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Zambolin F, Duro Ocana P, Goulding R, Sanderson A, Venturelli M, Wood G, McPhee J, Parr JVV. The corticomuscular response to experimental pain via blood flow occlusion when applied to the ipsilateral and contralateral leg during an isometric force task. Psychophysiology 2024; 61:e14466. [PMID: 37872004 DOI: 10.1111/psyp.14466] [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: 04/24/2023] [Revised: 08/21/2023] [Accepted: 10/08/2023] [Indexed: 10/25/2023]
Abstract
Blood flow occlusion (BFO) has been previously used to investigate physiological responses to muscle ischemia, showing increased perceptual effort (RPE) and pain along with impaired neuromuscular performance. However, at present, it is unclear how BFO alters corticomuscular activities when either applied to the exercising or nonexercising musculature. The present study therefore set out to assess the corticomuscular response to these distinct BFO paradigms during an isometric contraction precision task. In a repeated measures design, fifteen participants (age = 27.00 ± 5.77) completed 15 isometric contractions across three experimental conditions; no occlusion (CNTRL), occlusion of the contralateral (i.e., nonexercising) limb (CON-OCC), and occlusion of the ipsilateral (i.e., exercising) limb (IPS-OCC). Measures of force, electroencephalographic (EEG), and electromyographic (EMG) were recorded during contractions. We observed that IPS-OCC broadly impaired force steadiness, elevated EMG of the vastus lateralis, and heightened RPE and pain. IPSI-OCC also significantly decreased corticomuscular coherence during the early phase of contraction and decreased EEG alpha activity across the sensorimotor and temporoparietal regions during the middle and late phases of contraction compared with CNTRL. By contrast, CON-OCC increased perceived levels of pain (but not RPE) and decreased EEG alpha activity across the prefrontal cortex during the middle and late phases of contraction, with no changes observed for EMG and force steadiness. Together, these findings highlight distinctive psychophysiological responses to experimental pain via BFO showing altered cortical activities (CON-OCC) and altered cortical, corticomuscular, and neuromuscular activities (IPS-OCC) when applied to the lower limbs during an isometric force precision task.
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Affiliation(s)
- F Zambolin
- Institute of Sport, Manchester Metropolitan University, Manchester, UK
- Department of Sport and Exercise Science, Manchester Metropolitan University, Manchester, UK
| | - P Duro Ocana
- Department of Life Science, Manchester Metropolitan University, Manchester, UK
| | - R Goulding
- Laboratory for Myology, Faculty of Behavioural and Movement Sciences, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - A Sanderson
- Institute of Sport, Manchester Metropolitan University, Manchester, UK
- Department of Sport and Exercise Science, Manchester Metropolitan University, Manchester, UK
| | - M Venturelli
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
- Department of Internal Medicine, University of Utah, Salt Lake City, Utah, USA
| | - G Wood
- Institute of Sport, Manchester Metropolitan University, Manchester, UK
- Department of Sport and Exercise Science, Manchester Metropolitan University, Manchester, UK
| | - J McPhee
- Institute of Sport, Manchester Metropolitan University, Manchester, UK
- Department of Sport and Exercise Science, Manchester Metropolitan University, Manchester, UK
| | - J V V Parr
- Institute of Sport, Manchester Metropolitan University, Manchester, UK
- Department of Sport and Exercise Science, Manchester Metropolitan University, Manchester, UK
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Dotan R, Woods S, Langille J, Falk B. Boys-men mean-power-frequency differences in progressive exercise to exhaustion, confounded by variability and adiposity. Eur J Appl Physiol 2024; 124:491-505. [PMID: 37553549 DOI: 10.1007/s00421-023-05292-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 07/26/2023] [Indexed: 08/10/2023]
Abstract
BACKGROUND Only scant research has compared children's mean power frequency (MPF) to adults', with a clear overview still lacking. A significant obstacle has been MPF's high variability, which this study aimed to overcome by elucidating the MPF characteristics distinguishing boys from men in progressive exhaustive exercise. METHODS Electromyographic (EMG) data of 20 men (23.5 ± 2.5yrs) and 17 boys (10.2 ± 1.0 yrs), who performed progressively exhausting, intermittent isometric knee extensions, were subjected to secondary MPF analysis. Participants' vastus lateralis MPF data series were transformed to third-order polynomial regressions and expressed as percentages of the peak polynomial MPF values (%MPFpeak). The resulting curves were compared at 5-% time-to-exhaustion (TTE) intervals, using repeated-measures ANOVA. Raw MPFpeak values were adiposity corrected to 0% fat and used to convert the %MPFpeak data back to absolute MPF values (Hz) for estimating muscle-level MPF. RESULTS No overall interaction or group effects could be shown between the %MPFpeak plots, but pairwise comparisons revealed significantly higher men's values at 50-70%TTE and lower at 100%TTE, i.e. boys' shallower MPF rise and decline. The adiposity-corrected boys' and men's composite MPF values peaked at 125.7 ± 2.5 and 166.0 ± 2.4 Hz, respectively (110.7 ± 1.7 and 122.5 ± 2.1 Hz, uncorrected), with a significant group effect (p < 0.05) and pairwise differences at all %TTE points. CONCLUSIONS The boys were lower than the men in both the observed and, more so, in the adiposity-corrected MPF values that presumably estimate muscle-level MPF. The boys' shallower MPF rise and decline conform to children's claimed type-II motor-unit activation and/or compositional deficits and their related known advantage in muscular endurance.
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Affiliation(s)
- Raffy Dotan
- Kinesiology Department, Faculty of Applied Health Sciences, Brock University, St Catharines, ON, Canada.
| | - Stacey Woods
- Kinesiology Department, Faculty of Applied Health Sciences, Brock University, St Catharines, ON, Canada
| | - Jordan Langille
- Kinesiology Department, Faculty of Applied Health Sciences, Brock University, St Catharines, ON, Canada
| | - Bareket Falk
- Kinesiology Department, Faculty of Applied Health Sciences, Brock University, St Catharines, ON, Canada
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Carr JC, King AC. Sex differences in the fractal dynamics of force control during maximal handgrip. Neurosci Lett 2024; 820:137588. [PMID: 38086520 DOI: 10.1016/j.neulet.2023.137588] [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: 07/01/2023] [Revised: 12/04/2023] [Accepted: 12/06/2023] [Indexed: 12/17/2023]
Abstract
This work examines the temporal structure of force fluctuations during maximal handgrip with detrended fluctuation analysis (DFA α). Here, we assess the influence of fatigue and sex on force complexity during unimanual handgrip for the fatigued and the contralateral, non-fatigued hand. Participants randomly completed experimental sessions requiring fatiguing handgrip contractions or control measurements only. Maximal unimanual forces of both hands were measured before and after the fatigue trial or a time-matched control visit. DFA revealed substantially lower alpha values for females (PRE = 1.15, POST = 1.25) compared to males (PRE = 1.30, POST = 1.33) regardless of fatigue (p < 0.01, d = 0.738) for the dominant hand with a similar pattern observed for the contralateral, non-fatigued hand (p = 0.045, d = 0.561). Females also showed greater alpha changes (Δ = 0.09) versus males (Δ = 0.01) following fatigue (p = 0.028, ηp2 = 0.151). The data provide evidence of reduced force complexity during successive maximal handgrip contractions for females, but not males. Our findings highlight task-specific factors involving force control and demonstrate the utility of complexity analyses to provide insights regarding the influence of sex on motor control strategies.
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Affiliation(s)
- Joshua C Carr
- Texas Christian University, Department of Kinesiology, Fort Worth, TX, United States; Anne Burnett Marion School of Medicine at Texas Christian University, Department of Medical Education, Fort Worth, TX, United States.
| | - Adam C King
- Texas Christian University, Department of Kinesiology, Fort Worth, TX, United States; Anne Burnett Marion School of Medicine at Texas Christian University, Department of Medical Education, Fort Worth, TX, United States.
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Ricotta JM, De SD, Nardon M, Benamati A, Latash ML. Effects of fatigue on intramuscle force-stabilizing synergies. J Appl Physiol (1985) 2023; 135:1023-1035. [PMID: 37732378 DOI: 10.1152/japplphysiol.00419.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/22/2023] [Accepted: 09/14/2023] [Indexed: 09/22/2023] Open
Abstract
We applied the recently introduced concept of intramuscle synergies in spaces of motor units (MUs) to quantify indexes of such synergies in the tibialis anterior during ankle dorsiflexion force production tasks and their changes with fatigue. We hypothesized that MUs would be organized into robust groups (MU modes), which would covary across trials to stabilize force magnitude, and the indexes of such synergies would drop under fatigue. Healthy, young subjects (n = 15; 8 females) produced cyclical, isometric dorsiflexion forces while surface electromyography was used to identify action potentials of individual MUs. Principal component analysis was used to define MU modes. The framework of the uncontrolled manifold (UCM) was used to analyze intercycle variance and compute the synergy index, ΔVZ. Cyclical force production tasks were repeated after a nonfatiguing exercise (control) and a fatiguing exercise. Across subjects, fatigue led, on average, to a 43% drop in maximal force and fewer identified MUs per subject (29.6 ± 2.1 vs. 32.4 ± 2.1). The first two MU modes accounted for 81.2 ± 0.08% of variance across conditions. Force-stabilizing synergies were present across all conditions and were diminished after fatiguing exercise (1.49 ± 0.40) but not control exercise (1.76 ± 0.75). Decreased stability after fatigue was caused by an increase in the amount of variance orthogonal to the UCM. These findings contrast with earlier studies of multieffector synergies demonstrating increased synergy index under fatigue. We interpret the results as reflections of a drop in the gain of spinal reflex loops under fatigue. The findings corroborate an earlier hypothesis on the spinal nature of intramuscle synergies.NEW & NOTEWORTHY Across multielement force production tasks, fatigue of an element leads to increased indexes of force stability (synergy indexes). Here, however, we show that groups of motor units in the tibialis anterior show decreased indexes of force-stabilizing synergies after fatiguing exercise. These findings align intramuscle synergies with spinal mechanisms, in contrast to the supraspinal control of multimuscle synergies.
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Affiliation(s)
- Joseph M Ricotta
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
- Clinical and Translational Science Institute, Penn State College of Medicine, Hershey, Pennsylvania, United States
| | - Sayan D De
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - Mauro Nardon
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Anna Benamati
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Mark L Latash
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
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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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Avila ER, Williams SE, Disselhorst-Klug C. Advances in EMG measurement techniques, analysis procedures, and the impact of muscle mechanics on future requirements for the methodology. J Biomech 2023; 156:111687. [PMID: 37339541 DOI: 10.1016/j.jbiomech.2023.111687] [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: 06/02/2023] [Accepted: 06/11/2023] [Indexed: 06/22/2023]
Abstract
Muscular coordination enables locomotion and interaction with the environment. For more than 50 years electromyography (EMG) has provided insights into the central nervous system control of individual muscles or muscle groups, enabling both fine and gross motor functions. This information is available either at individual motor units (Mus) level or on a more global level from the coordination of different muscles or muscle groups. In particular, non-invasive EMG methods such as surface EMG (sEMG) or, more recently, spatial mapping methods (High-Density EMG - HDsEMG) have found their place in research into biomechanics, sport and exercise, ergonomics, rehabilitation, diagnostics, and increasingly for the control of technical devices. With further technical advances and a growing understanding of the relationship between EMG and movement task execution, it is expected that with time, especially non-invasive EMG methods will become increasingly important in movement sciences. However, while the total number of publications per year on non-invasive EMG methods is growing exponentially, the number of publications on this topic in journals with a scope in movement sciences has stagnated in the last decade. This review paper contextualizes non-invasive EMG development over the last 50 years, highlighting methodological progress. Changes in research topics related to non-invasive EMG were identified. Today non-invasive EMG procedures are increasingly used to control technical devices, where muscle mechanics have a minor influence. In movement science, however, the effect of muscle mechanics on the EMG signal cannot be neglected. This explains why non-invasive EMG's relevance in movement sciences has not developed as expected.
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Affiliation(s)
- Elisa Romero Avila
- Department of Rehabilitation and Prevention Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, Germany
| | - Sybele E Williams
- Department of Rehabilitation and Prevention Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, Germany
| | - Catherine Disselhorst-Klug
- Department of Rehabilitation and Prevention Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, Germany.
