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Lebesque L, Scaglioni G, Manckoundia P, Martin A. Neuromuscular fatigability is not affected by the contraction pattern of exercises with a similar mean torque. Eur J Appl Physiol 2024:10.1007/s00421-024-05660-7. [PMID: 39586887 DOI: 10.1007/s00421-024-05660-7] [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: 01/30/2024] [Accepted: 11/05/2024] [Indexed: 11/27/2024]
Abstract
PURPOSE Neuromuscular fatigability is task-dependent, but the influence of the contraction pattern on neuromuscular fatigability is largely unknown. Therefore, the present study aims to investigate if neuromuscular fatigability is affected by the contraction pattern of exhausting isometric exercises. METHODS Thirteen participants sustained a plantar flexors MVC for 1 min (MVC1-MIN) before and after exhausting exercises designed to produce a similar mean torque (30% MVC), and following a 10-min rest period. Exercises consisted of intermittent (INT), continuous (CON) or variable (continuous contraction alternating between moderate and low intensity, VAR) contractions performed until task failure. RESULTS The INT resulted in greater exercise duration and torque-time integral than CON and VAR. MVC similarly decreased after all exercises due to neural and muscular impairments. The torque loss during the MVC1-MIN increased after all exercises to a similar extent, mainly because of neural alterations. Contrary to MVC, the torque loss during the MVC1-MIN returned to baseline value after the recovery period. CONCLUSION INT, CON and VAR exercises, performed with identical mean torque and until exhaustion, led to a similar neuromuscular fatigability. When the mean torque is matched among exercises, the contraction pattern does not influence the extent of neuromuscular fatigability, assessed through the maximal torque production and sustainability. The present findings are crucial to consider for the management of neuromuscular fatigability in physical conditioning in both athletes and patients.
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Affiliation(s)
- Loïc Lebesque
- INSERM UMR1093-CAPS, Université de Bourgogne, UFR Des Sciences du Sport, UFR STAPS, Campus Universitaire, BP 27877, F-21000, Dijon, France.
| | - Gil Scaglioni
- INSERM UMR1093-CAPS, Université de Bourgogne, UFR Des Sciences du Sport, UFR STAPS, Campus Universitaire, BP 27877, F-21000, Dijon, France
| | - Patrick Manckoundia
- INSERM UMR1093-CAPS, Université de Bourgogne, UFR Des Sciences du Sport, UFR STAPS, Campus Universitaire, BP 27877, F-21000, Dijon, France
- Geriatrics Internal Medicine Department, University Hospital of Dijon Bourgogne, 21079, Dijon Cedex, France
| | - Alain Martin
- INSERM UMR1093-CAPS, Université de Bourgogne, UFR Des Sciences du Sport, UFR STAPS, Campus Universitaire, BP 27877, F-21000, Dijon, France
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Bauer P, Gomes JS, Oliveira J, Santos P, Pezarat-Correia P, Vaz JR. Torque Regulation Is Influenced by the Nature of the Isometric Contraction. SENSORS (BASEL, SWITZERLAND) 2023; 23:726. [PMID: 36679523 PMCID: PMC9861772 DOI: 10.3390/s23020726] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 12/07/2022] [Accepted: 01/03/2023] [Indexed: 06/17/2023]
Abstract
The present study aimed to investigate the effects of a continuous visual feedback and the isometric contraction nature on the complexity and variability of force. Thirteen healthy and young male adults performed three MVCs followed by three submaximal isometric force tasks at a target force of 40% of their MVC for 30 s, as follows: (i) push isometric task with visual feedback (Pvisual); (ii) hold isometric task with visual feedback (Hvisual); (iii) hold isometric task without visual feedback (Hnon-visual). Force complexity was evaluated through sample entropy (SampEn) of the force output. Force variability was analyzed through the coefficient of variation (CV). Results showed that differences were task-related, with Pvisual showing higher complexity (i.e., higher SampEn) and decreased variability (i.e., lower CV) when compared with the remaining tasks. Additionally, no significant differences were found between the two hold isometric force tasks (i.e., no influence of visual feedback). Our results are promising as we showed these two isometric tasks to induce different motor control strategies. Furthermore, we demonstrated that visual feedback's influence is also dependent on the type of isometric task. These findings should motivate researchers and physiologists to shift training paradigms and incorporate different force control evaluation tasks.
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Affiliation(s)
- Philipp Bauer
- Centro Interdisciplinar de Performance Humana (CIPER), Neuromuscular Research Lab, Faculty of Human Kinetics, University of Lisbon, 1495-751 Lisbon, Portugal
- Interdisciplinary Research Centre Egas Moniz (CiiEM), Egas Moniz School of Health & Science, 2829-511 Almada, Portugal
| | - João Sá Gomes
- Centro Interdisciplinar de Performance Humana (CIPER), Neuromuscular Research Lab, Faculty of Human Kinetics, University of Lisbon, 1495-751 Lisbon, Portugal
- Interdisciplinary Research Centre Egas Moniz (CiiEM), Egas Moniz School of Health & Science, 2829-511 Almada, Portugal
| | - João Oliveira
- Centro Interdisciplinar de Performance Humana (CIPER), Neuromuscular Research Lab, Faculty of Human Kinetics, University of Lisbon, 1495-751 Lisbon, Portugal
| | - Paulo Santos
- Centro Interdisciplinar de Performance Humana (CIPER), Neuromuscular Research Lab, Faculty of Human Kinetics, University of Lisbon, 1495-751 Lisbon, Portugal
| | - Pedro Pezarat-Correia
- Centro Interdisciplinar de Performance Humana (CIPER), Neuromuscular Research Lab, Faculty of Human Kinetics, University of Lisbon, 1495-751 Lisbon, Portugal
| | - João R. Vaz
- Centro Interdisciplinar de Performance Humana (CIPER), Neuromuscular Research Lab, Faculty of Human Kinetics, University of Lisbon, 1495-751 Lisbon, Portugal
- Interdisciplinary Research Centre Egas Moniz (CiiEM), Egas Moniz School of Health & Science, 2829-511 Almada, Portugal
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Lebesque L, Scaglioni G, Martin A. The impact of submaximal fatiguing exercises on the ability to generate and sustain the maximal voluntary contraction. Front Physiol 2022; 13:970917. [DOI: 10.3389/fphys.2022.970917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 08/04/2022] [Indexed: 11/13/2022] Open
Abstract
Neuromuscular fatigability is a failure to produce or maintain a required torque, and commonly quantified with the decrease of maximal torque production during a few seconds-long maximal voluntary contraction (MVC). The literature shows that the MVC reduction after exercises with different torque-time integral (TTI), is often similar. However, it was shown that after a fatiguing exercise, the decline in the capacity to sustain the maximal voluntary contraction for 1 min (MVC1-MIN) differs from the decrease in the capacity to perform a brief-MVC, suggesting that this latter can only partially assess neuromuscular fatigability. This study aims to highlight the relevance of using a sustained MVC to further explore the neuromuscular alterations induced by fatiguing exercises with different TTI. We used two contraction intensities (i.e., 20% and 40% MVC) to modulate the TTI, and two exercise modalities [i.e., voluntary (VOL) and electrical induced (NMES)], since the letter are known to be more fatiguing for a given TTI. Thirteen subjects performed a plantar-flexors MVC1-MIN before and after the fatiguing exercises. A similar MVC loss was obtained for the two exercise intensities despite a greater TTI at 40% MVC, regardless of the contraction modality. On the other hand, the torque loss during MVC1-MIN was significantly greater after the 40% compared to 20% MVC exercise. These findings are crucial because they demonstrate that maximal torque production and sustainability are two complementary features of neuromuscular fatigability. Hence, MVC1-MIN assessing simultaneously both capacities is essential to provide a more detailed description of neuromuscular fatigability.
