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Sherman DA, Rush J, Stock MS, D. Ingersoll C, E. Norte G. Neural drive and motor unit characteristics after anterior cruciate ligament reconstruction: implications for quadriceps weakness. PeerJ 2023; 11:e16261. [PMID: 37818333 PMCID: PMC10561646 DOI: 10.7717/peerj.16261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 09/18/2023] [Indexed: 10/12/2023] Open
Abstract
Purpose The purpose of this investigation was to compare the quality of neural drive and recruited quadriceps motor units' (MU) action potential amplitude (MUAPAMP) and discharge rate (mean firing rate (MFR)) relative to recruitment threshold (RT) between individuals with anterior cruciate ligament reconstruction (ACLR) and controls. Methods Fourteen individuals with ACLR and 13 matched controls performed trapezoidal knee extensor contractions at 30%, 50%, 70%, and 100% of their maximal voluntary isometric contraction (MVIC). Decomposition electromyography (dEMG) and torque were recorded concurrently. The Hoffmann reflex (H-reflex) and central activation ratio (CAR) were acquired bilaterally to detail the proportion of MU pool available and volitionally activated. We examined MUAPAMP-RT and MFR-RT relationships with linear regression and extracted the regression line slope, y-intercept, and RT range for each contraction. Linear mixed effect modelling used to analyze the effect of group and limb on regression line slope and RT range. Results Individuals with ACLR demonstrated lower MVIC torque in the involved limb compared to uninvolved limb. There were no differences in H-reflex or CAR between groups or limbs. The ACLR involved limb demonstrated smaller mass-normalized RT range and slower MU firing rates at high contraction intensities (70% and 100% MVIC) compared to uninvolved and control limbs. The ACLR involved limb also demonstrated larger MU action potentials in the VM compared to the contralateral limb. These differences were largely attenuated with relative RT normalization. Conclusions These results suggest that persistent strength deficits following ACLR may be attributable to a diminished quadriceps motor neuron pool and inability to upregulate the firing rate of recruited MUs.
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Affiliation(s)
- David A. Sherman
- Live4 Physical Therapy and Wellness, Acton, Massachusetts, United States of America
- Chobanian & Avedisian School of Medicine, Boston University, Boston, Massachusetts, United States of America
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States of America
| | - Justin Rush
- Division of Physical Therapy, School of Rehabilitation and Communication Sciences, College of Health Sciences and Professions, Ohio University, Athens, Ohio, United States of America
| | - Matt S. Stock
- Cognition, Neuroplasticity, & Sarcopenia (CNS) Lab, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, United States of America
| | - Christopher D. Ingersoll
- College of Health Professions and Sciences, School of Kinesiology and Rehabilitation Sciences, University of Central Florida, Orlando, Florida, United States of America
| | - Grant E. Norte
- Cognition, Neuroplasticity, & Sarcopenia (CNS) Lab, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, United States of America
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Beausejour JP, Bohlen P, Harmon KK, Girts RM, Pagan JI, Hahs-Vaughn DL, Herda TJ, Stock MS. A comparison of techniques for verifying the accuracy of precision decomposition-derived relationships between motor unit firing rates and recruitment thresholds from surface EMG signals. Exp Brain Res 2023; 241:2547-2560. [PMID: 37707570 DOI: 10.1007/s00221-023-06694-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 08/21/2023] [Indexed: 09/15/2023]
Abstract
Approaches for validating motor unit firing times following surface electromyographic (EMG) signal decomposition with the precision decomposition III (PDIII) algorithm have not been agreed upon. Two approaches have been common: (1) "reconstruct-and-test" and (2) spike-triggered averaging (STA). We sought to compare motor unit results following the application of these approaches. Surface EMG signals were recorded from the vastus lateralis of 13 young males performing trapezoidal, isometric knee extensions at 50% and 80% of maximum voluntary contraction (MVC) force. The PDIII algorithm was used to quantify motor unit firing rates. Motor units were excluded using eight combinations of the reconstruct-and-test approach with accuracy thresholds of 0, 90, 91, and 92% with and without STA. The mean firing rate versus recruitment threshold relationship was minimally affected by STA. At 80% MVC, slopes acquired at the 0% accuracy threshold were significantly greater (i.e., less negative) than when 91% (p = .010) and 92% (p = .030) accuracy thresholds were applied. The application of STA has minimal influence on surface EMG signal decomposition results. Stringent reconstruct-and-test accuracy thresholds influence motor unit-derived relationships at high forces, perhaps explained through the increased presence of large motor unit action potentials. Investigators using the PDIII algorithm can expect negligible changes in motor unit-derived linear regression relationships with the application of secondary validation procedures.