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García-Aguilar F, Caballero C, Sabido R, Moreno FJ. The use of non-linear tools to analyze the variability of force production as an index of fatigue: A systematic review. Front Physiol 2022; 13:1074652. [PMID: 36589460 PMCID: PMC9795073 DOI: 10.3389/fphys.2022.1074652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 11/16/2022] [Indexed: 12/15/2022] Open
Abstract
Background: Fatigue is a process that results in a decreased ability to produce force, and which could eventually affect performance and increase the risk of injury. Force variability analysis has been proposed to describe the level of fatigue with the purpose of detecting the development of fatigue. Variability is credited to play a functional and adaptive role through which the components of a system self-organize to solve a motor problem. Non-linear tools have been applied to analyze the variability of physiological signals, revealing that the structure of motor fluctuations provides relevant information about the functional role of variability. It has been suggested that the presence of lower complexity in the variability structure could reveal a less functional and adaptative state (e.g., ageing or illness). In the last years, an increased number of studies have applied these techniques to force variability analysis in relation to fatigue. Objective: To provide an overview of the current knowledge on the use of non-linear tools on force variability as a fatigue index. Methods: Following PRISMA guidelines, a systematic search of SPORTDiscus, Scopus, Web of Science and PubMed was carried out. Studies included were: a) original studies that analyzed the effect of fatigue on humans during an action focused on force production; b) published studies with their title and abstract in English; c) studies that applied non-linear tools on a signal directly related to force production. Results: Twenty-five studies were included in this review. The relationship between fatigue and the complexity of force variability, the type of action and relative intensity, the nature of the signal and the non-linear tools used, and the methods of data acquisition and processing were identified. Conclusion: The articles reviewed suggest that fatigue leads to a decrease in complexity mostly in isometric contractions, but this is not as clear in dynamic contractions. This fatigue-induced loss of complexity seems to be a result of changes in the nervous system at the central level, albeit triggered by peripheral mechanisms. It should be noted that non-linear tools are affected by the relative intensity of contraction, non-stationarity, and the acquisition and treatment of the signal.
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Hirono T, Kunugi S, Yoshimura A, Holobar A, Watanabe K. Acute changes in motor unit discharge property after concentric versus eccentric contraction exercise in knee extensor. J Electromyogr Kinesiol 2022; 67:102704. [PMID: 36137408 DOI: 10.1016/j.jelekin.2022.102704] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 08/26/2022] [Accepted: 09/12/2022] [Indexed: 12/14/2022] Open
Abstract
This study aimed to investigate the motor unit firing property immediately after concentric or eccentric contraction exercise. Eighteen healthy men performed repetitive maximal isokinetic knee extension exercises with only concentric or eccentric contraction until they exerted less than 80% of the baseline strength. Before and after the fatiguing exercise, high-density surface electromyography of the vastus lateralis was recorded during submaximal ramp-up isometric contraction and individual motor units were identified. Only motor units that could be tracked before and after exercise were analyzed. Muscle cross-sectional area of the vastus lateralis was measured using ultrasound, and electrically evoked torque was recorded before and after the exercise. Sixty-five and fifty-three motor units were analyzed before and after the concentric and eccentric contractions, respectively. The results showed that motor units with moderate to high recruitment thresholds significantly decreased recruitment thresholds under both conditions, and the motor unit discharge rates significantly increased after concentric contraction compared to eccentric contraction. A greater muscle cross-sectional area was observed with concentric contraction. The evoked torque was significantly decreased under both conditions, but no difference between the conditions. These results suggest that fatiguing exercise with concentric contraction contributes to greater neural input to muscles and metabolic responses than eccentric contraction.
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Affiliation(s)
- Tetsuya Hirono
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Science, Chukyo University, 101 Tokodachi, Kaizu-cho, Toyota, Aichi 470-0393, Japan; Research Fellow of Japan Society for the Promotion of Science, Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan.
| | - Shun Kunugi
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Science, Chukyo University, 101 Tokodachi, Kaizu-cho, Toyota, Aichi 470-0393, Japan; Center for General Education, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392, Japan
| | - Akane Yoshimura
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Science, Chukyo University, 101 Tokodachi, Kaizu-cho, Toyota, Aichi 470-0393, Japan; Faculty of Education and Integrated Arts and Sciences, Waseda University, 1-6-1, Nishiwaseda, Shinjuku-ku, Tokyo 169-8050, Japan
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Koroška cesta 46, SI-2000 Maribor, Slovenia
| | - Kohei Watanabe
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Science, Chukyo University, 101 Tokodachi, Kaizu-cho, Toyota, Aichi 470-0393, Japan
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Saini H, Röhrle O. A biophysically guided constitutive law of the musculotendon-complex: modelling and numerical implementation in Abaqus. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 226:107152. [PMID: 36194967 DOI: 10.1016/j.cmpb.2022.107152] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 08/25/2022] [Accepted: 09/20/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND AND OBJECTIVE Many biomedical, clinical, and industrial applications may benefit from musculoskeletal simulations. Three-dimensional macroscopic muscle models (3D models) can more accurately represent muscle architecture than their 1D (line-segment) counterparts. Nevertheless, 3D models remain underutilised in academic, clinical, and commercial environments. Among the reasons for this is a lack of modelling and simulation standardisation, verification, and validation. Here, we strive towards a solution by providing an open-access, characterised, constitutive relation (CR) for 3D musculotendon models. METHODS The musculotendon complex is modelled following the state-of-the-art active stress approach and is treated as hyperelastic, transversely isotropic, and nearly incompressible. Furthermore, force-length and -velocity relationships are incorporated, and muscle activation is derived from motor-unit information. The CR was implemented within the commercial finite-element software package Abaqus as a user-subroutine. A masticatory system model with left and right masseters was used to demonstrate active and passive movement. RESULTS The CR was characterised by various experimental data sets and was able to capture a wide variety of passive and active behaviours. Furthermore, the masticatory simulations revealed that joint movement was sensitive to the muscle's in-fibre passive response. CONCLUSIONS This user-material provides a "plug and play" template for 3D neuro-musculoskeletal finite element modelling. We hope that this reduces modelling effort, fosters exchange, and contributes to the standardisation of such models.
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Affiliation(s)
- Harnoor Saini
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Pfaffenwalding 5a, 70569 Stuttgart, Germany.
| | - Oliver Röhrle
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Pfaffenwalding 5a, 70569 Stuttgart, Germany; Stuttgart Center for Simulation Sciences (SC SimTech), Pfaffenwaldring 5a, 70569 Stuttgart, Germany
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10
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Effect of New Zealand Blackcurrant Extract on Force Steadiness of the Quadriceps Femoris Muscle during Sustained Submaximal Isometric Contraction. J Funct Morphol Kinesiol 2022; 7:jfmk7020044. [PMID: 35736015 PMCID: PMC9225559 DOI: 10.3390/jfmk7020044] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Revised: 05/15/2022] [Accepted: 05/27/2022] [Indexed: 11/25/2022] Open
Abstract
Intake of anthocyanin-rich New Zealand blackcurrant (NZBC) can alter physiological responses that enhance exercise performance. In two studies, we examined the effects of NZBC extract on force steadiness during a sustained submaximal isometric contraction of the quadriceps femoris muscle. With repeated measures designs, male participants in study one (n = 13) and study two (n = 19) performed a 120 s submaximal (30%) isometric contraction of the quadriceps femoris muscle following a 7-day intake of NZBC extract and placebo (study one) and following 0 (control), 1-, 4- and 7-day intake of NZBC extract (study two). Participants for both studies were different. In study one, NZBC extract enhanced isometric force steadiness during the 120 s contraction (placebo: 6.58 ± 2.24%, NZBC extract: 6.05 ± 2.24%, p = 0.003), with differences in the third (60-89 s) and fourth quartile (90-120 s) of the contraction. In study two, isometric force steadiness was not changed following 1 and 4 days but was enhanced following 7-day intake of NZBC extract in comparison to control. In study two, the enhanced isometric force steadiness following 7-day intake did occur in the second (30-59 s), third (60-89 s) and fourth (90-120 s) quartiles. Daily supplementation of anthocyanin-rich NZBC extract can enhance force steadiness of the quadriceps femoris muscle during a sustained submaximal isometric contraction. Our observations may have implications for human tasks that require postural stability.
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Ranaldi S, Corvini G, De Marchis C, Conforto S. The Influence of the sEMG Amplitude Estimation Technique on the EMG–Force Relationship. SENSORS 2022; 22:s22113972. [PMID: 35684590 PMCID: PMC9182811 DOI: 10.3390/s22113972] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 05/11/2022] [Accepted: 05/20/2022] [Indexed: 12/07/2022]
Abstract
The estimation of the sEMG–force relationship is an open problem in the scientific literature; current methods show different limitations and can achieve good performance only on limited scenarios, failing to identify a general solution to the optimization of this kind of analysis. In this work, this relationship has been estimated on two different datasets related to isometric force-tracking experiments by calculating the sEMG amplitude using different fixed-time constant moving-window filters, as well as an adaptive time-varying algorithm. Results show how the adaptive methods might be the most appropriate choice for the estimation of the correlation between the sEMG signal and the force time course. Moreover, the comparison between adaptive and standard filters highlights how the time constants exploited in the estimation strategy is not the only influence factor on this kind of analysis; a time-varying approach is able to constantly capture more information with respect to fixed stationary approaches with comparable window lengths.
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Affiliation(s)
- Simone Ranaldi
- Department of Industrial, Electronics and Mechanical Engineering, Roma Tre University, 00154 Roma, Italy; (S.R.); (G.C.)
| | - Giovanni Corvini
- Department of Industrial, Electronics and Mechanical Engineering, Roma Tre University, 00154 Roma, Italy; (S.R.); (G.C.)
| | | | - Silvia Conforto
- Department of Industrial, Electronics and Mechanical Engineering, Roma Tre University, 00154 Roma, Italy; (S.R.); (G.C.)
- Correspondence:
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12
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da Silva MC, da Silva CR, de Lima FF, Lara JR, Gustavson JP, Magalhães FH. Effects of Fatigue on Postural Sway and Electromyography Modulation in Young Expert Acrobatic Gymnasts and Healthy Non-trained Controls During Unipedal Stance. Front Physiol 2022; 13:782838. [PMID: 35222070 PMCID: PMC8864175 DOI: 10.3389/fphys.2022.782838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 01/14/2022] [Indexed: 11/13/2022] Open
Abstract
This study investigated whether expert acrobatic gymnasts respond differentially than their non-trained counterparts during a single-legged stance task performed before and after a protocol designed to induce fatigue in the ankle plantarflexor muscles in terms of (a) postural steadiness and (b) electromyography (EMG) activation. We hypothesized that neuromuscular adaptation due to training would lead to different behavior of center of pressure (COP) and EMG quantifiers after fatigue. Twenty eight female volunteers (aged 11 to 24 years) formed two groups: expert acrobatic gymnastics athletes (GYN, n = 14) and age-matched non-gymnasts [control (CTRL), n = 14]. Fatigue of the ankle plantarflexors (dominant leg) was induced by a sustained posture (standing on the toes) until exhaustion. Traditional COP parameters (area, RMS, mean velocity, and power spectrum at low and high frequency ranges) were obtained with a force plate, and time and frequency-domain EMG parameters were obtained by surface electrodes positioned on the tibialis anterior, soleus, lateral gastrocnemius, medial gastrocnemius, vastus lateralis, biceps femoris, spinal erector and rectus abdominis muscles. The main results showed that fatigue induced a significant increase in postural oscillations in the ML axis (including RMS, velocity and frequency components of the power spectrum), with no significant effects in the AP axis. In terms of postural sway parameters (i.e., COP quantifiers), no superior balance stability was found for the GYN group as compared to CTRL, irrespective of the fatigue condition. On the other hand, the modulation of EMG parameters (in both time and frequency domains) indicated that expert acrobatic gymnastics athletes (as compared to healthy untrained matched controls) used different neuromuscular control strategies to keep their postures on single-legged quiet standing after the fatiguing protocol. The present results improve our knowledge of the mechanisms behind the interplay between fatigue and postural performance associated with the neuromuscular adaptations induced by sport practice. The design of gymnastics training might consider strategies aimed at improving the performance of specific muscles (i.e., tibialis anterior, soleus, biceps femoris, spinal erector) for which particular activation patterns were used by the acrobatic gymnastics to control single-legged quiet standing.