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4
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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: 6.3] [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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Marion R, Power GA. Residual force enhancement due to active muscle lengthening allows similar reductions in neuromuscular activation during position- and force-control tasks. JOURNAL OF SPORT AND HEALTH SCIENCE 2020; 9:670-676. [PMID: 32693172 PMCID: PMC7749268 DOI: 10.1016/j.jshs.2020.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 05/24/2020] [Accepted: 07/08/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Residual torque enhancement (rTE) is the increase in torque observed during the isometric steady state following active muscle lengthening when compared with a fixed-end isometric contraction at the same muscle length and level of neuromuscular activation. In the rTE state, owing to an elevated contribution of passive force to total force production, less active force is required, and there is a subsequent reduction in activation. In vivo studies of rTE reporting an activation reduction are often performed using a dynamometer, where participants contract against a rigid restraint, resisting a torque motor. rTE has yet to be investigated during a position task, which involves the displacement of an inertial load with positional control. METHODS A total of 12 participants (6 males, 6 females; age = 22.8 ± 1.1 years, height = 174.7 ± 8.6 cm, mass = 82.1 ± 37.7 kg; mean ± SD) completed torque- and position-matching tasks at 60% maximum voluntary contraction for a fixed-end isometric contraction and an isometric contraction following active lengthening of the ankle dorsiflexors. RESULTS There were no significant differences in activation between torque- and position-matching tasks (p = 0.743), with ∼27% activation reduction following active lengthening for both task types (p < 0.001). CONCLUSION These results indicate that rTE is a feature of voluntary, position-controlled contractions. These findings support and extend previous findings of isometric torque-control conditions to position-controlled contractions that represent different tasks of daily living.
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Affiliation(s)
- Rhiannon Marion
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
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Jeon S, Miller WM, Ye X. A Comparison of Motor Unit Control Strategies between Two Different Isometric Tasks. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17082799. [PMID: 32325707 PMCID: PMC7215511 DOI: 10.3390/ijerph17082799] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/12/2020] [Accepted: 04/15/2020] [Indexed: 11/17/2022]
Abstract
Background: This study examined the motor unit (MU) control strategies for non-fatiguing isometric elbow flexion tasks at 40% and 70% maximal voluntary isometric contraction. Methods: Nineteen healthy individuals performed two submaximal tasks with similar torque levels: contracting against an immovable object (force task), and maintaining the elbow joint angle against an external load (position task). Surface electromyographic (EMG) signals were collected from the agonist and antagonist muscles. The signals from the agonist were decomposed into individual action potential trains. The linear regression analysis was used to examine the MU recruitment threshold (RT) versus mean firing rates (MFR), and RT versus derecruitment threshold (DT) relationships. Results: Both agonist and antagonist muscles’ EMG amplitudes did not differ between two tasks. The linear slopes of the MU RT versus MFR and RT versus DT relationships during the position task were more negative (p = 0.010) and more positive (p = 0.023), respectively, when compared to the force task. Conclusions: To produce a similar force output, the position task may rely less on the recruitment of relatively high-threshold MUs. Additionally, as the force output decreases, MUs tend to derecruit at a higher force level during the position task.
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Affiliation(s)
| | | | - Xin Ye
- Correspondence: ; Tel.: +1-662-915-1630
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7
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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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8
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Dideriksen JL, Feeney DF, Almuklass AM, Enoka RM. Control of force during rapid visuomotor force-matching tasks can be described by discrete time PID control algorithms. Exp Brain Res 2017; 235:2561-2573. [PMID: 28555275 DOI: 10.1007/s00221-017-4995-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 05/23/2017] [Indexed: 11/30/2022]
Abstract
Force trajectories during isometric force-matching tasks involving isometric contractions vary substantially across individuals. In this study, we investigated if this variability can be explained by discrete time proportional, integral, derivative (PID) control algorithms with varying model parameters. To this end, we analyzed the pinch force trajectories of 24 subjects performing two rapid force-matching tasks with visual feedback. Both tasks involved isometric contractions to a target force of 10% maximal voluntary contraction. One task involved a single action (pinch) and the other required a double action (concurrent pinch and wrist extension). 50,000 force trajectories were simulated with a computational neuromuscular model whose input was determined by a PID controller with different PID gains and frequencies at which the controller adjusted muscle commands. The goal was to find the best match between each experimental force trajectory and all simulated trajectories. It was possible to identify one realization of the PID controller that matched the experimental force produced during each task for most subjects (average index of similarity: 0.87 ± 0.12; 1 = perfect similarity). The similarities for both tasks were significantly greater than that would be expected by chance (single action: p = 0.01; double action: p = 0.04). Furthermore, the identified control frequencies in the simulated PID controller with the greatest similarities decreased as task difficulty increased (single action: 4.0 ± 1.8 Hz; double action: 3.1 ± 1.3 Hz). Overall, the results indicate that discrete time PID controllers are realistic models for the neural control of force in rapid force-matching tasks involving isometric contractions.