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Affiliation(s)
- Jonathan P Beausejour
- Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, 4000 Central Florida Blvd, Orlando, FL, 32816-2205, USA
- School of Kinesiology and Rehabilitation Sciences, University of Central Florida, Orlando, FL, USA
| | - Paul Bohlen
- Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, 4000 Central Florida Blvd, Orlando, FL, 32816-2205, USA
- School of Kinesiology and Rehabilitation Sciences, University of Central Florida, Orlando, FL, USA
| | - Kylie K Harmon
- Department of Exercise Science, Syracuse University, Syracuse, NY, USA
| | - Ryan M Girts
- Department of Natural and Health Sciences, Pfeiffer University, Misenheimer, NC, USA
| | - Jason I Pagan
- Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, 4000 Central Florida Blvd, Orlando, FL, 32816-2205, USA
- School of Kinesiology and Rehabilitation Sciences, University of Central Florida, Orlando, FL, USA
| | - Debbie L Hahs-Vaughn
- College of Community Innovation and Education, University of Central Florida, Orlando, FL, USA
| | - Trent J Herda
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, USA
| | - Matt S Stock
- Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, 4000 Central Florida Blvd, Orlando, FL, 32816-2205, USA.
- School of Kinesiology and Rehabilitation Sciences, University of Central Florida, Orlando, FL, USA.
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Becker K, Goethel M, Fonseca P, Vilas-Boas JP, Ervilha U. The Strategy of the Brain to Maintain the Force Production in Painful Contractions-A Motor Units Pool Reorganization. Cells 2022; 11:cells11203299. [PMID: 36291165 PMCID: PMC9601229 DOI: 10.3390/cells11203299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/04/2022] [Accepted: 10/18/2022] [Indexed: 12/29/2022] Open
Abstract
A common symptom in neuromuscular diseases is pain, which changes human movement in many ways. Using the decomposed electromyographic signal, we investigate the strategy of the brain in recruiting different pools of motor units (MUs) to produce torque during induced muscle pain in terms of firing rate (FR), recruitment threshold (RT) and action potential amplitude (MUAPAMP). These properties were used to define two groups (G1/G2) based on a K-means clusterization method. A 2.0 mL intramuscular hypertonic (6%) or isotonic (0.9%) saline solution was injected to induce pain or act as a placebo during isometric and isokinetic knee extension contractions. While isometric torque decreases after pain induction with hypertonic solution, this does not occur in isokinetic torque. This occurs because the MUs re-organized after the injection of both solutions. This is supported by an increase in RT, in both G1 and G2 MUs. However, when inducing pain with the hypertonic solution, RT increase is exacerbated. In this condition, FR also decreases, while MUAPAMP increases only for G1 MUs. Therefore, this study proposes that the strategy for maintaining force production during pain is to recruit MUs with higher RT and MUAPAMP.
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Affiliation(s)
- Klaus Becker
- Porto Biomechanics Laboratory, University of Porto, 4200-450 Porto, Portugal
- Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, 4200-450 Porto, Portugal
- Correspondence:
| | - Márcio Goethel
- Porto Biomechanics Laboratory, University of Porto, 4200-450 Porto, Portugal
- Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, 4200-450 Porto, Portugal
| | - Pedro Fonseca
- Porto Biomechanics Laboratory, University of Porto, 4200-450 Porto, Portugal
| | - João Paulo Vilas-Boas
- Porto Biomechanics Laboratory, University of Porto, 4200-450 Porto, Portugal
- Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, 4200-450 Porto, Portugal
| | - Ulysses Ervilha
- Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, 4200-450 Porto, Portugal
- Laboratory of Physical Activity Sciences, School of Arts, Sciences, and Humanities, University of São Paulo, São Paulo 03828-000, Brazil
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MacLennan RJ, Ogilvie D, McDorman J, Vargas E, Grusky AR, Kim Y, Garcia JM, Stock MS. The time course of neuromuscular impairment during short-term disuse in young women. Physiol Rep 2021; 9:e14677. [PMID: 33426809 PMCID: PMC7797948 DOI: 10.14814/phy2.14677] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 11/14/2020] [Indexed: 12/27/2022] Open
Abstract
Skeletal muscle disuse results in rapid functional declines. Previous studies have typically been at least 1 week in duration and focused on the responsiveness of men. Herein, we report the timeline of initial impairments in strength, voluntary activation (VA), and motor unit control during 2 weeks of knee joint immobilization. Thirteen women (mean age =21 years) underwent 2 weeks of left knee joint immobilization via ambulation on crutches and use of a brace. Participants visited the laboratory for testing on seven occasions (two familiarization visits, pretest, 48 and 72 h, 1 and 2 weeks). Knee extensor isometric and concentric isokinetic strength at two velocities (180 and 360 degrees⋅s-1 ), VA, and submaximal vastus lateralis motor unit activity were evaluated. Moderate-to-large decreases in isometric and concentric strength at 180 degrees⋅s-1 and VA were observed within 48 hours. Isometric strength continued to decline beyond 72 h, whereas other variables plateaued. The B-term of the motor unit mean firing rate versus action potential amplitude relationship demonstrated a moderate increase 1 week into immobilization, suggesting that greater firing rates were necessary to maintain pretest torque levels. Concentric strength at a velocity of 360 degrees s-1 was not affected. Decreases in knee extensor strength occur within a matter of days after immobilization, although the time course and magnitude vary among assessment methods. These changes are mediated by the nervous system's capacity to activate skeletal muscle. Clinically appropriate interventions which target nervous system plasticity should be implemented early to minimize the rapid functional impairments associated with disuse.