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Affiliation(s)
- Marcos Camargo da Silva
- School of Arts, Sciences and Humanities, Universidade de São Paulo, EACH-USP, São Paulo, Brazil
| | - Cristiano Rocha da Silva
- Biomedical Engineering Laboratory and Neuroscience Program, Universidade de São Paulo, EPUSP, PTC, São Paulo, Brazil
| | - Felipe Fava de Lima
- Biomedical Engineering Laboratory and Neuroscience Program, Universidade de São Paulo, EPUSP, PTC, São Paulo, Brazil
| | - Jéssica Rodriguez Lara
- School of Arts, Sciences and Humanities, Universidade de São Paulo, EACH-USP, São Paulo, Brazil
| | - Jackson Paiva Gustavson
- School of Arts, Sciences and Humanities, Universidade de São Paulo, EACH-USP, São Paulo, Brazil
| | - Fernando Henrique Magalhães
- School of Arts, Sciences and Humanities, Universidade de São Paulo, EACH-USP, São Paulo, Brazil
- Biomedical Engineering Laboratory and Neuroscience Program, Universidade de São Paulo, EPUSP, PTC, São Paulo, Brazil
- *Correspondence: Fernando Henrique Magalhães, ;
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13
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Rossato J, Tucker KJ, Avrillon S, Lacourpaille L, Holobar A, Hug F. Less common synaptic input between muscles from the same group allows for more flexible coordination strategies during a fatiguing task. J Neurophysiol 2022; 127:421-433. [PMID: 35020505 DOI: 10.1152/jn.00453.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study aimed to determine whether neural drive is redistributed between muscles during a fatiguing isometric contraction, and if so, whether the initial level of common synaptic input between these muscles constrains this redistribution. We studied two muscle groups: triceps surae (14 participants) and quadriceps (15 participants). Participants performed a series of submaximal isometric contractions and a torque-matched contraction maintained until task failure. We used high-density surface electromyography to identify the behavior of 1874 motor units from the soleus, gastrocnemius medialis (GM), gastrocnemius lateralis(GL), rectus femoris, vastus lateralis (VL), and vastus medialis(VM). We assessed the level of common drive between muscles in absence of fatigue using a coherence analysis. We also assessed the redistribution of neural drive between muscles during the fatiguing contraction through the correlation between their cumulative spike trains (index of neural drive). The level of common drive between VL and VM was significantly higher than that observed for the other muscle pairs, including GL-GM. The level of common drive increased during the fatiguing contraction, but the differences between muscle pairs persisted. We also observed a strong positive correlation of neural drive between VL and VM during the fatiguing contraction (r=0.82). This was not observed for the other muscle pairs, including GL-GM, which exhibited differential changes in neural drive. These results suggest that less common synaptic input between muscles allows for more flexible coordination strategies during a fatiguing task, i.e., differential changes in neural drive across muscles. The role of this flexibility on performance remains to be elucidated.
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Affiliation(s)
- Julien Rossato
- Nantes Université, Laboratory "Movement, Interactions, Performance" (EA 4334), Nantes, France
| | - Kylie J Tucker
- The University of Queensland, School of Biomedical Sciences, Brisbane, Queensland, Australia
| | - Simon Avrillon
- Legs + Walking AbilityLab, Shirley Ryan AbilityLab, Chicago, IL, United States.,Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, United States
| | - Lilian Lacourpaille
- Nantes Université, Laboratory "Movement, Interactions, Performance" (EA 4334), Nantes, France
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Slovenia
| | - François Hug
- Nantes Université, Laboratory "Movement, Interactions, Performance" (EA 4334), Nantes, France.,Institut Universitaire de France (IUF), Paris, France.,Université Côte d'Azur, LAMHESS, Nice, France
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14
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Olmos AA, Herda TJ, Sontag SA, Trevino MA. The influence of chronic training status on the mechanical behavior of the vastus lateralis during repetitive trapezoidal contractions. JOURNAL OF MUSCULOSKELETAL & NEURONAL INTERACTIONS 2022; 22:161-171. [PMID: 35642696 PMCID: PMC9186455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
OBJECTIVES To examine maximal strength and fatigability of the knee extensors, and mechanomyographic amplitude (MMGRMS)-force relationships of the vastus lateralis (VL) during repetitive muscle actions for 5 aerobically-(AT), 5 resistance-trained-(RT), and 5 sedentary (SED) individuals. METHODS Participants performed maximal voluntary contractions before (MVCPRE) and after (MVCPOST) attempting 20 isometric trapezoidal muscle actions at 50% MVCPRE. MMG was recorded from the VL. b terms (slopes) were calculated from the natural log-transformed MMGRMS-force relationships for each participant (increasing and decreasing segments). MMGRMS was averaged during steady force. RESULTS RT had greater MVCPRE (P<0.001) and MVCPOST (P=0.001-0.004) than AT and SED. Only AT completed 20 muscle actions and exhibited no decrease in MVCPOST (P=0.149). The b terms were greater for RT than AT during the increasing segment of the first contraction (P=0.001) and decreasing segment of the last contraction (P=0.033). The b terms were also greater for RT (P=0.006) during the increasing than decreasing segment for the first contraction. MMGRMS during steady force was greater during the last contraction when collapsed across training status (P=0.021). CONCLUSION Knee extensor MVC and fatigability, and motor unit control strategies for the VL during a series of repetitive contractions were influenced by chronic training status.
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Affiliation(s)
- Alex A. Olmos
- Applied Neuromuscular Physiology Laboratory, Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, USA
| | - Trent J. Herda
- Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences, The University of Kansas, Lawrence, USA
| | - Stephanie A. Sontag
- Applied Neuromuscular Physiology Laboratory, Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, USA
| | - Michael A. Trevino
- Applied Neuromuscular Physiology Laboratory, Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, USA,Corresponding author: Michael A. Trevino, Ph.D., Assistant Professor, Applied Neuromuscular Physiology Laboratory, Department of Health and Human Performance, Oklahoma State University, 191 CRC, Stillwater, OK 74074, USAE-mail:
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15
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Keller JL, Anders JPV, Neltner TJ, Housh TJ, Schmidt RJ, Johnson GO. Sex differences in muscle excitation and oxygenation, but not in force fluctuations or active hyperemia resulting from a fatiguing, bilateral isometric task. Physiol Meas 2021; 42. [PMID: 34847546 DOI: 10.1088/1361-6579/ac3e86] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 11/30/2021] [Indexed: 01/25/2023]
Abstract
It remains to be fully elucidated if there are sex-specific physiological adjustments within the human neuromuscular and vascular systems that contribute to symptoms of fatigue during a sustained bilateral task. This, in part, is likely due to various limitations in experimental design such as an inability to independently record force fluctuations from each limb.Objective. Therefore, the purpose of the current study was to examine the fatigue-induced changes in muscle excitation, force fluctuations, skeletal muscle tissue saturation (StO2), and muscle blood flow resulting from a sustained, bilateral task.Approach. Thirty healthy, college-aged adults (15 males, 15 females) performed a bilateral leg task at 25% of maximum voluntary isometric (MVIC). Before and after the task, MVICs were completed. Resting and post-task femoral artery blood flow (FABF) were determined. Muscle excitation was quantified as electromyographic amplitude (EMG AMP) from the right and left vastus lateralis. During the task, force fluctuations were determined independently from each leg. The StO2signal was collected with a near-infrared spectroscopy device attached to the right vastus lateralis. The rate of change in these variables was calculated via simple linear regression. The exercise-induced magnitude of change in MVIC (i.e. performance fatigability) and FABF (i.e. active hyperemia) was determined.Main Results. There was no sex difference in the percent decline in MVIC (20.5 ± 20.1% versus 16.4 ± 3.5%;p> 0.05). There were no inter-leg differences in EMG AMP or force fluctuations. The males exhibited a faster rate of increase in EMG AMP (b= 0.13 versusb= 0.08;p< 0.001), whereas the females exhibited a slower rate of decline in StO2(b= -0.049 versusb= -0.080). There was no sex difference in force fluctuations or change in FABF.Significance. Males and females likely have different neuromuscular strategies and muscle characteristics, but these did not elicit a sex difference in performance fatigability.
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Affiliation(s)
- Joshua L Keller
- Integrative Laboratory of Exercise and Applied Physiology (iLEAP), Department of Health, Kinesiology, and Sport, College of Education and Professional Studies, University of South Alabama, Mobile, AL 36606, United States of America
| | - John Paul V Anders
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, College of Education, University of Nebraska-Lincoln, Lincoln, NE 68588, United States of America
| | - Tyler J Neltner
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, College of Education, University of Nebraska-Lincoln, Lincoln, NE 68588, United States of America
| | - Terry J Housh
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, College of Education, University of Nebraska-Lincoln, Lincoln, NE 68588, United States of America
| | - Richard J Schmidt
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, College of Education, University of Nebraska-Lincoln, Lincoln, NE 68588, United States of America
| | - Glen O Johnson
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, College of Education, University of Nebraska-Lincoln, Lincoln, NE 68588, United States of America
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16
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Forman GN, Sonne MW, Kociolek AM, Gabriel DA, Holmes MWR. Influence of muscle fatigue on motor task performance of the hand and wrist: A systematic review. Hum Mov Sci 2021; 81:102912. [PMID: 34929434 DOI: 10.1016/j.humov.2021.102912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 08/06/2021] [Accepted: 12/03/2021] [Indexed: 11/16/2022]
Abstract
Muscle fatigue is represented as a reduction in force production capability; however, fatigue does not necessarily result in performance impairments. As the distal upper limb serves as the end effector when interacting or manipulating objects, it is important to understand how muscle fatigue may impact motor functionality. The aim of this study was to systematically review the literature to identify how various aspects of motor performance of the distal upper limb are impaired following muscle fatigue. Four databases were searched using 23 search terms describing the distal upper limb, muscle fatigue, and various performance metrics. A total of 4561 articles were screened with a total of 28 articles extracted and critically appraised. Evidence extracted indicates that muscle fatigue results in unique impairments based on the type of motor performance being evaluated. Furthermore, much data suggests that muscle fatigue does not result in consistent, predictable performance impairments, particularly while performing submaximal tasks. Additionally, magnitude of fatigue does not directly correlate with reductions in performance outcomes at the hand and wrist. Fatiguing protocols used highlighted the importance of fatigue specificity. When fatiguing and performance tasks are similar, performance impairment is likely to be observed. The numerous muscles found in the hand and wrist, often considered redundant, play a critical role in maintaining task performance in the presence of muscle fatigue. The presence of motor abundance (e.g. multiple muscles with similar function) is shown to reduce the impairment in multiple performance metrics by compensating for reduced function of fatigued muscles. Continued exploration into various fatiguing protocols (i.e. maximal or submaximal) will provide greater insights into performance impairments in the distal upper limb.
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Affiliation(s)
- Garrick N Forman
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada
| | | | - Aaron M Kociolek
- Department of Physical and Health Education, Nipissing University, North Bay, ON, Canada
| | - David A Gabriel
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada
| | - Michael W R Holmes
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada.
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17
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Liu X, Zhou M, Geng Y, Meng L, Wan H, Ren H, Zhang X, Dai C, Chen W, Ye X. Changes in synchronization of the motor unit in muscle fatigue condition during the dynamic and isometric contraction in the Biceps Brachii muscle. Neurosci Lett 2021; 761:136101. [PMID: 34237415 DOI: 10.1016/j.neulet.2021.136101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 07/01/2021] [Accepted: 07/01/2021] [Indexed: 11/28/2022]
Abstract
The fatigue-induced neuromuscular mechanism remains to be fully elucidated. So far, the macroscopic mechanism using global surface electromyogram (sEMG) has been widely investigated. However, the microscopic mechanism using high-level neural information based on motor unit (MU) spike train from the spinal cord lacks attention, especially for the conditions under dynamic contraction task. The synchronization of the MU spike train is generally assumed to be an excellent indicator to represent the activities of spinal nerves. Accordingly, this study employed synchronization of MU spike train decomposed from high-density sEMG (HD-sEMG) to investigate the fatigue condition in muscular contractions within the Biceps Brachii muscle under both isometric and dynamic contraction tasks, giving a complete picture of the microscopic fatigue mechanism. We compared the synchronization of MU in Delta (1-4 Hz), alpha (8-12 Hz), Beta (15-30 Hz), and Gamma (30-60 Hz) frequency bands during the fatigue condition induced by different contractions. Our results showed that MU synchronization increased significantly (p<0.05) in all frequency bands across the two contraction tasks. The results indicate that the microscopic fatigue mechanism of Biceps Brachii muscle does not vary due to different contraction tasks.
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Affiliation(s)
- Xiangyu Liu
- School of Art Design and Media, East China University of Science and Technology, Shanghai, China.
| | - Meiyu Zhou
- School of Art Design and Media, East China University of Science and Technology, Shanghai, China.
| | - Yanjuan Geng
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, China.
| | - Long Meng
- School of Information and Technology, Fudan University, Shanghai, China.
| | - Huiying Wan
- School of Information and Technology, Fudan University, Shanghai, China.
| | - Haoran Ren
- School of Information and Technology, Fudan University, Shanghai, China.
| | - Xinyue Zhang
- School of Education, Hangzhou Normal University, Hangzhou Zhejiang, China.
| | - Chenyun Dai
- School of Information and Technology, Fudan University, Shanghai, China.
| | - Wei Chen
- School of Information and Technology, Fudan University, Shanghai, China.
| | - Xinming Ye
- School of Sports Science and Engineering, East China University of Science and Technology, Shanghai, China.
