1 ). OG and YG possessed similar CSAs (OG: 2·09 ± 0·31 cm2 ; YG: 2·08 ± 0·41 cm2 ); however, OG (53·25 ± 7·56 AU) had greater EI than YG (43·87 ± 7·59 AU). The lower OG mean APslope was due to smaller MUAPsizes of higher-threshold MUs, likely due to atrophy of muscle fibres that comprise those MUs. In support, similar CSA with greater EI indicated increased adipose and fibrous tissue and reduced contractile tissue in OG. Thus, MUAPsize versus RT relationship may provide a non-invasive measure of MU atrophy.
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Affiliation(s)
- Adam J Sterczala
- Neuromechanics Laboratory, University of Kansas, Lawrence, KS, USA
| | - Trent J Herda
- Neuromechanics Laboratory, University of Kansas, Lawrence, KS, USA
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168
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Miller JD, Herda TJ, Trevino MA, Sterczala AJ, Ciccone AB. Time-related changes in firing rates are influenced by recruitment threshold and twitch force potentiation in the first dorsal interosseous. Exp Physiol 2017; 102:950-961. [PMID: 28544046 DOI: 10.1113/ep086262] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 05/18/2017] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? The influences of motor unit recruitment threshold and twitch force potentiation on the changes in firing rates during steady-force muscular contractions are not well understood. What is the main finding and its importance? The behaviour of motor units during steady force was influenced by recruitment threshold, such that firing rates decreased for lower-threshold motor units but increased for higher-threshold motor units. In addition, individuals with greater changes in firing rates possessed greater twitch force potentiation. There are contradictory reports regarding changes in motor unit firing rates during steady-force contractions. Inconsistencies are likely to be the result of previous studies disregarding motor unit recruitment thresholds and not examining firing rates on a subject-by-subject basis. It is hypothesized that firing rates are manipulated by twitch force potentiation during contractions. Therefore, in this study we examined time-related changes in firing rates at steady force in relationship to motor unit recruitment threshold in the first dorsal interosseous and the influence of twitch force potentiation on such changes in young versus aged individuals. Subjects performed a 12 s steady-force contraction at 50% maximal voluntary contraction, with evoked twitches before and after the contraction to quantify potentiation. Firing rates, in relationship to recruitment thresholds, were determined at the beginning, middle and end of the steady force. There were no firing rate changes for aged individuals. For the young, firing rates decreased slightly for lower-threshold motor units but increased for higher-threshold motor units. Twitch force potentiation was greater for young than aged subjects, and changes in firing rates were correlated with twitch force potentiation. Thus, individuals with greater increases in firing rates of higher-threshold motor units and decreases in lower-threshold motor units possessed greater twitch force potentiation. Overall, changes in firing rates during brief steady-force contractions are dependent on recruitment threshold and explained in part by twitch force potentiation. Given that firing rate changes were measured in relationship to recruitment threshold, this study illustrates a more complete view of firing rate changes during steady-force contractions.
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Affiliation(s)
- Jonathan D Miller
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS, 66044, USA
| | - Trent J Herda
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS, 66044, USA
| | - Michael A Trevino
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS, 66044, USA
| | - Adam J Sterczala
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS, 66044, USA
| | - Anthony B Ciccone
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS, 66044, USA
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169
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Potvin JR, Fuglevand AJ. A motor unit-based model of muscle fatigue. PLoS Comput Biol 2017; 13:e1005581. [PMID: 28574981 PMCID: PMC5473583 DOI: 10.1371/journal.pcbi.1005581] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 06/16/2017] [Accepted: 05/15/2017] [Indexed: 11/18/2022] Open
Abstract
Muscle fatigue is a temporary decline in the force and power capacity of skeletal muscle resulting from muscle activity. Because control of muscle is realized at the level of the motor unit (MU), it seems important to consider the physiological properties of motor units when attempting to understand and predict muscle fatigue. Therefore, we developed a phenomenological model of motor unit fatigue as a tractable means to predict muscle fatigue for a variety of tasks and to illustrate the individual contractile responses of MUs whose collective action determines the trajectory of changes in muscle force capacity during prolonged activity. An existing MU population model was used to simulate MU firing rates and isometric muscle forces and, to that model, we added fatigue-related changes in MU force, contraction time, and firing rate associated with sustained voluntary contractions. The model accurately estimated endurance times for sustained isometric contractions across a wide range of target levels. In addition, simulations were run for situations that have little experimental precedent to demonstrate the potential utility of the model to predict motor unit fatigue for more complicated, real-world applications. Moreover, the model provided insight into the complex orchestration of MU force contributions during fatigue, that would be unattainable with current experimental approaches.
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Affiliation(s)
- Jim R. Potvin
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
- * E-mail:
| | - Andrew J. Fuglevand
- Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona, United States of America
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170
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Dai C, Suresh NL, Suresh AK, Rymer WZ, Hu X. Altered Motor Unit Discharge Coherence in Paretic Muscles of Stroke Survivors. Front Neurol 2017; 8:202. [PMID: 28555126 PMCID: PMC5430034 DOI: 10.3389/fneur.2017.00202] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 04/25/2017] [Indexed: 11/24/2022] Open
Abstract
After a cerebral stroke, a series of changes at the supraspinal and spinal nervous system can alter the control of muscle activation, leading to persistent motor impairment. However, the relative contribution of these different levels of the nervous system to impaired muscle activation is not well understood. The coherence of motor unit (MU) spike trains is considered to partly reflect activities of higher level control, with different frequency band representing different levels of control. Accordingly, the objective of this study was to quantify the different sources of contribution to altered muscle activation. We examined the coherence of MU spike trains decomposed from surface electromyogram (sEMG) of the first dorsal interosseous muscle on both paretic and contralateral sides of 14 hemispheric stroke survivors. sEMG was obtained over a range of force contraction levels at 40, 50, and 60% of maximum voluntary contraction. Our results showed that MU coherence increased significantly in delta (1–4 Hz), alpha (8–12 Hz), and beta (15–30 Hz) bands on the affected side compared with the contralateral side, but was maintained at the same level in the gamma (30–60 Hz) band. In addition, no significant alteration was observed across medium–high force levels (40–60%). These results indicated that the common synaptic input to motor neurons increased on the paretic side, and the increased common input can originate from changes at multiple levels, including spinal and supraspinal levels following a stroke. All these changes can contribute to impaired activation of affected muscles in stroke survivors. Our findings also provide evidence regarding the different origins of impaired muscle activation poststroke.
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Affiliation(s)
- Chenyun Dai
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Raleigh, NC, USA
| | - Nina L Suresh
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Aneesha K Suresh
- Committee on Computational Neuroscience, University of Chicago, Chicago, IL, USA
| | - William Zev Rymer
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Xiaogang Hu
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Raleigh, NC, USA
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171
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Marco G, Alberto B, Taian V. Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue. Physiol Meas 2017; 38:R27-R60. [DOI: 10.1088/1361-6579/aa60b9] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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172
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Chen YC, Lin YT, Chang GC, Hwang IS. Paradigm Shifts in Voluntary Force Control and Motor Unit Behaviors with the Manipulated Size of Visual Error Perception. Front Physiol 2017; 8:140. [PMID: 28348530 PMCID: PMC5346555 DOI: 10.3389/fphys.2017.00140] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Accepted: 02/23/2017] [Indexed: 12/13/2022] Open
Abstract
The detection of error information is an essential prerequisite of a feedback-based movement. This study investigated the differential behavior and neurophysiological mechanisms of a cyclic force-tracking task using error-reducing and error-enhancing feedback. The discharge patterns of a relatively large number of motor units (MUs) were assessed with custom-designed multi-channel surface electromyography following mathematical decomposition of the experimentally-measured signals. Force characteristics, force-discharge relation, and phase-locking cortical activities in the contralateral motor cortex to individual MUs were contrasted among the low (LSF), normal (NSF), and high scaling factor (HSF) conditions, in which the sizes of online execution errors were displayed with various amplification ratios. Along with a spectral shift of the force output toward a lower band, force output with a more phase-lead became less irregular, and tracking accuracy was worse in the LSF condition than in the HSF condition. The coherent discharge of high phasic (HP) MUs with the target signal was greater, and inter-spike intervals were larger, in the LSF condition than in the HSF condition. Force-tracking in the LSF condition manifested with stronger phase-locked EEG activity in the contralateral motor cortex to discharge of the (HP) MUs (LSF > NSF, HSF). The coherent discharge of the (HP) MUs during the cyclic force-tracking predominated the force-discharge relation, which increased inversely to the error scaling factor. In conclusion, the size of visualized error gates motor unit discharge, force-discharge relation, and the relative influences of the feedback and feedforward processes on force control. A smaller visualized error size favors voluntary force control using a feedforward process, in relation to a selective central modulation that enhance the coherent discharge of (HP) MUs.