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Affiliation(s)
- Jakob Lund Dideriksen
- SMI, Department of Health Science and Technology, Aalborg University, Fredrik Bajersvej 7-D3, 9220, Aalborg Ø, Denmark.
| | - Daniel F Feeney
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
| | - Awad M Almuklass
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA.,College of Medicine, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
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9
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Russ DW, Ross AJ, Clark BC, Thomas JS. The Effects of Task Type on Time to Task Failure During Fatigue: A Modified Sørensen Test. J Mot Behav 2017; 50:96-103. [DOI: 10.1080/00222895.2017.1286628] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- David W. Russ
- School of Rehabilitation and Communication Sciences, Division of Physical Therapy, Ohio University, Athens
- Ohio Musculoskeletal & Neurological Institute, Ohio University, Athens
| | - Andrew J. Ross
- School of Rehabilitation and Communication Sciences, Division of Physical Therapy, Ohio University, Athens
| | - Brian C. Clark
- Ohio Musculoskeletal & Neurological Institute, Ohio University, Athens
- Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, Athens
| | - James S. Thomas
- School of Rehabilitation and Communication Sciences, Division of Physical Therapy, Ohio University, Athens
- Ohio Musculoskeletal & Neurological Institute, Ohio University, Athens
- Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, Athens
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10
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Abstract
This minireview focuses on selected, noninvasive imaging techniques that have been used in the study of exercise physiology. These imaging modalities can be roughly divided into two categories: tracer based and nontracer based. Tracer-based methods use radiolabeled substrates whose location and quantity can subsequently be imaged once they are incorporated into metabolic processes. Nontracer-based imaging modalities rely on specific properties of substrates to identify metabolites and determine their concentrations. Identification and quantification of metabolites is usually based on magnetic properties or on differences in light absorption. In this review, we will highlight two tracer-based imaging modalities, positron emission tomography and single-photon-emission computed tomography, as well as two nontracer-based methods, magnetic resonance spectroscopy and near-infrared spectroscopy. Some of the recent findings that each technique has provided on cerebral and skeletal muscle metabolism during exercise, as well as the strengths and limitations of each technique, will be discussed.
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Affiliation(s)
- Thorsten Rudroff
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
| | - Nathaniel B Ketelhut
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
| | - John H Kindred
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
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11
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Justice JN, Johnson LC, DeVan AE, Cruickshank-Quinn C, Reisdorph N, Bassett CJ, Evans TD, Brooks FA, Bryan NS, Chonchol MB, Giordano T, McQueen MB, Seals DR. Improved motor and cognitive performance with sodium nitrite supplementation is related to small metabolite signatures: a pilot trial in middle-aged and older adults. Aging (Albany NY) 2016; 7:1004-21. [PMID: 26626856 PMCID: PMC4694069 DOI: 10.18632/aging.100842] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Advancing age is associated with reductions in nitric oxide bioavailability and changes in metabolic activity, which are implicated in declines in motor and cognitive function. In preclinical models, sodium nitrite supplementation (SN) increases plasma nitrite and improves motor function, whereas other nitric oxide-boosting agents improve cognitive function. This pilot study was designed to translate these findings to middle-aged and older (MA/O) humans to provide proof-of-concept support for larger trials. SN (10 weeks, 80 or 160 mg/day capsules, TheraVasc, Inc.) acutely and chronically increased plasma nitrite and improved performance on measures of motor and cognitive outcomes (all p<0.05 or better) in healthy MA/O adults (62 ± 7 years). Untargeted metabolomics analysis revealed that SN significantly altered 33 (160 mg/day) to 45 (80 mg/day) different metabolites, 13 of which were related to changes in functional outcomes; baseline concentrations of 99 different metabolites predicted functional improvements with SN. This pilot study provides the first evidence that SN improves aspects of motor and cognitive function in healthy MA/O adults, and that these improvements are associated with, and predicted by, the plasma metabolome. Our findings provide the necessary support for larger clinical trials on this promising pharmacological strategy for preserving physiological function with aging.
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Affiliation(s)
- Jamie N Justice
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Lawrence C Johnson
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Allison E DeVan
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Charmion Cruickshank-Quinn
- Integrated Department of Immunology, University of Colorado Anschutz Medical Campus and National Jewish Hospital, Denver, CO 80045, USA
| | - Nichole Reisdorph
- Integrated Department of Immunology, University of Colorado Anschutz Medical Campus and National Jewish Hospital, Denver, CO 80045, USA
| | - Candace J Bassett
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Trent D Evans
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Forrest A Brooks
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA
| | | | - Michel B Chonchol
- Division of Renal Diseases and Hypertension, University of Colorado Denver, Aurora, CO 80045, USA
| | | | - Matthew B McQueen
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Douglas R Seals
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA
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12
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Lauber B, Keller M, Leukel C, Gollhofer A, Taube W. Force and Position Control in Humans - The Role of Augmented Feedback. J Vis Exp 2016. [PMID: 27404742 DOI: 10.3791/53291] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
During motor behaviour, humans interact with the environment by for example manipulating objects and this is only possible because sensory feedback is constantly integrated into the central nervous system and these sensory inputs need to be weighted in order meet the task specific goals. Additional feedback presented as augmented feedback was shown to have an impact on motor control and motor learning. A number of studies investigated whether force or position feedback has an influence on motor control and neural activation. However, as in the previous studies the presentation of the force and position feedback was always identical, a recent study assessed whether not only the content but also the interpretation of the feedback has an influence on the time to fatigue of a sustained submaximal contraction and the (inhibitory) activity of the primary motor cortex using subthreshold transcranial magnetic stimulation. This paper describes one possible way to investigate the influence of the interpretation of feedback on motor behaviour by investigating the time to fatigue of submaximal sustained contractions together with the neuromuscular adaptations that can be investigated using surface EMG. Furthermore, the current protocol also describes how motor cortical (inhibitory) activity can be investigated using subthreshold TMS, a method known to act solely on the cortical level. The results show that when participants interpret the feedback as position feedback, they display a significantly shorter time to fatigue of a submaximal sustained contraction. Furthermore, subjects also displayed an increased inhibitory activity of the primary cortex when they believed to receive position feedback compared when they believed to receive force feedback. Accordingly, the results show that interpretation of feedback results in differences on a behavioural level (time to fatigue) that is also reflected in interpretation-specific differences in the amount of inhibitory M1 activity.
