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Montgomery TR, Olmos A, Sears KN, Succi PJ, Hammer SM, Bergstrom HC, Hill EC, Trevino MA, Dinyer-McNeely TK. Influence of Blood Flow Restriction on Neuromuscular Function and Fatigue During Forearm Flexion in Men. J Strength Cond Res 2024; 38:e349-e358. [PMID: 38900183 DOI: 10.1519/jsc.0000000000004762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
ABSTRACT Montgomery, TR Jr, Olmos, A, Sears, KN, Succi, PJ, Hammer, SM, Bergstrom, HC, Hill, EC, Trevino, MA, and Dinyer-McNeely, TK. Influence of blood flow restriction on neuromuscular function and fatigue during forearm flexion in men. J Strength Cond Res 38(7): e349-e358, 2024-To determine the effects of blood flow restriction (BFR) on the mean firing rate (MFR) and motor unit action potential amplitude (MUAPAMP) vs. recruitment threshold (RT) relationships during fatiguing isometric elbow flexions. Ten men (24.5 ± 4.0 years) performed isometric trapezoidal contractions at 50% maximum voluntary contraction to task failure with or without BFR, on 2 separate days. For BFR, a cuff was inflated to 60% of the pressure required for full brachial artery occlusion at rest. During both visits, surface electromyography was recorded from the biceps brachii of the dominant limb and the signal was decomposed. A paired-samples t test was used to determine the number of repetitions completed between BFR and CON. ANOVAs (repetition [first, last] × condition [BFR, CON]) were used to determine differences in MFR vs. RT and MUAPAMP vs. RT relationships. Subjects completed more repetitions during CON (12 ± 4) than BFR (9 ± 2; p = 0.012). There was no significant interaction (p > 0.05) between the slopes and y-intercepts during the repetition × condition interaction for MUAPAMP vs. MFR. However, there was a main effect of repetition for the slopes of the MUAPAMP vs. RT (p = 0.041) but not the y-intercept (p = 0.964). Post hoc analysis (collapsed across condition) indicated that the slopes of the MUAPAMP vs. RT during the first repetition was less than the last repetition (first: 0.022 ± 0.003 mv/%MVC; last: 0.028 ± 0.004 mv/%MVC; p = 0.041). Blood flow restriction resulted in the same amount of higher threshold MU recruitment in approximately 75% of the repetitions. Furthermore, there was no change in MFR for either condition, even when taken to task failure. Thus, BFR training may create similar MU responses with less total work completed than training without BFR.
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Affiliation(s)
- Tony R Montgomery
- Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, Oklahoma
| | - Alex Olmos
- Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, Oklahoma
| | - Kylie N Sears
- Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, Oklahoma
| | - Pasquale J Succi
- Department of Kinesiology and Health Promotion, University of Kentucky, Lexington, Kentucky; and
| | - Shane M Hammer
- Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, Oklahoma
| | - Haley C Bergstrom
- Department of Kinesiology and Health Promotion, University of Kentucky, Lexington, Kentucky; and
| | - Ethan C Hill
- Division of Kinesiology, School of Kinesiology and Physical Therapy, University of Central Florida, Orlando, Florida
| | - Michael A Trevino
- Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, Oklahoma
| | - Taylor K Dinyer-McNeely
- Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, Oklahoma
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Angius L, Del Vecchio A, Goodall S, Thomas K, Ansdell P, Atkinson E, Farina D, Howatson G. Supraspinal, spinal, and motor unit adjustments to fatiguing isometric contractions of the knee extensors at low and high submaximal intensities in males. J Appl Physiol (1985) 2024; 136:1546-1558. [PMID: 38695356 DOI: 10.1152/japplphysiol.00675.2023] [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: 09/22/2023] [Revised: 04/04/2024] [Accepted: 04/23/2024] [Indexed: 06/16/2024] Open
Abstract
Contraction intensity is a key factor determining the development of muscle fatigue, and it has been shown to induce distinct changes along the motor pathway. The role of cortical and spinal inputs that regulate motor unit (MU) behavior during fatiguing contractions is poorly understood. We studied the cortical, spinal, and neuromuscular response to sustained fatiguing isometric tasks performed at 20% and 70% of the maximum isometric voluntary contraction (MVC), together with MU behavior of knee extensors in healthy active males. Neuromuscular function was assessed before and after performance of both tasks. Cortical and spinal responses during exercise were measured via stimulation of the motor cortex and spinal cord. High-density electromyography was used to record individual MUs from the vastus lateralis (VL). Exercise at 70%MVC induced greater decline in MVC (P = 0.023) and potentiated twitch force compared with 20%MVC (P < 0.001), with no difference in voluntary activation (P = 0.514). Throughout exercise, corticospinal responses were greater during the 20%MVC task (P < 0.001), and spinal responses increased over time in both tasks (P ≤ 0.042). MU discharge rate increased similarly after both tasks (P ≤ 0.043), whereas recruitment and derecruitment thresholds were unaffected (P ≥ 0.295). These results suggest that increased excitability of cortical and spinal inputs might be responsible for the increase in MU discharge rate. The increase in evoked responses together with the higher MU discharge rate might be required to compensate for peripheral adjustments to sustain fatiguing contractions at different intensities.NEW & NOTEWORTHY Changes in central nervous system and muscle function occur in response to fatiguing exercise and are specific to exercise intensity. This study measured corticospinal, neuromuscular, and motor unit behavior to fatiguing isometric tasks performed at different intensities. Both tasks increased corticospinal excitability and motor unit discharge rate. Our findings suggest that these acute adjustments are required to compensate for the exercise-induced decrements in neuromuscular function caused by fatiguing tasks.
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Affiliation(s)
- Luca Angius
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Alessandro Del Vecchio
- Department of Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Stuart Goodall
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Kevin Thomas
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Paul Ansdell
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Elliot Atkinson
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Glyn Howatson
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
- Water Research Group, North-West University, Potchefstroom, South Africa
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Olmos AA, Sontag SA, Sterczala AJ, Parra ME, Dimmick HL, Miller JD, Deckert JA, Herda TJ, Trevino MA. High-Intensity Cycling Training Necessitates Increased Neuromuscular Demand of the Vastus Lateralis During a Fatiguing Contraction. RESEARCH QUARTERLY FOR EXERCISE AND SPORT 2024; 95:313-324. [PMID: 37369135 DOI: 10.1080/02701367.2023.2201311] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 04/05/2023] [Indexed: 06/29/2023]
Abstract
Purpose: To examine the effects of a 5-week continuous cycling training intervention on electromyographic amplitude (EMGRMS)- and mechanomyographic amplitude (MMGRMS)-torque relationships of the vastus lateralis (VL) during a prolonged contraction. Methods: Twenty-four sedentary, young adults performed maximal voluntary contractions (MVCs) and a prolonged isometric trapezoidal contraction at the same absolute 40% MVC for the knee extensors before (PRE) and after training (POSTABS). Individual b- (slopes) and a-terms (y-intercepts) were calculated from the log-transformed electromyographic amplitude (EMGRMS)- and mechanomyographic amplitude (MMGRMS)-torque relationships during the increasing and decreasing segments of the trapezoid. EMGRMS and MMGRMS was normalized for the 45-s steady torque segment. Results: At PRE, b-terms for the EMGRMS-torque relationships during the linearly decreasing segment were greater than the increasing segment (p < .001), and decreased from PRE to POSTABS (p = .027). a-terms were greater during the linearly increasing than decreasing segment at PRE, while the a-terms for the linearly decreasing segment increased from PRE to POSTABS (p = .027). For the MMGRMS-torque relationships, b-terms during the linearly decreasing segment decreased from PRE to POSTABS (p = .013), while a-terms increased from PRE to POSTABS when collapsed across segments (p = .022). Steady torque EMGRMS increased for POSTABS (p < .001). Conclusion: Although cycling training increased aerobic endurance, incorporating resistance training may benefit athletes/individuals as the alterations in neuromuscular parameters post-training suggest a greater neural cost (EMGRMS) and mechanical output (MMGRMS) to complete the same pre-training fatiguing contraction.
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Azevedo J, Moreira-Silva I, Seixas A, Fonseca P, Oliveira J, Vilas-Boas JP. The Effect of Muscle Fatigue on the Knee Proprioception: A Systematic Review. J Mot Behav 2024:1-33. [PMID: 38810655 DOI: 10.1080/00222895.2024.2341753] [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: 08/22/2023] [Accepted: 04/07/2024] [Indexed: 05/31/2024]
Abstract
This study aimed to systematically review and summarise the evidence about the effect of muscle fatigue on the knee proprioception of trained and non-trained individuals. A search in PubMed, Scopus, Web of Science and EBSCO databases and Google Scholar was conducted using the expression: "fatigue" AND ("proprioception" OR "position sense" OR "repositioning" OR "kinesthesia" OR "detection of passive motion" OR "force sense" OR "sense of resistance") AND "knee". Forty-two studies were included. Regarding joint-position sense, higher repositioning errors were reported after local and general protocols. Kinesthesia seems to be more affected when fatigue is induced locally, and force sense when assessed at higher target forces and after eccentric protocols. Muscle fatigue, both induced locally or generally, has a negative impact on the knee proprioception.
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Affiliation(s)
- Joana Azevedo
- FP-I3ID, FP-BHS, Escola Superior de Saúde Fernando Pessoa, Porto, Portugal
- Faculty of Sport, University of Porto, Porto, Portugal
- Porto Biomechanics Laboratory (LABIOMEP-UP), University of Porto, Porto, Portugal
| | - Isabel Moreira-Silva
- FP-I3ID, FP-BHS, Escola Superior de Saúde Fernando Pessoa, Porto, Portugal
- Research Centre in Physical Activity, Health and Leisure-CIAFEL, Faculty of Sports, University of Porto, Porto, Portugal
| | - Adérito Seixas
- FP-I3ID, FP-BHS, Escola Superior de Saúde Fernando Pessoa, Porto, Portugal
- LABIOMEP, INEGI-LAETA, Faculdade de Desporto, Universidade do Porto, Porto, Portugal
| | - Pedro Fonseca
- Faculty of Sport, University of Porto, Porto, Portugal
- Porto Biomechanics Laboratory (LABIOMEP-UP), University of Porto, Porto, Portugal
| | - José Oliveira
- Research Centre in Physical Activity, Health and Leisure-CIAFEL, Faculty of Sports, University of Porto, Porto, Portugal
- Laboratory for Integrative and Translational Research in Population Health (ITR), University of Porto, Porto, Portugal
| | - João Paulo Vilas-Boas
- Porto Biomechanics Laboratory (LABIOMEP-UP), University of Porto, Porto, Portugal
- Centre of Research, Education, Innovation, and Intervention in Sport (CIFI2D), Faculty of Sport, University of Porto, Porto, Portugal
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Valenčič T, Ansdell P, Brownstein CG, Spillane PM, Holobar A, Škarabot J. Motor unit discharge rate modulation during isometric contractions to failure is intensity- and modality-dependent. J Physiol 2024; 602:2287-2314. [PMID: 38619366 DOI: 10.1113/jp286143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 03/25/2024] [Indexed: 04/16/2024] Open
Abstract
The physiological mechanisms determining the progressive decline in the maximal muscle torque production capacity during isometric contractions to task failure are known to depend on task demands. Task-specificity of the associated adjustments in motor unit discharge rate (MUDR), however, remains unclear. This study examined MUDR adjustments during different submaximal isometric knee extension tasks to failure. Participants performed a sustained and an intermittent task at 20% and 50% of maximal voluntary torque (MVT), respectively (Experiment 1). High-density surface EMG signals were recorded from vastus lateralis (VL) and medialis (VM) and decomposed into individual MU discharge timings, with the identified MUs tracked from recruitment to task failure. MUDR was quantified and normalised to intervals of 10% of contraction time (CT). MUDR of both muscles exhibited distinct modulation patterns in each task. During the 20% MVT sustained task, MUDR decreased until ∼50% CT, after which it gradually returned to baseline. Conversely, during the 50% MVT intermittent task, MUDR remained stable until ∼40-50% CT, after which it started to continually increase until task failure. To explore the effect of contraction intensity on the observed patterns, VL and VM MUDR was quantified during sustained contractions at 30% and 50% MVT (Experiment 2). During the 30% MVT sustained task, MUDR remained stable until ∼80-90% CT in both muscles, after which it continually increased until task failure. During the 50% MVT sustained task the increase in MUDR occurred earlier, after ∼70-80% CT. Our results suggest that adjustments in MUDR during submaximal isometric contractions to failure are contraction modality- and intensity-dependent. KEY POINTS: During prolonged muscle contractions a constant motor output can be maintained by recruitment of additional motor units and adjustments in their discharge rate. Whilst contraction-induced decrements in neuromuscular function are known to depend on task demands, task-specificity of motor unit discharge behaviour adjustments is still unclear. In this study, we tracked and compared discharge activity of several concurrently active motor units in the vastii muscles during different submaximal isometric knee extension tasks to failure, including intermittent vs. sustained contraction modalities performed in the same intensity domain (Experiment 1), and two sustained contractions performed at different intensities (Experiment 2). During each task, motor units modulated their discharge rate in a distinct, biphasic manner, with the modulation pattern depending on contraction intensity and modality. These results provide insight into motoneuronal adjustments during contraction tasks posing different demands on the neuromuscular system.
