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Sahinis C, Amiridis IG, Varvariotis N, Lykidis A, Kannas TM, Negro F, Enoka RM. Foot-dominance does not influence force variability during ankle dorsiflexion and foot adduction. J Sports Sci 2024:1-11. [PMID: 39023311 DOI: 10.1080/02640414.2024.2379699] [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: 01/11/2024] [Accepted: 07/05/2024] [Indexed: 07/20/2024]
Abstract
The aim of our study was to compare the force steadiness and the discharge characteristics of motor units in the tibialis anterior (TA) during ankle dorsiflexion and foot adduction produced by submaximal isometric contractions with the dominant and non-dominant foot. Fifteen young men performed maximal and submaximal contractions at five target forces with both legs, and motor unit activity in TA was recorded using high-density electromyography. Maximal force and the fluctuations in force during submaximal contractions were similar between the two legs (p > 0.05). Motor unit activity was characterized by measures of mean discharge rate (MDR), coefficient of variation for interspike interval (CoV for ISI), and standard deviation of the filtered cumulative spike train (SD of fCST). There were no statistically significant differences in motor unit activity between legs during ankle dorsiflexion. In contrast, the MDR and the CoV for ISI but not the SD of fCST, were greater for the non-dominant foot compared with the dominant foot during foot adduction. Nonetheless, these differences in motor unit activity were not sufficient to influence the force fluctuations during the submaximal contractions. These results indicate that control of the force produced by TA during the two actions was not influenced by limb dominance.
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Affiliation(s)
- Chrysostomos Sahinis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Ioannis G Amiridis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Nikolaos Varvariotis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Anastasios Lykidis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Theodoros M Kannas
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
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Guo Y, Jones EJ, Smart TF, Altheyab A, Gamage N, Stashuk DW, Piasecki J, Phillips BE, Atherton PJ, Piasecki M. Sex disparities of human neuromuscular decline in older humans. J Physiol 2024. [PMID: 38857412 DOI: 10.1113/jp285653] [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: 09/08/2023] [Accepted: 05/07/2024] [Indexed: 06/12/2024] Open
Abstract
Females typically live longer than males but, paradoxically, spend a greater number of later years in poorer health. The neuromuscular system is a critical component of the progression to frailty, and motor unit (MU) characteristics differ by sex in healthy young individuals and may adapt to ageing in a sex-specific manner due to divergent hormonal profiles. The purpose of this study was to investigate sex differences in vastus lateralis (VL) MU structure and function in early to late elderly humans. Intramuscular electromyography signals from 50 healthy older adults (M/F: 26/24) were collected from VL during standardized submaximal contractions and decomposed to quantify MU characteristics. Muscle size and neuromuscular performance were also measured. Females had higher MU firing rate (FR) than males (P = 0.025), with no difference in MU structure or neuromuscular junction transmission (NMJ) instability. All MU characteristics increased from low- to mid-level contractions (P < 0.05) without sex × level interactions. Females had smaller cross-sectional area of VL, lower strength and poorer force steadiness (P < 0.05). From early to late elderly, both sexes showed decreased neuromuscular function (P < 0.05) without sex-specific patterns. Higher VL MUFRs at normalized contraction levels previously observed in young are also apparent in old individuals, with no sex-based difference of estimates of MU structure or NMJ transmission instability. From early to late elderly, the deterioration of neuromuscular function and MU characteristics did not differ between sexes, yet function was consistently greater in males. These parallel trajectories underscore the lower initial level for older females and may offer insights into identifying critical intervention periods. KEY POINTS: Females generally exhibit an extended lifespan when compared to males, yet this is accompanied by a poorer healthspan and higher rates of frailty. In healthy young people, motor unit firing rate (MUFR) at normalized contraction intensities is widely reported to be higher in females than in age-matched males. Here we show in 50 people that older females have higher MUFR than older males with little difference in other MU parameters. The trajectory of decline from early to late elderly does not differ between sexes, yet function is consistently lower in females. These findings highlight distinguishable sex disparities in some MU characteristics and neuromuscular function, and suggest early interventions are needed for females to prevent functional deterioration to reduce the ageing health-sex paradox.
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Affiliation(s)
- Yuxiao Guo
- Institute of Sports Medicine and Health, Chengdu Sport University, Chengdu, China
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
| | - Eleanor J Jones
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
| | - Thomas F Smart
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
| | - Abdulmajeed Altheyab
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
- College of Applied Medical Sciences, King Saud bin Abdulaziz University for Health Science, Riyadh, Saudi Arabia
| | - Nishadi Gamage
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
- Neurophysiology of Human Movement Group, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia
| | - Daniel W Stashuk
- Department of Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Jessica Piasecki
- Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement Research Centre, Nottingham Trent University, Nottingham, UK
| | - Bethan E Phillips
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
| | - Philip J Atherton
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
| | - Mathew Piasecki
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
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Guo Y, Jones EJ, Škarabot J, Inns TB, Phillips BE, Atherton PJ, Piasecki M. Common synaptic inputs and persistent inward currents of vastus lateralis motor units are reduced in older male adults. GeroScience 2024; 46:3249-3261. [PMID: 38238546 PMCID: PMC11009172 DOI: 10.1007/s11357-024-01063-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 01/02/2024] [Indexed: 04/13/2024] Open
Abstract
Although muscle atrophy may partially account for age-related strength decline, it is further influenced by alterations of neural input to muscle. Persistent inward currents (PIC) and the level of common synaptic inputs to motoneurons influence neuromuscular function. However, these have not yet been described in the aged human quadriceps. High-density surface electromyography (HDsEMG) signals were collected from the vastus lateralis of 15 young (mean ± SD, 23 ± 5 y) and 15 older (67 ± 9 y) men during submaximal sustained and 20-s ramped contractions. HDsEMG signals were decomposed to identify individual motor unit discharges, from which PIC amplitude and intramuscular coherence were estimated. Older participants produced significantly lower knee extensor torque (p < 0.001) and poorer force tracking ability (p < 0.001) than young. Older participants also had lower PIC amplitude (p = 0.001) and coherence estimates in the alpha frequency band (p < 0.001) during ramp contractions when compared to young. Persistent inward currents and common synaptic inputs are lower in the vastus lateralis of older males when compared to young. These data highlight altered neural input to the clinically and functionally important quadriceps, further underpinning age-related loss of function which may occur independently of the loss of muscle mass.
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Affiliation(s)
- Yuxiao Guo
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research &, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Royal Derby Hospital Centre (Room 3011), Derby, DE22 3DT, UK
| | - Eleanor J Jones
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research &, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Royal Derby Hospital Centre (Room 3011), Derby, DE22 3DT, UK
| | - Jakob Škarabot
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Thomas B Inns
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research &, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Royal Derby Hospital Centre (Room 3011), Derby, DE22 3DT, UK
| | - Bethan E Phillips
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research &, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Royal Derby Hospital Centre (Room 3011), Derby, DE22 3DT, UK
| | - Philip J Atherton
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research &, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Royal Derby Hospital Centre (Room 3011), Derby, DE22 3DT, UK
| | - Mathew Piasecki
- Centre of Metabolism, Ageing & Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research &, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Royal Derby Hospital Centre (Room 3011), Derby, DE22 3DT, UK.