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Affiliation(s)
- Benedikt Lauber
- Department of Sport Science, University of Freiburg; Department of Medicine, Movement and Sport Science, University of Fribourg;
| | - Martin Keller
- Department of Medicine, Movement and Sport Science, University of Fribourg
| | - Christian Leukel
- Department of Sport Science, University of Freiburg; Bernsteincenter Freiburg
| | | | - Wolfgang Taube
- Department of Medicine, Movement and Sport Science, University of Fribourg
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13
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Poortvliet PC, Tucker KJ, Finnigan S, Scott D, Sowman P, Hodges PW. Cortical activity differs between position- and force-control knee extension tasks. Exp Brain Res 2015; 233:3447-57. [DOI: 10.1007/s00221-015-4404-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 08/03/2015] [Indexed: 11/24/2022]
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14
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Onushko T, Schmit BD, Hyngstrom A. The Effect of Antagonist Muscle Sensory Input on Force Regulation. PLoS One 2015; 10:e0133561. [PMID: 26186590 PMCID: PMC4506057 DOI: 10.1371/journal.pone.0133561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 06/27/2015] [Indexed: 11/26/2022] Open
Abstract
The purpose of this study was to understand how stretch-related sensory feedback from an antagonist muscle affects agonist muscle output at different contraction levels in healthy adults. Ten young (25.3 ± 2.4 years), healthy subjects performed constant isometric knee flexion contractions (agonist) at 6 torque levels: 5%, 10%, 15%, 20%, 30%, and 40% of their maximal voluntary contraction. For half of the trials, subjects received patellar tendon taps (antagonist sensory feedback) during the contraction. We compared error in targeted knee flexion torque and hamstring muscle activity, with and without patellar tendon tapping, across the 6 torque levels. At lower torque levels (5%, 10%, and 15%), subjects produced greater knee torque error following tendon tapping compared with the same torque levels without tendon tapping. In contrast, we did not find any difference in torque output at higher target levels (20%, 30%, and 40%) between trials with and without tendon tapping. We also observed a load-dependent increase in the magnitude of agonist muscle activity after tendon taps, with no associated load-dependent increase in agonist and antagonist co-activation, or reflex inhibition from the antagonist tapping. The findings suggest that at relatively low muscle activity there is a deficiency in the ability to correct motor output after sensory disturbances, and cortical centers (versus sub-cortical) are likely involved.
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Affiliation(s)
- Tanya Onushko
- Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, United States of America
| | - Brian D. Schmit
- Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, United States of America
| | - Allison Hyngstrom
- Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States of America
- * E-mail:
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15
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Experimental pain has a greater effect on single motor unit discharge during force-control than position-control tasks. Clin Neurophysiol 2015; 126:1378-86. [DOI: 10.1016/j.clinph.2014.10.139] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 10/04/2014] [Accepted: 10/12/2014] [Indexed: 11/22/2022]
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16
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Kindred JH, Kalliokoski KK, Bojsen-Møller J, Rudroff T. Regional differences of [(18)F]-FDG uptake within the brain during fatiguing muscle contractions. Brain Behav 2015; 5:e00319. [PMID: 25798334 PMCID: PMC4356841 DOI: 10.1002/brb3.319] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/13/2015] [Accepted: 01/16/2015] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND AND PURPOSE Many studies have shown that a position task is more difficult than a force task although both are performed at a similar net muscle force. Thus, the time to task failure is consistently shown to be briefer during the position task. The contributions of the central nervous system to these two types of fatiguing contractions are not completely understood. The purpose of this pilot study was to examine differences in regional brain activity between force and position tasks using positron emission tomography (PET) with [(18)F]-Fluorodeoxyglucose (FDG). METHODS Two participants performed both a force and position task, separated by 7 days, with the elbow flexor muscles at 15% maximal voluntary contraction force. During both tasks, each participant was injected with ≈ 256 (SD 11) MBq of FDG. Immediately after both tasks PET imaging was performed and images were analyzed to determine FDG uptake within regions of the brain. RESULTS FDG uptake was greater in the occipital and temporal cortices of the brain during the position task compared to the force task. CONCLUSIONS These findings suggest that differences in visual-spatial feedback and processing may play a role in the reduced time to failure of position tasks. Future application of these findings may lead to improved designs of rehabilitative strategies involving different types of visual feedback.
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Affiliation(s)
- John H Kindred
- Department of Health and Exercise Science, Colorado State University Fort Collins, Colorado
| | - Kari K Kalliokoski
- Turku PET Centre, University of Turku and Turku University Hospital Turku, Finland
| | - Jens Bojsen-Møller
- Department of Physical Performance, Norwegian School of Sport Sciences Oslo, Norway
| | - Thorsten Rudroff
- Department of Health and Exercise Science, Colorado State University Fort Collins, Colorado
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17
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Pereira HM, Spears VC, Schlinder-Delap B, Yoon T, Nielson KA, Hunter SK. Age and sex differences in steadiness of elbow flexor muscles with imposed cognitive demand. Eur J Appl Physiol 2015; 115:1367-79. [PMID: 25633070 DOI: 10.1007/s00421-015-3113-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 01/14/2015] [Indexed: 01/25/2023]
Abstract
PURPOSE These studies determined (1) age- and sex-related differences in steadiness of isometric contractions when high cognitive demand was imposed across a range of forces with the elbow flexor muscles (study 1) and; (2) sex differences in steadiness among older adults when low cognitive demand was imposed (study 2). METHODS 36 young adults (18-25 years; 18 women) and 30 older adults (60-82 years; 17 women) performed isometric contractions at 5, 30 and 40 % of maximum voluntary contraction (MVC). Study 1 involved a high-cognitive demand session (serial subtractions by 13 during the contraction) and a control session (no mental math). Study 2 (older adults only) involved a low-cognitive demand session (subtracting by 1s). RESULTS Older individuals exhibited greater increases in force fluctuations (coefficient of variation of force, CV) with high cognitive demand than young adults, with the largest age difference at 5 % MVC (P = 0.01). Older adults had greater agonist EMG activity with high-cognitive demand and women had greater coactivation than men (P < 0.05). In study 2, CV of force increased with low cognitive demand for the older women but not for the older men (P = 0.03). CONCLUSION Older adults had reduced steadiness and increased muscle activation when high cognitive demand was imposed while low cognitive demand induced increased force fluctuations in older women but not older men. These findings have implications for daily and work-related tasks that involve cognitive demand performed simultaneously during submaximal isometric contractions in an aging workforce.