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18
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Hedayatpour N, Mohammed Sediq Rashid D, Izanloo Z, Seylaneh H, Falla D. Men and women show different adaptations of quadriceps activity following fatiguing contractions: An explanation for the increased incidence of sports-related knee injuries in women? J Electromyogr Kinesiol 2021; 58:102552. [PMID: 33930804 DOI: 10.1016/j.jelekin.2021.102552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 04/14/2021] [Accepted: 04/15/2021] [Indexed: 11/19/2022] Open
Abstract
We investigated whether adaptations of quadriceps muscle activity to fatiguing exercise differs between sexes. Fifteen healthy men (age, mean ± SD; 22. ± 2.4 yr, body mass 70.5 ± 11.4 kg, height 1.72 ± 0.06 m) and 15 healthy women (age, mean ± SD; 21 ± 1.8 yr, body mass 60 ± 7.5 kg, height 1.62 ± 0.07 m), all right leg dominant, participated in the study. Participants performed a submaximal isometric knee extension contraction at 50% of the maximum voluntary contraction (MVC) sustained until task failure before and after a fatiguing exercise. Surface electromyography (EMG) was simultaneously recorded from nine regions distributed over the medial, middle and lateral locations of the quadriceps muscles in a longitudinal direction corresponding to the vastus medialis, rectus femoris (RF) and vastus lateralis muscle, respectively. A significant reduction in maximal force and time to task failure were observed after fatiguing exercise for both sexes (P < 0.001). However, women displayed greater myoelectric manifestations of fatigue specifically for the RF during the post-fatigue sustained contraction (P < 0.05). The RF is more susceptible to fatiguing exercise in women compared to men which may partly explain the higher risk of knee injuries among female athletes during competitive sports.
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Affiliation(s)
- Nosratollah Hedayatpour
- Center for Biomechanics and Motor Control (BMC), Department of Physical Education and Sport Science, University of Bojnord, Bojnord, Iran
| | | | - Zahra Izanloo
- Center for Biomechanics and Motor Control (BMC), Department of Physical Education and Sport Science, University of Bojnord, Bojnord, Iran
| | | | - Deborah Falla
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, United Kingdom.
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19
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Fiogbé E, Vassimon-Barroso V, Catai AM, de Melo RC, Quitério RJ, Porta A, Takahashi ACDM. Complexity of Knee Extensor Torque: Effect of Aging and Contraction Intensity. J Strength Cond Res 2021; 35:1050-1057. [PMID: 30289867 DOI: 10.1519/jsc.0000000000002888] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/20/2023]
Abstract
ABSTRACT Fiogbé, E, Vassimon-Barroso, V, Catai, AM, de Melo, RC, Quitério, RJ, Porta, A, and Takahashi, ACdM. Complexity of knee extensor torque: effect of aging and contraction intensity. J Strength Cond Res 35(4): 1050-1057, 2021-Assessing the knee extensors' torque complexity in older adults is relevant because these muscles are among the most involved in functional daily activities. This study aimed to investigate the effects of aging and isometric contraction intensity on knee extensor torque complexity. Eight young (24 ± 2.8 years) and 13 old adults (63 ± 2.8 years) performed 3 maximal (maximum voluntary contraction [MVC], duration = 10 seconds) and submaximal isometric contractions (SICs, targeted at 15, 30, and 40% of MVC, respectively) of knee extensors. Torque signals were sampled continuously, and the metrics of variability and complexity were calculated basing on the SIC torque data. The coefficient of variation (CV) was used to quantify the torque variability. The torque complexity was determined by calculating the corrected approximate entropy (CApEn) and sample entropy (SampEn) and its normalized versions (NCApEn and NSampEn). Young subjects produced greater isometric torque than older adults, and the CV was similar between both groups except at the highest force level (40% MVC) where young subjects' value was higher. The major novel finding of this investigation was that although the knee extensor torque complexity is reduced in older adults, its relationship with contraction intensity is similar to young subjects. This means that despite the age-related decrease of the interactions between the components of the neuromuscular system, the organization of force control remains preserved in older adults, at least up to just below the force midrange.
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Affiliation(s)
- Elie Fiogbé
- Department of Physiotherapy, Federal University of Sao Carlos, São Carlos-SP, Brazil
| | | | - Aparecida Maria Catai
- Department of Physiotherapy, Federal University of Sao Carlos, São Carlos-SP, Brazil
| | - Ruth Caldeira de Melo
- Department of Gerontology, School of Arts, Sciences and Humanities, University of Sao Paulo, São Paulo-SP, Brazil
| | - Robison José Quitério
- Department of Physiotherapy and Occupational Therapy, Sao Paulo State University, Marília-SP, Brazil
| | - Alberto Porta
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy ; and
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCSPoliclinico San Donato, San Donato Milanese, Milan, Italy
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20
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Inglis JG, Gabriel DA. Sex differences in the modulation of the motor unit discharge rate leads to reduced force steadiness. Appl Physiol Nutr Metab 2021; 46:1065-1072. [PMID: 33667116 DOI: 10.1139/apnm-2020-0953] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to evaluate the relationship between the variability in the motor unit inter-pulse interval and force steadiness at submaximal and maximal force outputs between the sexes. Twenty-four male and 24 female participants were recruited to perform isometric dorsiflexion contractions at 20, 40, 60, 80, and 100% maximum voluntary contraction. Tibialis anterior myoelectric signal was recorded by an intramuscular electrode. Females had lower force steadiness (coefficient of variation of force (CoV-Force), 27.3%, p < 0.01) and a greater coefficient of variation of motor unit action potential inter-pulse interval (CoV-IPI), compared with males (9.6%, p < 0.01). There was no significant correlation between the normalized CoV-IPI and CoV-Force (r = 0.19, p > 0.01), but there was a significant repeated measures correlation between the raw scores for root-mean-square force error and the standard deviation of motor unit discharge rate (r = 0.65, p < 0.01). Females also had a greater incidence of doublet discharges on average across force levels (p < 0.01). The sex differences may result from motor unit behaviours (i.e., doublet and rapid discharges, synchronization, rate coding or recruitment), leading to lower force steadiness and greater CoV-IPI in females. Novelty: Sex differences in force steadiness may be due to neural strategies. Females have lower force steadiness compared with males. Greater incidence of doublet discharges in females may result in lesser force steadiness.
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Affiliation(s)
- J Greig Inglis
- Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.,Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - David A Gabriel
- Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.,Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
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21
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Proessl F, Beckner ME, Sinnott AM, Eagle SR, LaGoy AD, Conkright WR, Canino MC, Sterczala AJ, Midhe Ramkumar PP, Sciavolino BM, Connaboy C, Ferrarelli F, Germain A, Nindl BC, Flanagan SD. Reliability of corticospinal excitability estimates for the vastus lateralis: Practical considerations for lower limb TMS task selection. Brain Res 2021; 1761:147395. [PMID: 33662340 DOI: 10.1016/j.brainres.2021.147395] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 02/14/2021] [Accepted: 02/16/2021] [Indexed: 11/29/2022]
Abstract
Transcranial magnetic stimulation (TMS) is increasingly used to examine lower extremity corticospinal excitability (CSE) in clinical and sports research. Because CSE is task-specific, there is growing emphasis on the use of ecological tasks. Nevertheless, the comparative reliability of CSE measurements during established (e.g. knee extensions; KE) and more recent ecological (e.g. squats; SQT) lower extremity tasks has received less attention. The aim of this study was to compare the test-retest reliability of CSE, force, and muscle activity (EMG) during isometric SQT and KE. 19 right-footed men (age: 25 ± 5 yrs) with similar fitness and body composition performed SQT (N = 7) or KE (N = 12) on two consecutive days. Force and EMG were recorded during maximum voluntary isometric contractions (MVC). Corticospinal excitability was determined in the dominant leg during light (15% MVC) contractions based on motor evoked potential (MEP) stimulus-response-curves (SRC). Test-retest reliability, absolute agreement, and consistency were determined for force, EMG, and SRC MEP maximum (MEPMAX) and rising phase midpoint (V50). As a secondary analysis, all outcomes were compared between groups with mixed-methods ANCOVAs (Task × Time, covariate: body-fat-percentage). Compared with SQT, KE displayed better test-retest reliability and agreement for MEPMAX whereas V50, force, and EMG were similarly reliable. Force (p = 0.01) and MEPMAX (p = 0.02) were also greater during KE despite a similar V50 (p = 0.11). Differences in test-retest reliability, absolute agreement, and between-group comparisons highlight the need to carefully select lower limb TMS assessment tasks and encourage future efforts to balance ecological validity with statistical sensitivity.
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Affiliation(s)
- F Proessl
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - M E Beckner
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - A M Sinnott
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - S R Eagle
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - A D LaGoy
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA; Department of Psychiatry, University of Pittsburgh Medical School, Pittsburgh, PA, USA
| | - W R Conkright
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - M C Canino
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - A J Sterczala
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - P P Midhe Ramkumar
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - B M Sciavolino
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - C Connaboy
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - F Ferrarelli
- Department of Psychiatry, University of Pittsburgh Medical School, Pittsburgh, PA, USA
| | - A Germain
- Department of Psychiatry, University of Pittsburgh Medical School, Pittsburgh, PA, USA
| | - B C Nindl
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA
| | - S D Flanagan
- Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition University of Pittsburgh, Pittsburgh, PA, USA.
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PETHICK JAMIE, CASSELTON CHARLOTTE, WINTER SAMANTHAL, BURNLEY MARK. Ischemic Preconditioning Blunts Loss of Knee Extensor Torque Complexity with Fatigue. Med Sci Sports Exerc 2021; 53:306-315. [PMID: 32735115 PMCID: PMC7803438 DOI: 10.1249/mss.0000000000002475] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Neuromuscular fatigue reduces the temporal structure, or complexity, of muscle torque output, purportedly through an effect on motor unit behavior. Ischemic preconditioning (IPC), an emerging ergogenic aid, has been demonstrated to have a potent effect on muscular output and endurance. We therefore tested the hypothesis that IPC would attenuate the fatigue-induced loss of muscle torque complexity. METHODS Ten healthy participants (6 males/4 females) performed intermittent isometric knee extension contractions (6 s contraction, 4 s rest) to task failure at 40% maximal voluntary contraction. Contractions were preceded by either IPC (three bouts of 5 min proximal thigh occlusion at 225 mm Hg, interspersed with 5 min rest) or SHAM (as IPC, but occlusion at only 20 mm Hg) treatments. Torque and EMG signals were sampled continuously. Complexity and fractal scaling were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Muscle oxygen consumption (mV˙O2) was determined using near-infrared spectroscopy. RESULTS IPC increased time to task failure by 43% ± 13% (mean ± SEM, P = 0.047). Complexity decreased in both trials (decreased ApEn, increased DFA α; both P < 0.001), although the rate of decrease was significantly lower after IPC (ApEn, -0.2 ± 0.1 vs -0.4 ± 0.1, P = 0.013; DFA α, 0.2 ± 0.1 vs 0.3 ± 0.1, P = 0.037). Similarly, the rates of increase in EMG amplitude (P = 0.022) and mV˙O2 (P = 0.043) were significantly slower after IPC. CONCLUSION These results suggest that the ergogenic effect of IPC observed here is of neural origin and accounts for the slowing of the rates of change in torque complexity, EMG amplitude, and mV˙O2 as fatigue develops.
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Fidalgo-Herrera A, Miangolarra-Page JC, Carratalá-Tejada M. Electromyographic traces of motor unit synchronization of fatigued lower limb muscles during gait. Hum Mov Sci 2020; 75:102750. [PMID: 33373857 DOI: 10.1016/j.humov.2020.102750] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 12/14/2020] [Accepted: 12/17/2020] [Indexed: 10/22/2022]
Abstract
BACKGROUND The study of the signal in the frequency domain has shown to be a good tool to identify muscular fatigue. Previous research has shown that the low frequency band and 40 Hz frequency band increase their relative intensity with the onset of fatigue. These findings were obtained in rectus femoris, but the behaviours of other muscles of the lower limb are unknown. In this article we explored the changes in the low frequency and 40 Hz frequency band of lower limb muscles with respect to fatigue. METHODS Thirty healthy subjects were recruited to analyse the electromyography (EMG) of biceps femoris, tibialis anterior and gastrocnemius medialis and lateralis of both legs during gait. Four two-minutes walks at a self-selected speed were recorded, the first two walks with a normal muscular function and the last two walks after a fatigue protocol. All the signals were decomposed using wavelet transformations. The signals were normalized in time and spectral intensities normalized to the sum of intensities in the frequency domain. Two frequency bands were studied in each walk: the 40-Hz (34-53 Hz) and the low frequency (< 25 Hz) bands. A ratio of the spectral intensities of those frequency bands at each walk was obtained by dividing the 40-Hz frequency band spectral intensity by the low frequency band spectral intensity. Statistical parametric mapping techniques were used to compare the ratios of the prefatigue walks against the postfatigue walks. RESULTS The results of the Statistical Non-Parametric Mapping (SnPM) analysis of all muscles depict a higher relative spectral intensity in the low frequency band in the comparison of fatigue versus prefatigue recordings except for the right gastrocnemius lateralis. The critical thresholds F* were exceeded by multiple suprathreshold clusters with p values <0.05, showing that the low frequency band increased its relative spectral intensity in the case of fatigue. CONCLUSION The obtained results suggest that the low frequency band increases its relative spectral intensity in all the studied muscles when fatigue onsets. This increase in relative spectral intensity may be linked to an increase in motor unit synchronization promoted by the central nervous system to ensure good motor control.