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Affiliation(s)
- Yi-Ching Chen
- School of Physical Therapy, Chung Shan Medical UniversityTaichung, Taiwan; Physical Therapy Room, Chung Shan Medical University HospitalTaichung, Taiwan
| | - Yen-Ting Lin
- Physical Education Room, Asian University Taichung, Taiwan
| | - Gwo-Ching Chang
- Department of Information Engineering, I-Shou University Kaohsiung, Taiwan
| | - Ing-Shiou Hwang
- Institute of Allied Health Sciences, College of Medicine, National Cheng Kung UniversityTainan, Taiwan; Department of Physical Therapy, College of Medicine, National Cheng Kung UniversityTainan, Taiwan
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173
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Johnson MD, Thompson CK, Tysseling VM, Powers RK, Heckman CJ. The potential for understanding the synaptic organization of human motor commands via the firing patterns of motoneurons. J Neurophysiol 2017; 118:520-531. [PMID: 28356467 DOI: 10.1152/jn.00018.2017] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 03/07/2017] [Accepted: 03/21/2017] [Indexed: 12/19/2022] Open
Abstract
Motoneurons are unique in being the only neurons in the CNS whose firing patterns can be easily recorded in human subjects. This is because of the one-to-one relationship between the motoneuron and muscle cell behavior. It has long been appreciated that the connection of motoneurons to their muscle fibers allows their action potentials to be amplified and recorded, but only recently has it become possible to simultaneously record the firing pattern of many motoneurons via array electrodes placed on the skin. These firing patterns contain detailed information about the synaptic organization of motor commands to the motoneurons. This review focuses on parameters in these firing patterns that are directly linked to specific features of this organization. It is now well established that motor commands consist of three components, excitation, inhibition, and neuromodulation; the importance of the third component has become increasingly evident. Firing parameters linked to each of the three components are discussed, along with consideration of potential limitations in their utility for understanding the underlying organization of motor commands. Future work based on realistic computer simulations of motoneurons may allow quantitative "reverse engineering" of human motoneuron firing patterns to provide good estimates of the relative amplitudes and temporal patterns of all three components of motor commands.
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Affiliation(s)
- Michael D Johnson
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois;
| | | | - Vicki M Tysseling
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Randall K Powers
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington
| | - Charles J Heckman
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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174
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Wang Z, Kwon M, Mohanty S, Schmitt LM, White SP, Christou EA, Mosconi MW. Increased Force Variability Is Associated with Altered Modulation of the Motorneuron Pool Activity in Autism Spectrum Disorder (ASD). Int J Mol Sci 2017; 18:E698. [PMID: 28346344 PMCID: PMC5412284 DOI: 10.3390/ijms18040698] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 03/20/2017] [Accepted: 03/22/2017] [Indexed: 11/20/2022] Open
Abstract
Force control deficits have been repeatedly documented in autism spectrum disorder (ASD). They are associated with worse social and daily living skill impairments in patients suggesting that developing a more mechanistic understanding of the central and peripheral processes that cause them may help guide the development of treatments that improve multiple outcomes in ASD. The neuromuscular mechanisms underlying force control deficits are not yet understood. Seventeen individuals with ASD and 14 matched healthy controls completed an isometric index finger abduction test at 60% of their maximum voluntary contraction (MVC) during recording of the first dorsal interosseous (FDI) muscle to determine the neuromuscular processes associated with sustained force variability. Central modulation of the motorneuron pool activation of the FDI muscle was evaluated at delta (0-4 Hz), alpha (4-10 Hz), beta (10-35 Hz) and gamma (35-60 Hz) frequency bands. ASD patients showed greater force variability than controls when attempting to maintain a constant force. Relative to controls, patients also showed increased central modulation of the motorneuron pool at beta and gamma bands. For controls, reduced force variability was associated with reduced delta frequency modulation of the motorneuron pool activity of the FDI muscle and increased modulation at beta and gamma bands. In contrast, delta, beta, and gamma frequency oscillations were not associated with force variability in ASD. These findings suggest that alterations of central mechanisms that control motorneuron pool firing may underlie the common and often impairing symptoms of ASD.
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Affiliation(s)
- Zheng Wang
- Schiefelbusch Institute for Life Span Studies, University of Kansas, 1000 Sunnyside Ave., Lawrence, KS 66045, USA.
- Clinical Child Psychology Program, University of Kansas, 1000 Sunnyside Ave., Lawrence, KS 66045, USA.
- Kansas Center for Autism Research and Training (K-CART), University of Kansas Medical School, Overland Park, KS 66213, USA.
| | - Minhyuk Kwon
- Schiefelbusch Institute for Life Span Studies, University of Kansas, 1000 Sunnyside Ave., Lawrence, KS 66045, USA.
- Clinical Child Psychology Program, University of Kansas, 1000 Sunnyside Ave., Lawrence, KS 66045, USA.
- Kansas Center for Autism Research and Training (K-CART), University of Kansas Medical School, Overland Park, KS 66213, USA.
| | - Suman Mohanty
- Center for Autism and Developmental Disabilities, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Lauren M Schmitt
- Schiefelbusch Institute for Life Span Studies, University of Kansas, 1000 Sunnyside Ave., Lawrence, KS 66045, USA.
- Clinical Child Psychology Program, University of Kansas, 1000 Sunnyside Ave., Lawrence, KS 66045, USA.
- Kansas Center for Autism Research and Training (K-CART), University of Kansas Medical School, Overland Park, KS 66213, USA.
| | - Stormi P White
- Center for Autism and Developmental Disabilities, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Evangelos A Christou
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL 32611, USA.
| | - Matthew W Mosconi
- Schiefelbusch Institute for Life Span Studies, University of Kansas, 1000 Sunnyside Ave., Lawrence, KS 66045, USA.
- Clinical Child Psychology Program, University of Kansas, 1000 Sunnyside Ave., Lawrence, KS 66045, USA.
- Kansas Center for Autism Research and Training (K-CART), University of Kansas Medical School, Overland Park, KS 66213, USA.