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Amiridis IG, Kannas T, Sahinis C, Negro F, Trypidakis G, Kellis E, Enoka RM. More Variability in Tibialis Anterior Function during the Adduction of the Foot than Dorsiflexion of the Ankle. Med Sci Sports Exerc 2024; 56:851-859. [PMID: 38190382 DOI: 10.1249/mss.0000000000003377] [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: 01/10/2024]
Abstract
INTRODUCTION The aim of the study was to compare maximal force, force steadiness, and the discharge characteristics of motor units in the tibialis anterior (TA) muscle during submaximal isometric contractions for ankle dorsiflexion and adduction of the foot. METHODS Nineteen active young adults performed maximal and submaximal isometric dorsiflexion and adduction contractions at five target forces (5%, 10%, 20%, 40%, and 60% maximal voluntary contraction [MVC]). The activity of motor units in TA was recorded by high-density EMG. RESULTS The maximal force was similar between dorsiflexion and adduction, despite EMG amplitude for TA being greater ( P < 0.05) during dorsiflexion than adduction. Τhe coefficient of variation (CV) for force (force steadiness) during dorsiflexion was always less ( P < 0.05) than during adduction, except of 5% MVC force. No differences were observed for mean discharge rate; however, the regression between the changes in discharge rate relative to the change of force was significant for dorsiflexion ( R2 = 0.25, P < 0.05) but not for adduction. Discharge variability, however, was usually less during dorsiflexion. The CV for interspike interval was less ( P < 0.05) at 10%, 20%, and 40% MVC but greater at 60% MVC during dorsiflexion than adduction. Similarly, the SD values of the filtered cumulative spike train of the motor units in TA were less ( P < 0.05) at 5%, 10%, 20%, and 40% MVC during dorsiflexion than adduction. CONCLUSIONS Although the mean discharge rate of motor units in TA was similar during foot adduction and ankle dorsiflexion, discharge variability was less during dorsiflexion resulting in less accurate performance of the steady adduction contractions. The neural drive to bifunctional muscles differs during their accessory function, which must be considered for training and rehabilitation interventions.
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Affiliation(s)
- Ioannis G Amiridis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Theodoros Kannas
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Chrysostomos Sahinis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, ITALY
| | - Georgios Trypidakis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Eleftherios Kellis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO
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Piasecki J, Škarabot J, Spillane P, Piasecki M, Ansdell P. Sex Differences in Neuromuscular Aging: The Role of Sex Hormones. Exerc Sport Sci Rev 2024; 52:54-62. [PMID: 38329342 DOI: 10.1249/jes.0000000000000335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Males and females experience different trajectories of neuromuscular function across the lifespan, with females demonstrating accelerated deconditioning in later life. We hypothesize that the menopause is a critical period in the female lifespan, during which the dramatic reduction in sex hormone concentrations negatively impacts synaptic input to the motoneuron pool, as well as motor unit discharge properties.
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Affiliation(s)
- Jessica Piasecki
- Sport, Health and Performance Enhancement Research Centre, Nottingham Trent University, Nottingham, UK
| | - Jakob Škarabot
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Padraig Spillane
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Mathew Piasecki
- Centre of Metabolism, Ageing and Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK
| | - Paul Ansdell
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
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Petrović I, Amiridis IG, Holobar A, Trypidakis G, Sahinis C, Kannas T, Kellis E, Enoka RM. Alternating or Bilateral Exercise Training does not Influence Force Control during Single-Leg Submaximal Contractions with the Dorsiflexors. J Sports Sci Med 2023; 22:245-253. [PMID: 37293414 PMCID: PMC10244987 DOI: 10.52082/jssm.2023.245] [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: 02/07/2023] [Accepted: 04/26/2023] [Indexed: 06/10/2023]
Abstract
The aim of the study was to assess the influence of habitual training history on force steadiness and the discharge characteristics of motor units in tibialis anterior during submaximal isometric contractions. Fifteen athletes whose training emphasized alternating actions (11 runners and 4 cyclists) and fifteen athletes who relied on bilateral actions with leg muscles (7 volleyball players, 8 weight-lifters) performed 2 maximal voluntary contractions (MVC) with the dorsiflexors, and 3 steady contractions at 8 target forces (2.5%, 5%, 10%, 20%, 30%, 40%, 50% and 60% MVC). The discharge characteristics of motor units in tibialis anterior were recorded using high-density electromyography grids. The MVC force and the absolute (standard deviation) and normalized (coefficient of variation) amplitudes of the force fluctuations at all target forces were similar between groups. The coefficient of variation for force decreased progressively from 2.5% to 20% MVC force, then it plateaued until 60% MVC force. Mean discharge rate of the motor units in tibialis anterior was similar at all target forces between groups. The variability in discharge times (coefficient of variation for interspike interval) and the variability in neural drive (coefficient of variation of filtered cumulative spike train) was also similar for the two groups. These results indicate that athletes who have trained with either alternating or bilateral actions with leg muscles has similar effects on maximal force, force control, and variability in the independent and common synaptic input during a single-limb isometric task with the dorsiflexors.
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Affiliation(s)
- Ivana Petrović
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
- Faculty of Sport and Physical Education, University of Niš, Serbia
| | - Ioannis G Amiridis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Slovenia
| | - Georgios Trypidakis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Chrysostomos Sahinis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Theodoros Kannas
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Eleftherios Kellis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
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Lee JH, Kang N. Altered Bimanual Kinetic and Kinematic Motor Control Capabilities in Older Women. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:2153. [PMID: 36767520 PMCID: PMC9915092 DOI: 10.3390/ijerph20032153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 01/23/2023] [Accepted: 01/24/2023] [Indexed: 06/18/2023]
Abstract
Older women may experience critical neuromuscular impairments interfering with controlling successful bimanual motor actions. Our study aimed to investigate altered bimanual motor performances in older women compared with younger women by focusing on kinetic and kinematic motor properties. Twenty-two older women and 22 younger women performed bimanual kinetic and kinematic motor tasks. To estimate bimanual kinetic functions, we calculated bimanual maximal voluntary contractions (i.e., MVC) and force control capabilities (i.e., mean force, accuracy, variability, and regularity of the total force produced by two hands) during bimanual hand-grip submaximal force control tasks. For bimanual kinematic performances, we assessed the scores of the Purdue Pegboard Test (i.e., PPT) in both hands and assembly tasks, respectively. For the bimanual MVC and PPT, we conducted an independent t-test between two groups. The bimanual force control capabilities were analyzed using two-way mixed ANOVAs (Group × Force Level; 2 × 2). Our findings revealed that the older women showed less bimanual MVC (p = 0.046) and submaximal force outputs (p = 0.036) and greater changes in bimanual force control capabilities as indicated by a greater force variability (p = 0.017) and regularity (p = 0.014). Further, the older women revealed lower scores of PPT in both the hands condition (p < 0.001) and assembly task condition (p < 0.001). The additional correlation analyses for the older women showed that lower levels of skeletal muscle mass were related to less bimanual MVC (r = 0.591; p = 0.004). Furthermore, a higher age was related to lower scores in the bimanual PPT assembly task (r = -0.427; p = 0.048). These findings suggested that older women experience greater changes in bimanual motor functions compared with younger women.