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Affiliation(s)
- A Fidalgo-Herrera
- LAMBECOM, Universidad Rey Juan Carlos, Alcorcón, calle Atenas S/N, Madrid, Spain.
| | - J C Miangolarra-Page
- LAMBECOM, Universidad Rey Juan Carlos, Alcorcón, calle Atenas S/N, Madrid, Spain; Fuenlabrada's Clinical University Hospital, Fuenalbrada, Camino del Molino, 2, Madrid, Spain.
| | - M Carratalá-Tejada
- LAMBECOM, Universidad Rey Juan Carlos, Alcorcón, calle Atenas S/N, Madrid, Spain.
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Sharp MH, Sahin K, Stefan MW, Gheith RH, Reber DD, Ottinger CR, Orhan C, Tuzcu M, Sahin N, Lowery RP, Durkee S, Wilson JM. Marine Phytoplankton Improves Exercise Recovery in Humans and Activates Repair Mechanisms in Rats. Int J Sports Med 2020; 42:1070-1082. [PMID: 33352600 PMCID: PMC8566026 DOI: 10.1055/a-1320-1061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
This study investigated the effects of marine phytoplankton supplementation on 1) perceived recovery and ground reaction forces in humans following a non-functional overreaching resistance-training program and 2) myogenic molecular markers associated with muscle cell recovery in a rat model. In the human trial, a 5-week resistance-training program with intentional overreaching on weeks 2 and 5 was implemented. Results indicate that marine phytoplankton prompted positive changes in perceived recovery at post-testing and, while both marine phytoplankton and placebo conditions demonstrated decreased peak and mean rate of force development following the overreaching weeks, placebo remained decreased at post-testing while marine phytoplankton returned to baseline levels. In the rat model, rats were divided into four conditions: (i) control, (ii) exercise, (iii) exercise + marine phytoplankton 2.55 mg·d-1, or (iv) exercise+marine phytoplankton 5.1 mg·d-1. Rats in exercising conditions performed treadmill exercise 5 d·wk-1 for 6 weeks. Marine phytoplankton in exercising rats increased positive and decrease negative myogenic factors regulating satellite cell proliferation. Taken together, marine phytoplankton improved perceptual and functional indices of exercise recovery in an overreaching human model and, mechanistically, this could be driven through cell cycle regulation and a potential to improve protein turnover.
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Affiliation(s)
- Matthew H Sharp
- Research Department, Applied Science & Performance Institute, Tampa, United States
| | - Kazim Sahin
- Department of Animal Nutrition, Firat University School of Veterinary Medicine, Elazig, Turkey
| | - Matt W Stefan
- Research Department, Applied Science & Performance Institute, Tampa, United States
| | - Raad H Gheith
- Research Department, Applied Science & Performance Institute, Tampa, United States
| | - Dallen D Reber
- Research Department, Applied Science & Performance Institute, Tampa, United States
| | - Charlie R Ottinger
- Research Department, Applied Science & Performance Institute, Tampa, United States
| | - Cemal Orhan
- Department of Animal Nutrition, Firat University School of Veterinary Medicine, Elazig, Turkey
| | - Mehmet Tuzcu
- Faculty of Science, Department of Biology, Firat University, Elazig, Turkey
| | - Nurhan Sahin
- Department of Animal Nutrition, Firat University School of Veterinary Medicine, Elazig, Turkey
| | - Ryan P Lowery
- Research Department, Applied Science & Performance Institute, Tampa, United States
| | - Shane Durkee
- Department of Consumer Health, Lonza Inc, Morristown, United States
| | - Jacob M Wilson
- Research Department, Applied Science & Performance Institute, Tampa, United States
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Is the 'reverse onion skin' phenomenon more prevalent than we thought during intramuscular myoelectric recordings from low to maximal force outputs? Neurosci Lett 2020; 743:135583. [PMID: 33352279 DOI: 10.1016/j.neulet.2020.135583] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 12/10/2020] [Accepted: 12/14/2020] [Indexed: 11/21/2022]
Abstract
There are isolated instances in the literature that suggest the 'onion skin' phenomenon is not always present. That is, newly recruited high threshold motor units (MU) have higher discharge rates than previously recruited low threshold MUs. Therefore, the purpose of this paper was to investigate the presence of the 'onion skin' phenomenon in a large sample of intramuscular myoelectric recordings from low to maximal force outputs. Forty-eight participants performed rapid isometric dorsiflexion contractions at 20, 40, 60, 80 and 100 % MVC while intramuscular electrical activity was recorded. A bivariate frequency-distribution of the motor unit discharge rate and motor unit action potential peak-to-peak (P-P) amplitude was assessed. There was a significant difference in bivariate frequency-distribution across force levels (D's = 0.1083-0.3094, p's < 0.001). Newly recruited high threshold MUs did have lower discharge rates, but there was an increase in the presence of high threshold, large P-P amplitude MUs with higher discharge rates than lower threshold MUs (reverse onion skin) during the stable portion of the force output. The recruitment of high threshold MUs with higher discharge rates decreased the level of common drive from the cross-correlation (Rxy) = 0.79 at 20 % MVC to Rxy = 0.68 at 100 % MVC (p < 0.01), but it remained high. As the interference pattern becomes more complex with the recruitment of more motor units at higher force outputs, intramuscular electrodes may be more discriminating while recording motor unit activity leading to the identification of both the 'reverse onion skin' and 'onion skin' phenomenon being present.
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Tyagi O, Zhu Y, Johnson C, Mehta RK, Sasangohar F, Erraguntla M, Qaraqe K. Neural Signatures of Handgrip Fatigue in Type 1 Diabetic Men and Women. Front Hum Neurosci 2020; 14:564969. [PMID: 33240061 PMCID: PMC7680760 DOI: 10.3389/fnhum.2020.564969] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Accepted: 10/14/2020] [Indexed: 01/22/2023] Open
Abstract
Type 1 diabetes (T1D) is associated with reduced muscular strength and greater muscle fatigability. Along with changes in muscular mechanisms, T1D is also linked to structural changes in the brain. How the neurophysiological mechanisms underlying muscle fatigue is altered with T1D and sex related differences of these mechanisms are still not well investigated. The aim of this study was to determine the impact of T1D on the neural correlates of handgrip fatigue and examine sex and T1D related differences in neuromuscular performance parameters, neural activation and functional connectivity patterns between the motor regions of the brain. Forty-two adults, balanced by condition (healthy vs T1D) and sex (male vs female), and performed submaximal isometric handgrip contractions until voluntary exhaustion. Initial strength, endurance time, strength loss, force variability, and complexity measures were collected. Additionally, hemodynamic responses from motor-function related cortical regions, using functional near-infrared spectroscopy (fNIRS), were obtained. Overall, females exhibited lower initial strength (p < 0.0001), and greater strength loss (p = 0.023) than males. While initial strength was significantly lower in the T1D group (p = 0.012) compared to the healthy group, endurance times and strength loss were comparable between the two groups. Force complexity, measured as approximate entropy, was found to be lower throughout the experiment for the T1D group (p = 0.0378), indicating lower online motor adaptability. Although, T1D and healthy groups fatigued similarly, only the T1D group exhibited increased neural activation in the left (p = 0.095) and right (p = 0.072) supplementary motor areas (SMA) over time. A sex × condition × fatigue interaction effect (p = 0.044) showed that while increased activation was observed in both T1D females and healthy males from the Early to Middle phase, this was not observed in healthy females or T1D males. These findings demonstrate that T1D adults had lower adaptability to fatigue which they compensated for by increasing neural effort. This study highlights the importance of examining both neural and motor performance signatures when investigating the impact of chronic conditions on neuromuscular fatigue. Additionally, the findings have implications for developing intervention strategies for training, rehabilitation, and ergonomics considerations for individuals with chronic conditions.
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Affiliation(s)
- Oshin Tyagi
- Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX, United States
| | - Yibo Zhu
- Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX, United States
| | - Connor Johnson
- Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX, United States
| | - Ranjana K. Mehta
- Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX, United States
| | - Farzan Sasangohar
- Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX, United States
| | - Madhav Erraguntla
- Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX, United States
| | - Khalid Qaraqe
- Department of Electrical and Computer Engineering, Texas A&M University at Qatar, Doha, Qatar
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Mahoney S, Klawitter L, Hackney KJ, Dahl L, Herrmann SD, Edwards B, McGrath R. Examining Additional Aspects of Muscle Function with a Digital Handgrip Dynamometer and Accelerometer in Older Adults: A Pilot Study. Geriatrics (Basel) 2020; 5:geriatrics5040086. [PMID: 33142897 PMCID: PMC7709634 DOI: 10.3390/geriatrics5040086] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 10/27/2020] [Accepted: 10/30/2020] [Indexed: 12/19/2022] Open
Abstract
Background: Maximal handgrip strength (HGS) could be an incomplete and unidimensional measure of muscle function. This pilot study sought to examine the relationships between maximal HGS, radial and ulnar digit grip strength, submaximal HGS force control, HGS fatigability, neuromuscular HGS steadiness, and HGS asymmetry in older adults. Methods: A digital handgrip dynamometer and accelerometer was used to collect several HGS measurements from 13 adults aged 70.9 ± 4.0 years: maximal strength, radial and ulnar digit grip strength, submaximal force control, fatigability, neuromuscular steadiness, and asymmetry. Pearson correlations determined the relationships between individual HGS measurements. A principal component analysis was used to derive a collection of new uncorrelated variables from the HGS measures we examined. Results: The individual HGS measurements were differentially correlated. Maximal strength (maximal HGS, radial digit strength, ulnar digits strength), contractile steadiness (maximal HGS steadiness, ulnar digit grip strength steadiness), and functional strength (submaximal HGS force control, HGS fatigability, HGS asymmetry, HGS fatigability steadiness) emerged as dimensions from the HGS measurements that we evaluated. Conclusion: Our findings suggest that these additional measures of muscle function may differ from maximal HGS alone. Continued research is warranted for improving how we assess muscle function with more modern technologies, including handgrip dynamometry and accelerometry.
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Affiliation(s)
- Sean Mahoney
- Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND 58108, USA; (S.M.); (L.K.); (K.J.H.)
| | - Lukus Klawitter
- Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND 58108, USA; (S.M.); (L.K.); (K.J.H.)
| | - Kyle J. Hackney
- Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND 58108, USA; (S.M.); (L.K.); (K.J.H.)
| | - Lindsey Dahl
- Sanford Health, Fargo, ND 58103, USA;
- Department of Geriatrics, Grand Forks, ND 58202, USA
| | | | | | - Ryan McGrath
- Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND 58108, USA; (S.M.); (L.K.); (K.J.H.)
- Correspondence: ; Tel.: +701-231-7474
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A model-based estimation of critical torques reduces the experimental effort compared to conventional testing. Eur J Appl Physiol 2020; 120:1263-1276. [PMID: 32277257 PMCID: PMC7237533 DOI: 10.1007/s00421-020-04358-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 03/21/2020] [Indexed: 11/18/2022]
Abstract
Purpose Critical torque (CT) is an important fatigue threshold in exercise physiology and can be used to analyze, predict, or optimize performance. The objective of this work is to reduce the experimental effort when estimating CTs for sustained and intermittent isometric contractions using a model-based approach. Materials and methods We employ a phenomenological model of the time course of maximum voluntary isometric contraction (MVIC) torque and compute the highest sustainable torque output by solving an optimization problem. We then show that our results are consistent with the steady states obtained when simulating periodic maximum loading schemes. These simulations correspond to all-out tests, which are used to estimate CTs in practice. Based on these observations, the estimation of CTs can be formulated mathematically as a parameter estimation problem. To minimize the statistical uncertainty of the parameter estimates and consequently of the estimated CTs, we compute optimized testing sessions. This reduces the experimental effort even further. Results We estimate CTs of the elbow flexors for sustained isometric contractions to be 28% of baseline MVIC torque and for intermittent isometric contractions consisting of a 3 s contraction followed by 2 s rest to be 41% of baseline MVIC torque. We show that a single optimized testing session is sufficient when using our approach. Conclusions Our approach reduces the experimental effort considerably when estimating CTs for sustained and intermittent isometric contractions.