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175
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Miller JD, Herda TJ, Trevino MA, Sterczala AJ, Ciccone AB, Nicoll JX. Age-related differences in twitch properties and muscle activation of the first dorsal interosseous. Clin Neurophysiol 2017; 128:925-934. [PMID: 28402868 DOI: 10.1016/j.clinph.2017.03.032] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 02/08/2017] [Accepted: 03/12/2017] [Indexed: 01/08/2023]
Abstract
OBJECTIVE To examine twitch force potentiation and twitch contraction duration, as well as electromyographic amplitude (EMGRMS) and motor unit mean firing rates (MFR) at targeted forces between young and old individuals in the first dorsal interosseous (FDI). Ultrasonography was used to assess muscle quality. METHODS Twenty-two young (YG) (age=22.6±2.7years) and 14 older (OD) (age=62.1±4.7years) individuals completed conditioning contractions at 10% and 50% maximal voluntary contraction, (MVC) during which EMGRMS and MFRs were assessed. Evoked twitches preceded and followed the conditioning contractions. Ultrasound images were taken to quantify muscle quality (cross-sectional area [CSA] and echo intensity [EI]). RESULTS No differences were found between young and old for CSA, pre-conditioning contraction twitch force, or MFRs (P>0.05). However, OD individuals exhibited greater EI and contraction duration (P<0.05), and EMGRMS (YG=35.4±8.7%, OD=43.4±13.2%; P=0.034). Twitch force potentiation was lower for OD (0.311±0.15N) than YG (0.619±0.26N) from pre- to post-50% conditioning contraction (P<0.001). CONCLUSIONS Lower levels of potentiation with elongated contraction durations likely contributed to greater muscle activation during the conditioning contractions in the OD rather than altered MFRs. Ultrasonography suggested age-related changes in muscle structure contributed to altered contractile properties in the OD. SIGNIFICANCE Greater muscle activation requirements can have negative implications on fatigue resistance at low to moderate intensities in older individuals.
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Affiliation(s)
- Jonathan D Miller
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66044, USA.
| | - Trent J Herda
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66044, USA.
| | - Michael A Trevino
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66044, USA.
| | - Adam J Sterczala
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66044, USA.
| | - Anthony B Ciccone
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66044, USA.
| | - Justin X Nicoll
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS 66044, USA.
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176
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Karimimehr S, Marateb HR, Muceli S, Mansourian M, Mañanas MA, Farina D. A Real-Time Method for Decoding the Neural Drive to Muscles Using Single-Channel Intra-Muscular EMG Recordings. Int J Neural Syst 2017; 27:1750025. [PMID: 28427290 DOI: 10.1142/s0129065717500253] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The neural command from motor neurons to muscles - sometimes referred to as the neural drive to muscle - can be identified by decomposition of electromyographic (EMG) signals. This approach can be used for inferring the voluntary commands in neural interfaces in patients with limb amputations. This paper proposes for the first time an innovative method for fully automatic and real-time intramuscular EMG (iEMG) decomposition. The method is based on online single-pass density-based clustering and adaptive classification of bivariate features, using the concept of potential measure. No attempt was made to resolve superimposed motor unit action potentials. The proposed algorithm was validated on sets of simulated and experimental iEMG signals. Signals were recorded from the biceps femoris long-head, vastus medialis and lateralis and tibialis anterior muscles during low-to-moderate isometric constant-force and linearly-varying force contractions. The average number of missed, duplicated and erroneous clusters for the examined signals was [Formula: see text], [Formula: see text], and [Formula: see text], respectively. The average decomposition accuracy (defined similar to signal detection theory but without using True Negatives in the denominator) and coefficient of determination (variance accounted for) for the cumulative discharge rate estimation were [Formula: see text], and [Formula: see text], respectively. The time cost for processing each 200[Formula: see text]ms iEMG interval was [Formula: see text] (21-97)[Formula: see text]ms. However, computational time generally increases over time as a function of frames/signal epochs. Meanwhile, the incremental accuracy defined as the accuracy of real-time analysis of each signal epoch, was [Formula: see text]% for epochs recorded after initial one second. The proposed algorithm is thus a promising new tool for neural decoding in the next-generation of prosthetic control.
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Affiliation(s)
- Saeed Karimimehr
- Faculty of Engineering, Biomedical Engineering Department, University of Isfahan, HezarJerib st., 81746-73441 Isfahan, Iran
- Brain Engineering Research Center, Institute for Research in Fundamental Sciences (IPM), P. O. Box 19395-5746 Tehran, Iran
| | - Hamid Reza Marateb
- Faculty of Engineering, Biomedical Engineering Department, University of Isfahan, HezarJerib st., 81746-73441 Isfahan, Iran
- Department of Automatic Control, Biomedical Engineering Research Center, Universitat Politècnica de Catalunya BarcelonaTech (UPC), 08028 Barcelona, Spain
| | - Silvia Muceli
- Institute of Neurorehabilitation Systems, University Medical Center Göttingen, Georg-August University, 37075 Göttingen, Germany
- Clinic for Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany
| | - Marjan Mansourian
- Department of Biostatistics and Epidemiology, School of Public Health, Isfahan University of Medical Sciences, HezarJerib St., 81745 Isfahan, Iran
| | - Miguel Angel Mañanas
- Department of Automatic Control, Biomedical Engineering Research Center, Universitat Politècnica de Catalunya BarcelonaTech (UPC), 08028 Barcelona, Spain
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), 08028, Barcelona, Spain
| | - Dario Farina
- Department of Bioengineering, Imperial College London, SW7 2AZ London, UK
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177
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Girard O, Malatesta D, Millet GP. Walking in Hypoxia: An Efficient Treatment to Lessen Mechanical Constraints and Improve Health in Obese Individuals? Front Physiol 2017; 8:73. [PMID: 28232806 PMCID: PMC5298970 DOI: 10.3389/fphys.2017.00073] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 01/26/2017] [Indexed: 11/13/2022] Open
Affiliation(s)
- Olivier Girard
- Athlete Health and Performance Research Center, Aspetar Orthopaedic and Sports Medicine HospitalDoha, Qatar; Faculty of Biology and Medicine, Institute of Sport Sciences, University of LausanneLausanne, Switzerland
| | - Davide Malatesta
- Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne Lausanne, Switzerland
| | - Grégoire P Millet
- Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne Lausanne, Switzerland
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178
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Hwang IS, Lin YT, Huang WM, Yang ZR, Hu CL, Chen YC. Alterations in Neural Control of Constant Isometric Contraction with the Size of Error Feedback. PLoS One 2017; 12:e0170824. [PMID: 28125658 PMCID: PMC5268650 DOI: 10.1371/journal.pone.0170824] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 01/11/2017] [Indexed: 11/18/2022] Open
Abstract
Discharge patterns from a population of motor units (MUs) were estimated with multi-channel surface electromyogram and signal processing techniques to investigate parametric differences in low-frequency force fluctuations, MU discharges, and force-discharge relation during static force-tracking with varying sizes of execution error presented via visual feedback. Fourteen healthy adults produced isometric force at 10% of maximal voluntary contraction through index abduction under three visual conditions that scaled execution errors with different amplification factors. Error-augmentation feedback that used a high amplification factor (HAF) to potentiate visualized error size resulted in higher sample entropy, mean frequency, ratio of high-frequency components, and spectral dispersion of force fluctuations than those of error-reducing feedback using a low amplification factor (LAF). In the HAF condition, MUs with relatively high recruitment thresholds in the dorsal interosseous muscle exhibited a larger coefficient of variation for inter-spike intervals and a greater spectral peak of the pooled MU coherence at 13-35 Hz than did those in the LAF condition. Manipulation of the size of error feedback altered the force-discharge relation, which was characterized with non-linear approaches such as mutual information and cross sample entropy. The association of force fluctuations and global discharge trace decreased with increasing error amplification factor. Our findings provide direct neurophysiological evidence that favors motor training using error-augmentation feedback. Amplification of the visualized error size of visual feedback could enrich force gradation strategies during static force-tracking, pertaining to selective increases in the discharge variability of higher-threshold MUs that receive greater common oscillatory inputs in the β-band.