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Affiliation(s)
- Tamara Valenčič
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Paul Ansdell
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, UK
| | - Callum G Brownstein
- School of Biomedical, Nutritional and Sport Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Padraig M Spillane
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, UK
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Jakob Škarabot
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
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Marina M, Torrado P, Duchateau J, Baudry S. Neural Adjustments during Repeated Braking and Throttle Actions on a Motorcycle Setup. Int J Sports Med 2024; 45:125-133. [PMID: 38096909 DOI: 10.1055/a-2197-0967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
The aim of the study was to assess neuromuscular changes during an intermittent fatiguing task designed to replicate fundamental actions and ergonomics of road race motorcycling. Twenty-eight participants repeated a sequence of submaximal brake-pulling and gas throttle actions, interspaced by one maximal brake-pulling, until failure. During the submaximal brake-pulling actions performed at 30% MVC, force fluctuations, surface EMG, maximal M-wave (Mmax) and H-reflex were measured in the flexor digitorum superficialis. At the end of the task, the MVC force and associated EMG activity decreased (P<0.001) by 46% and 26%, respectively. During the task, force fluctuation and EMG activity increased gradually (106% and 61%, respectively) with respect to the pre-fatigue state (P≤0.029). The Mmax first phase did not change (P≥0.524), whereas the H-reflex amplitude, normalized to Mmax, increased (149%; P≤0.039). Noteworthy, the relative increase in H-reflex amplitude was correlated with the increase in EMG activity during the task (r=0.63; P<0.001). During the 10-min recovery, MVC force and EMG activity remained depressed (P≤0.05) whereas H-reflex amplitude and force fluctuation returned to pre-fatigue values. In conclusion, contrarily to other studies, our results bring forward that when mimicking motorcycling brake-pulling and gas throttle actions, supraspinal neural mechanisms primarily limit the duration of the performance.
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Affiliation(s)
- Michel Marina
- Research Group in Physical Activity and Health (GRAFAiS), Institut Nacional d'Educació Física de Catalunya (INEFC) - Universitat de Barcelona (UB), Barcelona, Spain
| | - Priscila Torrado
- Research Group in Physical Activity and Health (GRAFAiS), Institut Nacional d'Educació Física de Catalunya (INEFC) - Universitat de Barcelona (UB), Barcelona, Spain
| | - Jacques Duchateau
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), ULB Université Libre de Bruxelles, Bruxelles, Belgium
| | - Stephane Baudry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), ULB Université Libre de Bruxelles, Bruxelles, Belgium
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Nishikawa T, Takeda R, Hirono T, Okudaira M, Ohya T, Watanabe K. Differences in acute neuromuscular response after single session of resistance exercise between young and older adults. Exp Gerontol 2024; 185:112346. [PMID: 38104744 DOI: 10.1016/j.exger.2023.112346] [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: 10/24/2023] [Revised: 12/07/2023] [Accepted: 12/10/2023] [Indexed: 12/19/2023]
Abstract
AIMS The purpose of this study was to investigate differences in the acute response after resistance exercise between young and older adults. METHODS Seventeen young and 18 older adults performed a single session of resistance exercise, consisting of 3 sets of 10 isometric knee extensions. Maximal voluntary contraction (MVC), motor unit (MU) activity of the vastus lateralis, and electrically elicited torque of the knee extensor were measured before and after the resistance exercise. RESULTS Although both groups showed the same degree of decline in MVC (young: -15.2 ± 14.3 %, older: -16.4 ± 7.9 %, p = 0.839), electrically elicited torque markedly decreased in the young group (young: -21.5 ± 7.7 %, older: -14.3 ± 9.5 %, p < 0.001), and the decrease in the MU firing rate was greater in the older group (young: -26.1 ± 24.1 %, older: -44.7 ± 24.5 %, p < 0.001). Changes in the MU firing rate following the exercise were correlated with the MU recruitment threshold in the older group (p < 0.001, rs = 0.457), but not young group (p = 0.960). DISCUSSION These results showed that young adults exhibited a greater acute response in the peripheral component, whereas older adults showed a greater acute response in the central component of the neuromuscular system, and the acute response in MUs with a high recruitment threshold following resistance exercise was smaller than in those with a low recruitment threshold in older adults. These findings may partly explain why there are different chronic adaptations to resistance training between young and older adults.
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Affiliation(s)
- Taichi Nishikawa
- Graduate School of Health and Sport Sciences, Chukyo University, Toyota, Japan; Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan
| | - Ryosuke Takeda
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan
| | - Tetsuya Hirono
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan; Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
| | - Masamichi Okudaira
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan; Faculty of Education, Iwate University, Iwate, Japan
| | - Toshiyuki Ohya
- Laboratory for Exercise Physiology and Biomechanics, Graduate School of Health and Sport Sciences, Chukyo University, Toyota, Japan
| | - Kohei Watanabe
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan.
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Yung M, Rose LM, Neumann WP, Yazdani A, Kapellusch J. Is there a u-shaped relationship between load levels and fatigue and recovery? An examination of possible mechanisms. ERGONOMICS 2023; 66:2058-2073. [PMID: 36846950 DOI: 10.1080/00140139.2023.2183850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 02/18/2023] [Indexed: 06/18/2023]
Abstract
In a previous study, an unexpected u-shaped relationship was observed between load level and fatigue/recovery responses. Moderate load levels resulted in lower perceived discomfort, pain, and fatigue, and shorter recovery times compared to either low or high load levels. This phenomenon has been reported in other studies, but no article has examined the possible mechanisms that might explain this u-shaped relationship. In this paper, we re-examined the previously published data and found that the phenomenon does not appear to be due to the experimental artefact; the u-shape may be due to unexpectedly lower fatigue effects at moderate loads, and higher fatigue effects at lower loads. We then conducted a literature review and identified several possible physiological, perceptual, and biomechanical explanatory mechanisms. No single mechanism explains the entirety of the phenomenon. Further research is needed on the relationship between work exposures, fatigue, and recovery, and the mechanisms related to the u-shaped relationship.Practitioner summary: We examine a previously observed u-shaped relationship between load level and fatigue/recovery, where moderate force resulted in lower perceived fatigue and shorter recovery times. A u-shaped fatigue response suggests that simply minimising load levels might not be an optimal approach to reduce the risk of workplace injuries.
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Affiliation(s)
- Marcus Yung
- Canadian Institute for Safety, Wellness, & Performance, Conestoga College Institute of Technology and Advanced Learning, Kitchener, Canada
| | - Linda M Rose
- Division of Ergonomics, Department of Biomedical Engineering and Health Systems, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Huddinge, Sweden
| | - W Patrick Neumann
- Department of Mechanical and Industrial Engineering, Faculty of Engineering and Architectural Science, Toronto Metropolitan University, Toronto, Canada
| | - Amin Yazdani
- Canadian Institute for Safety, Wellness, & Performance, Conestoga College Institute of Technology and Advanced Learning, Kitchener, Canada
| | - Jay Kapellusch
- Department of Rehabilitation Sciences & Technology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
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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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Malaya CA, Parikh PJ, Smith DL, Riaz A, Chandrasekaran S, Layne CS. Effects of simulated hypo-gravity on lower limb kinematic and electromyographic variables during anti-gravitational treadmill walking. Front Physiol 2023; 14:1141015. [PMID: 37362436 PMCID: PMC10285399 DOI: 10.3389/fphys.2023.1141015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 05/26/2023] [Indexed: 06/28/2023] Open
Abstract
Introduction: This study investigated kinematic and EMG changes in gait across simulated gravitational unloading levels between 100% and 20% of normal body weight. This study sought to identify if each level of unloading elicited consistent changes-particular to that percentage of normal body weight-or if the changes seen with unloading could be influenced by the previous level(s) of unloading. Methods: 15 healthy adult participants (26.3 ± 2.5 years; 53% female) walked in an Alter-G anti-gravity treadmill unloading system (mean speed: 1.49 ± 0.37 mph) for 1 min each at 100%, 80%, 60%, 40% and 20% of normal body weight, before loading back to 100% in reverse order. Lower-body kinematic data were captured by inertial measurement units, and EMG data were collected from the rectus femoris, biceps femoris, medial gastrocnemius, and anterior tibialis. Data were compared across like levels of load using repeated measures ANOVA and statistical parametric mapping. Difference waveforms for adjacent levels were created to examine the rate of change between different unloading levels. Results: This study found hip, knee, and ankle kinematics as well as activity in the rectus femoris, and medial gastrocnemius were significantly different at the same level of unloading, having arrived from a higher, or lower level of unloading. There were no significant changes in the kinematic difference waveforms, however the waveform representing the change in EMG between 100% and 80% load was significantly different from all other levels. Discussion: This study found that body weight unloading from 100% to 20% elicited distinct responses in the medial gastrocnemius, as well as partly in the rectus femoris. Hip, knee, and ankle kinematics were also affected differentially by loading and unloading, especially at 40% of normal body weight. These findings suggest the previous level of gravitational load is an important factor to consider in determining kinematic and EMG responses to the current level during loading and unloading below standard g. Similarly, the rate of change in kinematics from 100% to 20% appears to be linear, while the rate of change in EMG was non-linear. This is of particular interest, as it suggests that kinematic and EMG measures decouple with unloading and may react to unloading uniquely.