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Affiliation(s)
- Hugo M Pereira
- Department of Physical Therapy, Marquette University, P.O. Box 1881, Milwaukee, WI, 53201, USA
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18
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Kirimoto H, Tamaki H, Suzuki M, Matsumoto T, Sugawara K, Kojima S, Onishi H. Sensorimotor modulation differs with load type during constant finger force or position. PLoS One 2014; 9:e108058. [PMID: 25233353 PMCID: PMC4169486 DOI: 10.1371/journal.pone.0108058] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/23/2014] [Indexed: 11/19/2022] Open
Abstract
During submaximal isometric contraction, there are two different load types: production of a constant force against a rigid restraint (force task), and maintenance of position against a constant load (position task). Previous studies reported that the time to task failure during a fatigue task was twice as long in the force task compared with the position task. Sensory feedback processing may contribute to these differences. The purpose of the current study was to determine the influence of load types during static muscle contraction tasks on the gating effect, i.e., attenuation of somatosensory-evoked potentials (SEPs) and the cortical silent period (cSP). Ten healthy subjects contracted their right first dorsal interosseus muscle by abducting their index finger for 90 s, to produce a constant force against a rigid restraint that was 20% of the maximum voluntary contraction (force task), or to maintain a constant position with 10° abduction of the metacarpophalangeal joint against the same load (position task). Somatosensory evoked potentials (SEPs) were recorded from C3' by stimulating either the right ulnar or median nerve at the wrist while maintaining contraction. The cortical silent period (cSP) was also elicited by transcranial magnetic stimulation. Reduction of the amplitude of the P45 component of SEPs was significantly larger during the position task than during the force task and under control rest conditions when the ulnar nerve, but not the median nerve, was stimulated. The position task had a significantly shorter cSP duration than the force task. These results suggest the need for more proprioceptive information during the position task than the force task. The shorter duration of the cSP during the position task may be attributable to larger amplitude of heteronymous short latency reflexes. Sensorimotor modulations may differ with load type during constant finger force or position tasks.
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Affiliation(s)
- Hikari Kirimoto
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Hiroyuki Tamaki
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Makoto Suzuki
- School of Allied Health Sciences, Kitasato University, Kanagawa, Japan
| | - Takuya Matsumoto
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
- Graduate School of Health and Welfare, Niigata University of Health and Welfare, Niigata, Japan
| | - Kazuhiro Sugawara
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Syo Kojima
- Graduate School of Health and Welfare, Niigata University of Health and Welfare, Niigata, Japan
- Tokyo Bay Rehabilitation Hospital, Chiba, Japan
| | - Hideaki Onishi
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
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19
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Rudroff T, Kindred JH, Benson JM, Tracy BL, Kalliokoski KK. Greater glucose uptake heterogeneity in knee muscles of old compared to young men during isometric contractions detected by [(18)F]-FDG PET/CT. Front Physiol 2014; 5:198. [PMID: 24904432 PMCID: PMC4035600 DOI: 10.3389/fphys.2014.00198] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 05/09/2014] [Indexed: 11/16/2022] Open
Abstract
We used positron emission tomography/computed tomography (PET/CT) and [18F]-FDG to test the hypothesis that glucose uptake (GU) heterogeneity in skeletal muscles as a measure of heterogeneity in muscle activity is greater in old than young men when they perform isometric contractions. Six young (26 ± 6 years) and six old (77 ± 6 years) men performed two types of submaximal isometric contractions that required either force or position control. [18F]-FDG was injected during the task and PET/CT scans were performed immediately after the task. Within-muscle heterogeneity of knee muscles was determined by calculating the coefficient of variation (CV) of GU in PET image voxels within the muscles of interest. The average GU heterogeneity (mean ± SD) for knee extensors and flexors was greater for the old (35.3 ± 3.3%) than the young (28.6 ± 2.4%) (P = 0.006). Muscle volume of the knee extensors were greater for the young compared to the old men (1016 ± 163 vs. 598 ± 70 cm3, P = 0.004). In a multiple regression model, knee extensor muscle volume was a predictor (partial r = −0.87; P = 0.001) of GU heterogeneity for old men (R2 = 0.78; P < 0.001), and MVC force predicted GU heterogeneity for young men (partial r = −0.95, P < 0.001). The findings demonstrate that GU is more spatially variable for old than young men and especially so for old men who exhibit greater muscle atrophy.
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Affiliation(s)
- Thorsten Rudroff
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University Fort Collins, CO, USA
| | - John H Kindred
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University Fort Collins, CO, USA
| | - John-Michael Benson
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University Fort Collins, CO, USA
| | - Brian L Tracy
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University Fort Collins, CO, USA
| | - Kari K Kalliokoski
- Turku PET Centre, University of Turku and Turku University Hospital Turku, Finland
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20
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Justice JN, Mani D, Pierpoint LA, Enoka RM. Fatigability of the dorsiflexors and associations among multiple domains of motor function in young and old adults. Exp Gerontol 2014; 55:92-101. [PMID: 24703888 DOI: 10.1016/j.exger.2014.03.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 02/22/2014] [Accepted: 03/24/2014] [Indexed: 10/25/2022]
Abstract
Declines in neuromuscular function, including measures of mobility, muscle strength, steadiness, and patterns of muscle activation, accompany advancing age and are often associated with reduced quality of life and mortality. Paradoxically, older adults are less fatigable than young adults in some tasks. The purpose of this study was to determine the influence of age on fatigability of the dorsiflexors and to evaluate the ecological validity of this test by comparing it to motor function subdomains known to decline with advancing age. The community-dwelling older adults (n=52, 75.2±6.0years) were more fatigable than young adults (n=26, 22.2±3.7years), as assessed by endurance time for supporting a submaximal load (20% of one-repetition maximum; 1-RM) with an isometric contraction of the dorsiflexor muscles (8.9±0.6min and 15.5±0.9min, p<0.001), including participants matched for 1-RM load and sex (Y: 13.3±4.0min, O: 8.5±6.1min, n=11 pairs, 6 women, p<0.05). When the older adults were separated into two groups (65-75 and 76-90years), however, only endurance time for the oldest group was less than that for the other two groups (p<0.01). All measures of motor function were significantly correlated (all p<0.05) with dorsiflexor endurance time for the older adults, and multiple regression analysis revealed that the variance in endurance time was most closely associated with age, steadiness, and knee flexor strength (R(2)=0.50, p<0.001). These findings indicate that dorsiflexor fatigability provides a valid biomarker of motor function in older adults.
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Affiliation(s)
- Jamie N Justice
- Department of Integrative Physiology, University of Colorado Boulder, 354 UCB CO, 80309-0354, USA.
| | - Diba Mani
- Department of Integrative Physiology, University of Colorado Boulder, 354 UCB CO, 80309-0354, USA.
| | - Lauren A Pierpoint
- Department of Integrative Physiology, University of Colorado Boulder, 354 UCB CO, 80309-0354, USA.