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Affiliation(s)
- Ing-Shiou Hwang
- Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
- Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
| | - Yen-Ting Lin
- Physical Education Office, Asian University, Taichung City, Taiwan
| | - Wei-Min Huang
- Department of Management Information System, National Chung Cheng University, Chia-Yi, Taiwan
| | - Zong-Ru Yang
- Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
| | - Chia-Ling Hu
- Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
| | - Yi-Ching Chen
- School of Physical Therapy, College of Medical Science and Technology, Chung Shan Medical University, Taichung City, Taiwan
- Physical Therapy Room, Chung Shan Medical University Hospital, Taichung City, Taiwan
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179
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Piotrkiewicz M, Türker KS. Onion Skin or Common Drive? Front Cell Neurosci 2017; 11:2. [PMID: 28154526 PMCID: PMC5243795 DOI: 10.3389/fncel.2017.00002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 01/05/2017] [Indexed: 11/13/2022] Open
Affiliation(s)
- Maria Piotrkiewicz
- Department of Engineering of Nervous and Muscular System, Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences Warsaw, Poland
| | - Kemal S Türker
- Laboratory of Neuromuscular Research, Koç University School of Medicine Istanbul, Turkey
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180
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Revill AL, Fuglevand AJ. Inhibition linearizes firing rate responses in human motor units: implications for the role of persistent inward currents. J Physiol 2017; 595:179-191. [PMID: 27470946 PMCID: PMC5199728 DOI: 10.1113/jp272823] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 07/21/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Motor neurons are the output neurons of the central nervous system and are responsible for controlling muscle contraction. When initially activated during voluntary contraction, firing rates of motor neurons increase steeply but then level out at modest rates. Activation of an intrinsic source of excitatory current at recruitment onset may underlie the initial steep increase in firing rate in motor neurons. We attempted to disable this intrinsic excitatory current by artificially activating an inhibitory reflex. When motor neuron activity was recorded while the inhibitory reflex was engaged, firing rates no longer increased steeply, suggesting that the intrinsic excitatory current was probably responsible for the initial sharp rise in motor neuron firing rate. ABSTRACT During graded isometric contractions, motor unit (MU) firing rates increase steeply upon recruitment but then level off at modest rates even though muscle force continues to increase. The mechanisms underlying such firing behaviour are not known although activation of persistent inward currents (PICs) might be involved. PICs are intrinsic, voltage-dependent currents that activate strongly when motor neurons (MNs) are first recruited. Such activation might cause a sharp escalation in depolarizing current and underlie the steep initial rise in MU firing rate. Because PICs can be disabled with synaptic inhibition, we hypothesized that artificial activation of an inhibitory pathway might curb this initial steep rise in firing rate. To test this, human subjects performed slow triangular ramp contractions of the ankle dorsiflexors in the absence and presence of tonic synaptic inhibition delivered to tibialis anterior (TA) MNs by sural nerve stimulation. Firing rate profiles (expressed as a function of contraction force) of TA MUs recorded during these tasks were compared for control and stimulation conditions. Under control conditions, during the ascending phase of the triangular contractions, 93% of the firing rate profiles were best fitted by rising exponential functions. With stimulation, however, firing rate profiles were best fitted with linear functions or with less steeply rising exponentials. Firing rate profiles for the descending phases of the contractions were best fitted with linear functions for both control and stimulation conditions. These results seem consistent with the idea that PICs contribute to non-linear firing rate profiles during ascending but not descending phases of contractions.
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Affiliation(s)
- Ann L. Revill
- Department of PhysiologyCollege of MedicineUniversity of ArizonaTucsonAZUSA
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181
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Balshaw TG, Pahar M, Chesham R, Macgregor LJ, Hunter AM. Reduced firing rates of high threshold motor units in response to eccentric overload. Physiol Rep 2017; 5:e13111. [PMID: 28108648 PMCID: PMC5269413 DOI: 10.14814/phy2.13111] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 12/08/2016] [Accepted: 12/09/2016] [Indexed: 11/24/2022] Open
Abstract
Acute responses of motor units were investigated during submaximal voluntary isometric tasks following eccentric overload (EO) and constant load (CL) knee extension resistance exercise. Ten healthy resistance-trained participants performed four experimental test sessions separated by 5 days over a 20 day period. Two sessions involved constant load and the other two used eccentric overload. EO and CL used both sessions for different target knee eccentric extension phases; one at 2 sec and the other at 4 sec. Maximal voluntary contractions (MVC) and isometric trapezoid efforts for 10 sec at 70% MVC were completed before and after each intervention and decomposed electromyography was used to measure motor unit firing rate. The firing rate of later recruited, high-threshold motor units declined following the 2-sec EO but was maintained following 2sec CL (P < 0.05), whereas MUFR for all motor units were maintained for both loading types following 4-sec extension phases. MVC and rate of force development where maintained following both EO and CL and 2 and 4 sec phases. This study demonstrates a slower firing rate of high-threshold motor units following fast eccentric overload while MVC was maintained. This suggests that there was a neuromuscular stimulus without cost to the force-generating capacity of the knee extensors.
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Affiliation(s)
- Tom G Balshaw
- Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, Scotland, United Kingdom
| | - Madhu Pahar
- Computing Science and Mathematics, University of Stirling, Stirling, Scotland, United Kingdom
| | - Ross Chesham
- Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, Scotland, United Kingdom
| | - Lewis J Macgregor
- Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, Scotland, United Kingdom
| | - Angus M Hunter
- Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, Scotland, United Kingdom
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182
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Mosier EM, Herda TJ, Trevino MA, Miller JD. The influence of prolonged vibration on motor unit behavior. Muscle Nerve 2016; 55:500-507. [PMID: 27465016 DOI: 10.1002/mus.25270] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 07/13/2016] [Accepted: 07/26/2016] [Indexed: 11/12/2022]
Abstract
INTRODUCTION The purpose of this study was to determine the effects of vibration (VIB) on motor unit (MU) behavior of the vastus lateralis (VL) muscle during a 40% maximal voluntary contraction (MVC). METHODS Eleven healthy (age 21.3 ± 2.6 years) individuals participated in the study. Surface electromyography (EMG) data were recorded from the VL during isometric trapezoidal muscle contractions at 40% MVC. Firing events of single MUs and EMG amplitude were reported for the first, middle, and final seconds of a 12-second steady force segment at 40% MVC. VIB was applied at 55 Hz to the patellar tendon for 15 minutes before and continued throughout the remainder of testing (VIB) or remained off (CON). RESULTS There were significant increases in MU firing rates during VIB in comparison to CON and no differences in EMG amplitude between VIB and CON. CONCLUSION The VIB-mediated reduction in muscle spindle function altered MU behavior at 40% MVC. Muscle Nerve 55: 500-507, 2017.