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Affiliation(s)
- Christopher A. Malaya
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, TX, United States
- Grail Laboratory, Parker University, Dallas, TX, United States
| | - Pranav J. Parikh
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, TX, United States
| | - Dean L. Smith
- Nutrition and Health, Department of Kinesiology, Miami University, Oxford, OH, United States
| | - Arshia Riaz
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, TX, United States
| | - Subhalakshmi Chandrasekaran
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, TX, United States
| | - Charles S. Layne
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, TX, United States
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11
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Marzouk M, McKeown DJ, Borg DN, Headrick J, Kavanagh JJ. Perceptions of fatigue and neuromuscular measures of performance fatigability during prolonged low-intensity elbow flexions. Exp Physiol 2023; 108:465-479. [PMID: 36763088 PMCID: PMC10103868 DOI: 10.1113/ep090981] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 01/24/2023] [Indexed: 02/11/2023]
Abstract
NEW FINDINGS What is the central question of this study? What is the predictive relationship between self-reported scales to quantify perceptions of fatigue during exercise and gold standard measures used to quantify the development of neuromuscular fatigue? What is the main finding and its importance? No scale was determined to be substantively more effective than another. However, the number of ongoing contractions performed was shown to be a better predictor of fatigue in the motor system than any of the subjective scales. ABSTRACT The purpose of this study was to determine the relationship between transcranial magnetic stimulation (TMS) measures of performance fatigability and commonly used scales that quantify perceptions of fatigue during exercise. Twenty healthy participants (age 23 ± 3 years, 10 female) performed 10 submaximal isometric elbow flexions at 20% maximal voluntary contraction (MVC) for 2 min, separated by 45 s of rest. Biceps brachii muscle electromyography and elbow flexion torque responses to single-pulse TMS were obtained at the end of each contraction to assess central factors of performance fatigability. A rating of perceived exertion (RPE) scale, Omnibus Resistance scale, Likert scale, Rating of Fatigue scale and a visual analogue scale (VAS) were used to assess perceptions of fatigue at the end of each contraction. The RPE (root mean square error (RMSE) = 0.144) and Rating of Fatigue (RMSE = 0.145) scales were the best predictors of decline in MVC torque, whereas the Likert (RMSE= 0.266) and RPE (RMSE= 0.268) scales were the best predictors of electromyographic amplitude. Although the Likert (RMSE = 7.6) and Rating of Fatigue (RMSE = 7.6) scales were the best predictors of voluntary muscle activation of any scale, the number of contractions performed during the protocol was a better predictor (RMSE = 7.3). The ability of the scales to predict TMS measures of performance fatigability were in general similar. Interestingly, the number of contractions performed was a better predictor of TMS measures than the scales themselves.
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Affiliation(s)
- Monica Marzouk
- Neural Control of Movement LaboratoryMenzies Health Institute QueenslandGriffith UniversityGold CoastQueenslandAustralia
| | - Daniel J. McKeown
- Neural Control of Movement LaboratoryMenzies Health Institute QueenslandGriffith UniversityGold CoastQueenslandAustralia
| | - David N. Borg
- The Australian Centre for Health Services Innovation and Centre for Healthcare Transformation, School of Public Health and Social WorkQueensland University of TechnologyBrisbaneQueenslandAustralia
| | - Jonathon Headrick
- Neural Control of Movement LaboratoryMenzies Health Institute QueenslandGriffith UniversityGold CoastQueenslandAustralia
| | - Justin J. Kavanagh
- Neural Control of Movement LaboratoryMenzies Health Institute QueenslandGriffith UniversityGold CoastQueenslandAustralia
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12
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Dideriksen J, Del Vecchio A. Adaptations in motor unit properties underlying changes in recruitment, rate coding, and maximum force. J Neurophysiol 2023; 129:235-246. [PMID: 36515411 DOI: 10.1152/jn.00222.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Changes in the discharge characteristics of motor units as well as in the maximum force-producing capacity of the muscle are observed following training, aging, and fatiguability. The ability to measure the adaptations in the neuromuscular properties underlying these changes experimentally, however, is limited. In this study we used a computational model to systematically investigate the effects of various neural and muscular adaptations on motor unit recruitment thresholds, average motor unit discharge rates in submaximal contractions, and maximum force. The primary focus was to identify candidate adaptations that can explain experimentally observed changes in motor unit discharge characteristics after 4 wk of strength training (Del Vecchio A, Casolo A, Negro F, Scorcelletti M, Bazzucchi I, Enoka R, Felici F, Farina D. J Physiol 597: 1873-1887, 2019). The simulation results indicated that multiple combinations of adaptations, likely involving an increase in maximum discharge rate across motor units, may occur after such training. On a more general level, we found that the magnitude of the adaptations scales linearly with the change in recruitment thresholds, discharge rates, and maximum force. In addition, the combination of multiple adaptations can be predicted as the linear sum of their individual effects. Together, this implies that the outcomes of the simulations can be generalized to predict the effect of any combination of neural and muscular adaptations. In this way, the study provides a tool for estimating potential underlying adaptations in neural and muscular properties to explain any change in commonly used measures of rate coding, recruitment, and maximum force.NEW & NOTEWORTHY Our ability to measure adaptations in neuromuscular properties in vivo is limited. Using a computational model, we quantify the effect of multiple neuromuscular adaptations on common measures of motor unit recruitment, rate coding, and force-producing capacity. Scaling and combining adaptations had a near-linear effect on these measures, indicating that the results can explain and predict neuromuscular adaptations in a wide range of conditions, including, but not limited to, strength training.
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Affiliation(s)
- Jakob Dideriksen
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Alessandro Del Vecchio
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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13
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Abitante TJ, Rutkove SB, Duda KR, Newman DJ. Effect of Athletic Training on Fatigue During Neuromuscular Electrical Stimulation. Front Sports Act Living 2022; 4:894395. [PMID: 35774382 PMCID: PMC9237484 DOI: 10.3389/fspor.2022.894395] [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: 03/11/2022] [Accepted: 05/09/2022] [Indexed: 11/25/2022] Open
Abstract
The purpose of this study was to explore the effect an individual's exercise training type will have on muscle fatigability during repetitive contractions induced by Neuromuscular Electrical Stimulation (NMES). Thirty-four subjects comprising of competitive athletes and controls were recruited into three cohorts: Endurance (runners/cyclists) n = 13; nine male, four female; 27 ± 8 years old, Explosive (Lifters/Sprinters) n = 11; nine male, two female; 30 ± 7 years old, and controls n = 10, six male, four female, 26 ± 4 years old. Subjects were placed in a custom-made leg extension rig, and received NMES against a fixed resistance (NMES-FR), to the Vastus Medialis muscle resulting in isometric leg extensions, at a duty cycle of 1 s on/3 s rest, for 20 min. The force of the isometric contractions was recorded using a Hogan MicroFet2 dynamometer, and three separate fatigue metrics were calculated to compare the different cohorts, sports within each cohort, and gender within each cohort. For every fatigue metric, the endurance group fatigued significantly less than both the explosive and control cohorts, with no difference observed between the explosive and the controls. Within each cohort, no significant difference was observed in any fatigue metric between sport or gender, but these comparisons lacked power. The results show that only high capacity endurance activity will have any effect on reducing one's fatigability during repetitive NMES. The implications of this conclusion can aid in the development of NMES regimens for use in healthy populations, such as athletic training or astronaut musculoskeletal countermeasures, as well as clinical applications when fatigue is to be minimized.
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Affiliation(s)
- Thomas J. Abitante
- Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States
- The Charles Stark Draper Laboratory, Inc., Cambridge, MA, United States
- *Correspondence: Thomas J. Abitante
| | - Seward B. Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States
| | - Kevin R. Duda
- The Charles Stark Draper Laboratory, Inc., Cambridge, MA, United States
| | - Dava J. Newman
- MIT Media Lab, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA, United States
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14
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Marina M, Torrado P, Bou-Garcia S, Baudry S, Duchateau J. Changes of agonist and synergist muscles activity during a sustained submaximal brake-pulling gesture. J Electromyogr Kinesiol 2022; 65:102677. [PMID: 35717829 DOI: 10.1016/j.jelekin.2022.102677] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 05/31/2022] [Accepted: 06/01/2022] [Indexed: 11/16/2022] Open
Abstract
We analyzed the time course of changes in muscle activity of the prime mover and synergist muscles during a sustained brake-pulling action and investigated the relationship between muscle activity and braking force fluctuation (FF). Thirty-two participants performed a continuous fatiguing protocol (CFP) at 30% of maximal voluntary contraction (MVC) until failure. Surface electromyography was used to analyze root mean square (RMS) values in the flexor digitorum superficialis (FD), flexor carpi radialis (FC), extensor digitorum communis (ED), extensor carpi radialis (EC), brachioradialis (BR), biceps brachii (BB), and triceps brachii (TB). The FF and RMS in all muscles increased progressively (P<0.01) during the CFP, with sharp increments at time limit particularly in FD and FC (P<0.001). The RMS of the FD and FC were comparable to the baseline MVC values at time limit, in comparison to the other muscles that did not reach such levels of activity (P<0.003). The three flexor/extensor ratios used to measure coactivation levels decreased significantly (P<0.001). In contrast to RMS, MVC was still depressed at the minute 10 of recovery. The results suggest that the time limit was mainly constrained by fatigue-related mechanisms of the FD and FC but not by those of other synergist and antagonist muscles.
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Affiliation(s)
- Michel Marina
- Institut Nacional d'Educació Física de Catalunya (INEFC) -Universitat de Barcelona (UB). Research Group in Physical Activity and Health (GRAFiS), Barcelona, Spain.
| | - Priscila Torrado
- Institut Nacional d'Educació Física de Catalunya (INEFC) -Universitat de Barcelona (UB). Research Group in Physical Activity and Health (GRAFiS), Barcelona, Spain
| | - Sergi Bou-Garcia
- Institut Nacional d'Educació Física de Catalunya (INEFC) -Universitat de Barcelona (UB). Research Group in Physical Activity and Health (GRAFiS), Barcelona, Spain
| | - Stéphane Baudry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Université Libre de Bruxelles (ULB). Bruxelles, Belgium
| | - Jacques Duchateau
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Université Libre de Bruxelles (ULB). Bruxelles, Belgium
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15
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De la Fuente C, Neira A, Torres G, Silvestre R, Roby M, Yañez R, Herrera S, Martabit V, McKay I, Carpes FP. Effects of Elbow Crutch Locomotion on Gluteus Medius Activation During Stair Ascending. Front Bioeng Biotechnol 2022; 10:890004. [PMID: 35694225 PMCID: PMC9174514 DOI: 10.3389/fbioe.2022.890004] [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: 03/04/2022] [Accepted: 04/21/2022] [Indexed: 11/13/2022] Open
Abstract
Crutches can help with the locomotion of people with walking disorders or functional limitations. However, little is known about hip muscle activation during stair ascending using different crutch locomotion patterns in people without disorders and limitations. Thus, we determined the acute effects of elbow crutch locomotion on gluteus medius (GM) activity during stair ascending. This comparative analytic cross-sectional study enrolled ten healthy men (22.0 ± 0.47 years). Participants climbed up the stairs with elbow crutches using one or two crutches, with ipsilateral or contralateral use, and after loading or unloading a limb. EMG signals were recorded from anterior, middle, and posterior portions of the GM and compared between the crutch conditions. The Kruskal–Wallis test and Dunn’s multiple comparison test were performed (α = 5%). The activation of the GM increased with the ipsilateral use of crutches, with two crutches and three points, and when all the load depended only on one limb. GM activation decreased with contralateral use and in the unload limb. In conclusion, ascending stairs with elbow crutches alters the GM activation. The more critical factors were choosing the crutches’ lateral use, the number of crutches, and if the limb is loaded or unloaded while ascending the stairs. Our findings can be helpful to increase or decrease the GM activation for those who use or will use crutches.