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Affiliation(s)
- Joon Ho Lee
- Department of Human Movement Science, Incheon National University, Incheon 22012, Republic of Korea
- Neuromechanical Rehabilitation Research Laboratory, Incheon National University, Incheon 22012, Republic of Korea
| | - Nyeonju Kang
- Department of Human Movement Science, Incheon National University, Incheon 22012, Republic of Korea
- Neuromechanical Rehabilitation Research Laboratory, Incheon National University, Incheon 22012, Republic of Korea
- Division of Sport Science, Sport Science Institute, Incheon National University, Incheon 22012, Republic of Korea
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Lin YT, Chen YC, Chang GC, Hwang IS. Failure to improve task performance after visuomotor training with error reduction feedback for young adults. Front Physiol 2023; 14:1066325. [PMID: 36969593 PMCID: PMC10030953 DOI: 10.3389/fphys.2023.1066325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 02/22/2023] [Indexed: 03/29/2023] Open
Abstract
Visual feedback that reinforces accurate movements may motivate skill acquisition by promoting self-confidence. This study investigated neuromuscular adaptations to visuomotor training with visual feedback with virtual error reduction. Twenty-eight young adults (24.6 ± 1.6 years) were assigned to error reduction (ER) (n = 14) and control (n = 14) groups to train on a bi-rhythmic force task. The ER group received visual feedback and the displayed errors were 50% of the real errors in size. The control group was trained with visual feedback with no reduction in errors. Training-related differences in task accuracy, force behaviors, and motor unit discharge were contrasted between the two groups. The tracking error of the control group progressively declined, whereas the tracking error of the ER group was not evidently reduced in the practice sessions. In the post-test, only the control group exhibited significant task improvements with smaller error size (p = .015) and force enhancement at the target frequencies (p = .001). The motor unit discharge of the control group was training-modulated, as indicated by a reduction of the mean inter-spike interval (p = .018) and smaller low-frequency discharge fluctuations (p = .017) with enhanced firing at the target frequencies of the force task (p = .002). In contrast, the ER group showed no training-related modulation of motor unit behaviors. In conclusion, for young adults, ER feedback does not induce neuromuscular adaptations to the trained visuomotor task, which is conceptually attributable to intrinsic error dead-zones.
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Affiliation(s)
- Yen-Ting Lin
- Department of Ball Sport, National Taiwan University of Sport, Taichung City, Taiwan
| | - Yi-Ching Chen
- Department of Physical Therapy, College of Medical Science and Technology, Chung Shan Medical University, Taichung City, Taiwan
- Physical Therapy Room, Chung Shan Medical University Hospital, Taichung City, Taiwan
| | - Gwo-Ching Chang
- Department of Information Engineering, I-Shou University, Kaohsiung City, Taiwan
| | - Ing-Shiou Hwang
- Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
- Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
- *Correspondence: Ing-Shiou Hwang,
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Yamaguchi T, Xu J, Sasaki K. Age and sex differences in force steadiness and intermuscular coherence of lower leg muscles during isometric plantar flexion. Exp Brain Res 2023; 241:277-288. [PMID: 36484793 DOI: 10.1007/s00221-022-06517-1] [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: 06/15/2022] [Accepted: 11/24/2022] [Indexed: 12/13/2022]
Abstract
Age- and sex-related alterations in the control of multiple muscles during contractions are not well understood. The purpose of the present study was to examine the age and sex differences in force steadiness and intermuscular coherence (IMC), and thereby to clarify the functional role of IMC during plantar flexion. Twenty-six young (YNG, 23-34 years), thirty middle-aged (MID, 35-64 years) and twenty-four older adults (OLD, 65-82 years) performed submaximal isometric contractions of plantar flexion, while electromyography was recorded from the soleus (SOL), gastrocnemius lateralis/medialis (GL/GM) and tibialis anterior (TA) muscles. Coefficient of variation (CV) of torque and IMC in the alpha, beta and gamma bands was calculated. We found that OLD demonstrated significantly higher torque CV than YNG and MID, and males demonstrated significantly higher torque CV than females (both p < 0.05). The IMC in the gamma band (five out of the six pairs) was significantly higher in YNG than MID and/or OLD (p < 0.05), while the gamma band IMC between GL and SOL was significantly higher in females. However, age or sex differences were not detected in the alpha or beta band. Moreover, the gamma band IMC between SOL and TA had a weak (r = - 0.229) but significant (p < 0.05) negative correlation with torque CV. These results suggest that force steadiness differs with age and sex, and that the higher gamma band IMC may contribute to more stable force control during plantar flexion.
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Affiliation(s)
- Tatsuhiro Yamaguchi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, 153-8902, Japan.
| | - Jierui Xu
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, 153-8902, Japan
| | - Kazushige Sasaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, 153-8902, Japan
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Tempo-controlled resistance training of the hip abductors and ankle dorsiflexors with light loads does not improve postural sway in older adults. Exp Brain Res 2022; 240:3049-3060. [PMID: 36227344 DOI: 10.1007/s00221-022-06477-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 09/30/2022] [Indexed: 11/04/2022]
Abstract
The force steadiness capabilities of the hip abductors and ankle dorsiflexors can explain a significant amount of the variance in postural sway during four types of standing balance tests. Control over balance, as well as force steadiness, generally worsens with aging, although the latter can be improved with unique training interventions. The purpose of our study was to assess how tempo-controlled, light-load resistance training of the hip abductors and ankle dorsiflexors influences performance in clinical movement tests, postural sway, muscle strength, and force steadiness in older adults. Participants (n = 28, 70 ± 7 years, 8 men) completed nine training sessions for either the hip abductors or ankle dorsiflexors in the nondominant leg. Training involved lifting a load equal to 15% of the maximal force achieved during an isometric contraction. Linear mixed-effects models revealed no changes (p > 0.05) in Sit-To-Stand test, Timed Up-and-Go test, maximal voluntary contraction (MVC) torque, or postural sway from before to after either training intervention. Only the dorsiflexor group significantly improved nondominant leg dorsiflexion force steadiness, but this did not translate to any other tasks. However, absolute and relative measures of MVC torque and force steadiness of the hip abductors and ankle dorsiflexors in the dominant and nondominant legs could predict sway-area rate in each of the four standing balance conditions. The responsiveness of leg muscles to light-load steadiness training in older adults appears to depend on the type of exercises performed during the intervention.
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Pethick J, Taylor MJD, Harridge SDR. Ageing and skeletal muscle force control: current perspectives and future directions. Scand J Med Sci Sports 2022; 32:1430-1443. [PMID: 35815914 PMCID: PMC9541459 DOI: 10.1111/sms.14207] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 05/23/2022] [Accepted: 06/22/2022] [Indexed: 11/29/2022]
Abstract
During voluntary muscle contractions, force output is characterized by constant inherent fluctuations, which can be quantified either according to their magnitude or temporal structure, that is, complexity. The presence of such fluctuations when targeting a set force indicates that control of force is not perfectly accurate, which can have significant implications for task performance. Compared to young adults, older adults demonstrate a greater magnitude and lower complexity in force fluctuations, indicative of decreased steadiness, and adaptability of force output, respectively. The nature of this loss‐of‐force control depends not only on the age of the individual but also on the muscle group performing the task, the intensity and type of contraction and whether the task is performed with additional cognitive load. Importantly, this age‐associated loss‐of‐force control is correlated with decreased performance in a range of activities of daily living and is speculated to be of greater importance for functional capacity than age‐associated decreases in maximal strength. Fortunately, there is evidence that acute physical activity interventions can reverse the loss‐of‐force control in older individuals, though whether this translates to improved functional performance and whether lifelong physical activity can protect against the changes have yet to be established. A number of mechanisms, related to both motor unit properties and the behavior of motor unit populations, have been proposed for the age‐associated changes in force fluctuations. It is likely, though, that age‐associated changes in force control are related to increased common fluctuations in the discharge times of motor units.