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Affiliation(s)
- Eric M Mosier
- Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences, University of Kansas, 1301 Sunnyside Avenue, Lawrence, Kansas, 66045, USA
| | - Trent J Herda
- Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences, University of Kansas, 1301 Sunnyside Avenue, Lawrence, Kansas, 66045, USA
| | - Michael A Trevino
- Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences, University of Kansas, 1301 Sunnyside Avenue, Lawrence, Kansas, 66045, USA
| | - Jonathan D Miller
- Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences, University of Kansas, 1301 Sunnyside Avenue, Lawrence, Kansas, 66045, USA
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183
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Marateb HR, Farahi M, Rojas M, Mañanas MA, Farina D. Detection of Multiple Innervation Zones from Multi-Channel Surface EMG Recordings with Low Signal-to-Noise Ratio Using Graph-Cut Segmentation. PLoS One 2016; 11:e0167954. [PMID: 27978535 PMCID: PMC5158322 DOI: 10.1371/journal.pone.0167954] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 11/23/2016] [Indexed: 11/24/2022] Open
Abstract
Knowledge of the location of muscle Innervation Zones (IZs) is important in many applications, e.g. for minimizing the quantity of injected botulinum toxin for the treatment of spasticity or for deciding on the type of episiotomy during child delivery. Surface EMG (sEMG) can be noninvasively recorded to assess physiological and morphological characteristics of contracting muscles. However, it is not often possible to record signals of high quality. Moreover, muscles could have multiple IZs, which should all be identified. We designed a fully-automatic algorithm based on the enhanced image Graph-Cut segmentation and morphological image processing methods to identify up to five IZs in 60-ms intervals of very-low to moderate quality sEMG signal detected with multi-channel electrodes (20 bipolar channels with Inter Electrode Distance (IED) of 5 mm). An anisotropic multilayered cylinder model was used to simulate 750 sEMG signals with signal-to-noise ratio ranging from -5 to 15 dB (using Gaussian noise) and in each 60-ms signal frame, 1 to 5 IZs were included. The micro- and macro- averaged performance indices were then reported for the proposed IZ detection algorithm. In the micro-averaging procedure, the number of True Positives, False Positives and False Negatives in each frame were summed up to generate cumulative measures. In the macro-averaging, on the other hand, precision and recall were calculated for each frame and their averages are used to determine F1-score. Overall, the micro (macro)-averaged sensitivity, precision and F1-score of the algorithm for IZ channel identification were 82.7% (87.5%), 92.9% (94.0%) and 87.5% (90.6%), respectively. For the correctly identified IZ locations, the average bias error was of 0.02±0.10 IED ratio. Also, the average absolute conduction velocity estimation error was 0.41±0.40 m/s for such frames. The sensitivity analysis including increasing IED and reducing interpolation coefficient for time samples was performed. Meanwhile, the effect of adding power-line interference and using other image interpolation methods on the deterioration of the performance of the proposed algorithm was investigated. The average running time of the proposed algorithm on each 60-ms sEMG frame was 25.5±8.9 (s) on an Intel dual-core 1.83 GHz CPU with 2 GB of RAM. The proposed algorithm correctly and precisely identified multiple IZs in each signal epoch in a wide range of signal quality and is thus a promising new offline tool for electrophysiological studies.
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Affiliation(s)
- Hamid Reza Marateb
- The Biomedical Engineering Department, Engineering Faculty, the University of Isfahan, Isfahan, Iran
- Department of Automatic Control, Biomedical Engineering Research Center, Universitat Politècnica de Catalunya. BarcelonaTech (UPC), Barcelona, Spain
- * E-mail:
| | - Morteza Farahi
- The Biomedical Engineering Department, Engineering Faculty, the University of Isfahan, Isfahan, Iran
| | - Monica Rojas
- Department of Automatic Control, Biomedical Engineering Research Center, Universitat Politècnica de Catalunya. BarcelonaTech (UPC), Barcelona, Spain
- Department of Bioengineering, Universidad El Bosque, Bogotá, Colombia
| | - Miguel Angel Mañanas
- Department of Automatic Control, Biomedical Engineering Research Center, Universitat Politècnica de Catalunya. BarcelonaTech (UPC), Barcelona, Spain
| | - Dario Farina
- Department of NeuroRehabilitation Engineering, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
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184
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Yang CC, Su FC, Yang PC, Lin HT, Guo LY. Characteristics of the Motor Units during Sternocleidomastoid Isometric Flexion among Patients with Mechanical Neck Disorder and Asymptomatic Individuals. PLoS One 2016; 11:e0167737. [PMID: 27941995 PMCID: PMC5152896 DOI: 10.1371/journal.pone.0167737] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 11/18/2016] [Indexed: 12/03/2022] Open
Abstract
Mechanical neck disorder is a widespread and non-neurological musculoskeletal condition resulting from modern lifestyles. Presently, the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles and the characteristics of the short-term synchronization of the motor unit in patients with neck pain are ambiguous. This study therefore aims to clarify the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles in patients with mechanical neck disorder and in asymptomatic individuals. We further investigated whether alterations in the degree of motor unit short-term synchronization occur. The surface electrophysiological signals of the bilateral sternal heads of the sternocleidomastoid muscles of twelve patients with mechanical neck disorder and asymptomatic individuals were detected at 25% of the maximum voluntary contraction during cervical isometric flexion and then decomposed into individual motor unit action potential trains. We found that the patients with mechanical neck disorder showed significantly higher initial and mean firing rates of the sternocleidomastoid muscles and displayed substantially lower motor unit short-term synchronization values compared with the asymptomatic subjects. Consequently, these convincing findings support the assertion that patients with mechanical neck disorder display altered neuromuscular control strategies, such as the reinforcement of motor unit recruitment firing rates in the sternocleidomastoid muscles. The motor units of these patients also revealed neural recruitment strategies with relatively poor efficiency when executing the required motor tasks.
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Affiliation(s)
- Chia-Chi Yang
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Fong-Chin Su
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
- Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan
| | - Po-Ching Yang
- Department of Sports Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Hwai-Ting Lin
- Department of Sports Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Lan-Yuen Guo
- Department of Sports Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
- * E-mail:
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185
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Silva MF, Dias JM, Pereira LM, Mazuquin BF, Lindley S, Richards J, Cardoso JR. Determination of the motor unit behavior of lumbar erector spinae muscles through surface EMG decomposition technology in healthy female subjects. Muscle Nerve 2016; 55:28-34. [PMID: 27170098 DOI: 10.1002/mus.25184] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 04/30/2016] [Accepted: 05/09/2016] [Indexed: 11/06/2022]
Abstract
INTRODUCTION The aims of this study were to determine the motor unit behavior of the erector spinae muscles and to assess whether differences exist between the dominant/nondominant sides of the back muscles. METHODS Nine healthy women, aged 21.7 years (SD = 0.7), performed a back extension test. Surface electromyographic decomposition data were collected from both sides of the erector spinae and decomposed into individual motor unit action potential trains. The mean firing rate for each motor unit was calculated, and a regression analysis was performed against the corresponding recruitment thresholds. RESULTS The mean firing rate ranged from 15.9 to 23.9 pps and 15.8 to 20.6 pps on the dominant and nondominant sides, respectively. However, the early motor unit potentials of the nondominant lumbar erector spinae muscles were recruited at a lower firing rate. CONCLUSIONS This technique may further our understanding of individuals with back pain and other underlying neuromuscular diseases. Muscle Nerve 55: 28-34, 2017.