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Affiliation(s)
- Carlos De la Fuente
- Departamento de Cs. de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- Laboratory of Neuromechanics, Universidade Federal do Pampa, Uruguaiana, Brazil
- Servicio de Biomecánica, Centro de Innovación, Clínica MEDS, Santiago, Chile
| | - Alejandro Neira
- Escuela Kinesiología, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Gustavo Torres
- Departamento de Cs. de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rony Silvestre
- Servicio de Biomecánica, Centro de Innovación, Clínica MEDS, Santiago, Chile
| | - Matias Roby
- Servicio de Biomecánica, Centro de Innovación, Clínica MEDS, Santiago, Chile
- Traumatología, Clínica MEDS, Santiago, Chile
| | - Roberto Yañez
- Servicio de Biomecánica, Centro de Innovación, Clínica MEDS, Santiago, Chile
- Traumatología, Clínica MEDS, Santiago, Chile
| | - Sofia Herrera
- Departamento de Cs. de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Virgina Martabit
- Departamento de Cs. de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Isabel McKay
- Departamento de Cs. de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Felipe P. Carpes
- Laboratory of Neuromechanics, Universidade Federal do Pampa, Uruguaiana, Brazil
- *Correspondence: Felipe P. Carpes,
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16
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Esen O, Faisal A, Zambolin F, Bailey SJ, Callaghan MJ. Effect of nitrate supplementation on skeletal muscle motor unit activity during isometric blood flow restriction exercise. Eur J Appl Physiol 2022; 122:1683-1693. [PMID: 35460359 PMCID: PMC9197866 DOI: 10.1007/s00421-022-04946-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 03/17/2022] [Indexed: 12/26/2022]
Abstract
Background Nitrate (NO3−) supplementation has been reported to lower motor unit (MU) firing rate (MUFR) during dynamic resistance exercise; however, its impact on MU activity during isometric and ischemic exercise is unknown. Purpose To assess the effect of NO3− supplementation on knee extensor MU activities during brief isometric contractions and a 3 min sustained contraction with blood flow restriction (BFR). Methods Sixteen healthy active young adults (six females) completed two trials in a randomized, double-blind, crossover design. Trials were preceded by 5 days of either NO3− (NIT) or placebo (PLA) supplementation. Intramuscular electromyography was used to determine the M. vastus lateralis MU potential (MUP) size, MUFR and near fibre (NF) jiggle (a measure of neuromuscular stability) during brief (20 s) isometric contractions at 25% maximal strength and throughout a 3 min sustained BFR isometric contraction. Results Plasma nitrite (NO2−) concentration was elevated after NIT compared to PLA (475 ± 93 vs. 198 ± 46 nmol L−1, p < 0.001). While changes in MUP area, NF jiggle and MUFR were similar between NIT and PLA trials (all p > 0.05), MUP duration was shorter with NIT compared to PLA during brief isometric contractions and the sustained ischemic contraction (p < 0.01). In addition, mean MUP duration, MUP area and NF jiggle increased, and MUFR decreased over the 3 min sustained BFR isometric contraction for both conditions (all p < 0.05). Conclusions These findings provide insight into the effect of NO3− supplementation on MUP properties and reveal faster MUP duration after short-term NO3− supplementation which may have positive implications for skeletal muscle contractile performance.
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Affiliation(s)
- Ozcan Esen
- Department of Health Professions, Manchester Metropolitan University, Manchester, M15 6GX, UK.
- Manchester Metropolitan University Institute of Sport, Manchester, UK.
| | - Azmy Faisal
- Department of Sport and Exercise Sciences, Manchester Metropolitan University, Manchester, UK
- Manchester Metropolitan University Institute of Sport, Manchester, UK
- Faculty of Physical Education for Men, Alexandria University, Alexandria, Egypt
| | - Fabio Zambolin
- Department of Sport and Exercise Sciences, Manchester Metropolitan University, Manchester, UK
- Manchester Metropolitan University Institute of Sport, Manchester, UK
| | - Stephen J Bailey
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Michael J Callaghan
- Department of Health Professions, Manchester Metropolitan University, Manchester, M15 6GX, UK
- Manchester University Hospital Foundation Trust, Manchester, UK
- Arthritis Research UK Centre for Epidemiology, Centre for Musculoskeletal Research, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
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17
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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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18
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Dimmick HL, Trevino MA, Miller JD, Parra ME, Sterczala AJ, Herda TJ. Method of analysis influences interpretations of sex-related differences in firing rates during prolonged submaximal isometric contractions. JOURNAL OF MUSCULOSKELETAL & NEURONAL INTERACTIONS 2022; 22:27-36. [PMID: 35234156 PMCID: PMC8919653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE This study examined motor unit (MU) firing rates during a prolonged isometric contraction of the vastus lateralis (VL) for females and males. METHODS Surface electromyographic (sEMG) signals were recorded from the VL for eleven females and twelve males during a 45-second isometric trapezoid muscle actions at 40% of maximal voluntary contraction (MVC). For each MU, mean firing rate (MFR) was calculated for the initial and final 10-second epochs of the steady torque segment and regressed against recruitment threshold (RT, expressed as %MVC), as well as time at recruitment (TREC, seconds). MFR was also averaged for each subject. RESULTS Significant differences existed across epochs for the y-intercepts (P=0.009) of the MFR vs. TREC relationship, as well as the grouped MFR analysis (P<0.001); no differences were observed between epochs for the MFR vs. RT relationship. Significant differences existed between sexes for the grouped MFR analysis (P=0.049), but no differences were observed for the MFR vs. TREC or MFR vs. RT relationships. CONCLUSION Analysis method may impact interpretation of firing rate behavior; increases in MU firing rates across a prolonged isometric contraction were observed in the MFR vs. TREC relationship and the grouped MFR analysis.
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Affiliation(s)
- Hannah L. Dimmick
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Michael A. Trevino
- Applied Neuromuscular Physiology Laboratory Department of Health and Human Performance, Oklahoma State University, Stillwater, OK, USA
| | - Jonathan D. Miller
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS, USA
| | - Mandy E. Parra
- Mayborn College of Health Sciences, University of Mary Hardin-Baylor, Belton, TX, USA
| | - Adam J. Sterczala
- Neuromuscular Research Laboratory, Department of Sports Medicine and Nutrition, University of Pittsburg, Pittsburgh, PA, USA
| | - Trent J. Herda
- Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS, USA,Corresponding author: Trent J. Herda, Associate Professor, Neuromechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, 1301 Sunnyside Avenue, Room 101BE, Lawrence, KS 66045 E-mail:
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Pethick J, Winter SL, Burnley M. Physiological complexity: influence of ageing, disease and neuromuscular fatigue on muscle force and torque fluctuations. Exp Physiol 2021; 106:2046-2059. [PMID: 34472160 DOI: 10.1113/ep089711] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 08/26/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the topic of this review? Physiological complexity in muscle force and torque fluctuations, specifically the quantification of complexity, how neuromuscular complexityis altered by perturbations and the potential mechanism underlying changes in neuromuscular complexity. What advances does it highlight? The necessity to calculate both magnitude- and complexity-based measures for the thorough evaluation of force/torque fluctuations. Also the need for further research on neuromuscular complexity, particularly how it relates to the performance of functional activities (e.g. manual dexterity, balance, locomotion). ABSTRACT Physiological time series produce inherently complex fluctuations. In the last 30 years, methods have been developed to characterise these fluctuations, and have revealed that they contain information about the function of the system producing them. Two broad classes of metrics are used: (1) those which quantify the regularity of the signal (e.g. entropy metrics); and (2) those which quantify the fractal properties of the signal (e.g. detrended fluctuation analysis). Using these techniques, it has been demonstrated that ageing results in a loss of complexity in the time series of a multitude of signals, including heart rate, respiration, gait and, crucially, muscle force or torque output. This suggests that as the body ages, physiological systems become less adaptable (i.e. the systems' ability to respond rapidly to a changing external environment is diminished). More recently, it has been shown that neuromuscular fatigue causes a substantial loss of muscle torque complexity, a process that can be observed in a few minutes, rather than the decades it requires for the same system to degrade with ageing. The loss of torque complexity with neuromuscular fatigue appears to occur exclusively above the critical torque (at least for tasks lasting up to 30 min). The loss of torque complexity can be exacerbated with previous exercise of the same limb, and reduced by the administration of caffeine, suggesting both peripheral and central mechanisms contribute to this loss. The mechanisms underpinning the loss of complexity are not known but may be related to altered motor unit behaviour as the muscle fatigues.
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Affiliation(s)
- Jamie Pethick
- School of Sport, Rehabilitation and Exercise Sciences, University of Essex, Colchester, UK
| | - Samantha L Winter
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Mark Burnley
- Endurance Research Group, School of Sport and Exercise Sciences, University of Kent, Chatham Maritime, UK
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20
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Watanabe K, Holobar A. Quercetin ingestion modifies human motor unit firing patterns and muscle contractile properties. Exp Brain Res 2021; 239:1567-1579. [PMID: 33742251 PMCID: PMC8144122 DOI: 10.1007/s00221-021-06085-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/10/2021] [Indexed: 11/30/2022]
Abstract
Quercetin is a polyphenolic flavonoid that has reported to block the binding of adenosine to A1 receptors at central nervous system and increase calcium release from the sarcoplasmic reticulum at skeletal muscle. The aim of the present study was to investigate the acute effect of quercetin ingestion on motor unit activation and muscle contractile properties. High-density surface electromyography during submaximal contractions and electrically elicited contraction torque in knee extensor muscles were measured before (PRE) and 60 min after (POST) quercetin glycosides or placebo ingestions in 13 young males. Individual motor units of the vastus lateralis muscle were identified from high-density surface electromyography by the Convolution Kernel Compensation technique. Firing rates of motor units recruited at 30–50% of the maximal voluntary contraction torque (MVC) were increased from PRE to POST only with quercetin (9.0 ± 2.3 to 10.5 ± 2.0 pps, p = 0.034). Twitch torque during doublet stimulation was decreased from PRE to POST with placebo (77.1 ± 17.1 to 73.9 ± 17.6 Nm, p = 0.005), but not with quercetin (p > 0.05). For motor units recruited at < 10% of MVC, normalized firing rate were decreased with quercetin (1.52 ± 0.33 to 1.58 ± 0.35%MVC/pps, p = 0.002) but increased with placebo (1.61 ± 0.32 to 1.57 ± 0.31%MVC/pps, p = 0.005). These results suggest that ingested quercetin has the functional roles to: mitigate reduction in the muscle contractile properties, enhance activations of relatively higher recruitment threshold motor units, and inhibit activation of relatively lower recruitment threshold motor units.
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Affiliation(s)
- Kohei Watanabe
- Laboratory of Neuromuscular Biomechanics, Faculty of Liberal Studies and Sciences and School of International Liberal Studies, Chukyo University, Showa-ku, YagotohonmachiNagoya, 466-8666, Japan.
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
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21
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Enoka RM, Farina D. Force Steadiness: From Motor Units to Voluntary Actions. Physiology (Bethesda) 2021; 36:114-130. [DOI: 10.1152/physiol.00027.2020] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Voluntary actions are controlled by the synaptic inputs that are shared by pools of spinal motor neurons. The slow common oscillations in the discharge times of motor units due to these synaptic inputs are strongly correlated with the fluctuations in force during submaximal isometric contractions (force steadiness) and moderately associated with performance scores on some tests of motor function. However, there are key gaps in knowledge that limit the interpretation of differences in force steadiness.
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Affiliation(s)
- Roger M. Enoka
- Department of Integrative Physiology, University of Colorado Boulder, Colorado
| | - Dario Farina
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, United Kingdom
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22
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Nagamori A, Laine CM, Loeb GE, Valero-Cuevas FJ. Force variability is mostly not motor noise: Theoretical implications for motor control. PLoS Comput Biol 2021; 17:e1008707. [PMID: 33684099 PMCID: PMC7971898 DOI: 10.1371/journal.pcbi.1008707] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 03/18/2021] [Accepted: 01/15/2021] [Indexed: 11/19/2022] Open
Abstract
Variability in muscle force is a hallmark of healthy and pathological human behavior. Predominant theories of sensorimotor control assume 'motor noise' leads to force variability and its 'signal dependence' (variability in muscle force whose amplitude increases with intensity of neural drive). Here, we demonstrate that the two proposed mechanisms for motor noise (i.e. the stochastic nature of motor unit discharge and unfused tetanic contraction) cannot account for the majority of force variability nor for its signal dependence. We do so by considering three previously underappreciated but physiologically important features of a population of motor units: 1) fusion of motor unit twitches, 2) coupling among motoneuron discharge rate, cross-bridge dynamics, and muscle mechanics, and 3) a series-elastic element to account for the aponeurosis and tendon. These results argue strongly against the idea that force variability and the resulting kinematic variability are generated primarily by 'motor noise.' Rather, they underscore the importance of variability arising from properties of control strategies embodied through distributed sensorimotor systems. As such, our study provides a critical path toward developing theories and models of sensorimotor control that provide a physiologically valid and clinically useful understanding of healthy and pathologic force variability.