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Hwang IS, Lin YT, Huang CC, Chen YC. Fatigue-related modulation of low-frequency common drive to motor units. Eur J Appl Physiol 2020; 120:1305-1317. [PMID: 32297005 DOI: 10.1007/s00421-020-04363-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 04/01/2020] [Indexed: 10/24/2022]
Abstract
PURPOSE This study investigated fatigue-related modulation of common neural inputs to motor units (MUs) under 5 Hz, which determines force precision control. METHODS Twenty-seven adults performed a sequence of fatiguing contractions. The participants were assessed with a static isometric index abduction at 20% maximal voluntary contraction in the pre-test and post-test. Discharge characteristics of MUs of the first dorsal interosseous muscle were analyzed with decomposed EMG signals. RESULTS Along with increases in the mean (58.40 ± 11.76 ms → 62.55 ± 10.83 ms, P = 0.029) and coefficient of variation (0.204 ± .014 → 0.215 ± 0.017, P = 0.002) in inter-spike intervals, the fatiguing contraction caused reductions in the mean frequency (16.84 ± 3.31 Hz → 15.59 ± 3.21 Hz, P = 0.027) and spectral dispersions (67.54 ± 4.49 → 62.64 ± 6.76 Hz, P = 0.007) of common neural drive, as estimated with smoothed cumulative motor unit spike trains (SCMUSTs). Stabilogram diffusion analysis of SCMUSTs revealed significant fatigue-related reductions in the long-term effective diffusion coefficient (1.91 ± 0.77 Hz2/s → 1.61 ± 0.61 Hz2/s, P = 0.020) and long-term scaling exponent (0.480 ± 0.013 Hz2/s → 0.471 ± 0.017 Hz2/s, P = 0.014). After fatiguing contraction, mutual information of force fluctuations and SCMUSTs was augmented roughly by 12.95% (P = 0.041). CONCLUSIONS Muscular fatigue could compress and shift the low-frequency common drive to MUs toward lower spectral bands, thereby enhancing transmission of twitch forces through the muscle-tendon complex with a low-pass filter property. The fatigue-induced changes involve increased closed-loop control of the common modulation of MU discharge rates.
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Affiliation(s)
- Ing-Shiou Hwang
- Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan.,Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan
| | - Yen-Ting Lin
- Physical Education Office, Asian University, Taichung, 41354, Taiwan
| | - Chien-Chun Huang
- Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan
| | - Yi-Ching Chen
- Department of Physical Therapy, College of Medical Science and Technology, Chung Shan Medical University, Taichung, 40201, Taiwan. .,Physical Therapy Room, Chung Shan Medical University Hospital, Taichung, 40201, Taiwan.
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Tweedell AJ, Tenan MS. motoRneuron: an open-source R toolbox for time-domain motor unit analyses. PeerJ 2019; 7:e7907. [PMID: 31844560 PMCID: PMC6910107 DOI: 10.7717/peerj.7907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 09/16/2019] [Indexed: 11/20/2022] Open
Abstract
Motor unit synchronization is the tendency of motor neurons and their associated muscle fibers to discharge near-simultaneously. It has been theorized as a control mechanism for force generation by common excitatory inputs to these motor neurons. Magnitude of synchronization is calculated from peaks in cross-correlation histograms between motor unit discharge trains. However, there are many different methods for detecting these peaks and even more indices for calculating synchronization from them. Methodology is diverse, typically laboratory-specific and requires expensive software, like Matlab or LabView. This lack of standardization makes it difficult to draw definitive conclusions about motor unit synchronization. A free, open-source toolbox, "motoRneuron", for the R programming language, has been developed which contains functions for calculating time domain synchronization using different methods found in the literature. The objective of this paper is to detail the toolbox's functionality and present a case study showing how the same synchronization index can differ when different methods are used to compute it. A pair of motor unit action potential trains were collected from the forearm during a isometric finger flexion task using fine wire electromyography. The motoRneuron package was used to analyze the discharge time of the motor units for time-domain synchronization. The primary function "mu_synch" automatically performed the cross-correlation analysis using three different peak detection methods, the cumulative sum method, the z-score method, and a subjective visual method. As function parameters defined by the user, only first order recurrence intervals were calculated and a 1 ms bin width was used to create the cross correlation histogram. Output from the function were six common synchronization indices, the common input strength (CIS), k', k' - 1, E, S, and Synch Index. In general, there was a high degree of synchronization between the two motor units. However, there was a varying degree of synchronization between methods. For example, the widely used CIS index, which represents a rate of synchronized discharges, shows a 45% difference between the visual and z-score methods. This singular example demonstrates how a lack of consensus in motor unit synchronization methodologies may lead to substantially differing results between studies. The motoRneuron toolbox provides researchers with a standard interface and software to examine time-domain motor unit synchronization.
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Affiliation(s)
- Andrew J Tweedell
- Human Research and Engineering Directorate, United States Army Research Laboratory, Aberdeen Proving Ground, MD, United States of America
| | - Matthew S Tenan
- Defense Health Agency, Falls Church, VA, United States of America
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Mesin L. Single channel surface electromyogram deconvolution to explore motor unit discharges. Med Biol Eng Comput 2019; 57:2045-2054. [PMID: 31350669 DOI: 10.1007/s11517-019-02010-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 07/04/2019] [Indexed: 11/28/2022]
Abstract
Interference surface electromyogram (EMG) reflects many bioelectric properties of active motor units (MU), which are however difficult to estimate due to the asynchronous summation of their discharges. This paper introduces a deconvolution technique to estimate the cumulative firings of MUs. Tests in simulations show that the power spectral density of the estimated MU firings has a low-frequency peak corresponding to the mean firing rate of MUs in the detection volume of the recording system, weighted by the amplitudes of MU action potentials. The peak increases in amplitude and its centroid shifts to a higher frequency when MU synchronization is simulated (mainly due to the shift of discharges of large MUs). The peak is found even at high force levels, when such a contribution does not emerge from the EMG. This result is also confirmed in preliminary applications to experimental data. Moreover, the simulated cumulative firings of MUs are estimated with a correlation above 90% (considering frequency contributions up to 150 Hz), for all force levels. The method requires a single EMG channel, thus being feasible even in applied studies using simple recording systems. It may open many potential applications, e.g., in the study of the modulation of MU firing rate induced by either fatigue or pathology and in coherency analysis. Graphical Abstract Examples of application of the deconvolution (Deconv) algorithm and comparison with the cumulative firings and the cumulated weighted firings (CWF, i.e., each firing pattern is weighted by the root mean squared amplitude of the corresponding MU action potential). Portions of data are shown on the left, the power spectral densities (PSD) on the right (Welch method applied to 3 s of data, sub-epochs of 0.5 s, mean value removed from each of them, 50% of overlap). A) Simulated signal (50% of maximal voluntary contraction, MVC) with random MU firings. B) Simulated signal (50% MVC) with a level of synchronization equal to 10%. C) Experimental data from vastus medialis at 40% MVC (data decomposed by the algorithm of Holobar and Zazula, IEEE Trans. Sig. Proc. 2007; PSD of the cumulated firings almost identical to that of CWF, as few MUs were identified).
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Affiliation(s)
- Luca Mesin
- Mathematical Biology and Physiology, Department of Electronics and Telecommunications, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 10129, Italy.
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Fiogbé E, Carnavale BF, Takahashi ACDM. Exercise training in older adults, what effects on muscle force control? A systematic review of randomized clinical trials. Arch Gerontol Geriatr 2019; 83:138-150. [PMID: 31026723 DOI: 10.1016/j.archger.2019.04.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 04/02/2019] [Accepted: 04/09/2019] [Indexed: 12/17/2022]
Abstract
AIM To determine the magnitude of the effects of different exercise training (ET) modalities on variables of muscle force control in older adults. METHODS Relevant articles were searched in PubMed, Web of Science, Science Direct and Scopus, using the keywords: Aged AND "Exercise Movement Techniques" AND ("Complexity of torque" OR "Complexity of force" OR "Variability of torque" OR "Variability of force" OR "Force Steadiness" OR "Force fluctuations"). To be included in the full analysis, the studies had to be randomized controlled trials in which older adults were submitted to ET programs and muscle force control assessment. RESULTS The searches resulted in 702 articles from which 6 met all the inclusion criteria. The trials involved 171 healthy and functionally limited older adults (71.64 ± 1.53 years). Studies included resistance, steadiness and functional training programs. Training sessions were 2-3 time per week, lasted 6-16 months with intensities determined as percentage of the one repetition maximum loads. There is a heterogeneity regarding experimental set-up and data analysis parameters between studies. The findings show an improved muscle force control in older adults after ET. Such response is better evidenced by the assessment of the coefficient of variation (CV) of the force signals. There is moderate evidence that resistance training programs are effective to decrease CV of knee extensor force signals at lower force targets. CONCLUSIONS The findings from this review suggest that ET programs are effective to improve muscle force control in older adults.
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Affiliation(s)
- Elie Fiogbé
- Department of Physiotherapy, Federal University of Sao Carlos, Rodovia Washington Luiz, km 235, São Carlos, SP, CEP: 13565-905, Brazil.
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Furui A, Hayashi H, Tsuji T. A Scale Mixture-Based Stochastic Model of Surface EMG Signals With Variable Variances. IEEE Trans Biomed Eng 2019; 66:2780-2788. [PMID: 30703005 DOI: 10.1109/tbme.2019.2895683] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Surface electromyogram (EMG) signals have typically been assumed to follow a Gaussian distribution. However, the presence of non-Gaussian signals associated with muscle activity has been reported in recent studies, and there is no general model of the distribution of EMG signals that can explain both non-Gaussian and Gaussian distributions within a unified scheme. METHODS In this paper, we describe the formulation of a non-Gaussian EMG model based on a scale mixture distribution. In the model, an EMG signal at a certain time follows a Gaussian distribution, and its variance is handled as a random variable that follows an inverse gamma distribution. Accordingly, the probability distribution of EMG signals is assumed to be a mixture of Gaussians with the same mean but different variances. The EMG variance distribution is estimated via marginal likelihood maximization. RESULTS Experiments involving nine participants revealed that the proposed model provides a better fit to recorded EMG signals than conventional EMG models. It was also shown that variance distribution parameters may reflect underlying motor unit activity. CONCLUSION This study proposed a scale mixture distribution-based stochastic EMG model capable of representing changes in non-Gaussianity associated with muscle activity. A series of experiments demonstrated the validity of the model and highlighted the relationship between the variance distribution and muscle force. SIGNIFICANCE The proposed model helps to clarify conventional wisdom regarding the probability distribution of surface EMG signals within a unified scheme.
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Spatial Reorganization of Myoelectric Activities in Extensor Digitorum for Sustained Finger Force Production. SENSORS 2019; 19:s19030555. [PMID: 30699981 PMCID: PMC6386817 DOI: 10.3390/s19030555] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 01/23/2019] [Accepted: 01/28/2019] [Indexed: 11/16/2022]
Abstract
The study aims to explore the spatial distribution of multi-tendinous muscle modulated by central nervous system (CNS) during sustained contraction. Nine subjects were recruited to trace constant target forces with right index finger extension. Surface electromyography (sEMG) of extensor digitorum (ED) were recorded with a 32-channel electrode array. Nine successive topographic maps (TM) were obtained. Pixel wise analysis was utilized to extract subtracted topographic maps (STM), which exhibited inhomogeneous distribution. STMs were characterized into hot, warm, and cool regions corresponding to higher, moderate, and lower change ranges, respectively. The relative normalized area (normalized to the first phase) of these regions demonstrated different changing trends as rising, plateauing, and falling over time, respectively. Moreover, the duration of these trends were found to be affected by force level. The rising/falling periods were longer at lower force levels, while the plateau can be achieved from the initial phase for higher force output (45% maximal voluntary contraction). The results suggested muscle activity reorganization in ED plays a role to maintain sustained contraction. Furthermore, the decreased dynamical regulation ability to spatial reorganization may be prone to induce fatigue. This finding implied that spatial reorganization of muscle activity as a regulation mechanism contribute to maintain constant force production.