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Affiliation(s)
- Mariana Felipe Silva
- Laboratory of Biomechanics and Clinical Epidemiology, PAIFIT Research Group, Universidade Estadual de Londrina, Londrina, PR, Brazil
| | - Josilainne Marcelino Dias
- Laboratory of Biomechanics and Clinical Epidemiology, PAIFIT Research Group, Universidade Estadual de Londrina, Londrina, PR, Brazil
| | - Ligia Maxwell Pereira
- Laboratory of Biomechanics and Clinical Epidemiology, PAIFIT Research Group, Universidade Estadual de Londrina, Londrina, PR, Brazil
| | - Bruno Fles Mazuquin
- Allied Health Research Unit, University Central of Lancashire, Preston, Lancashire, United Kingdom
| | - Steven Lindley
- Allied Health Research Unit, University Central of Lancashire, Preston, Lancashire, United Kingdom
| | - Jim Richards
- Allied Health Research Unit, University Central of Lancashire, Preston, Lancashire, United Kingdom
| | - Jefferson Rosa Cardoso
- Laboratory of Biomechanics and Clinical Epidemiology, PAIFIT Research Group, Universidade Estadual de Londrina, Londrina, PR, Brazil
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186
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Trevino MA, Herda TJ, Fry AC, Gallagher PM, Vardiman JP, Mosier EM, Miller JD. Influence of the contractile properties of muscle on motor unit firing rates during a moderate-intensity contraction in vivo. J Neurophysiol 2016; 116:552-62. [PMID: 27146989 PMCID: PMC4978784 DOI: 10.1152/jn.01021.2015] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 05/02/2016] [Indexed: 11/22/2022] Open
Abstract
It is suggested that firing rate characteristics of motor units (MUs) are influenced by the physical properties of the muscle. However, no study has correlated MU firing rates at recruitment, targeted force, or derecruitment with the contractile properties of the muscle in vivo. Twelve participants (age = 20.67 ± 2.35 yr) performed a 40% isometric maximal voluntary contraction of the leg extensors that included linearly increasing, steady force, and decreasing segments. Muscle biopsies were collected with myosin heavy chain (MHC) content quantified, and surface electromyography (EMG) was recorded from the vastus lateralis. The EMG signal was decomposed into the firing events of single MUs. Slopes and y-intercepts were calculated for 1) firing rates at recruitment vs. recruitment threshold, 2) mean firing rates at steady force vs. recruitment threshold, and 3) firing rates at derecruitment vs. derecruitment threshold relationships for each subject. Correlations among type I %MHC isoform content and the slopes and y-intercepts from the three relationships were examined. Type I %MHC isoform content was correlated with MU firing rates at recruitment (y-intercepts: r = -0.577; slopes: r = 0.741) and targeted force (slopes: r = 0.853) vs. recruitment threshold and MU firing rates at derecruitment (y-intercept: r = -0.597; slopes: r = 0.701) vs. derecruitment threshold relationships. However, the majority of the individual MU firing rates vs. recruitment and derecruitment relationships were not significant (P > 0.05) and, thus, revealed no systematic pattern. In contrast, MU firing rates during the steady force demonstrated a systematic pattern with higher firing rates for the lower- than higher-threshold MUs and were correlated with the physical properties of MUs in vivo.
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Affiliation(s)
| | - Trent J Herda
- Neuromechanics Laboratory, University of Kansas, Lawrence, Kansas;
| | - Andrew C Fry
- Applied Physiology Laboratory, University of Kansas, Lawrence, Kansas; and
| | - Philip M Gallagher
- Applied Physiology Laboratory, University of Kansas, Lawrence, Kansas; and
| | - John P Vardiman
- Applied Physiology and Sports Medicine Laboratory, Kansas State University, Manhattan, Kansas
| | - Eric M Mosier
- Neuromechanics Laboratory, University of Kansas, Lawrence, Kansas
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187
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Hu X, Suresh AK, Rymer WZ, Suresh NL. Altered motor unit discharge patterns in paretic muscles of stroke survivors assessed using surface electromyography. J Neural Eng 2016; 13:046025. [PMID: 27432656 DOI: 10.1088/1741-2560/13/4/046025] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Hemispheric stroke survivors often show impairments in voluntary muscle activation. One potential source of these impairments could come from altered control of muscle, via disrupted motor unit (MU) firing patterns. In this study, we sought to determine whether MU firing patterns are modified on the affected side of stroke survivors, as compared with the analogous contralateral muscle. APPROACH Using a novel surface electromyogram (EMG) sensor array, coupled with advanced template recognition software (dEMG) we recorded surface EMG signals over the first dorsal interosseous (FDI) muscle on both paretic and contralateral sides. Recordings were made as stroke survivors produced isometric index finger abductions over a large force range (20%-60% of maximum). Utilizing the dEMG algorithm, MU firing rates, recruitment thresholds, and action potential amplitudes were estimated for concurrently active MUs in each trial. MAIN RESULTS Our results reveal significant changes in the firing rate patterns in paretic FDI muscle, in that the discharge rates, characterized in relation to recruitment force threshold and to MU size, were less clearly correlated with recruitment force than in contralateral FDI muscles. Firing rates in the affected muscle also did not modulate systematically with the level of voluntary muscle contraction, as would be expected in intact muscles. These disturbances in firing properties also correlated closely with the impairment of muscle force generation. SIGNIFICANCE Our results provide strong evidence of disruptions in MU firing behavior in paretic muscles after a hemispheric stroke, suggesting that modified control of the spinal motoneuron pool could be a contributing factor to muscular weakness in stroke survivors.
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Affiliation(s)
- Xiaogang Hu
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, USA. Department of Biomedical Engineering, University of North Carolina at Chapel Hill and NC State University at Raleigh, USA
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188
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Contessa P, De Luca CJ, Kline JC. The compensatory interaction between motor unit firing behavior and muscle force during fatigue. J Neurophysiol 2016; 116:1579-1585. [PMID: 27385798 DOI: 10.1152/jn.00347.2016] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 07/05/2016] [Indexed: 11/22/2022] Open
Abstract
Throughout the literature, different observations of motor unit firing behavior during muscle fatigue have been reported and explained with varieties of conjectures. The disagreement amongst previous studies has resulted, in part, from the limited number of available motor units and from the misleading practice of grouping motor unit data across different subjects, contractions, and force levels. To establish a more clear understanding of motor unit control during fatigue, we investigated the firing behavior of motor units from the vastus lateralis muscle of individual subjects during a fatigue protocol of repeated voluntary constant force isometric contractions. Surface electromyographic decomposition technology provided the firings of 1,890 motor unit firing trains. These data revealed that to sustain the contraction force as the muscle fatigued, the following occurred: 1) motor unit firing rates increased; 2) new motor units were recruited; and 3) motor unit recruitment thresholds decreased. Although the degree of these adaptations was subject specific, the behavior was consistent in all subjects. When we compared our empirical observations with those obtained from simulation, we found that the fatigue-induced changes in motor unit firing behavior can be explained by increasing excitation to the motoneuron pool that compensates for the fatigue-induced decrease in muscle force twitch reported in empirical studies. Yet, the fundamental motor unit control scheme remains invariant throughout the development of fatigue. These findings indicate that the central nervous system regulates motor unit firing behavior by adjusting the operating point of the excitation to the motoneuron pool to sustain the contraction force as the muscle fatigues.
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Affiliation(s)
| | - Carlo J De Luca
- Delsys Incorporated, Natick, Massachusetts; and Department of Biomedical Engineering, Boston University, Boston, Massachusetts
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189
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Herda TJ, Miller JD, Trevino MA, Mosier EM, Gallagher PM, Fry AC, Vardiman JP. The change in motor unit firing rates at de-recruitment relative to recruitment is correlated with type I myosin heavy chain isoform content of the vastus lateralis in vivo. Acta Physiol (Oxf) 2016; 216:454-63. [PMID: 26513624 DOI: 10.1111/apha.12624] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 08/26/2015] [Accepted: 10/28/2015] [Indexed: 11/30/2022]
Abstract
AIM To investigate the change in motor unit (MU) firing rates (FR) at de-recruitment relative to recruitment and the relation to % type I myosin heavy chain isoform content (type I %MHC) of the vastus lateralis (VL) in vivo. METHODS Ten subjects performed a 22-s submaximal isometric trapezoid muscle action that included a linearly increasing, steady force at 50% maximal voluntary contraction, and linearly decreasing segments. Surface electromyographic signals were collected from the VL and were decomposed into constituent MU action potentials trains. A tissue sample from the VL was taken to calculate type I %MHC. The y-intercepts and slopes were calculated for the changes (Δ) in FR at de-recruitment (FRDEREC ) relative to FR at recruitment (FRREC ) vs. FRREC relationship for each subject. Correlations were performed between the y-intercepts and slopes with type I %MHC. RESULTS The majority of MUs had greater FRDEREC than FRREC . The y-intercepts (r = -0.600, P = 0.067) were not significantly correlated, but the slopes (r = -0.793, P = 0.006) were significantly correlated with type I %MHC. CONCLUSION The majority of the motoneuron pool had greater FRDEREC than FRREC , however, individuals with higher type I %MHC had a greater propensity to have MUs with FRREC > FRDEREC as indicated by the slope values. Overall, the contractile properties of the muscle (MHC) could partially explain the differences in MU firing rates at de-recruitment relative to recruitment. Thus, suggesting the fatigability of the muscle influences the alterations in MU firing rates from recruitment to de-recruitment.