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Affiliation(s)
- Jamie Pethick
- School of Sport, Rehabilitation and Exercise Sciences, University of Essex, Essex, UK
| | - Matthew J D Taylor
- School of Sport, Rehabilitation and Exercise Sciences, University of Essex, Essex, UK
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12
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Effect of New Zealand Blackcurrant Extract on Force Steadiness of the Quadriceps Femoris Muscle during Sustained Submaximal Isometric Contraction. J Funct Morphol Kinesiol 2022; 7:jfmk7020044. [PMID: 35736015 PMCID: PMC9225559 DOI: 10.3390/jfmk7020044] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Revised: 05/15/2022] [Accepted: 05/27/2022] [Indexed: 11/25/2022] Open
Abstract
Intake of anthocyanin-rich New Zealand blackcurrant (NZBC) can alter physiological responses that enhance exercise performance. In two studies, we examined the effects of NZBC extract on force steadiness during a sustained submaximal isometric contraction of the quadriceps femoris muscle. With repeated measures designs, male participants in study one (n = 13) and study two (n = 19) performed a 120 s submaximal (30%) isometric contraction of the quadriceps femoris muscle following a 7-day intake of NZBC extract and placebo (study one) and following 0 (control), 1-, 4- and 7-day intake of NZBC extract (study two). Participants for both studies were different. In study one, NZBC extract enhanced isometric force steadiness during the 120 s contraction (placebo: 6.58 ± 2.24%, NZBC extract: 6.05 ± 2.24%, p = 0.003), with differences in the third (60-89 s) and fourth quartile (90-120 s) of the contraction. In study two, isometric force steadiness was not changed following 1 and 4 days but was enhanced following 7-day intake of NZBC extract in comparison to control. In study two, the enhanced isometric force steadiness following 7-day intake did occur in the second (30-59 s), third (60-89 s) and fourth (90-120 s) quartiles. Daily supplementation of anthocyanin-rich NZBC extract can enhance force steadiness of the quadriceps femoris muscle during a sustained submaximal isometric contraction. Our observations may have implications for human tasks that require postural stability.
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13
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Mazzo MR, Holobar A, Enoka RM. Association between effective neural drive to the triceps surae and fluctuations in plantar-flexion torque during submaximal isometric contractions. Exp Physiol 2022; 107:489-507. [PMID: 35218261 DOI: 10.1113/ep090228] [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] [Received: 11/19/2021] [Accepted: 02/11/2022] [Indexed: 11/08/2022]
Abstract
What is the central question of this study? What is the association between the fluctuations in various estimates of effective neural drive to the triceps surae muscles and fluctuations in net plantar-flexion torque during steady submaximal contractions? What is the main finding and its importance? The fluctuations in estimates of effective neural drive to the triceps surae were moderately correlated with fluctuations in net torque at light and moderate plantar-flexion torques. Significant variability was observed in the association between neural drive and torque across participants, trials, short epochs of individual contractions, and varying motor unit number. ABSTRACT: The influence of effective neural drive on low-frequency fluctuations in torque during steady contractions can be estimated from the cumulative spike train (CST) or first principal component (FPC) of smoothed motor unit discharge rates obtained with high-density electromyography. However, the association between these estimates of total neural drive to synergist muscles and the fluctuations in net torque has not been investigated. We exposed the variability and compared the correlations between estimates of effective neural drive to the triceps surae muscles and fluctuations in plantar-flexion torque during steady contractions at 10% and 35% of maximal voluntary contraction (MVC) torque. Both neural drive estimates were moderately correlated with torque (CST, 0.55 ± 0.14, FPC, 0.58 ± 0.16) and highly correlated with one another (0.81 ± 0.1) during the 30-s steady contractions. There was substantial variability in cross-correlation values across participants, trials, and the 1-s and 5-s epochs of single contractions. Moreover, epoch duration significantly influenced cross-correlation values. Motor unit number was weakly associated with cross-correlation strength at 35% MVC (marginal R2 0.09 - 0.11; all p < 2.2×10-5 ), but not at 10% MVC (all p > 0.37). Approximately one fifth of the variance in the coefficient of variation (CV) for torque was explained by CV for the CST estimate of neural drive (p = 6.6×10-13 , R2 = 0.21). Estimates of total neural drive to the synergistic triceps surae muscles obtained by pooling motor unit discharge times were moderately correlated with fluctuations in net plantar-flexion torque. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Melissa R Mazzo
- Department of Integrative Physiology, University of Colorado, Boulder, CO
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO
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14
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Hanson MR, Swanson CW, Whittier TT, Fling BW. Inhibitory signaling as a predictor of leg force control in young and older adults. Exp Brain Res 2022; 240:1005-1016. [PMID: 35171308 DOI: 10.1007/s00221-022-06321-x] [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: 11/08/2021] [Accepted: 01/29/2022] [Indexed: 11/04/2022]
Abstract
As the populations of the United States and developed nations age, motor control performance is adversely impacted, resulting in functional impairments that can diminish quality of life. Generally, force control in the lower limb worsens with age, with older adults (OA) displaying more variable and less accurate submaximal forces. Corticospinal inhibitory signaling may influence force control, with those OA who maintain corticospinal inhibitory signaling capacity achieving steadier forces. This study aimed to assess the relationships between lower limb force control and transcranial magnetic stimulation (TMS) measures of corticospinal inhibition (i.e., cortical silent period (cSP) duration and depth). 15 OA and 14 young adults (YA) were recruited for this study. All subjects underwent a TMS protocol to elicit the cSP while maintaining 15% of their maximal force in their knee extensor muscles. OA and YA did not display differences in force control metrics or corticospinal inhibitory measures. However, in OA, maximal cSP depth (%dSP max) was associated with lower force variability. No other significant relationships existed in the YA or OA groups. Future studies will benefit from evaluating a range of target forces and target muscles to assess potential relationships between sensorimotor inhibitory capacity and control of muscle force output.
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Affiliation(s)
- Moriah R Hanson
- Department of Occupational Therapy, Colorado State University, Fort Collins, CO, USA
| | - Clayton W Swanson
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA
| | - Tyler T Whittier
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA
| | - Brett W Fling
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA. .,Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, USA.
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15
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Divjak M, Sedej G, Murks N, Gerževič M, Marusic U, Pišot R, Šimunič B, Holobar A. Inter-Person Differences in Isometric Coactivations of Triceps Surae and Tibialis Anterior Decrease in Young, but Not in Older Adults After 14 Days of Bed Rest. Front Physiol 2022; 12:809243. [PMID: 35153817 PMCID: PMC8832055 DOI: 10.3389/fphys.2021.809243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 12/24/2021] [Indexed: 11/13/2022] Open
Abstract
We examined activation patterns of the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), soleus (SO), and tibialis anterior (TA) muscles in eight older (58.4 ± 3.3 years) and seven young (23.1 ± 2.9 years) participants, before and after 14 days of horizontal bed rest. Visual feedback on the exerted muscle torque was provided to the participants. The discharge patterns of individual motor units (MUs) were studied in three repetitions of isometric plantar flexion at 30 and 60% of Maximum Voluntary Contraction (MVC), before, and 1 day after the 14-day bed rest, respectively. In the GL and GM muscles, the older participants demonstrated higher MU discharge rates than the young, regardless of the contraction level, both before and after the bed rest. In the TA and SO muscles, the differences between the older and young participants were less consistent. Detailed analysis revealed person-specific changes in the MU discharge rates after the bed rest. To quantify the coactivation patterns we calculated the correlation coefficients between the cumulative spike trains of identified MUs from each muscle, and measured the root mean square difference of the correlation coefficients between the trials of the same session (intra-session variability) and between different sessions (inter-session variability) in each participant (intra-person comparison) and across participants (inter-person comparison). In the intra-person comparison, the inter-session variability was higher than the intra-session variability, either before or after the bed rest. At 60% MVC torque, the young demonstrated higher inter-person variability of coactivation than the older participants, but this variability decreased significantly after the bed rest. In older participants, inter-person variability was consistently lower at 60% than at 30% MVC torque. In young participants, inter-person variability became lower at 60% than at 30% MVC torque only after the bed rest. Precaution is required when analyzing the MU discharge and coactivation patterns, as individual persons demonstrate individual adaptations to aging or bed rest.