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Affiliation(s)
- Rob J MacLennan
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, OK, USA
| | - David Ogilvie
- School of Kinesiology & Physical Therapy, University of Central Florida, Orlando, FL, USA.,Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, USA
| | - John McDorman
- School of Kinesiology & Physical Therapy, University of Central Florida, Orlando, FL, USA.,Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, USA
| | - Ernest Vargas
- School of Kinesiology & Physical Therapy, University of Central Florida, Orlando, FL, USA.,Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, USA
| | - Arielle R Grusky
- School of Kinesiology & Physical Therapy, University of Central Florida, Orlando, FL, USA.,Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, USA
| | - Youngdeok Kim
- Department of Kinesiology and Health Sciences, Virginia Commonwealth University, Richmond, VA, USA
| | - Jeanette M Garcia
- Department of Health Sciences, University of Central Florida, Orlando, FL, USA
| | - Matt S Stock
- School of Kinesiology & Physical Therapy, University of Central Florida, Orlando, FL, USA.,Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, USA
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Jeon S, Miller WM, Ye X. A Comparison of Motor Unit Control Strategies between Two Different Isometric Tasks. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17082799. [PMID: 32325707 PMCID: PMC7215511 DOI: 10.3390/ijerph17082799] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/12/2020] [Accepted: 04/15/2020] [Indexed: 11/17/2022]
Abstract
Background: This study examined the motor unit (MU) control strategies for non-fatiguing isometric elbow flexion tasks at 40% and 70% maximal voluntary isometric contraction. Methods: Nineteen healthy individuals performed two submaximal tasks with similar torque levels: contracting against an immovable object (force task), and maintaining the elbow joint angle against an external load (position task). Surface electromyographic (EMG) signals were collected from the agonist and antagonist muscles. The signals from the agonist were decomposed into individual action potential trains. The linear regression analysis was used to examine the MU recruitment threshold (RT) versus mean firing rates (MFR), and RT versus derecruitment threshold (DT) relationships. Results: Both agonist and antagonist muscles’ EMG amplitudes did not differ between two tasks. The linear slopes of the MU RT versus MFR and RT versus DT relationships during the position task were more negative (p = 0.010) and more positive (p = 0.023), respectively, when compared to the force task. Conclusions: To produce a similar force output, the position task may rely less on the recruitment of relatively high-threshold MUs. Additionally, as the force output decreases, MUs tend to derecruit at a higher force level during the position task.
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Affiliation(s)
| | | | - Xin Ye
- Correspondence: ; Tel.: +1-662-915-1630
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Harmon KK, Girts RM, MacLennan RJ, Stock MS. Is the motor unit mean firing rate versus recruitment threshold relationship linear? Physiol Meas 2019; 40:095002. [PMID: 31470424 DOI: 10.1088/1361-6579/ab4025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Advances in surface electromyographic (EMG) signal decomposition allow researchers to analyze data for 20-50 motor units per contraction. To simplify interpretation, some investigators rely on group mean analysis of the mean firing rate versus recruitment threshold relationship, but it is unclear if this association is linear. OBJECTIVE To determine whether this relationship is strongest when analyzed via linear, quadratic, or cubic regression. APPROACH Twenty-one men (mean ± SD age = 24 ± 4 years) and 16 women (21 ± 2 years) performed isometric contractions of the knee extensors at 50% of maximal force while bipolar surface EMG signals were recorded from the vastus lateralis. A decomposition algorithm was used to calculate the mean firing rate and recruitment threshold of each motor unit at accuracy levels ranging from 90.0%-93.0%. Polynominal regression was used to determine if each relationship was best fit with a linear, quadratic, or cubic model. We examined individual contractions and grouped data. MAIN RESULTS Overall, 80% of the relationships were best fit with a linear model. Quadratic and cubic relationships were more appropriate for 16% and 2% of the contractions, respectively. Selecting varying accuracy levels within a range of 90.0%-93.0% had little influence on whether a given dataset was best fit with a linear, quadratic, or cubic model. Grouping of data provided different relationships than otherwise found on a contraction-by-contraction basis. SIGNIFICANCE The mean firing rate versus recruitment threshold relationship is typically best fit with a linear model. These relationships should be examined on an individual contraction basis.
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Affiliation(s)
- Kylie K Harmon
- Neuromuscular Plasticity Laboratory, School of Kinesiology and Physical Therapy, University of Central Florida, 12354 Research Parkway, Orlando, FL, 32826, United States of America
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