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Affiliation(s)
- T. J. Herda
- Neuromechanics Laboratory; Department of Health, Sport and Exercise Sciences; University of Kansas; Lawrence KS USA
| | - J. D. Miller
- Neuromechanics Laboratory; Department of Health, Sport and Exercise Sciences; University of Kansas; Lawrence KS USA
| | - M. A. Trevino
- Neuromechanics Laboratory; Department of Health, Sport and Exercise Sciences; University of Kansas; Lawrence KS USA
| | - E. M. Mosier
- Neuromechanics Laboratory; Department of Health, Sport and Exercise Sciences; University of Kansas; Lawrence KS USA
| | - P. M. Gallagher
- Applied Physiology Laboratory; Department of Health Sport and Exercise Sciences; University of Kansas; Lawrence KS USA
| | - A. C. Fry
- Neuromechanics Laboratory; Department of Health, Sport and Exercise Sciences; University of Kansas; Lawrence KS USA
| | - J. P. Vardiman
- Applied Physiology Laboratory; Department of Health Sport and Exercise Sciences; University of Kansas; Lawrence KS USA
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190
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McManus L, Hu X, Rymer WZ, Suresh NL, Lowery MM. Muscle fatigue increases beta-band coherence between the firing times of simultaneously active motor units in the first dorsal interosseous muscle. J Neurophysiol 2016; 115:2830-9. [PMID: 26984420 DOI: 10.1152/jn.00097.2016] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 03/15/2016] [Indexed: 11/22/2022] Open
Abstract
Synchronization between the firing times of simultaneously active motor units (MUs) is generally assumed to increase during fatiguing contractions. To date, however, estimates of MU synchronization have relied on indirect measures, derived from surface electromyographic (EMG) interference signals. This study used intramuscular coherence to investigate the correlation between MU discharges in the first dorsal interosseous muscle during and immediately following a submaximal fatiguing contraction, and after rest. Coherence between composite MU spike trains, derived from decomposed surface EMG, were examined in the delta (1-4 Hz), alpha (8-12 Hz), beta (15-30 Hz), and gamma (30-60 Hz) frequency band ranges. A significant increase in MU coherence was observed in the delta, alpha, and beta frequency bands postfatigue. In addition, wavelet coherence revealed a tendency for delta-, alpha-, and beta-band coherence to increase during the fatiguing contraction, with subjects exhibiting low initial coherence values displaying the greatest relative increase. This was accompanied by an increase in MU short-term synchronization and a decline in mean firing rate of the majority of MUs detected during the sustained contraction. A model of the motoneuron pool and surface EMG was used to investigate factors influencing the coherence estimate. Simulation results indicated that changes in motoneuron inhibition and firing rates alone could not directly account for increased beta-band coherence postfatigue. The observed increase is, therefore, more likely to arise from an increase in the strength of correlated inputs to MUs as the muscle fatigues.
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Affiliation(s)
- Lara McManus
- University College Dublin, Belfield, Dublin, Ireland;
| | - Xiaogang Hu
- Joint Department of Biomedical Engineering, University of North Carolina-Chapel Hill and North Carolina State University, Chapel Hill, North Carolina
| | - William Z Rymer
- Rehabilitation Institute of Chicago, Chicago, Illinois; and Northwestern University, Evanston, Illinois
| | - Nina L Suresh
- Rehabilitation Institute of Chicago, Chicago, Illinois; and
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191
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Park SH, Kwon M, Solis D, Lodha N, Christou EA. Motor control differs for increasing and releasing force. J Neurophysiol 2016; 115:2924-30. [PMID: 26961104 DOI: 10.1152/jn.00715.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 03/09/2016] [Indexed: 11/22/2022] Open
Abstract
Control of the motor output depends on our ability to precisely increase and release force. However, the influence of aging on force increase and release remains unknown. The purpose of this study, therefore, was to determine whether force control differs while increasing and releasing force in young and older adults. Sixteen young adults (22.5 ± 4 yr, 8 females) and 16 older adults (75.7 ± 6.4 yr, 8 females) increased and released force at a constant rate (10% maximum voluntary contraction force/s) during an ankle dorsiflexion isometric task. We recorded the force output and multiple motor unit activity from the tibialis anterior (TA) muscle and quantified the following outcomes: 1) variability of force using the SD of force; 2) mean discharge rate and variability of discharge rate of multiple motor units; and 3) power spectrum of the multiple motor units from 0-4, 4-10, 10-35, and 35-60 Hz. Participants exhibited greater force variability while releasing force, independent of age (P < 0.001). Increased force variability during force release was associated with decreased modulation of multiple motor units from 35 to 60 Hz (R(2) = 0.38). Modulation of multiple motor units from 35 to 60 Hz was further correlated to the change in mean discharge rate of multiple motor units (r = 0.66) and modulation from 0 to 4 Hz (r = -0.64). In conclusion, these findings suggest that force control is altered while releasing due to an altered modulation of the motor units.
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Affiliation(s)
- Seoung Hoon Park
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida; and
| | - MinHyuk Kwon
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida; and
| | - Danielle Solis
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida; and
| | - Neha Lodha
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida; and
| | - Evangelos A Christou
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida; and Department of Physical Therapy, University of Florida, Gainesville, Florida
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192
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Pope ZK, Hester GM, Benik FM, DeFreitas JM. Action potential amplitude as a noninvasive indicator of motor unit-specific hypertrophy. J Neurophysiol 2016; 115:2608-14. [PMID: 26936975 DOI: 10.1152/jn.00039.2016] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 03/02/2016] [Indexed: 11/22/2022] Open
Abstract
Skeletal muscle fibers hypertrophy in response to strength training, with type II fibers generally demonstrating the greatest plasticity in regards to cross-sectional area (CSA). However, assessing fiber type-specific CSA in humans requires invasive muscle biopsies. With advancements in the decomposition of surface electromyographic (sEMG) signals recorded using multichannel electrode arrays, the firing properties of individual motor units (MUs) can now be detected noninvasively. Since action potential amplitude (APSIZE) has a documented relationship with muscle fiber size, as well as with its parent MU's recruitment threshold (RT) force, our purpose was to examine if MU APSIZE, as a function of its RT (i.e., the size principle), could potentially be used as a longitudinal indicator of MU-specific hypertrophy. By decomposing the sEMG signals from the vastus lateralis muscle of 10 subjects during maximal voluntary knee extensions, we noninvasively assessed the relationship between MU APSIZE and RT before and immediately after an 8-wk strength training intervention. In addition to significant increases in muscle size and strength (P < 0.02), our data show that training elicited an increase in MU APSIZE of high-threshold MUs. Additionally, a large portion of the variance (83.6%) in the change in each individual's relationship between MU APSIZE and RT was explained by training-induced changes in whole muscle CSA (obtained via ultrasonography). Our findings suggest that the noninvasive, electrophysiological assessment of longitudinal changes to MU APSIZE appears to reflect hypertrophy specific to MUs across the RT continuum.