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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
- Chan Division of Occupational Science and Occupational Therapy, University of Southern California, Los Angeles, California, United States of America
| | - Gerald E. Loeb
- Department of Biomedical Engineering, 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
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23
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Sonkodi B. Delayed Onset Muscle Soreness (DOMS): The Repeated Bout Effect and Chemotherapy-Induced Axonopathy May Help Explain the Dying-Back Mechanism in Amyotrophic Lateral Sclerosis and Other Neurodegenerative Diseases. Brain Sci 2021; 11:brainsci11010108. [PMID: 33467407 PMCID: PMC7830646 DOI: 10.3390/brainsci11010108] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/07/2021] [Accepted: 01/13/2021] [Indexed: 12/12/2022] Open
Abstract
Delayed onset muscle soreness (DOMS) is hypothesized to be caused by glutamate excitotoxicity-induced acute compression axonopathy of the sensory afferents in the muscle spindle. Degeneration of the same sensory afferents is implicated in the disease onset and progression of amyotrophic lateral sclerosis (ALS). A series of “silent” acute compression proprioceptive axonopathies with underlying genetic/environmental factors, damaging eccentric contractions and the non-resolving neuroinflammatory process of aging could lead to ALS disease progression. Since the sensory terminals in the muscle spindle could not regenerate from the micro-damage in ALS, unlike in DOMS, the induced protective microcircuits and their long-term functional plasticity (the equivalent of the repeated bout effect in DOMS) will be dysfunctional. The acute stress invoking osteocalcin, bradykinin, COX1, COX2, GDNF, PGE2, NGF, glutamate and N-methyl-D-aspartate (NMDA) receptors are suggested to be the critical signalers of this theory. The repeated bout effect of DOMS and the dysfunctional microcircuits in ALS are suggested to involve several dimensions of memory and learning, like pain memory, inflammation, working and episodic memory. The spatial encoding of these memory dimensions is compromised in ALS due to blunt position sense from the degenerating proprioceptive axon terminals of the affected muscle spindles. Dysfunctional microcircuits progressively and irreversibly interfere with postural control, with motor command and locomotor circuits, deplete the neuroenergetic system, and ultimately interfere with life-sustaining central pattern generators in ALS. The activated NMDA receptor is suggested to serve the “gate control” function in DOMS and ALS in line with the gate control theory of pain. Circumvention of muscle spindle-loading could be a choice of exercise therapy in muscle spindle-affected neurodegenerative diseases.
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Affiliation(s)
- Balázs Sonkodi
- Department of Health Sciences and Sport Medicine, University of Physical Education, Alkotas u. 44, H-1123 Budapest, Hungary
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24
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Rinaldin CDP, Avila de Oliveira J, Ribeiro de Souza C, Scheeren EM, Coelho DB, Teixeira LA. Compensatory control between the legs in automatic postural responses to stance perturbations under single-leg fatigue. Exp Brain Res 2021; 239:639-653. [PMID: 33388814 DOI: 10.1007/s00221-020-06003-6] [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: 08/15/2020] [Accepted: 12/03/2020] [Indexed: 01/04/2023]
Abstract
In response to sudden perturbations of stance stability, muscles of both legs are activated for balance recovery. In conditions that one of the legs has a reduced capacity to respond, the opposite leg is predicted to compensate by responding more powerfully to restore stable upright stance. In this investigation, we aimed to evaluate between-leg compensatory control in automatic postural responses to sudden perturbations in a situation in which plantar flexor muscles of a single leg were fatigued. Young participants were evaluated in response to a series of perturbations inducing forward body sway, with a focus on activation of plantar flexor muscles: lateral and medial gastrocnemii and soleus. Muscular responses were analyzed through activation magnitude and latency of muscular activation onset. For evaluation of balance and postural stability, we also analyzed the center of pressure and upper trunk displacement and weight-bearing asymmetry between the legs. Responses were assessed in three conditions: pre-fatigue, under single-leg fatigue, and following the recovery of muscular function. Results showed (a) compensation of the non-fatigued leg through the increased magnitude of muscular activation in the first perturbation under fatigue; (b) adaptation in the non-fatigued leg over repetitive perturbations, with a progressive decrement of muscular activation over trials; and (c) maintenance of increased muscular activation of the non-fatigued leg following fatigue dissipation. These findings suggest that the central nervous system is able to modulate the descending motor drive individually for each leg's muscles apparently based on their potential contribution for the achievement of the behavioral aim of recovering stable body balance following stance perturbations.
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Affiliation(s)
- Carla Daniele Pacheco Rinaldin
- Graduate Program on Health Technology, Pontifical Catholic University of Paraná, St. Imaculada Conceição, 1155, Prado Velho, Curitiba, Paraná, 80215-901, Brazil.
| | - Júlia Avila de Oliveira
- Human Motor Systems Laboratory, School of Physical Education and Sport, University of São Paulo, Av. Professor Mello Moraes, 65, Butantã, São Paulo, 05508-030, Brazil
| | - Caroline Ribeiro de Souza
- Human Motor Systems Laboratory, School of Physical Education and Sport, University of São Paulo, Av. Professor Mello Moraes, 65, Butantã, São Paulo, 05508-030, Brazil
| | - Eduardo Mendonça Scheeren
- Graduate Program on Health Technology, Pontifical Catholic University of Paraná, St. Imaculada Conceição, 1155, Prado Velho, Curitiba, Paraná, 80215-901, Brazil
| | - Daniel Boari Coelho
- Human Motor Systems Laboratory, School of Physical Education and Sport, University of São Paulo, Av. Professor Mello Moraes, 65, Butantã, São Paulo, 05508-030, Brazil.,Biomedical Engineering, Federal University of ABC, Av. da Universidade, Anchieta, São Bernardo do Campo, São Paulo, 09606-045, Brazil
| | - Luis Augusto Teixeira
- Human Motor Systems Laboratory, School of Physical Education and Sport, University of São Paulo, Av. Professor Mello Moraes, 65, Butantã, São Paulo, 05508-030, Brazil
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25
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Beretta-Piccoli M, Cescon C, D’Antona G. Evaluation of performance fatigability through surface EMG in health and muscle disease: state of the art. ARAB JOURNAL OF BASIC AND APPLIED SCIENCES 2020. [DOI: 10.1080/25765299.2020.1862985] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Matteo Beretta-Piccoli
- Criams-Sport Medicine Centre Voghera, University of Pavia, Pavia, Italy
- 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
- Criams-Sport Medicine Centre Voghera, University of Pavia, Pavia, Italy
- Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Pavia, Italy
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26
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Barreto RV, de Lima LCR, Denadai BS. Moving forward with backward pedaling: a review on eccentric cycling. Eur J Appl Physiol 2020; 121:381-407. [PMID: 33180156 DOI: 10.1007/s00421-020-04548-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 10/31/2020] [Indexed: 12/18/2022]
Abstract
PURPOSE There is a profound gap in the understanding of the eccentric cycling intensity continuum, which prevents accurate exercise prescription based on desired physiological responses. This may underestimate the applicability of eccentric cycling for different training purposes. Thus, we aimed to summarize recent research findings and screen for possible new approaches in the prescription and investigation of eccentric cycling. METHOD A search for the most relevant and state-of-the-art literature on eccentric cycling was conducted on the PubMed database. Literature from reference lists was also included when relevant. RESULTS Transversal studies present comparisons between physiological responses to eccentric and concentric cycling, performed at the same absolute power output or metabolic load. Longitudinal studies evaluate responses to eccentric cycling training by comparing them with concentric cycling and resistance training outcomes. Only one study investigated maximal eccentric cycling capacity and there are no investigations on physiological thresholds and/or exercise intensity domains during eccentric cycling. No study investigated different protocols of eccentric cycling training and the chronic effects of different load configurations. CONCLUSION Describing physiological responses to eccentric cycling based on its maximal exercise capacity may be a better way to understand it. The available evidence indicates that clinical populations may benefit from improvements in aerobic power/capacity, exercise tolerance, strength and muscle mass, while healthy and trained individuals may require different eccentric cycling training approaches to benefit from similar improvements. There is limited evidence regarding the mechanisms of acute physiological and chronic adaptive responses to eccentric cycling.
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Affiliation(s)
- Renan Vieira Barreto
- Human Performance Laboratory, Department of Physical Education, São Paulo State University, Rio Claro, São Paulo, Brazil
| | | | - Benedito Sérgio Denadai
- Human Performance Laboratory, Department of Physical Education, São Paulo State University, Rio Claro, São Paulo, Brazil.
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27
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Martinez-Valdes E, Negro F, Falla D, Dideriksen JL, Heckman CJ, Farina D. Inability to increase the neural drive to muscle is associated with task failure during submaximal contractions. J Neurophysiol 2020; 124:1110-1121. [DOI: 10.1152/jn.00447.2020] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Motor unit firing and contractile properties during a submaximal contraction until failure were assessed with a new tracking technique. Two distinct phases in firing behavior were observed, which compensated for changes in twitch area and predicted time to failure. However, the late increase in firing rate was below the rates attained in the absence of fatigue, which points to an inability of the central nervous system to sufficiently increase the neural drive to muscle with fatigue.
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Affiliation(s)
- Eduardo Martinez-Valdes
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Research Centre for Neuromuscular Function and Adapted Physical Activity “Teresa Camplani,” Università degli Studi di Brescia, Brescia, Italy
| | - 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, Birmingham, United Kingdom
| | - Jakob Lund Dideriksen
- Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - C. J. Heckman
- Department of Physiology, Northwestern University, Chicago, Illinois
| | - Dario Farina
- Department of Bioengineering, Imperial College London, Royal School of Mines, London, United Kingdom
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28
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Ansdell P, Škarabot J, Atkinson E, Corden S, Tygart A, Hicks KM, Thomas K, Hunter SK, Howatson G, Goodall S. Sex differences in fatigability following exercise normalised to the power-duration relationship. J Physiol 2020; 598:5717-5737. [PMID: 32964441 DOI: 10.1113/jp280031] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 09/07/2020] [Indexed: 01/24/2023] Open
Abstract
KEY POINTS Knee-extensors demonstrate greater fatigue resistance in females compared to males during single-limb and whole-body exercise. For single-limb exercise, the intensity-duration relationship is different between sexes, with females sustaining a greater relative intensity of exercise. This study established the power-duration relationship during cycling, then assessed fatigability during critical power-matched exercise within the heavy and severe intensity domains. When critical power and the curvature constant were expressed relative to maximal ramp test power, no sex difference was observed. No sex difference in time to task failure was observed in either trial. During heavy and severe intensity cycling, females experienced lesser muscle de-oxygenation. Following both trials, females experienced lesser reductions in knee-extensor contractile function, and following heavy intensity exercise, females experienced less reduction in voluntary activation. These data demonstrate that whilst the relative power-duration relationship is not different between males and females, the mechanisms of fatigability during critical power-matched exercise are mediated by sex. ABSTRACT Due to morphological differences, females demonstrate greater fatigue resistance of locomotor muscle during single-limb and whole-body exercise modalities. Whilst females sustain a greater relative intensity of single-limb, isometric exercise than males, limited investigation has been performed during whole-body exercise. Accordingly, this study established the power-duration relationship during cycling in 18 trained participants (eight females). Subsequently, constant-load exercise was performed at critical power (CP)-matched intensities within the heavy and severe domains, with the mechanisms of fatigability assessed via non-invasive neurostimulation, near-infrared spectroscopy and pulmonary gas exchange during and following exercise. Relative CP (72 ± 5 vs. 74 ± 2% Pmax , P = 0.210) and curvature constant (51 ± 11 vs. 52 ± 10 J Pmax -1 , P = 0.733) of the power-duration relationship were similar between males and females. Subsequent heavy (P = 0.758) and severe intensity (P = 0.645) exercise time to task failures were not different between sexes. However, females experienced lesser reductions in contractile function at task failure (P ≤ 0.020), and greater vastus lateralis oxygenation (P ≤ 0.039) during both trials. Reductions in voluntary activation occurred following both trials (P < 0.001), but were less in females following the heavy trial (P = 0.036). Furthermore, during the heavy intensity trial only, corticospinal excitability was reduced at the cortical (P = 0.020) and spinal (P = 0.036) levels, but these reductions were not sex-dependent. Other than a lower respiratory exchange ratio in the heavy trial for females (P = 0.039), no gas exchange variables differed between sexes (P ≥ 0.052). Collectively, these data demonstrate that whilst the relative power-duration relationship is not different between males and females, the mechanisms of fatigability during CP-matched exercise above and below CP are mediated by sex.