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Affiliation(s)
- Matjaž Divjak
- System Software Laboratory, Institute of Computer Science, Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Gašper Sedej
- System Software Laboratory, Institute of Computer Science, Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Nina Murks
- System Software Laboratory, Institute of Computer Science, Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Mitja Gerževič
- Science and Research Centre Koper, Institute for Kinesiology Research, Koper, Slovenia
- Department of Health Sciences, Alma Mater Europaea – ECM, Maribor, Slovenia
| | - Uros Marusic
- Science and Research Centre Koper, Institute for Kinesiology Research, Koper, Slovenia
- Department of Health Sciences, Alma Mater Europaea – ECM, Maribor, Slovenia
| | - Rado Pišot
- Science and Research Centre Koper, Institute for Kinesiology Research, Koper, Slovenia
| | - Boštjan Šimunič
- Science and Research Centre Koper, Institute for Kinesiology Research, Koper, Slovenia
| | - Aleš Holobar
- System Software Laboratory, Institute of Computer Science, Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
- *Correspondence: Aleš Holobar,
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16
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Pethick J, Piasecki M. Alterations in Muscle Force Control With Aging: Is There a Modulatory Effect of Lifelong Physical Activity? Front Sports Act Living 2022; 4:817770. [PMID: 35392594 PMCID: PMC8980913 DOI: 10.3389/fspor.2022.817770] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 02/28/2022] [Indexed: 11/16/2022] Open
Abstract
Recent technological developments have enabled significant advances in our understanding of the ability to voluntarily control muscle force output. The fluctuations inherent to muscle force output can be quantified according to both their magnitude and temporal structure (or "complexity"), with such quantification facilitating comparison of force control between distinct populations. In comparison to young adults, older adults exhibit an increase in the magnitude (i.e., decreased steadiness) and a decrease in the complexity (i.e., decreased adaptability) of force fluctuations, both of which are indicative of a loss of force control. There remain, however, key gaps in knowledge that limit our interpretation of this age-related loss of force control. One such gap relates to the effect of lifelong physical activity on force control. To date, research on aging and force control has largely been conducted on inactive or moderately active older adults. However, high levels of lifelong physical activity, such as that exhibited by Masters athletes, have been shown to have protective effects on the function and morphology of the neuromuscular system. Some of these effects (e.g., on impaired inhibitory transmission in the motor cortex and on motor unit discharge rates) have the potential to attenuate the age-related loss of force control, while others (e.g., greater motor unit remodeling capacity) have the potential to worsen it. We therefore propose that, in order to progress our knowledge of the effects of aging on force control, future studies must consider the potential modulatory effect of lifelong physical activity.
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Affiliation(s)
- Jamie Pethick
- School of Sport, Rehabilitation and Exercise Sciences, University of Essex, Colchester, United Kingdom
- *Correspondence: Jamie Pethick
| | - Mathew Piasecki
- Centre of Metabolism, Ageing and Physiology (COMAP), MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, United Kingdom
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17
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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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18
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Trypidakis G, Amiridis IG, Enoka R, Tsatsaki I, Kellis E, Negro F. Ankle Angle but Not Knee Angle Influences Force Fluctuations During Plantar Flexion. Int J Sports Med 2021; 43:131-137. [PMID: 34282592 DOI: 10.1055/a-1502-6406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The purpose of the study was to evaluate the influence of changes in ankle- and knee-joint angles on force steadiness and the discharge characteristics of motor units (MU) in soleus when the plantar flexors performed steady isometric contractions. Submaximal contractions (5, 10, 20, and 40% of maximum) were performed at two ankle angles (75° and 105°) and two knee angles (120° and 180°) by 14 young adults. The coefficient of variation of force decreased as the target force increased from 5 to 20% of maximal force, then remained unaltered at 40%. Independently of knee angle, the coefficient of variation for force at the ankle angle of 75° (long length) was always less (p<0.05) than that at 105° (shorter length). Mean discharge rate, discharge variability, and variability in neural activation of soleus motor units were less (p<0.05) at the 75° angle than at 105°. It was not possible to record MUs from medial gastrocnemius at the knee angle of 120° due to its minimal activation. The changes in knee-joint angle did not influence any of the outcome measures. The findings underscore the dominant role of the soleus muscle in the control of submaximal forces produced by the plantar flexor muscles.
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Affiliation(s)
- Georgios Trypidakis
- Department of Physical Education and Sports Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Ioannis G Amiridis
- Department of Physical Education and Sports Science, Aristotle University of Thessaloniki, Serres, Greece
| | - Roger Enoka
- Department of Integrative Physiology, University of Colorado at Boulder, Boulder, United States
| | - Irini Tsatsaki
- Department of Physical Education and Sports Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Eleftherios Kellis
- Department of Physical Education and Sports Science, Aristotle University of Thessaloniki, Serres, Greece
| | - Francesco Negro
- Clinical and Experimental Sciences, Universita degli Studi di Brescia, Brescia, Italy
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19
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Tsatsaki E, Amiridis IG, Holobar A, Trypidakis G, Arabatzi F, Kellis E, Enoka RM. The length of tibialis anterior does not influence force steadiness during submaximal isometric contractions with the dorsiflexors. Eur J Sport Sci 2021; 22:539-548. [PMID: 33899692 DOI: 10.1080/17461391.2021.1922506] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The purpose of the study was to assess the influence of short, intermediate, and long muscle lengths on dorsiflexor force steadiness and the discharge characteristics of motor units in tibialis anterior during submaximal isometric contractions. Steady contractions were performed at 5 target forces (5, 10, 20, 40, and 60% maximal voluntary contraction, MVC) for 3 ankle angles (75°, 90°, and 105°). MVC force was less (p = 0.043) at the smallest joint angle compared with the other two angles. The absolute (standard deviation) and normalised amplitudes (coefficient of variation) of the force fluctuations were similar for all 3 ankle angles at each target force. The coefficient of variation for force decreased progressively from 5% to 20% MVC force and then it plateaued at 40% and 60% MVC force. At all target forces, the mean discharge rate (MDR) of the motor units at 75° was greater than at 90° (p = 0.006) and 105° (p = 0.034). Moreover, the MDR was similar for 5% and 10% MVC forces and then increased gradually until 60% MVC force (p < 0.005). The variability in discharge times (coefficient of variation for interspike interval) and variability in neural drive (coefficient of variation of filtered cumulative spike train) were similar at all ankle angles. Variability in neural drive had a greater influence on force steadiness than did the variability in discharge times. Changes in ankle-joint angle did not influence either the normalised amplitude force fluctuations during steady submaximal contractions or the underlying modulation of the discharge characteristics of motor units in tibialis anterior.
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Affiliation(s)
- Eirini Tsatsaki
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Ioannis G Amiridis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Georgios Trypidakis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Fotini Arabatzi
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Eleftherios Kellis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
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20
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Inglis JG, Gabriel DA. Sex differences in the modulation of the motor unit discharge rate leads to reduced force steadiness. Appl Physiol Nutr Metab 2021; 46:1065-1072. [PMID: 33667116 DOI: 10.1139/apnm-2020-0953] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to evaluate the relationship between the variability in the motor unit inter-pulse interval and force steadiness at submaximal and maximal force outputs between the sexes. Twenty-four male and 24 female participants were recruited to perform isometric dorsiflexion contractions at 20, 40, 60, 80, and 100% maximum voluntary contraction. Tibialis anterior myoelectric signal was recorded by an intramuscular electrode. Females had lower force steadiness (coefficient of variation of force (CoV-Force), 27.3%, p < 0.01) and a greater coefficient of variation of motor unit action potential inter-pulse interval (CoV-IPI), compared with males (9.6%, p < 0.01). There was no significant correlation between the normalized CoV-IPI and CoV-Force (r = 0.19, p > 0.01), but there was a significant repeated measures correlation between the raw scores for root-mean-square force error and the standard deviation of motor unit discharge rate (r = 0.65, p < 0.01). Females also had a greater incidence of doublet discharges on average across force levels (p < 0.01). The sex differences may result from motor unit behaviours (i.e., doublet and rapid discharges, synchronization, rate coding or recruitment), leading to lower force steadiness and greater CoV-IPI in females. Novelty: Sex differences in force steadiness may be due to neural strategies. Females have lower force steadiness compared with males. Greater incidence of doublet discharges in females may result in lesser force steadiness.