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Affiliation(s)
- Zachary K Pope
- Applied Musculoskeletal and Human Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Garrett M Hester
- Applied Musculoskeletal and Human Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Franklin M Benik
- Applied Musculoskeletal and Human Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| | - Jason M DeFreitas
- Applied Musculoskeletal and Human Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
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193
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Farina D, Negro F, Muceli S, Enoka RM. Principles of Motor Unit Physiology Evolve With Advances in Technology. Physiology (Bethesda) 2016; 31:83-94. [DOI: 10.1152/physiol.00040.2015] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Movements are generated by the coordinated activation of motor units. Recent technological advances have made it possible to identify the concurrent activity of several tens of motor units, in contrast with much smaller samples available in classic studies. We discuss how these advances in technology have enabled the development of a population perspective of how the central nervous system controls motor unit activity and thereby the forces exerted by muscles.
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Affiliation(s)
- Dario Farina
- Institute of Neurorehabilitation Systems, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany; and
| | - Francesco Negro
- Institute of Neurorehabilitation Systems, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany; and
| | - Silvia Muceli
- Institute of Neurorehabilitation Systems, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany; and
| | - Roger M. Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
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194
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Ye X, Beck TW, Wages NP. Influence of prolonged static stretching on motor unit firing properties. Muscle Nerve 2016; 53:808-17. [DOI: 10.1002/mus.24913] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/15/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Xin Ye
- Biophysics Laboratory, Department of Health and Exercise Science; University of Oklahoma; 1401 Asp Avenue. Room 104 Norman Oklahoma USA 73019
| | - Travis W. Beck
- Biophysics Laboratory, Department of Health and Exercise Science; University of Oklahoma; 1401 Asp Avenue. Room 104 Norman Oklahoma USA 73019
| | - Nathan P. Wages
- Biophysics Laboratory, Department of Health and Exercise Science; University of Oklahoma; 1401 Asp Avenue. Room 104 Norman Oklahoma USA 73019
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195
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Flanagan SD, Looney DP, Miller MJS, DuPont WH, Pryor L, Creighton BC, Sterczala AJ, Szivak TK, Hooper DR, Maresh CM, Volek JS, Ellis LA, Kraemer WJ. The Effects of Nitrate-Rich Supplementation on Neuromuscular Efficiency during Heavy Resistance Exercise. J Am Coll Nutr 2016; 35:100-7. [DOI: 10.1080/07315724.2015.1081572] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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196
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Na Y, Choi C, Lee HD, Kim J. A Study on Estimation of Joint Force Through Isometric Index Finger Abduction With the Help of SEMG Peaks for Biomedical Applications. IEEE TRANSACTIONS ON CYBERNETICS 2016; 46:2-8. [PMID: 25594990 DOI: 10.1109/tcyb.2014.2386856] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We propose a new method to estimate joint force using a biomechanical muscle model and peaks of surface electromyography (SEMG). The SEMG measurement was carried out from the first dorsal interosseous muscle during isometric index finger abduction. The SEMG peaks were used as the input of the biomechanical muscle model which is a transfer function to generate the force. The force estimation performance ( R(2) ) was evaluated using the proposed method with nine healthy subjects, and a former method using a mean absolute value (MAV), which is the full-wave rectified and averaged (or low-pass filtered) signal of SEMG in a time window, was compared with the proposed method; the performance of the proposed method (0.94 ± 0.03) was better than that of MAV (0.90 ± 0.02). The proposed method could be widely applied to quantitative analysis of muscle activities based on SEMG.
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197
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Kline JC, De Luca CJ. Synchronization of motor unit firings: an epiphenomenon of firing rate characteristics not common inputs. J Neurophysiol 2015; 115:178-92. [PMID: 26490288 DOI: 10.1152/jn.00452.2015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 10/16/2015] [Indexed: 01/21/2023] Open
Abstract
Synchronous motor unit firing instances have been attributed to anatomical inputs shared by motoneurons. Yet, there is a lack of empirical evidence confirming the notion that common inputs elicit synchronization under voluntary conditions. We tested this notion by measuring synchronization between motor unit action potential trains (MUAPTs) as their firing rates progressed within a contraction from a relatively low force level to a higher one. On average, the degree of synchronization decreased as the force increased. The common input notion provides no empirically supported explanation for the observed synchronization behavior. Therefore, we investigated a more probable explanation for synchronization. Our data set of 17,546 paired MUAPTs revealed that the degree of synchronization varies as a function of two characteristics of the motor unit firing rate: the similarity and the slope as a function of force. Both are measures of the excitation of the motoneurons. As the force generated by the muscle increases, the firing rate slope decreases, and the synchronization correspondingly decreases. Different muscles have motor units with different firing rate characteristics and display different amounts of synchronization. Although this association is not proof of causality, it consistently explains our observations and strongly suggests further investigation. So viewed, synchronization is likely an epiphenomenon, subject to countless unknown neural interactions. As such, synchronous firing instances may not be the product of a specific design and may not serve a specific physiological purpose. Our explanation for synchronization has the advantage of being supported by empirical evidence, whereas the common input does not.
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Affiliation(s)
- Joshua C Kline
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts; and Delsys Incorporated, Natick, Massachusetts
| | - Carlo J De Luca
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts; and Delsys Incorporated, Natick, Massachusetts
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198
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Hu X, Suresh AK, Rymer WZ, Suresh NL. Assessing altered motor unit recruitment patterns in paretic muscles of stroke survivors using surface electromyography. J Neural Eng 2015; 12:066001. [PMID: 26402920 DOI: 10.1088/1741-2560/12/6/066001] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The advancement of surface electromyogram (sEMG) recording and signal processing techniques has allowed us to characterize the recruitment properties of a substantial population of motor units (MUs) non-invasively. Here we seek to determine whether MU recruitment properties are modified in paretic muscles of hemispheric stroke survivors. APPROACH Using an advanced EMG sensor array, we recorded sEMG during isometric contractions of the first dorsal interosseous muscle over a range of contraction levels, from 20% to 60% of maximum, in both paretic and contralateral muscles of stroke survivors. Using MU decomposition techniques, MU action potential amplitudes and recruitment thresholds were derived for simultaneously activated MUs in each isometric contraction. MAIN RESULTS Our results show a significant disruption of recruitment organization in paretic muscles, in that the size principle describing recruitment rank order was materially distorted. MUs were recruited over a very narrow force range with increasing force output, generating a strong clustering effect, when referenced to recruitment force magnitude. Such disturbances in MU properties also correlated well with the impairment of voluntary force generation. SIGNIFICANCE Our findings provide direct evidence regarding MU recruitment modifications in paretic muscles of stroke survivors, and suggest that these modifications may contribute to weakness for voluntary contractions.
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Affiliation(s)
- Xiaogang Hu
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA
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199
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Herda TJ, Siedlik JA, Trevino MA, Cooper MA, Weir JP. Motor unit control strategies of endurance- versus resistance-trained individuals. Muscle Nerve 2015; 52:832-43. [DOI: 10.1002/mus.24597] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 01/29/2015] [Accepted: 02/03/2015] [Indexed: 11/05/2022]
Affiliation(s)
- Trent J. Herda
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
| | - Jacob A. Siedlik
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
| | - Michael A. Trevino
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
| | - Michael A. Cooper
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
| | - Joseph P. Weir
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
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200
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Farina D, Merletti R, Enoka RM. Reply to De Luca, Nawab, and Kline: The proposed method to validate surface EMG signal decomposition remains problematic. J Appl Physiol (1985) 2015; 118:1085. [PMID: 25878219 DOI: 10.1152/japplphysiol.00107.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Dario Farina
- Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany;
| | - Roberto Merletti
- Laboratory for Engineering of the Neuromuscular System, Department of Electronics and Telecommunications, Politecnico di Torino, Turin, Italy; and
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado Boulder, Colorado
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