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Affiliation(s)
- Paul Ansdell
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Jakob Škarabot
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK.,School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Elliott Atkinson
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Sarah Corden
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Amber Tygart
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Kirsty M Hicks
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Kevin Thomas
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Sandra K Hunter
- Department of Physical Therapy, Marquette University, Milwaukee, WI, USA
| | - Glyn Howatson
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK.,Water Research Group, School of Environmental Sciences and Development, North-West University, Potchefstroom, South Africa
| | - Stuart Goodall
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
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29
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Copithorne DB, Hali K, Rice CL. The effect of blood flow on tibialis anterior motor unit firing rates during sustained low-intensity isometric contractions. Appl Physiol Nutr Metab 2020; 46:63-68. [PMID: 32649835 DOI: 10.1139/apnm-2020-0437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Low-intensity contractions with blood flow occlusion (BFO) result in neuromuscular adaptations comparable with high-intensity (>70% maximal voluntary contraction, MVC) exercise. Because BFO exercise can only be applied to limb muscles, it is of interest to explore whether muscles proximal to the occlusion site are affected. Therefore, the purpose of this study was to assess neural activation of the tibialis anterior (TA) when flow is occluded proximal and distal to the active muscle. Five males completed three protocols to observe the effect of BFO on motor unit firing rates (MUFR) of the TA at a fatiguing contraction intensity of ∼15% MVC. Two occlusion protocols, one proximal (BFOprox) to and one distal (BFOdis) to the TA, were compared with a control (free-flow) protocol time-matched to BFOdis. MVC was significantly reduced following the BFOprox (∼41%; P < 0.001) and BFOdis (∼27%, P < 0.001), but not following the control protocol (∼15%; P = 0.13). Surface electromyography (EMG) during BFOdis and BFOprox increased ∼14% and ∼28%, respectively, but was not different among protocols. MUFRs for BFOdis and BFOprox were significantly reduced (by ∼33% and ∼23%, respectively; P < 0.01) at task failure. Results indicate that although BFOprox results in the largest reductions of MUFRs, BFOdis shows greater impairments compared with the free-flow control condition. Novelty Effects on motor unit firing rates of proximal versus distal blood flow occlusion were compared during low-intensity fatiguing task. Proximal occlusion results in greatest fatigue and reduction in motor unit rates, but distal occlusion elicits more fatigue and rate reduction than a control task.
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Affiliation(s)
- David B Copithorne
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6A 3K7, Canada
| | - Kalter Hali
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6A 3K7, Canada
| | - Charles L Rice
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6A 3K7, Canada.,Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 3K7, Canada
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30
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Gundelach LA, Hüser MA, Beutner D, Ruther P, Bruegmann T. Towards the clinical translation of optogenetic skeletal muscle stimulation. Pflugers Arch 2020; 472:527-545. [PMID: 32415463 PMCID: PMC7239821 DOI: 10.1007/s00424-020-02387-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 03/05/2020] [Accepted: 04/28/2020] [Indexed: 12/27/2022]
Abstract
Paralysis is a frequent phenomenon in many diseases, and to date, only functional electrical stimulation (FES) mediated via the innervating nerve can be employed to restore skeletal muscle function in patients. Despite recent progress, FES has several technical limitations and significant side effects. Optogenetic stimulation has been proposed as an alternative, as it may circumvent some of the disadvantages of FES enabling cell type–specific, spatially and temporally precise stimulation of cells expressing light-gated ion channels, commonly Channelrhodopsin2. Two distinct approaches for the restoration of skeletal muscle function with optogenetics have been demonstrated: indirect optogenetic stimulation through the innervating nerve similar to FES and direct optogenetic stimulation of the skeletal muscle. Although both approaches show great promise, both have their limitations and there are several general hurdles that need to be overcome for their translation into clinics. These include successful gene transfer, sustained optogenetic protein expression, and the creation of optically active implantable devices. Herein, a comprehensive summary of the underlying mechanisms of electrical and optogenetic approaches is provided. With this knowledge in mind, we substantiate a detailed discussion of the advantages and limitations of each method. Furthermore, the obstacles in the way of clinical translation of optogenetic stimulation are discussed, and suggestions on how they could be overcome are provided. Finally, four specific examples of pathologies demanding novel therapeutic measures are discussed with a focus on the likelihood of direct versus indirect optogenetic stimulation.
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Affiliation(s)
- Lili A Gundelach
- Institute of Cardiovascular Physiology, University Medical Center, Göttingen, Germany
| | - Marc A Hüser
- Institute of Cardiovascular Physiology, University Medical Center, Göttingen, Germany
- Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center, Göttingen, Germany
| | - Dirk Beutner
- Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center, Göttingen, Germany
| | - Patrick Ruther
- Microsystem Materials Laboratory, Department of Microsystems Engineering (IMTEK), University of Freiburg, Freiburg, Germany
- BrainLinks-BrainTools Cluster of Excellence at the University of Freiburg, Freiburg, Germany
| | - Tobias Bruegmann
- Institute of Cardiovascular Physiology, University Medical Center, Göttingen, Germany.
- DZHK e.V. (German Center for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany.
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31
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Sex-related differences in motor unit firing rates and action potential amplitudes of the first dorsal interosseous during high-, but not low-intensity contractions. Exp Brain Res 2020; 238:1133-1144. [PMID: 32232542 DOI: 10.1007/s00221-020-05759-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 02/19/2020] [Indexed: 12/20/2022]
Abstract
Despite ample evidence that females are weaker and possess smaller muscle cross-sectional areas (CSAs) compared to males, it remains unclear if there are sex-related differences in the properties of motor units (MU). Eleven males (age 22 ± 3 years) and 12 females (age 21 ± 1 years) performed isometric trapezoid muscle actions at 10% and 70% of maximal voluntary contraction (MVC). Surface electromyography signals were recorded and decomposed into MU action potential (AP) waveforms and firing instances. Average MUAP amplitudes (MUAPAMPS), mean firing rates (MFRs), initial firing rates (IFRs), and recruitment thresholds (RT) were calculated for the 10% MVC, while MUAPAMPS, IFRs, and MFRs were regressed against RT for the 70% MVC. Ultrasonography was used to measure CSA of the first dorsal interosseous (FDI). Males had greater CSAs (p < 0.001; males 2.34 ± 0.28 cm2, females 1.82 ± 0.18 cm2) and MVC strength (p < 0.001; males 25.9 ± 5.5 N, females 16.44 ± 2.5 N). No differences existed for MUAPAMPS, IFRs, MFRs, or RTs (p > 0.05) during the 10% MVC. For the 70% MVC, the y-intercepts from the MUAPAMPS vs. RT relationships were greater (p < 0.05) for the males (males - 0.19 ± 0.53 mV; females - 0.78 ± 0.75 mV), while the inverse was true for the MFR vs. RT relationships (males 31.55 ± 6.92 pps, females 38.65 ± 6.71 pps) with no differences (p > 0.05) in the slopes. Therefore, smaller CSAs and weaker MVCs are likely the result of smaller higher-threshold MUs for females.
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32
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Effects of mechanical assistance on muscle activity and motor performance during isometric elbow flexion. J Electromyogr Kinesiol 2019; 50:102380. [PMID: 31841884 DOI: 10.1016/j.jelekin.2019.102380] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 11/20/2019] [Accepted: 11/27/2019] [Indexed: 01/18/2023] Open
Abstract
Mechanical assistance on joint movement is generally beneficial; however, its effects on cooperative performance and muscle activity needs to be further explored. This study examined how motor performance and muscle activity are altered when mechanical assistance is provided during isometric force control of ramp-down and hold phases. Thirteen right-handed participants (age: 24.7 ± 1.8 years) performed trajectory tracking tasks. Participants were asked to maintain the reference magnitude of 47 N (REF) during isometric elbow flexion. The force was released to a step-down magnitude of either 75% REF or 50% REF and maintained, with and without mechanical assistance. The ramp-down durations of force release were set to 0.5, 2.5, or 5.0 s. Throughout the experiment, we measured the following: (1) the force output using load cells to compute force variability and overshoot ratio; (2) peak perturbation on the elbow movement using an accelerometer; (3) the surface electromyography (sEMG) from biceps brachii and triceps brachii muscles; and (4) EMG oscillation from the biceps brachii muscle in the bandwidth of 15-45 Hz. Our results indicated that mechanical assistance, which involved greater peak perturbation, demonstrated lower force variability than non-assistance (p < 0.01), while EMG oscillation in the biceps brachii muscle from 15 to 45 Hz was increased (p < 0.05). These findings imply that if assistive force is provided during isometric force control, the central nervous system actively tries to stabilize motor performance by controlling specific motor unit activity in the agonist muscle.
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33
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Kjeldsen SS, Næss-Schmidt ET, Hansen GM, Nielsen JF, Stubbs PW. Neuromuscular effects of dorsiflexor training with and without blood flow restriction. Heliyon 2019; 5:e02341. [PMID: 31467996 PMCID: PMC6710534 DOI: 10.1016/j.heliyon.2019.e02341] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/26/2019] [Accepted: 08/15/2019] [Indexed: 10/27/2022] Open
Abstract
Blood flow restriction training (BFRT) has been proposed for elderly and clinical populations with weakness. Before being used in these populations it is important to understand the neurological effects of, and subject perceptions to, BFRT. Seventeen healthy subjects were recruited and performed 2 experimental sessions, BFRT and training without blood flow restriction (TR-only), on separate days. Four sets of concentric/eccentric dorsiflexion contractions against theraband resistance were performed. Surface electromyography of the tibialis anterior was recorded during exercise and for the electrophysiological measures. At baseline, immediately-post, 10-min-post and 20-min-post exercise, motor evoked potentials (MEPs) from single pulse transcranial magnetic stimulation (TMS), paired-pulse TMS with interstimulus intervals of 2-ms (SICI) and 15-ms (ICF), and the M-max amplitude were recorded in the resting TA. Following training, subjects provided a numerical rating of the levels of pain, discomfort, fatigue, focus and difficulty during training. Muscle activation was higher in the last 20 contractions during BFRT compared to TR. There was no difference (time × condition interaction) between BFRT and TR for single-pulse MEP, SICI, ICF or M-max amplitude. There was a significant main effect of timepoint for single-pulse MEP and M-max amplitudes with both significantly reduced for 20-min-post exercise. No reductions were observed for SICI and ICF amplitudes. Taken together, BFRT and TR-only were only different during exercise and both regimes induced similar significant reductions in M-Max and MEP-amplitude post-training. Due to the lack of changes in SICI and ICF, it is unlikely that changes occurred in cortical sites related to these pathways. The increased surface electromyography activity in the last 20 contractions, indicate that the training regimes are different and that BFRT possibly induces more fatigue than TR. As such, BFRT could be used as an adjunct to conventional training. However, as subjects perceived BFRT as more painful, difficult and uncomfortable than TR-only, people should be selected carefully to undertake BFRT.