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Affiliation(s)
- J Greig Inglis
- Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.,Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - David A Gabriel
- Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.,Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
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21
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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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Age-associated increase in postural variability relate to greater low-frequency center of pressure oscillations. Gait Posture 2021; 85:103-109. [PMID: 33524665 PMCID: PMC8084964 DOI: 10.1016/j.gaitpost.2020.12.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 12/15/2020] [Accepted: 12/18/2020] [Indexed: 02/02/2023]
Abstract
BACKGROUND Postural control is impaired in older adults, as evidenced from greater variability of the center of pressure (COP) during postural tasks. Although COP variability associates with low-frequency COP oscillations (<1 Hz) in young adults, it remains unknown if the age-associated increase in COP variability relates to greater low-frequency COP oscillations. RESEARCH QUESTION Do low-frequency oscillations contribute to greater postural sway (center of pressure (COP) variability) in older adults when attempting to voluntarily maintain posture in a forward leaning position compared to young adults? METHODS Seven young (25.7 ± 4.8) and seven older (71.0 ± 7.0) adults performed a postural lean forward task and attempted to match a COP target in the anterior-posterior direction as steady as possible. We quantified the COP variability as the standard deviation (SD) of COP displacements in the anterior-posterior and medial-lateral directions and quantified the frequency modulation of COP as the power in COP displacement spectra from 0-1 Hz. RESULTS We found that older adults had significantly greater anterior-posterior SD of COP (p = 0.027) and power below 0.5 Hz (p = 0.048) than young adults, but power from 0.5-1 Hz was similar (p = 0.083). In contrast, the medial-lateral SD of COP (p = 0.5) and power from 0-1 Hz (p = 0.228) was similar for the two age groups. For both the anterior-posterior and medial-lateral direction, the SD of COP was related to low frequency oscillations below 0.5 Hz. SIGNIFICANCE For the first time, we show that the age-associated increase in postural variability relates to greater COP oscillations below 0.5 Hz.
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Suzuki R, Kanehisa H, Washino S, Watanabe H, Shinohara M, Yoshitake Y. Reconstruction of net force fluctuations from surface EMGs of multiple muscles in steady isometric plantarflexion. Exp Brain Res 2021; 239:601-612. [PMID: 33388812 DOI: 10.1007/s00221-020-05987-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 11/13/2020] [Indexed: 12/22/2022]
Abstract
The purposes of this study were to clarify if force fluctuations during steady multi-muscle contractions have a temporal correlation with a low-frequency component of rectified surface EMG (rEMG) in the involved muscles and collection of that component across muscles allows for the reconstruction of force fluctuations across a wide range of contraction intensities. Healthy young men (n = 15) exerted steady isometric plantarflexion force at 5-60% of maximal force. Surface EMG was recorded from the medial and lateral gastrocnemii, soleus, peroneus longus, abductor hallucis, and tibialis anterior muscles. The cross-correlation function (CCF) between plantarflexion force fluctuations and low-pass filtered rEMG in each muscle was calculated for 8 s. To reconstruct force fluctuations from rEMGs, the product of rEMG and an identified constant factor were summed across muscles with time-lag compensation for electro-mechanical delay. A distinct peak of the CCF was found between plantarflexion force fluctuations and rEMG in most cases except for the tibialis anterior. The CCF peak was greatest in the medial gastrocnemius and soleus. Reconstructed force from rEMGs was temporally correlated with measured force fluctuations across contraction intensities (average CCF peak: r = 0.65). The results indicate that individual surface rEMG has a low-frequency component that is temporally correlated with net force fluctuations during steady multi-muscle contractions and contributes to the reconstruction of force fluctuations across a wide range of contraction intensities. It suggests a potential applicability of individual surface EMGs for identifying the contributing muscles to controlling or disturbing isometric steady force in multi-muscle contractions.
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Affiliation(s)
- Ryosei Suzuki
- Graduate School of Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano, 3860018, Japan
| | - Hiroaki Kanehisa
- School of Sports and Health Sciences, Ritsumeikan University, 1-1-1 Nozihigashi, Kusatsu, Shiga, 5258577, Japan
| | - Sohei Washino
- Human Augmentation Research Center, National Institute of Advanced Industrial Science and Technology, 6-2-3 Kashiwanoha, Kashiwa, Chiba, 2770882, Japan
| | - Hironori Watanabe
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama, 3508585, Japan
| | - Minoru Shinohara
- School of Biological Sciences, Georgia Institute of Technology, 555 14th St NW, Atlanta, GA, 30332, USA
| | - Yasuhide Yoshitake
- Graduate School of Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano, 3860018, Japan. .,School of Human Movement and Nutrition Sciences, The University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia.
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Avrillon S, Del Vecchio A, Farina D, Pons JL, Vogel C, Umehara J, Hug F. Individual differences in the neural strategies to control the lateral and medial head of the quadriceps during a mechanically constrained task. J Appl Physiol (1985) 2021; 130:269-281. [DOI: 10.1152/japplphysiol.00653.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We observed that the distribution of the strength of neural drive between the vastus lateralis and vastus medialis during a single-joint isometric task varied across participants. Also, we observed that the proportion of neural drive that was shared within and between these muscles also varied across participants. These results provide evidence that the neural strategies to control the vastus lateralis and vastus medialis muscles widely vary across individuals, even during a mechanically constrained task.
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Affiliation(s)
- Simon Avrillon
- Legs + Walking AbilityLab, Shirley Ryan AbilityLab, Chicago, Illinois
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, Illinois
- Laboratory Movement, Interactions, Performance, Université de Nantes, Nantes, France
| | - Alessandro Del Vecchio
- Department of Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University, Erlangen-Nürnberg, Erlangen, Germany
- Neuromechanics and Rehabilitation Technology Group, Department of Bioengineering, Faculty of Engineering, Imperial College, London, United Kingdom
| | - Dario Farina
- Neuromechanics and Rehabilitation Technology Group, Department of Bioengineering, Faculty of Engineering, Imperial College, London, United Kingdom
| | - José L. Pons
- Legs + Walking AbilityLab, Shirley Ryan AbilityLab, Chicago, Illinois
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, Illinois
| | - Clément Vogel
- Laboratory Movement, Interactions, Performance, Université de Nantes, Nantes, France
| | - Jun Umehara
- Department of Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Japan Society for the Promotion of Science, Tokyo, Japan
| | - François Hug
- Laboratory Movement, Interactions, Performance, Université de Nantes, Nantes, France
- School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia
- Institut Universitaire de France, Paris, France
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Piasecki J, Inns TB, Bass JJ, Scott R, Stashuk DW, Phillips BE, Atherton PJ, Piasecki M. Influence of sex on the age-related adaptations of neuromuscular function and motor unit properties in elite masters athletes. J Physiol 2021; 599:193-205. [PMID: 33006148 DOI: 10.1113/jp280679] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 09/24/2020] [Indexed: 12/30/2022] Open
Abstract
KEY POINTS Masters athletes maintain high levels of activity into older age and allow an examination of the effects of aging dissociated from the effects of increased sedentary behaviour. Evidence suggests masters athletes are more successful at motor unit remodelling, the reinnervation of denervated fibres acting to preserve muscle fibre number, but little data are available in females. Here we used intramuscular electromyography to demonstrate that motor units sampled from the tibialis anterior show indications of remodelling from middle into older age and which does not differ between males and females. The age-related trajectory of motor unit discharge characteristic differs according to sex, with female athletes progressing to a slower firing pattern that was not observed in males. Our findings indicate motor unit remodelling from middle to older age occurs to a similar extent in male and female athletes, with discharge rates progressively slowing in females only. ABSTRACT Motor unit (MU) remodelling acts to minimise loss of muscle fibres following denervation in older age, which may be more successful in masters athletes. Evidence suggests performance and neuromuscular function decline with age in this population, although the majority of studies have focused on males, with little available data on female athletes. Functional assessments of strength, balance and motor control were performed in 30 masters athletes (16 male) aged 44-83 years. Intramuscular needle electrodes were used to sample individual motor unit potentials (MUPs) and near-fibre MUPs in the tibialis anterior (TA) during isometric contractions at 25% maximum voluntary contraction, and used to determine discharge characteristics (firing rate, variability) and biomarkers of peripheral MU remodelling (MUP size, complexity, stability). Multilevel mixed-effects linear regression models examined effects of age and sex. All aspects of neuromuscular function deteriorated with age (P < 0.05) with no age × sex interactions, although males were stronger (P < 0.001). Indicators of MU remodelling also progressively increased with age to a similar extent in both sexes (P < 0.05), whilst MU firing rate progressively decreased with age in females (p = 0.029), with a non-significant increase in males (p = 0.092). Masters athletes exhibit age-related declines in neuromuscular function that are largely equal across males and females. Notably, they also display features of MU remodelling with advancing age, probably acting to reduce muscle fibre loss. The age trajectory of MU firing rate assessed at a single contraction level differed between sexes, which may reflect a greater tendency for females to develop a slower muscle phenotype.