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado Boulder, 354 UCB CO, 80309-0354, USA.
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21
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Hunter SK. Sex differences in human fatigability: mechanisms and insight to physiological responses. Acta Physiol (Oxf) 2014; 210:768-89. [PMID: 24433272 DOI: 10.1111/apha.12234] [Citation(s) in RCA: 330] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 07/29/2013] [Accepted: 01/08/2014] [Indexed: 12/17/2022]
Abstract
Sex-related differences in physiology and anatomy are responsible for profound differences in neuromuscular performance and fatigability between men and women. Women are usually less fatigable than men for similar intensity isometric fatiguing contractions. This sex difference in fatigability, however, is task specific because different neuromuscular sites will be stressed when the requirements of the task are altered, and the stress on these sites can differ for men and women. Task variables that can alter the sex difference in fatigability include the type, intensity and speed of contraction, the muscle group assessed and the environmental conditions. Physiological mechanisms that are responsible for sex-based differences in fatigability may include activation of the motor neurone pool from cortical and subcortical regions, synaptic inputs to the motor neurone pool via activation of metabolically sensitive small afferent fibres in the muscle, muscle perfusion and skeletal muscle metabolism and fibre type properties. Non-physiological factors such as the sex bias of studying more males than females in human and animal experiments can also mask a true understanding of the magnitude and mechanisms of sex-based differences in physiology and fatigability. Despite recent developments, there is a tremendous lack of understanding of sex differences in neuromuscular function and fatigability, the prevailing mechanisms and the functional consequences. This review emphasizes the need to understand sex-based differences in fatigability to shed light on the benefits and limitations that fatigability can exert for men and women during daily tasks, exercise performance, training and rehabilitation in both health and disease.
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Affiliation(s)
- S. K. Hunter
- Exercise Science Program; Department of Physical Therapy; Marquette University; Milwaukee WI USA
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22
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Williams PS, Hoffman RL, Clark BC. Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions. PLoS One 2014; 9:e93284. [PMID: 24667484 PMCID: PMC3965562 DOI: 10.1371/journal.pone.0093284] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 03/04/2014] [Indexed: 01/19/2023] Open
Abstract
In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF) of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks). On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS), paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2-3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5 ± 7.9 min) than the position-matching task (26.9 ± 15.11 min; p<0.01); however, both tasks caused the same amount of muscle fatigue (p = 0.59). There were no task-specific differences for the total amount or rate of change in the neurophysiologic outcome variables over time (p>0.05). Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p<0.02, ES = 0.35-0.52) coupled with a similar mean increase in measures of corticospinal excitability (p<0.03, ES = 0.30-0.41). Additionally, the amount of intracortical inhibition decreased (p<0.03, ES = 0.32) and the amount of intracortical facilitation (p>0.10) and an index of upstream excitation of the motor cortex remained constant (p>0.40). Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure.
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Affiliation(s)
- Petra S. Williams
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
- Department of Physical Therapy and Athletic Training, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Richard L. Hoffman
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
| | - Brian C. Clark
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
- Department of Biomedical Sciences, Ohio University, Athens, Ohio, United States of America
- Department of Geriatric Medicine and Gerontology, Ohio University, Athens, Ohio, United States of America
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23
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Bouillard K, Jubeau M, Nordez A, Hug F. Effect of vastus lateralis fatigue on load sharing between quadriceps femoris muscles during isometric knee extensions. J Neurophysiol 2014; 111:768-76. [DOI: 10.1152/jn.00595.2013] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study aimed to investigate the effects of selective fatigue (i.e., one muscle of the quadriceps) on load sharing strategies during submaximal knee extensions. Shear wave elastography was used to measure muscle shear elastic modulus, as this is considered to be an index of individual muscle force. Sixteen participants attended two experimental sessions that each involved six 10-s knee extensions at 20% of maximal voluntary contraction (MVC) followed by a sustained submaximal isometric knee extension at 20% of MVC, until task failure (Tlim). Between the 10-s contractions and Tlim, participants were required to rest (5 min) for the control session or underwent 5 min of electromyostimulation (EMS) on vastus lateralis (EMS session). Compared with the control session, vastus lateralis shear elastic modulus values were significantly lower after EMS considering both the start of Tlim (54.6 ± 11.8 vs. 68.4 ± 19.2 kPa; P = 0.011) and the entire Tlim contraction (59.0 ± 14.0 vs. 74.4 ± 20.3 kPa; P = 0.019). However, no significant differences were observed for the other recorded muscles (vastus medialis and rectus femoris; both P = 1), i.e., different patterns of changes were found between participants. In conclusion, this study demonstrates that prefatiguing a single agonist muscle does not lead to a consistent redistribution of load sharing among the quadriceps muscles between individuals. These results suggest that the central nervous system does not use a common principle among individuals to control load sharing when neuromuscular fatigue occurs.
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Affiliation(s)
- Killian Bouillard
- Laboratory “Motricité, Interactions, Performance” (EA 4334), UFR STAPS, University of Nantes, Nantes, France; and
| | - Marc Jubeau
- Laboratory “Motricité, Interactions, Performance” (EA 4334), UFR STAPS, University of Nantes, Nantes, France; and
| | - Antoine Nordez
- Laboratory “Motricité, Interactions, Performance” (EA 4334), UFR STAPS, University of Nantes, Nantes, France; and
| | - François Hug
- Laboratory “Motricité, Interactions, Performance” (EA 4334), UFR STAPS, University of Nantes, Nantes, France; and
- NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia
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24
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Specific interpretation of augmented feedback changes motor performance and cortical processing. Exp Brain Res 2013; 227:31-41. [PMID: 23525572 DOI: 10.1007/s00221-013-3482-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 03/10/2013] [Indexed: 10/27/2022]
Abstract
It is well established that the presence of external feedback, also termed augmented feedback, can be used to improve performance of a motor task. The present study aimed to elucidate whether differential interpretation of the external feedback signal influences the time to task failure of a sustained submaximal contraction and modulates motor cortical activity. In Experiment 1, subjects had to maintain a submaximal contraction (30% of maximum force) performed with their thumb and index finger. Half of the tested subjects were always provided with feedback about joint position (pF-group), whereas the other half of the subjects were always provided with feedback about force (fF-group). Subjects in the pF-group were led to belief in half of their trials that they would receive feedback about the applied force, and subjects in the fF-group to receive feedback about the position. In both groups (fF and pF), the time to task failure was increased when subjects thought to receive feedback about the force. In Experiment 2, subthreshold transcranial magnetic stimulation was applied over the right motor cortex and revealed an increased motor cortical activity when subjects thought to receive feedback about the joint position. The results showed that the interpretation of feedback influences motor behavior and alters motor cortical activity. The current results support previous studies suggesting a distinct neural control of force and position.