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Affiliation(s)
- Simon Svanborg Kjeldsen
- Research Department, Hammel Neurorehabilitation and Research Center, Aarhus University, Hammel, Denmark
| | | | - Gunhild Mo Hansen
- Research Department, Hammel Neurorehabilitation and Research Center, Aarhus University, Hammel, Denmark
| | - Jørgen Feldbæk Nielsen
- Research Department, Hammel Neurorehabilitation and Research Center, Aarhus University, Hammel, Denmark
| | - Peter William Stubbs
- Research Department, Hammel Neurorehabilitation and Research Center, Aarhus University, Hammel, Denmark.,University of Technology Sydney, Graduate School of Health, Discipline of Physiotherapy, Sydney, Australia
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Enoka RM. A primer on motor unit physiology. J Electromyogr Kinesiol 2019; 47:123-124. [DOI: 10.1016/j.jelekin.2019.05.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 05/01/2019] [Indexed: 10/26/2022] Open
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Motor unit firing rates of the first dorsal interosseous differ between male and female children aged 8-10 years. Hum Mov Sci 2019; 66:416-424. [PMID: 31174016 DOI: 10.1016/j.humov.2019.04.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 04/22/2019] [Accepted: 04/23/2019] [Indexed: 11/21/2022]
Abstract
The purpose of this study was to examine possible differences in motor unit action potential amplitudes (MUAPAMPS) and firing rates of the first dorsal interosseous (FDI) in male and female children aged 8-10 years. Eight male (mean ± SD, age = 8.8 ± 0.7 yrs; BMI = 16.5 ± 1.3 kg/m2) and eight female (age = 9.3 ± 0.9 yrs; BMI = 16.1 ± 1.5 kg/m2) children volunteered to complete isometric trapezoidal muscle actions of the first dorsal interosseous at 50% of maximal voluntary contraction (MVC). Electromyographic signals were decomposed to yield MUAPAMPS and mean firing rates (MFR) at the targeted force. An exponential model was fitted to the MUAPAMPS vs. recruitment threshold (RT) while linear models were fitted to the MFRs vs. RT relationships for each subject. Ultrasonography determined the muscle cross-sectional area (CSA) of the FDI. Independent samples t-tests were used to examine possible differences between the male and female children for MVC strength, CSA, and the coefficients from the MU relationships. There were no differences in MVC strength, CSA, or the MUAPAMP vs. RT relationships between the male and female children (P < 0.05). Males, however, had greater MFRs of lower-threshold MUs as evident by significantly larger y-intercepts (P = 0.019) and more negative slopes (P = 0.004) from the MFR vs. RT relationships. Despite no differences in muscle strength, CSA, and MUAPAMPS, differences in firing rates existed between male and female children aged 8-10 years. Neural mechanisms may primarily contribute to sex-related differences in firing rates.
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McKeown DJ, Simmonds MJ, Kavanagh JJ. Reduced blood oxygen levels induce changes in low-threshold motor unit firing that align with the individual’s tolerance to hypoxia. J Neurophysiol 2019; 121:1664-1671. [DOI: 10.1152/jn.00071.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study aimed to quantify how acute hypoxia impacts firing characteristics of biceps brachii motor units (MUs) during sustained isometric elbow flexions. MU data were extracted from surface electromyography (EMG) during 25% maximal voluntary contractions (MVC) in 10 healthy subjects (age 22 ± 1 yr). Blood oxygen saturation (SpO2) was then stabilized at 80% by reducing 1% of the fraction of inspired oxygen every 3 min for 35 min. MU data were once again collected 1 h and 2 h following the 35-min desaturation phase. Although MVC remained unaffected during 2 h of 80% SpO2, subject-specific changes in MU firing rate were observed. Four of 10 subjects exhibited a decrease in firing rate 1 h postdesaturation (12 ± 11%) and 2 h postdesaturation (16 ± 12%), whereas 6 of 10 subjects exhibited an increase in firing rate 1 h (9 ± 6%) and 2 h (9 ± 4%) postdesaturation. These bidirectional changes in firing rate were strongly correlated to the desaturation phase and the subjects’ SpO2 sensitivity to oxygen availability, where subjects who had decreased firing rates reached the target SpO2 20 min into the desaturation phase ( R2 = 0.90–0.98) and those who had increased firing rates reached the target SpO2 35 min into the desaturation phase ( R2 = 0.87–0.98). It is unlikely that a single mechanism accounted for these subject-specific changes in firing rate. Instead, differences in intrinsic properties of the neurons, afferent input to the motoneurons, neuromodulators, and sympathetic nerve activity may exist between groups. NEW & NOTEWORTHY The mechanisms of compromised motor control when exposed to hypoxia are largely unknown. The current study examined how severe acute hypoxia affects motor unit firing rate during sustained isometric contractions of the bicep brachii. The response to hypoxia was different across subjects, where motor unit firing rate increased for some individuals and decreased for others. This bidirectional change in firing rate was associated with how fast subjects desaturated during hypoxic exposure.
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Affiliation(s)
- Daniel J. McKeown
- School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Gold Coast Campus, Queensland, Australia
| | - Michael J. Simmonds
- School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Gold Coast Campus, Queensland, Australia
| | - Justin J. Kavanagh
- School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Gold Coast Campus, Queensland, Australia
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Enoka RM. Physiological validation of the decomposition of surface EMG signals. J Electromyogr Kinesiol 2019; 46:70-83. [PMID: 31003192 DOI: 10.1016/j.jelekin.2019.03.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 02/15/2019] [Accepted: 03/20/2019] [Indexed: 11/30/2022] Open
Abstract
Advances in technology have ushered in a new era in the measurement and interpretation of surface-recorded electromyographic (EMG) signals. These developments have included improvements in detection systems, the algorithms used to decompose the interference signals, and the strategies used to edit the identified waveforms. To evaluate the validity of the results obtained with this new technology, the purpose of this review was to compare the results achieved by decomposing surface-recorded EMG signals into the discharge times of single motor units with what is known about the rate coding characteristics of single motor units based on recordings obtained with intramuscular electrodes. The characteristics compared were peak discharge rate, saturation of discharge rate during submaximal contractions, rate coding during fast contractions, the association between oscillations in force and discharge rate, and adjustments during fatiguing contractions. The comparison indicates that some decomposition methods are able to replicate many of the findings derived from intramuscular recordings, but additional improvements in the methods are required. Critically, more effort needs to be focused on editing the waveforms identified by the decomposition algorithms. With adequate attention to detail, this technology has the potential to augment our knowledge on motor unit physiology and to provide useful approaches that are being translated into clinical practice.
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Affiliation(s)
- Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA.
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Efficacy of a new strength training design: the 3/7 method. Eur J Appl Physiol 2019; 119:1093-1104. [DOI: 10.1007/s00421-019-04099-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 02/06/2019] [Indexed: 12/27/2022]
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Dideriksen JL, Negro F. Spike-triggered averaging provides inaccurate estimates of motor unit twitch properties under optimal conditions. J Electromyogr Kinesiol 2018; 43:104-110. [DOI: 10.1016/j.jelekin.2018.09.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/14/2018] [Accepted: 09/21/2018] [Indexed: 11/29/2022] Open
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Abdelmoula A, Baudry S, Duchateau J. Anodal transcranial direct current stimulation does not influence the neural adjustments associated with fatiguing contractions in a hand muscle. Eur J Appl Physiol 2018; 119:597-609. [PMID: 30421008 DOI: 10.1007/s00421-018-4027-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 10/24/2018] [Indexed: 11/28/2022]
Abstract
PURPOSE The objective of the current study was to investigate the mechanisms responsible for the briefer time to failure of a submaximal contraction (C2) when performed 60 min after a similar contraction (C1), and the influence of anodal transcranial direct current stimulation (a-tDCS) applied over the motor cortex on these mechanisms. METHODS In two sessions, ten adults sustained two isometric contractions (35% of maximum) to failure with the abductor pollicis brevis (APB). Before C2, either a-tDCS or sham stimulation was applied over the motor cortex. Fatigue-related changes in Hoffmann (H) and long-latency (LLR) reflexes, motor-evoked potential (MEP) induced by transcranial magnetic stimulation and associated silent period (SP), maximal motor wave (Mmax), voluntary activation (VA), electromyographic (EMG) activity and peak force (PT3) evoked by a 3 pulse-train (100 Hz) were investigated. RESULTS The results indicate that regardless of session, the time to failure was briefer (- 13%, p < 0.05) for C2 than C1, with no a-tDCS effect. During C1, MEP amplitude, SP duration and LLR amplitude increased, H-reflex amplitude did not change, and Mmax, VA and PT3 decreased (p < 0.05). Except for EMG activity that was greater during C2 than C1 (p < 0.001), all variables were similar in C1 and C2 (p > 0.05), and recovered their initial values after the 60-min rest, except PT3. CONCLUSIONS The results of the current study indicate that a-tDCS did not influence corticospinal excitability and time to failure of C2 when performed with the APB. These observations may reflect a peripheral origin of the briefer C2 time to failure in the APB.
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Affiliation(s)
- Achraf Abdelmoula
- Laboratory of Applied Neurophysiology and Biology, Faculty for Motor Sciences, ULB Neuroscience Institute (UNI), Université libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Stéphane Baudry
- Laboratory of Applied Neurophysiology and Biology, Faculty for Motor Sciences, ULB Neuroscience Institute (UNI), Université libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium.
| | - Jacques Duchateau
- Laboratory of Applied Neurophysiology and Biology, Faculty for Motor Sciences, ULB Neuroscience Institute (UNI), Université libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
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Deering RE, Cruz M, Senefeld JW, Pashibin T, Eickmeyer S, Hunter SK. Impaired Trunk Flexor Strength, Fatigability, and Steadiness in Postpartum Women. Med Sci Sports Exerc 2018; 50:1558-1569. [PMID: 29554014 PMCID: PMC6045430 DOI: 10.1249/mss.0000000000001609] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE To determine whether postpartum women (vaginal and cesarean delivery) have deficits in trunk flexor strength, fatigability and steadiness, compared with nulligravid women, up to 26 wk postpartum. We hypothesized that postpartum women would be weaker, more fatigable, and have greater torque fluctuations than controls, with cesarean delivery showing greater deficits than vaginal delivery. METHODS Twenty-two control women (nulligravid) and 29 postpartum women (20-40 yr, 19 who delivered via vaginal birth, 13 via Caesarian section) participated. Postpartum women were tested 8 to 10 wk and 24 to 26 wk postpartum. Control women were tested 16 to 18 wk apart. Maximal voluntary isometric contractions (MVC) were performed at multiple trunk positions with the trunk flexor muscles. To determine trunk flexor fatigability, subjects performed intermittent isometric contractions at 50% MVC (6-s contraction, 4-s rest) in upright sitting until task failure. An MVC was performed during the fatiguing task (one per minute) and at 10 and 20 min of recovery. RESULTS At 8 and 26 wk, postpartum women (groups pooled) were weaker at all trunk angles (38% and 44% respectively, P < 0.05) than controls despite no differences in handgrip strength. Postpartum women were more fatigable (71% and 52% respectively) and had greater torque fluctuations than controls (P < 0.05). At 8 wk postpartum, women who had a cesarean delivery, were 59% more fatigable (P = 0.004) than the vaginal delivery group, with no difference between delivery types at 26 wk postpartum. CONCLUSIONS Musculoskeletal recovery, including trunk flexor muscle strength and fatigability, is incomplete at 26 wk postpartum. These findings provide a rationale for future studies to address outcomes of rehabilitation programs specifically targeted at improving strength and fatigability of the trunk flexor muscles after pregnancy and childbirth.