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Affiliation(s)
- Jessica Piasecki
- Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, UK
| | - Thomas B Inns
- Clinical, Metabolic and Molecular Physiology, MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK
| | - Joseph J Bass
- Clinical, Metabolic and Molecular Physiology, MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK
| | - Reece Scott
- Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, UK
| | - Daniel W Stashuk
- Department of Systems Design Engineering, University of Waterloo, Ontario, Canada
| | - Bethan E Phillips
- Clinical, Metabolic and Molecular Physiology, MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK
| | - Philip J Atherton
- Clinical, Metabolic and Molecular Physiology, MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK
| | - Mathew Piasecki
- Clinical, Metabolic and Molecular Physiology, MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK
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Cogliati M, Cudicio A, Martinez-Valdes E, Tarperi C, Schena F, Orizio C, Negro F. Half marathon induces changes in central control and peripheral properties of individual motor units in master athletes. J Electromyogr Kinesiol 2020; 55:102472. [DOI: 10.1016/j.jelekin.2020.102472] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 09/08/2020] [Accepted: 09/11/2020] [Indexed: 11/30/2022] Open
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Felici F, Del Vecchio A. Surface Electromyography: What Limits Its Use in Exercise and Sport Physiology? Front Neurol 2020; 11:578504. [PMID: 33240204 PMCID: PMC7677519 DOI: 10.3389/fneur.2020.578504] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 10/21/2020] [Indexed: 12/31/2022] Open
Abstract
The aim of the present paper is to examine to what extent the application of surface electromyography (sEMG) in the field of exercise and, more in general, of human movement, is adopted by professionals on a regular basis. For this purpose, a brief history of the recent developments of modern sEMG techniques will be assessed and evaluated for a potential use in exercise physiology and clinical biomechanics. The idea is to understand what are the limitations that impede the translation of sEMG to applied fields such as exercise physiology. A cost/benefits evaluation will be drawn in order to understand possible causes that prevents sEMG from being routinely adopted. Among the possible causative factors, educational, economic and technical issues will be considered. Possible corrective interventions will be proposed. We will also give an overview of the parameters that can be extracted from the decomposition of the sHDEMG signals and how this can be related by professionals for assessing the health and disease of the neuromuscular system. We discuss how the decomposition of surface EMG signals might be adopted as a new non-invasive tool for assessing the status of the neuromuscular system. Recent evidences show that is possible to monitor the changes in neuromuscular function after training of longitudinally tracked populations of motoneurons, predict the maximal rate of force development by an individual via motoneuron interfacing, and identify possible causal relations between aging and the decrease in motor performance. These technologies will guide our understanding of motor control and provide a new window for the investigation of the underlying physiological processes determining force control, which is essential for the sport and exercise physiologist. We will also illustrate the challenges related to extraction of neuromuscular parameters from global EMG analysis (i.e., root-mean-square, and other global EMG metrics) and when the decomposition is needed. We posit that the main limitation in the application of sEMG techniques to the applied field is associated to problems in education and teaching, and that most of the novel technologies are not open source.
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Affiliation(s)
- Francesco Felici
- Department Motor, Human and Health Sciences, Rome University Foro Italico, Rome, Italy
| | - Alessandro Del Vecchio
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University, Erlangen, Germany
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Wu R, Ditroilo M, Delahunt E, De Vito G. Age Related Changes in Motor Function (II). Decline in Motor Performance Outcomes. Int J Sports Med 2020; 42:215-226. [PMID: 33137831 DOI: 10.1055/a-1265-7073] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Age-related impairments in motor performance are caused by a deterioration in mechanical and neuromuscular functions, which have been investigated from the macro-level of muscle-tendon unit to the micro-level of the single muscle fiber. When compared to the healthy young skeletal muscle, aged skeletal muscle is: (1) weaker, slower and less powerful during the performance of voluntary contractions; (2) less steady during the performance of isometric contractions, particularly at low levels of force; and (3) less susceptible to fatigue during the performance of sustained isometric contractions, but more susceptible to fatigue during the performance of high-velocity dynamic contractions. These impairments have been discussed to be mainly the result of: a) loss of muscle mass and selective atrophy of type II muscle fibers; b) altered tendon mechanical properties (decreased tendon stiffness); c) reduced number and altered function of motor units; d) slower muscle fiber shortening velocity; e) increased oscillation in common synaptic input to motor neurons; and f) altered properties and activity of sarcoplasmic reticulum. In this second part of a two-part review we have detailed the age-related impairments in motor performance with a reference to the most important mechanical and neuromuscular contributing factors.
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Affiliation(s)
- Rui Wu
- School of Public Health Physiotherapy and Sports Science, University College Dublin, Dublin
| | - Massimiliano Ditroilo
- School of Public Health Physiotherapy and Sports Science, University College Dublin, Dublin
| | - Eamonn Delahunt
- School of Public Health Physiotherapy and Sports Science, University College Dublin, Dublin
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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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31
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Spedden ME, Beck MM, Christensen MS, Dietz MJ, Karabanov AN, Geertsen SS, Nielsen JB, Lundbye-Jensen J. Directed connectivity between primary and premotor areas underlying ankle force control in young and older adults. Neuroimage 2020; 218:116982. [DOI: 10.1016/j.neuroimage.2020.116982] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 03/31/2020] [Accepted: 05/19/2020] [Indexed: 11/29/2022] Open
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Davis LA, Alenazy MS, Almuklass AM, Feeney DF, Vieira T, Botter A, Enoka RM. Force control during submaximal isometric contractions is associated with walking performance in persons with multiple sclerosis. J Neurophysiol 2020; 123:2191-2200. [PMID: 32347151 DOI: 10.1152/jn.00085.2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Individuals with multiple sclerosis (MS) experience progressive declines in movement capabilities, especially walking performance. The purpose of our study was to compare the amount of variance in walking performance that could be explained by the functional capabilities of lower leg muscles in persons with MS and a sex- and age-matched control group. Participants performed two walking tests (6-min walk and 25-ft walk), strength tests for the plantar flexor and dorsiflexor muscles, and steady submaximal (10% and 20% maximum) isometric contractions. High-density electromyography (EMG) was recorded during the steady contractions, and the signals were decomposed to identify the discharge times of concurrently active motor units. There were significant differences between the two groups in the force fluctuations during the steady contractions (force steadiness), the strength of the plantar flexor and dorsiflexor muscles, and the discharge characteristics during the steady contractions. Performance on the two walking tests by the MS group was moderately associated with force steadiness of the plantar flexor and dorsiflexor muscles; worse force steadiness was associated with poorer walking performance. In contrast, the performance of the control group was associated with muscle strength (25-ft test) and force steadiness of the dorsiflexors and variance in common input of motor units to the plantar flexors (6-min test). These findings indicate that a reduction in the ability to maintain a steady force during submaximal isometric contractions is moderately associated with walking performance of persons with MS.NEW & NOTEWORTHY The variance in walking endurance and walking speed was associated with force control of the lower leg muscles during submaximal isometric contractions in individuals with multiple sclerosis (MS). In contrast, the fast walking speed of a sex- and age-matched control group was associated with the strength of lower leg muscles. These findings indicate that moderate declines in the walking performance of persons with MS are more associated with impairments in force control rather than decreases in muscle strength.