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Effect of Task Failure on Intermuscular Coherence Measures in Synergistic Muscles. Appl Bionics Biomech 2018; 2018:4759232. [PMID: 29967654 PMCID: PMC6008706 DOI: 10.1155/2018/4759232] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 02/21/2018] [Indexed: 12/01/2022] Open
Abstract
The term “task failure” describes the point when a person is not able to maintain the level of force required by a task. As task failure approaches, the corticospinal command to the muscles increases to maintain the required level of force in the face of a decreased mechanical efficacy. Nevertheless, most motor tasks require the synergistic recruitment of several muscles. How this recruitment is affected by approaching task failure is still not clear. The increase in the corticospinal drive could be due to an increase in synergistic recruitment or to overlapping commands sent to the muscles individually. Herein, we investigated these possibilities by combining intermuscular coherence and synergy analysis on signals recorded from three muscles of the quadriceps during dynamic leg extension tasks. We employed muscle synergy analysis to investigate changes in the coactivation of the muscles. Three different measures of coherence were used. Pooled coherence was used to estimate the command synchronous to all three muscles, pairwise coherence the command shared across muscle pairs and residual coherence the command peculiar to each couple of muscles. Our analysis highlights an overall decrease in synergistic command at task failure and an intensification of the contribution of the nonsynergistic shared command.
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Macgregor LJ, Hunter AM. High-threshold motor unit firing reflects force recovery following a bout of damaging eccentric exercise. PLoS One 2018; 13:e0195051. [PMID: 29630622 PMCID: PMC5890972 DOI: 10.1371/journal.pone.0195051] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 03/11/2018] [Indexed: 11/18/2022] Open
Abstract
Exercise-induced muscle damage (EIMD) is associated with impaired muscle function and reduced neuromuscular recruitment. However, motor unit firing behaviour throughout the recovery period is unclear. EIMD impairment of maximal voluntary force (MVC) will, in part, be caused by reduced high-threshold motor unit firing, which will subsequently increase to recover MVC. Fourteen healthy active males completed a bout of eccentric exercise on the knee extensors, with measurements of MVC, rate of torque development and surface electromyography performed pre-exercise and 2, 3, 7 and 14 days post-exercise, on both damaged and control limb. EIMD was associated with decreased MVC (235.2 ± 49.3 Nm vs. 161.3 ± 52.5 Nm; p <0.001) and rate of torque development (495.7 ± 136.9 Nm.s-1 vs. 163.4 ± 163.7 Nm.s-1; p <0.001) 48h post-exercise. Mean motor unit firing rate was reduced (16.4 ± 2.2 Hz vs. 12.6 ± 1.7 Hz; p <0.01) in high-threshold motor units only, 48h post-exercise, and common drive was elevated (0.36 ± 0.027 vs. 0.56 ± 0.032; p< 0.001) 48h post-exercise. The firing rate of high-threshold motor units was reduced in parallel with impaired muscle function, whilst early recruited motor units remained unaltered. Common drive of motor units increased in offset to the firing rate impairment. These alterations correlated with the recovery of force decrement, but not of pain elevation. This study provides fresh insight into the central mechanisms associated with EIMD recovery, relative to muscle function. These findings may in turn lead to development of novel management and preventative procedures.
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Affiliation(s)
- Lewis J. Macgregor
- Faculty of Health Sciences and Sport, University of Stirling, Stirling, Scotland
| | - Angus M. Hunter
- Faculty of Health Sciences and Sport, University of Stirling, Stirling, Scotland
- * E-mail:
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Nagamori A, Laine CM, Valero-Cuevas FJ. Cardinal features of involuntary force variability can arise from the closed-loop control of viscoelastic afferented muscles. PLoS Comput Biol 2018; 14:e1005884. [PMID: 29309405 PMCID: PMC5774830 DOI: 10.1371/journal.pcbi.1005884] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 01/19/2018] [Accepted: 11/17/2017] [Indexed: 12/29/2022] Open
Abstract
Involuntary force variability below 15 Hz arises from, and is influenced by, many factors including descending neural drive, proprioceptive feedback, and mechanical properties of muscles and tendons. However, their potential interactions that give rise to the well-structured spectrum of involuntary force variability are not well understood due to a lack of experimental techniques. Here, we investigated the generation, modulation, and interactions among different sources of force variability using a physiologically-grounded closed-loop simulation of an afferented muscle model. The closed-loop simulation included a musculotendon model, muscle spindle, Golgi tendon organ (GTO), and a tracking controller which enabled target-guided force tracking. We demonstrate that closed-loop control of an afferented musculotendon suffices to replicate and explain surprisingly many cardinal features of involuntary force variability. Specifically, we present 1) a potential origin of low-frequency force variability associated with co-modulation of motor unit firing rates (i.e.,‘common drive’), 2) an in-depth characterization of how proprioceptive feedback pathways suffice to generate 5-12 Hz physiological tremor, and 3) evidence that modulation of those feedback pathways (i.e., presynaptic inhibition of Ia and Ib afferents, and spindle sensitivity via fusimotor drive) influence the full spectrum of force variability. These results highlight the previously underestimated importance of closed-loop neuromechanical interactions in explaining involuntary force variability during voluntary ‘isometric’ force control. Furthermore, these results provide the basis for a unifying theory that relates spinal circuitry to various manifestations of altered involuntary force variability in fatigue, aging and neurological disease. Involuntary fluctuations in muscle force are an unavoidable consequence of human motor control and underlie movement execution errors. Amplification and distortion of involuntary force variability are common phenomena found in various neurological conditions and in fatigue. However, the underlying mechanisms for this are often unclear. We investigated the generation and modulation of involuntary force variability arising from different sources, as well as their interactions. We used a closed-loop simulation which included a physiologically-grounded model of an afferented musculotendon and an error-controller. We show that interactions among neural noise, musculotendon mechanics, proprioceptive feedback, and error correction are critical components of force control, and by taking these into account, our model was able to both replicate and explain many cardinal features of involuntary force variability previously reported experimentally. Also, our results suggest previously unrecognized pathways through which force variability may be altered in fatigue and in certain neurological diseases. Finally, we emphasize the potential for important clinical and scientific information to be extracted from relatively simple, non-invasive measurements of force.
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Affiliation(s)
- Akira Nagamori
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California, United States of America
| | - Christopher M. Laine
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California, United States of America
| | - Francisco J. Valero-Cuevas
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California, United States of America
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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Normalised Mutual Information of High-Density Surface Electromyography during Muscle Fatigue. ENTROPY 2017. [DOI: 10.3390/e19120697] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Power output and fatigue properties using spatially distributed sequential stimulation in a dynamic knee extension task. Eur J Appl Physiol 2017; 117:1787-1798. [PMID: 28674921 PMCID: PMC5556133 DOI: 10.1007/s00421-017-3675-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 06/28/2017] [Indexed: 11/06/2022]
Abstract
Purpose The low power output and fatigue resistance during functional electrical stimulation (FES) limits its use for functional applications. The aim of this study was to compare the power output and fatigue properties of spatially distributed sequential stimulation (SDSS) against conventional single electrode stimulation (SES) in an isokinetic knee extension task simulating knee movement during recumbent cycling. Methods M. vastus lateralis and m. vastus medialis of eight able-bodied subjects were stimulated for 6 min on both legs with both setups. In the SES setup, target muscles were each stimulated by a pair of electrodes. In SDSS, four small electrodes replaced the SES active electrodes, but reference electrodes were the same. Torque was measured during knee extension movement by a dynamometer at an angular velocity of 110°/s. Mean power (Pmean) was calculated from stimulated extensions for the first 10 extensions, the final 20 extensions and overall. Fatigue is presented as an index, calculated as the decrease with respect to initial power. Results Pmean was significantly higher for SDSS than for SES in the final phase (9.9 ± 4.0 vs. 7.4 ± 4.3 W, p = 0.035) and overall (11.5 ± 4.0 vs. 9.2 ± 4.5 W, p = 0.037). With SDSS, the reduction in Pmean was significantly smaller compared to SES (from 14.9 to 9.9 vs. 14.6 to 7.4 W, p = 0.024). The absolute mean pulse width was substantially lower with SDSS (62.5 vs. 90.0 µs). Conclusion Although less stimulation was applied, SDSS showed a significantly higher mean power output than SES. SDSS also had improved fatigue resistance when compared to conventional stimulation. The SDSS approach may provide substantial performance benefits for cyclical FES applications.
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Cabral HV, de Souza LML, Mello RGT, Gallina A, de Oliveira LF, Vieira TM. Is the firing rate of motor units in different vastus medialis regions modulated similarly during isometric contractions? Muscle Nerve 2017; 57:279-286. [PMID: 28500671 DOI: 10.1002/mus.25688] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 04/20/2017] [Accepted: 05/07/2017] [Indexed: 11/09/2022]
Abstract
INTRODUCTION Previous evidence suggests the fibers of different motor units reside within distinct vastus medialis (VM) regions. It remains unknown whether the activity of these motor units may be modulated differently. Herein we assess the discharge rate of motor units detected proximodistally from the VM to address this issue. METHODS Surface electromyograms (EMGs) were recorded proximally and distally from the VM while 10 healthy subjects performed isometric contractions. Single motor units were decomposed from surface EMGs. The smoothed discharge rates of motor units identified from the same and from different VM regions were then cross-correlated. RESULTS During low-level contractions, the discharge rate varied more similarly for distal (cross-correlation peak; interquartile interval: 0.27-0.40) and proximal (0.28-0.52) than for proximodistal pairs of VM motor units (0.20-0.33; P = 0.006). DISCUSSION The discharge rates of motor units from different proximodistal VM regions show less similarity in their variations than those of pairs of units either distally or proximally. Muscle Nerve 57: 279-286, 2018.
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Affiliation(s)
- Hélio V Cabral
- Programa de Engenharia Biomédica, Universidade Federal do Rio de Janeiro, Avenida Horácio Macedo 2030, Centro de Tecnologia, Bloco I, Sala I044C, Rio de Janeiro, Brazil
| | - Leonardo M L de Souza
- Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Roger G T Mello
- Programa de Engenharia Biomédica, Universidade Federal do Rio de Janeiro, Avenida Horácio Macedo 2030, Centro de Tecnologia, Bloco I, Sala I044C, Rio de Janeiro, Brazil.,Departamento de Educação Física e Esportes, Escola Naval, Rio de Janeiro, Brazil
| | - Alessio Gallina
- Graduate Program in Rehabilitation Science, University of British Columbia, Vancouver, British Columbia, Canada
| | - Liliam F de Oliveira
- Programa de Engenharia Biomédica, Universidade Federal do Rio de Janeiro, Avenida Horácio Macedo 2030, Centro de Tecnologia, Bloco I, Sala I044C, Rio de Janeiro, Brazil.,Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Taian M Vieira
- Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Politecnico di Torino, Torino, Italia
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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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Beretta-Piccoli M, D’Antona G, Zampella C, Barbero M, Clijsen R, Cescon C. Test-retest reliability of muscle fiber conduction velocity and fractal dimension of surface EMG during isometric contractions. Physiol Meas 2017; 38:616-630. [DOI: 10.1088/1361-6579/aa614c] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Shortz AE, Mehta RK. Cognitive challenges, aging, and neuromuscular fatigue. Physiol Behav 2017; 170:19-26. [DOI: 10.1016/j.physbeh.2016.11.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 11/10/2016] [Accepted: 11/24/2016] [Indexed: 11/29/2022]
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Severijns D, Zijdewind I, Dalgas U, Lamers I, Lismont C, Feys P. The Assessment of Motor Fatigability in Persons With Multiple Sclerosis: A Systematic Review. Neurorehabil Neural Repair 2017; 31:413-431. [DOI: 10.1177/1545968317690831] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Background. Persons with multiple sclerosis (PwMS) are often characterized by increased motor fatigability, which is a performance change on an objectively measured criterion after any type of voluntary muscle contractions. This review summarizes the existing literature to determine which protocols and outcome measures are best to detect or study motor fatigability and the underlying mechanisms in MS. Methods. Two electronic databases, PubMed and Web of Science, were searched for relevant articles published until August 2016 with a combination of multiple sclerosis, fatigability, muscle fatigue, and motor fatigue. Results. A total of 48 articles were retained for data extraction. A variety of fatigability protocols were reported; protocols showed differences in type (isometric vs concentric), duration (15 to 180 s), and number of contractions (fixed or until exhaustion). Also, 12 articles reported motor fatigability during functional movements, predominantly assessed by changes in walking speed; 11 studies evaluated the mechanisms underlying motor fatigability, using additional electrical nerve or transcranial magnetic stimulation. Three articles reported psychometrics of the outcomes. Conclusions. The disparity of protocols and outcome measures to study different aspects of motor fatigability in PwMS impedes direct comparison between data. Most protocols use maximal single-joint isometric contractions, with the advantage of high standardization. Because there is no head-to-head comparison of the different protocols and only limited information on psychometric properties of outcomes, there is currently no gold standard to assess motor fatigability. The disability level, disease phenotype, and studied limb may influence the assessment of motor fatigability in PwMS.