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Affiliation(s)
- Rita E. Deering
- Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, WI
| | - Meredith Cruz
- Department of Obstetrics & Gynecology, Medical College of Wisconsin, Milwaukee, WI
| | - Jonathon W. Senefeld
- Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, WI
| | - Tatyana Pashibin
- Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, WI
| | - Sarah Eickmeyer
- Department of Rehabilitation Medicine, University of Kansas, Kansas City, KS
| | - Sandra K. Hunter
- Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, WI
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Emanuelsen A, Voigt M, Madeleine P, Kjær P, Dam S, Koefoed N, Hansen EA. Repeated Bout Rate Enhancement Is Elicited by Various Forms of Finger Tapping. Front Neurosci 2018; 12:526. [PMID: 30108479 PMCID: PMC6079229 DOI: 10.3389/fnins.2018.00526] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 07/13/2018] [Indexed: 01/19/2023] Open
Abstract
Voluntary rhythmic movements, such as, for example, locomotion and other cyclic tasks, are fundamental during everyday life. Patients with impaired neural or motor function often take part in rehabilitation programs, which include rhythmic movements. Therefore, it is imperative to have the best possible understanding of control and behaviour of human voluntary rhythmic movements. A behavioural phenomenon termed repeated bout rate enhancement has been established as an increase of the freely chosen index finger tapping frequency during the second of two consecutive tapping bouts. The present study investigated whether the phenomenon would be elicited when the first bout consisted of imposed passive finger tapping or air tapping. These two forms of tapping were applied since they can be performed without descending drive (passive tapping) and without afferent feedback related to impact (air tapping) – as compared to tapping on a surface. Healthy individuals (n = 33) performed 3-min tapping bouts separated by 10 min rest. Surface electromyographic, kinetic, and kinematic data were recorded. Supportive experiments were made to measure, for example, the cortical sensory evoked potential (SEP) response during the three different forms of tapping. Results showed that tapping frequencies in the second of two consecutive bouts increased by 12.9 ± 14.8% (p < 0.001), 9.9 ± 6.0% (p = 0.001), and 16.8 ± 13.6% (p = 0.005) when the first bout had consisted of tapping, passive tapping, and air tapping, respectively. Rate enhancement occurred without increase in muscle activation. Besides, the rate enhancements occurred despite that tapping, as compared with passive tapping and air tapping, resulted in different cortical SEP responses. Based on the present findings, it can be suggested that sensory feedback in an initial bout increases the excitability of the spinal central pattern generators involved in finger tapping. This can eventually explain the phenomenon of repeated bout rate enhancement seen after a consecutive bout of finger tapping.
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Affiliation(s)
- Anders Emanuelsen
- Sport Sciences, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Michael Voigt
- Sport Sciences, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Pascal Madeleine
- Sport Sciences, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Pia Kjær
- Sport Sciences, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Sebastian Dam
- Sport Sciences, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Nikolaj Koefoed
- Sport Sciences, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Ernst A Hansen
- Sport Sciences, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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Abstract
Performance fatigability is characterized as an acute decline in motor performance caused by an exercise-induced reduction in force or power of the involved muscles. Multiple mechanisms contribute to performance fatigability and originate from neural and muscular processes, with the task demands dictating the mechanisms. This review highlights that (1) inadequate activation of the motoneuron pool can contribute to performance fatigability, and (2) the demands of the task and the physiological characteristics of the population assessed, dictate fatigability and the involved mechanisms. Examples of task and population differences in fatigability highlighted in this review include contraction intensity and velocity, stability and support provided to the fatiguing limb, sex differences, and aging. A future challenge is to define specific mechanisms of fatigability and to translate these findings to real-world performance and exercise training in healthy and clinical populations across the life span.
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Affiliation(s)
- Sandra K Hunter
- Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin 53201
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Scheidegger O, Kamber N, Rösler KM. Estimation of voluntary elicited motor neuron discharge using a peripheral nerve collision technique at different contraction strengths. Clin Neurophysiol 2018; 129:1579-1587. [PMID: 29885647 DOI: 10.1016/j.clinph.2018.04.751] [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: 02/02/2018] [Revised: 03/24/2018] [Accepted: 04/25/2018] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To estimate non-invasively the amount, recruitment pattern and discharge frequency of spinal motor neurons (MN) at contraction strength >20% of maximal voluntary contraction (MVC) of small hand muscles. METHODS A peripheral collision technique was used and consisted of supramaximal electrical stimuli at Erb's point and at the wrist, synchronizing descending volleys of action potential during voluntary isometric contractions of the abductor digiti minimi muscle at 20-80% of MVC strength and 1-8 s of contraction duration. Responses of 13 healthy volunteers were quantified and analysed using a recently described model of MN behaviour. RESULTS A linear relationship between MN discharge and force generation was noticed with R2 = 0.996, and was confirmed using the simulation results (R2 = 0.997) for contraction durations up to 8 s. For each investigated force level, discharge frequency and recruitment pattern were calculated for individual MN. CONCLUSIONS Using this method, MN discharge properties during voluntary activity can be estimated non-invasively. SIGNIFICANCE This method provides new opportunities for the non-invasive study of MN behaviour, and could be expanded to patients with conduction failure and during fatigue.
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Affiliation(s)
- Olivier Scheidegger
- Department of Neurology, Inselspital, Bern University Hospital, and University of Bern, Switzerland.
| | - Nicole Kamber
- Department of Neurology, Inselspital, Bern University Hospital, and University of Bern, Switzerland
| | - Kai Michael Rösler
- Department of Neurology, Inselspital, Bern University Hospital, and University of Bern, Switzerland
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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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Muddle TWD, Colquhoun RJ, Magrini MA, Luera MJ, DeFreitas JM, Jenkins NDM. Effects of fatiguing, submaximal high- versus low-torque isometric exercise on motor unit recruitment and firing behavior. Physiol Rep 2018; 6:e13675. [PMID: 29673119 PMCID: PMC5907942 DOI: 10.14814/phy2.13675] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 03/02/2018] [Indexed: 12/04/2022] Open
Abstract
The purpose of this investigation was to evaluate the effects of repeated, high- (HT: 70% MVIC) versus low-torque (LT: 30% MVIC) isometric exercise performed to failure on motor unit (MU) recruitment and firing behavior of the vastus lateralis. Eighteen resistance-trained males (23.1 ± 3.8 years) completed familiarization, followed by separate experimental sessions in which they completed either HT or LT exercise to failure in random order. LT exercise resulted in a greater time to task failure and a more dramatic decline in the muscle's force capacity, but the total work completed was similar for HT and LT exercise. An examination of the firing trains from 4670 MUs recorded during exercise revealed that firing rates generally increased during HT and LT exercise, but were higher during HT than LT exercise. Furthermore, recruitment thresholds (RT) did not significantly change during HT exercise, whereas the RT of the smallest MUs increased and the RT for the moderate to large MUs decreased during LT exercise. Both HT and LT exercise resulted in the recruitment of additional higher threshold MUs in order to maintain torque production. However, throughout exercise, HT required the recruitment of larger MUs than did LT exercise. In a few cases, however, MUs were recruited by individuals during LT exercise that were similar in size and original (pre) RT to those detected during HT exercise. Thus, the ability to achieve full MU recruitment during LT exercise may be dependent on the subject. Consequently, our data emphasize the task and subject dependency of muscle fatigue.
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Affiliation(s)
- Tyler W. D. Muddle
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
| | - Ryan J. Colquhoun
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
| | - Mitchel A. Magrini
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
| | - Micheal J. Luera
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
| | - Jason M. DeFreitas
- Applied Neuromuscular Physiology LaboratoryOklahoma State UniversityStillwaterOklahoma
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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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Bingham A, Arjunan SP, Kumar DK. Measuring the interactions between different locations in a muscle to monitor localized muscle fatigue. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2017:3461-3464. [PMID: 29060642 DOI: 10.1109/embc.2017.8037601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this study we investigated a technique for estimating the progression of localized muscle fatigue. This technique measures the dependence between motor units using high density surface electromyogram (HD-sEMG) and is based on the Normalized Mutual Information (NMI) measure. The NMI between every pair combination of the electrode array is computed to measure the interactions between electrodes. Participants in the experiment had an array of 64 electrodes (16 by 4) placed over the TA of their dominate leg such that the columns of the array ran parallel with the muscle fibers. The HD-sEMG was recorded whilst the participants maintained an isometric dorsiflexion with their dominate foot until task failure at 40% and 80% of their maximum voluntary contraction (MVC). The interactions between different locations over the muscle were computed using the recorded HD-sEMG signals. The results show that the average interactions between various locations over the TA significantly increased during fatigue at both levels of contraction. This can be attributed to the dependence in the motor units.
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Negro F, Orizio C. Robust estimation of average twitch contraction forces of populations of motor units in humans. J Electromyogr Kinesiol 2017; 37:132-140. [PMID: 29101911 DOI: 10.1016/j.jelekin.2017.10.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 10/16/2017] [Accepted: 10/16/2017] [Indexed: 11/15/2022] Open
Abstract
The characteristics of motor unit force twitch profiles provide important information for the understanding of the muscle force generation. The twitch force is commonly estimated with the spike-triggered averaging technique, which, despite the many limitations, has been important for clarifying central issues in force generation. In this study, we propose a new technique for the estimation of the average twitch profile of populations of motor units with uniform contractile properties. The method encompasses a model-based deconvolution of the force signal using the identified discharge times of a population of motor units. The proposed technique was validated using simulations and tested on signals recorded during voluntary activation. The results of the simulations showed that the proposed method provides accurate estimates (relative error <25%) of the main parameters of the average twitch force when the number of identified motor units is between 5% and 15% of the total number of active motor units. It is discussed that current detection and decomposition methods of multi-channel surface EMG signals allow decoding this relative sample of the active motor unit pool. However, even when this condition is not met, our results show that the estimates provided by the new method are anyway always superior to those obtained by the spike triggered average approach, especially for high motor unit synchronization levels and when a relatively small number of triggers is available. In conclusion, we present a new method that overcome the main limitations of the spike-triggered average for the study of contractile properties of individual motor units. The method provides a new reliable tool for the investigation of the determinants of muscle force.
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Affiliation(s)
- Francesco Negro
- Department of Clinical and Experimental Sciences, University of Brescia, 25123 Brescia, Italy.
| | - Claudio Orizio
- Department of Clinical and Experimental Sciences, University of Brescia, 25123 Brescia, Italy
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Enoka RM, Duchateau J. Rate Coding and the Control of Muscle Force. Cold Spring Harb Perspect Med 2017; 7:cshperspect.a029702. [PMID: 28348173 DOI: 10.1101/cshperspect.a029702] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The force exerted by a muscle during a voluntary contraction depends on the number of motor units recruited for the action and the rates at which they discharge action potentials (rate coding). Over most of the operating range of a muscle, the nervous system controls muscle force by varying both motor unit recruitment and rate coding. Except at relatively low forces, however, the control of muscle force depends primarily on rate coding, especially during fast contractions. This review provides five examples of how the modulation of rate coding influences the force exerted by muscle during voluntary actions. The five examples comprise fast contractions, lengthening and shortening contractions, steady isometric contractions, fatiguing contractions, and contractions performed after a change in the daily level of physical activity.
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Affiliation(s)
- Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80309-0354
| | - Jacques Duchateau
- Laboratory of Applied Biology and Neurophysiology, Neuroscience Institute, Université Libre de Bruxelles, 1070 Brussels, Belgium
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