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25
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Baudry S, Sarrazin S, Duchateau J. Effects of load magnitude on muscular activity and tissue oxygenation during repeated elbow flexions until failure. Eur J Appl Physiol 2013; 113:1895-904. [PMID: 23471683 DOI: 10.1007/s00421-013-2618-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 02/22/2013] [Indexed: 11/30/2022]
Abstract
This study investigated the changes in muscular activity and tissue oxygenation while lifting and lowering a load of 20, 40, 60 or 80 % of one repetition maximum (1RM) with elbow flexor muscles until failure. The surface electromyogram (EMG) was recorded in biceps brachii (BB), brachioradialis (BRD) and triceps brachii (TB). For BB, a tissue oxygenation index (TOI) and a normalized total hemoglobin index (nTHI) were recorded by near-infrared spectroscopy. The number of repetitions decreased with the increase in load (P < 0.001), and the four loading conditions induced a decrease in MVC force immediately after failure (P < 0.001). The average of rectified EMG amplitude (aEMG) of elbow flexors increased for all loads during muscle shortening (SHO) and lengthening (LEN) phases of the movement (P < 0.05), except for the 80 % load during LEN phase. At failure, the aEMG was greater during the SHO than the LEN phase (P < 0.05), except for the 20 % load. TOI decreased for all loads and phases (P < 0.05) but less (P < 0.01) for the 20 % than 60 and 80 % loads (P < 0.01), and for LEN compared with SHO phase. At failure, TOI was negatively associated with aEMG during the SHO (r(2) = 0.99) and LEN (r(2) = 0.82) phases, while TOI and aEMG were positively associated with load magnitude (r(2) > 0.90) in both movement phases. This study emphasizes the influence of load magnitude and movement phase (SHO and LEN) on neuromuscular and oxydative adjustments during movements that involve lifting and lowering a load until failure.
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Affiliation(s)
- Stéphane Baudry
- Laboratory of Applied Biology, Faculty for Motor Sciences, Neuroscience Institute, Université Libre de Bruxelles, 808, Route de Lennik, CP 640, 1070 Brussels, Belgium.
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26
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Cavuoto LA, Nussbaum MA. Obesity-related differences in muscular capacity during sustained isometric exertions. APPLIED ERGONOMICS 2013; 44:254-260. [PMID: 22858008 DOI: 10.1016/j.apergo.2012.07.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 06/07/2012] [Accepted: 07/16/2012] [Indexed: 06/01/2023]
Abstract
Over one-third of the world adult population is overweight or obese, and the prevalence continues to increase. Obesity is a risk factor for injury, and the growing prevalence may be associated with increases in the future incidence and cost of injuries. In this study, we examined obesity-related differences in muscular capacity during sustained isometric exertions involving hand grip, shoulder flexion, and trunk extension. Thirty-six young individuals who were obese or not obese (aged 18-29) completed these exertions at fixed levels of absolute loads involving low-moderate levels of effort. Individuals who were obese had an overall ∼20% higher absolute strength, but ∼20% lower relative strength. These differences were most evident in the hand grip and shoulder exertions. Parameters of fitted exponential relationships between endurance time and task demands (as a percentage of strength) were similar in both groups. Perceptual and performance responses were also consistent between groups. Accordingly, we conclude that obesity may not substantially influence muscular capacity for these tasks.
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Affiliation(s)
- Lora A Cavuoto
- Department of Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
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27
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Rudroff T, Kalliokoski KK, Block DE, Gould JR, Klingensmith WC, Enoka RM. PET/CT imaging of age- and task-associated differences in muscle activity during fatiguing contractions. J Appl Physiol (1985) 2013; 114:1211-9. [PMID: 23412899 DOI: 10.1152/japplphysiol.01439.2012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The study compared positron emission tomography/computed tomography (PET/CT) of [(18)F]-2-fluoro-2-deoxy-D-glucose ([(18)F]-FDG) uptake by skeletal muscles and the amount of muscle activity as indicated by surface electromyographic (EMG) recordings when young and old men performed fatiguing isometric contractions that required either force or position control. EMG signals were recorded from thigh muscles of six young men (26 ± 6 yr) and six old men (77 ± 6 yr) during fatiguing contractions with the knee extensors. PET/CT scans were performed immediately after task failure. Glucose uptake in 24 leg muscles, quantified as standardized uptake values, was greater for the old men after the force task and differed across tasks for the young men (force, 0.64 ± 0.3 g/ml; position, 0.73 ± 0.3 g/ml), but not the old men (force, 0.84 ± 0.3 g/ml; position, 0.79 ± 0.26 g/ml) (age × task interaction; P < 0.001). In contrast, the rate of increase in EMG amplitude for the agonist muscles was greater for the young men during the two contractions and there was no difference for either group of subjects in the rate of increase in EMG amplitude across the two tasks. The imaging estimates of glucose uptake indicated age- and task-dependent differences in the spatial distribution of [(18)F]-FDG uptake by skeletal muscles during fatiguing contractions. The findings demonstrate that PET/CT imaging of [(18)F]-FDG uptake, but not surface EMG recordings, detected the modulation of muscle activity across the fatiguing tasks by the young men but not the old men.
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Affiliation(s)
- Thorsten Rudroff
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80523-1582, USA.
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28
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Poortvliet PC, Tucker KJ, Hodges PW. Changes in constraint of proximal segments effects time to task failure and activity of proximal muscles in knee position-control tasks. Clin Neurophysiol 2012; 124:732-9. [PMID: 23102994 DOI: 10.1016/j.clinph.2012.09.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 09/24/2012] [Accepted: 09/30/2012] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Maintenance of a limb position against external load (position-control) fails earlier (time to task failure: TTF) than maintenance of identical force against rigid restraint (force-control). Although possibly explained by physiological differences between contractions, we investigated whether less constraint of movements in other planes and proximal segments (commonly less in position-control tasks) shortens TTF. METHODS Seventeen adults (32±7 years) contracted knee extensor muscles to task failure in a position-control task, with and without constraint of motion in other planes and proximal segments, and a force-control task with constraints. Electromyography of knee extensors, their antagonist and hip muscles was recorded with force/position. RESULTS TTF was shorter for position-control without (161±55 s) than with constraint (184±51 s). Despite identical constraint, TTF was shorter in position- than force-control (216±56 s). Muscle activity and position variability at failure was greater without constraint. CONCLUSION Constraint of motion of proximal segments and other planes increases position-control TTF with less muscle activity and variability. As TTF differed between force- and position-control, despite equivalent constraint, other factors contribute to shorter position-control TTF. SIGNIFICANCE Results clarify that differences in the TTF between position- and force-control tasks are partly explained by unmatched restriction of motion in other planes and proximal segments.