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Affiliation(s)
- Deborah Severijns
- REVAL - Rehabilitation Research Research Center—BIOMED, Biomedical Research Institute, Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium
| | - Inge Zijdewind
- Department of Neuroscience, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Ulrik Dalgas
- Department Public Health, Section of Sport Science, Aarhus University, Aarhus, Denmark
| | - Ilse Lamers
- REVAL - Rehabilitation Research Research Center—BIOMED, Biomedical Research Institute, Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium
| | - Caroline Lismont
- REVAL - Rehabilitation Research Research Center—BIOMED, Biomedical Research Institute, Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium
| | - Peter Feys
- REVAL - Rehabilitation Research Research Center—BIOMED, Biomedical Research Institute, Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium
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Al Harrach M, Carriou V, Boudaoud S, Laforet J, Marin F. Analysis of the sEMG/force relationship using HD-sEMG technique and data fusion: A simulation study. Comput Biol Med 2017; 83:34-47. [PMID: 28219032 DOI: 10.1016/j.compbiomed.2017.02.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/08/2017] [Accepted: 02/10/2017] [Indexed: 10/20/2022]
Abstract
The relationship between the surface Electromyogram (sEMG) signal and the force of an individual muscle is still ambiguous due to the complexity of experimental evaluation. However, understanding this relationship should be useful for the assessment of neuromuscular system in healthy and pathological contexts. In this study, we present a global investigation of the factors governing the shape of this relationship. Accordingly, we conducted a focused sensitivity analysis of the sEMG/force relationship form with respect to neural, functional and physiological parameters variation. For this purpose, we used a fast generation cylindrical model for the simulation of an 8×8 High Density-sEMG (HD-sEMG) grid and a twitch based force model for the muscle force generation. The HD-sEMG signals as well as the corresponding force signals were simulated in isometric non-fatiguing conditions and were based on the Biceps Brachii (BB) muscle properties. A total of 10 isometric constant contractions of 5s were simulated for each configuration of parameters. The Root Mean Squared (RMS) value was computed in order to quantify the sEMG amplitude. Then, an image segmentation method was used for data fusion of the 8×8 RMS maps. In addition, a comparative study between recent modeling propositions and the model proposed in this study is presented. The evaluation was made by computing the Normalized Root Mean Squared Error (NRMSE) of their fitting to the simulated relationship functions. Our results indicated that the relationship between the RMS (mV) and muscle force (N) can be modeled using a 3rd degree polynomial equation. Moreover, it appears that the obtained coefficients are patient-specific and dependent on physiological, anatomical and neural parameters.
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Affiliation(s)
- Mariam Al Harrach
- Sorbonne Universites, Universite de Technologie de Compiegne, UMR CNRS 7338 Biomecanique et Bioingenieurie (BMBI), Centre de recherche Royallieu, CS 60203 Compiegne cedex, France.
| | - Vincent Carriou
- Sorbonne Universites, Universite de Technologie de Compiegne, UMR CNRS 7338 Biomecanique et Bioingenieurie (BMBI), Centre de recherche Royallieu, CS 60203 Compiegne cedex, France
| | - Sofiane Boudaoud
- Sorbonne Universites, Universite de Technologie de Compiegne, UMR CNRS 7338 Biomecanique et Bioingenieurie (BMBI), Centre de recherche Royallieu, CS 60203 Compiegne cedex, France
| | - Jeremy Laforet
- Sorbonne Universites, Universite de Technologie de Compiegne, UMR CNRS 7338 Biomecanique et Bioingenieurie (BMBI), Centre de recherche Royallieu, CS 60203 Compiegne cedex, France
| | - Frederic Marin
- Sorbonne Universites, Universite de Technologie de Compiegne, UMR CNRS 7338 Biomecanique et Bioingenieurie (BMBI), Centre de recherche Royallieu, CS 60203 Compiegne cedex, France
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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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Meduri F, Beretta-Piccoli M, Calanni L, Segreto V, Giovanetti G, Barbero M, Cescon C, D’Antona G. Inter-Gender sEMG Evaluation of Central and Peripheral Fatigue in Biceps Brachii of Young Healthy Subjects. PLoS One 2016; 11:e0168443. [PMID: 28002429 PMCID: PMC5176311 DOI: 10.1371/journal.pone.0168443] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 12/01/2016] [Indexed: 11/19/2022] Open
Abstract
Purpose The purpose of the present study was to evaluate inter-arm and inter-gender differences in fractal dimension (FD) and conduction velocity (CV) obtained from multichannel surface electromyographic (sEMG) recordings during sustained fatiguing contractions of the biceps brachii. Methods A total of 20 recreationally active males (24±6 years) and 18 recreationally active females (22±9 years) performed two isometric contractions at 120 degrees elbow joint angle: (1) at 20% maximal voluntary contraction (MVC) for 90 s, and (2) at 60% MVC until exhaustion the time to perform the task has been measured. Signals from sEMG were detected from the biceps brachii using bidimensional arrays of 64 electrodes and initial values and rate of change of CV and FD of the sEMG signal were calculated. Results No difference between left and right sides and no statistically significant interaction effect of sides with gender were found for all parameters measured. A significant inter-gender difference was found for MVC (p<0.0001). Initial values of CV were higher in females than in males at both force levels (20% MCV: p<0.0001; 60% MCV: p<0.05) whereas a lower initial estimate of FD was observed in females compared to males (20% MCV: p<0.05; 60% MCV: p<0.0001). No difference in CV and FD slopes was found at 20% MVC between genders. At 60% MVC significantly lower CV and FD slopes (CV and FD: p<0.05) and a more protracted time to exhaustion were found in females than in males (p<0.0001). When considering time to exhaustion at both levels of contraction no difference in percentage change (Δ%) of CV and FD slopes was found between genders (p>0.05). During the sustained 60% MVC no statistical correlation was found between MVC and CV or FD initial estimates nor between MVC and CV or FD slopes both in males and females whereas. A significant positive correlation between CV and FD slopes was found in both genders (males: r = 0,61; females: r = 0,55). Conclusions Fatigue determines changes in FD and CV values in biceps brachii during sustained contractions at 60% MVC. In particular males show greater increase in the rate of change of CV and FD than females whereas no difference in percentage change of these sEMG descriptors of fatigue was found. A significant correlation between FD and CV slopes found in both genders highlights that central and peripheral myoelectric components of fatigue may interact during submaximal isometric contractions.
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Affiliation(s)
- Federico Meduri
- Department of Public Health, Molecular and Forensic Medicine, and Sport Medicine Centre Voghera, University of Pavia, Pavia, Italy
| | - Matteo Beretta-Piccoli
- Rehabilitation Research Laboratory 2rLab, Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland
| | - Luca Calanni
- Department of Public Health, Molecular and Forensic Medicine, and Sport Medicine Centre Voghera, University of Pavia, Pavia, Italy
| | - Valentina Segreto
- Department of Public Health, Molecular and Forensic Medicine, and Sport Medicine Centre Voghera, University of Pavia, Pavia, Italy
| | - Giuseppe Giovanetti
- Department of Public Health, Molecular and Forensic Medicine, and Sport Medicine Centre Voghera, University of Pavia, Pavia, Italy
| | - Marco Barbero
- Rehabilitation Research Laboratory 2rLab, Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland
| | - Corrado Cescon
- Rehabilitation Research Laboratory 2rLab, Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland
| | - Giuseppe D’Antona
- Department of Public Health, Molecular and Forensic Medicine, and Sport Medicine Centre Voghera, University of Pavia, Pavia, Italy
- * E-mail:
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Laubacher M, Aksöz EA, Binder-Macleod S, Hunt KJ. Comparison of Proximally Versus Distally Placed Spatially Distributed Sequential Stimulation Electrodes in a Dynamic Knee Extension Task. Eur J Transl Myol 2016; 26:6016. [PMID: 27478563 PMCID: PMC4942706 DOI: 10.4081/ejtm.2016.6016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Spatially distributed sequential stimulation (SDSS) has demonstrated substantial power output and fatigue benefits compared to single electrode stimulation (SES) in the application of functional electrical stimulation (FES). This asymmetric electrode setup brings new possibilities but also new questions since precise placement of the electrodes is one critical factor for good muscle activation. The aim of this study was to compare the power output, fatigue and activation properties of proximally versus distally placed SDSS electrodes in an isokinetic knee extension task simulating knee movement during recumbent cycling. M. vastus lateralis and medialis of seven able-bodied subjects were stimulated with rectangular bi-phasic pulses of constant amplitude of 40 mA and at an SDSS frequency of 35 Hz for 6 min on both legs with both setups (i.e. n=14). Torque was measured during knee-extension movement by a dynamometer at an angular velocity of 110 deg/s. Mean power, peak power and activation time were calculated and compared for the initial and final stimulation phases, together with an overall fatigue index. Power output values (Pmean, Ppeak) were scaled to a standardised reference input pulse width of 100 μs (Pmean,s, Ppeak,s). The initial evaluation phase showed no significant differences between the two setups for all outcome measures. Ppeak and Ppeak,s were both significantly higher in the final phase for the distal setup (25.4 ± 8.1 W vs. 28.2 ± 6.2 W, p=0.0062 and 34.8 ± 9.5 W vs. 38.9 ± 6.7 W, p=0.021, respectively). With distal SDSS, there was modest evidence of higher Pmean and Pmean,s (p=0.071, p=0.14, respectively) but of longer activation time (p=0.096). The rate of fatigue was similar for both setups. For practical FES applications, distal placement of the SDSS electrodes is preferable.
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Affiliation(s)
- Marco Laubacher
- Institute for Rehabilitation and Performance Technology, Bern University of Applied Sciences, Burgdorf, Switzerland; Sensory Motor Systems Lab, ETH Zurich, Zürich, Switzerland
| | - Efe A Aksöz
- Institute for Rehabilitation and Performance Technology, Bern University of Applied Sciences, Burgdorf, Switzerland; Sensory Motor Systems Lab, ETH Zurich, Zürich, Switzerland
| | - Stuart Binder-Macleod
- Department of Physical Therapy, University of Delaware , Newark, United States of America
| | - Kenneth J Hunt
- Institute for Rehabilitation and Performance Technology, Bern University of Applied Sciences , Burgdorf, Switzerland
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Pethick J, Winter SL, Burnley M. Loss of knee extensor torque complexity during fatiguing isometric muscle contractions occurs exclusively above the critical torque. Am J Physiol Regul Integr Comp Physiol 2016; 310:R1144-53. [DOI: 10.1152/ajpregu.00019.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 04/11/2016] [Indexed: 11/22/2022]
Abstract
The complexity of knee extensor torque time series decreases during fatiguing isometric muscle contractions. We hypothesized that because of peripheral fatigue, this loss of torque complexity would occur exclusively during contractions above the critical torque (CT). Nine healthy participants performed isometric knee extension exercise (6 s of contraction, 4 s of rest) on six occasions for 30 min or to task failure, whichever occurred sooner. Four trials were performed above CT (trials S1–S4, S1 being the lowest intensity), and two were performed below CT (at 50% and 90% of CT). Global, central, and peripheral fatigue were quantified using maximal voluntary contractions (MVCs) with femoral nerve stimulation. The complexity of torque output was determined using approximate entropy (ApEn) and the detrended fluctuation analysis-α scaling exponent (DFA-α). The MVC torque was reduced in trials below CT [by 19 ± 4% (means ± SE) in 90%CT], but complexity did not decrease [ApEn for 90%CT: from 0.82 ± 0.03 to 0.75 ± 0.06, 95% paired-samples confidence intervals (CIs), 95% CI = −0.23, 0.10; DFA-α from 1.36 ± 0.01 to 1.32 ± 0.03, 95% CI −0.12, 0.04]. Above CT, substantial reductions in MVC torque occurred (of 49 ± 8% in S1), and torque complexity was reduced (ApEn for S1: from 0.67 ± 0.06 to 0.14 ± 0.01, 95% CI = −0.72, −0.33; DFA-α from 1.38 ± 0.03 to 1.58 ± 0.01, 95% CI 0.12, 0.29). Thus, in these experiments, the fatigue-induced loss of torque complexity occurred exclusively during contractions performed above the CT.
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Affiliation(s)
- Jamie Pethick
- Endurance Research Group, School of Sport and Exercise Sciences, University of Kent, United Kingdom
| | - Samantha L. Winter
- Endurance Research Group, School of Sport and Exercise Sciences, University of Kent, United Kingdom
| | - Mark Burnley
- Endurance Research Group, School of Sport and Exercise Sciences, University of Kent, United Kingdom
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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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