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Affiliation(s)
- Peter C Poortvliet
- The University of Queensland, Centre for Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, Brisbane, Australia
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29
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Lauber B, Leukel C, Gollhofer A, Taube W. Time to task failure and motor cortical activity depend on the type of feedback in visuomotor tasks. PLoS One 2012; 7:e32433. [PMID: 22427836 PMCID: PMC3302870 DOI: 10.1371/journal.pone.0032433] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 01/29/2012] [Indexed: 11/29/2022] Open
Abstract
The present study aimed to elucidate whether the type of feedback influences the performance and the motor cortical activity when executing identical visuomotor tasks. For this purpose, time to task failure was measured during position- and force-controlled muscular contractions. Subjects received either visual feedback about the force produced by pressing a force transducer or about the actual position between thumb and index finger. Participants were instructed to either match the force level of 30% MVC or the finger position corresponding to the thumb and index finger angle at this contraction intensity. Subjects demonstrated a shorter time to task failure when they were provided with feedback about their joint position (11.5±6.2 min) instead of force feedback (19.2±12.8 min; P = 0.01). To test differences in motor cortical activity between position- and force-controlled contractions, subthreshold transcranial magnetic stimulation (subTMS) was applied while executing submaximal (20% MVC) contractions. SubTMS resulted in a suppression of the first dorsal interosseus muscle (FDI) EMG in both tasks. However, the mean suppression for the position-controlled task was significantly greater (18.6±9.4% vs. 13.3±7.5%; P = 0.025) and lasted longer (13.9±7.5 ms vs. 9.3±4.3 ms; P = 0.024) compared to the force-controlled task. The FDI background EMG obtained without stimulation was comparable in all conditions. The present results demonstrate that the presentation of different feedback modalities influences the time to task failure as well as the cortical activity. As only the feedback was altered but not the mechanics of the task, the present results add to the body of evidence that suggests that the central nervous system processes force and position information in different ways.
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Affiliation(s)
- Benedikt Lauber
- Department of Sport Science, University of Freiburg, Freiburg, Germany.
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Dideriksen JL, Enoka RM, Farina D. Neuromuscular adjustments that constrain submaximal EMG amplitude at task failure of sustained isometric contractions. J Appl Physiol (1985) 2011; 111:485-94. [PMID: 21596915 DOI: 10.1152/japplphysiol.00186.2011] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The amplitude of the surface EMG does not reach the level achieved during a maximal voluntary contraction force at the end of a sustained, submaximal contraction, despite near-maximal levels of voluntary effort. The depression of EMG amplitude may be explained by several neural and muscular adjustments during fatiguing contractions, including decreased net neural drive to the muscle, changes in the shape of the motor unit action potentials, and EMG amplitude cancellation. The changes in these parameters for the entire motor unit pool, however, cannot be measured experimentally. The present study used a computational model to simulate the adjustments during sustained isometric contractions and thereby determine the relative importance of these factors in explaining the submaximal levels of EMG amplitude at task failure. The simulation results indicated that the amount of amplitude cancellation in the simulated EMG (∼ 40%) exhibited a negligible change during the fatiguing contractions. Instead, the main determinant of the submaximal EMG amplitude at task failure was a decrease in muscle activation (number of muscle fiber action potentials), due to a reduction in the net synaptic input to motor neurons, with a lesser contribution from changes in the shape of the motor unit action potentials. Despite the association between the submaximal EMG amplitude and reduced muscle activation, the deficit in EMG amplitude at task failure was not consistently associated with the decrease in neural drive (number of motor unit action potentials) to the muscle. This indicates that the EMG amplitude cannot be used as an index of neural drive.
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Affiliation(s)
- Jakob L Dideriksen
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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31
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Thomas JS, Ross AJ, Russ DW, Clark BC. Time to task failure of trunk extensor muscles differs with load type. J Mot Behav 2011; 43:27-9. [PMID: 21186461 DOI: 10.1080/00222895.2010.530305] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Time to task failure of trunk extensor muscles during seated submaximal isometric exertions was assessed in 18 healthy participants using 2 different load types. One required supporting an inertial load (position-matching task) whereas the 2nd required maintaining an equivalent torque against a rigid restraint (force-matching task). Time to task failure was significantly longer for position-matching tasks compared to the force-matching tasks. This finding is opposite to that reported for the appendicular muscles. A subset of 4 individuals completed a 2nd experiment to test the time to task failure of the elbow flexors in the position- and force-matching tasks. Time to task failure of the elbow flexors was significantly longer for the force-matching tasks compared to position matching. Thus, the same population shows that the effects of load type on time to task failure are opposite for the appendicular and axial muscles. This could be an important issue in understanding the mechanisms of task failure, and the endurance capacity of the trunk extensor muscles.
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Affiliation(s)
- James S Thomas
- School of Rehabilitation and Communication Sciences, Division of Physical Therapy, Ohio University, Athens 45701, USA.
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32
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Enoka RM, Baudry S, Rudroff T, Farina D, Klass M, Duchateau J. Unraveling the neurophysiology of muscle fatigue. J Electromyogr Kinesiol 2010; 21:208-19. [PMID: 21071242 DOI: 10.1016/j.jelekin.2010.10.006] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 10/13/2010] [Indexed: 11/16/2022] Open
Abstract
Despite 100years of research since the seminal work of Angelo Mosso (1846-1910), our understanding of the interactions between the nervous system and muscle during the performance of fatiguing contractions remains rather rudimentary. Although the nervous system simply needs to provide an activation signal that will elicit the net muscle torque required for a prescribed action, changes in the number and diversity of synaptic inputs that must be integrated by the spinal motor neurons to accommodate the changes in the force-producing capabilities of the muscle fibers complicate the process of generating the requisite activation signal. This brief review examines two ways in which the activation signal can be compromised during sustained contractions and thereby contribute to the rate at which the muscles fatigue. These examples provide insight on the types of adjustments that occur in the nervous system during fatiguing contractions, but emphasize that much remains to be learned about the physiological processes that contribute to the phenomenon known as muscle fatigue.
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Affiliation(s)
- Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA.
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