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Affiliation(s)
- Leah A Davis
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Mohammed S Alenazy
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Awad M Almuklass
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Daniel F Feeney
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Taian Vieira
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Alberto Botter
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Roger M Enoka
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
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Hirono T, Ikezoe T, Taniguchi M, Yamagata M, Miyakoshi K, Umehara J, Ichihashi N. Relationship between ankle plantar flexor force steadiness and postural stability on stable and unstable platforms. Eur J Appl Physiol 2020; 120:1075-1082. [DOI: 10.1007/s00421-020-04346-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 03/10/2020] [Indexed: 01/06/2023]
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Škarabot J, Ansdell P, Temesi J, Howatson G, Goodall S, Durbaba R. Neurophysiological responses and adaptation following repeated bouts of maximal lengthening contractions in young and older adults. J Appl Physiol (1985) 2019; 127:1224-1237. [DOI: 10.1152/japplphysiol.00494.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A bout of maximal lengthening contractions is known to produce muscle damage, but confers protection against subsequent damaging bouts, with both tending to be lower in older adults. Neural factors contribute to this adaptation, but the role of the corticospinal pathway remains unclear. Twelve young (27 ± 5 yr) and 11 older adults (66 ± 4 yr) performed two bouts of 60 maximal lengthening dorsiflexions 2 weeks apart. Neuromuscular responses were measured preexercise, immediately postexercise, and at 24 and 72 h following both bouts. The initial bout resulted in prolonged reductions in maximal voluntary torque (MVC; immediately postexercise onward, P < 0.001) and increased creatine kinase (from 24 h onward, P = 0.001), with both responses being attenuated following the second bout ( P < 0.015), demonstrating adaptation. Smaller reductions in MVC following both bouts occurred in older adults ( P = 0.005). Intracortical facilitation showed no changes ( P ≥ 0.245). Motor-evoked potentials increased 24 and 72 h postexercise in young ( P ≤ 0.038). Torque variability ( P ≤ 0.041) and H-reflex size ( P = 0.024) increased, while short-interval intracortical inhibition (SICI; P = 0.019) and the silent period duration (SP) decreased ( P = 0.001) in both groups immediately postexercise. The SP decrease was smaller following the second bout ( P = 0.021), and there was an association between the change in SICI and reduction in MVC 24 h postexercise in young adults ( R = −0.47, P = 0.036). Changes in neurophysiological responses were mostly limited to immediately postexercise, suggesting a modest role in adaptation. In young adults, neural inhibitory changes are linked to the extent of MVC reduction, possibly mediated by the muscle damage–related afferent feedback. Older adults incurred less muscle damage, which has implications for exercise prescription. NEW & NOTEWORTHY This is the first study to have collectively assessed the role of corticospinal, spinal, and intracortical activity in muscle damage attenuation following repeated bouts of exercise in young and older adults. Lower levels of muscle damage in older adults are not related to their neurophysiological responses. Neural inhibition transiently changed, which might be related to the extent of muscle damage; however, the role of processes along the corticospinal pathway in the adaptive response is limited.
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Affiliation(s)
- Jakob Škarabot
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
| | - Paul Ansdell
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
| | - John Temesi
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
| | - Glyn Howatson
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
- Water Research Group, School of Environmental Sciences and Development, Northwest University, Potchefstroom, South Africa
| | - Stuart Goodall
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
| | - Rade Durbaba
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
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Wu R, Delahunt E, Ditroilo M, Lowery MM, Segurado R, De Vito G. Changes in knee joint angle affect torque steadiness differently in young and older individuals. J Electromyogr Kinesiol 2019; 47:49-56. [DOI: 10.1016/j.jelekin.2019.05.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 05/13/2019] [Accepted: 05/13/2019] [Indexed: 12/01/2022] Open
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Del Vecchio A, Falla D, Felici F, Farina D. The relative strength of common synaptic input to motor neurons is not a determinant of the maximal rate of force development in humans. J Appl Physiol (1985) 2019; 127:205-214. [DOI: 10.1152/japplphysiol.00139.2019] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Correlation between motor unit discharge times, often referred to as motor unit synchronization, is determined by common synaptic input to motor neurons. Although it has been largely speculated that synchronization should influence the rate of force development, the association between the degree of motor unit synchronization and rapid force generation has not been determined. In this study, we examined this association with both simulations and experimental motor unit recordings. The analysis of experimental motor unit discharges from the tibialis anterior muscle of 20 healthy individuals during rapid isometric contractions revealed that the average motor unit discharge rate was associated with the rate of force development. Moreover, the extent of motor unit synchronization was entirely determined by the average motor unit discharge rate ( R > 0.7, P < 0.0001). The simulation model demonstrated that the relative proportion of common synaptic input received by motor neurons, which determines motor unit synchronization, does not influence the rate of force development ( R = 0.03, P > 0.05). Nonetheless, the estimates of correlation between motor unit spike trains were significantly correlated with the rate of force generation ( R > 0.8, P < 0.0001). These results indicate that the average motor unit discharge rate, but not the degree of motor unit synchronization, contributes to most of the variance of human contractile speed among individuals. In addition, estimates of correlation between motor unit discharge times depend strongly on the number of identified motor units and therefore are not indicative of the strength of common input. NEW & NOTEWORTHY It is commonly assumed that motor unit synchronization has an impact on the rate of force development of a muscle. Here we present computer simulations and experimental data of human tibialis anterior motor units during rapid contractions that show that motor unit synchronization is not a determinant of the rate of force production. This conclusion clarifies the neural determinants of rapid force generation.
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Affiliation(s)
| | - Deborah Falla
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Francesco Felici
- Department of Movement, Human and Health Sciences, University of Rome “Foro Italico,” Rome, Italy
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, United Kingdom
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37
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Influence of age on motor control accuracy during static ramp contractions. Exp Brain Res 2019; 237:1889-1897. [DOI: 10.1007/s00221-019-05524-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 03/20/2019] [Indexed: 11/30/2022]
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Pereira HM, Schlinder-DeLap B, Keenan KG, Negro F, Farina D, Hyngstrom AS, Nielson KA, Hunter SK. Oscillations in neural drive and age-related reductions in force steadiness with a cognitive challenge. J Appl Physiol (1985) 2019; 126:1056-1065. [PMID: 30817244 DOI: 10.1152/japplphysiol.00821.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
A cognitive challenge when imposed during a low-force isometric contraction will exacerbate sex- and age-related decreases in force steadiness, but the mechanism is not known. We determined the role of oscillations in the common synaptic input to motor units on force steadiness during a muscle contraction with a concurrent cognitive challenge. Forty-nine young adults (19-30 yr; 25 women, 24 men) and 36 old adults (60-85 yr; 19 women, 17 men) performed a cognitive challenge (counting backward by 13) during an isometric elbow flexion task at 5% of maximal voluntary contraction. Single-motor units were decomposed from high-density surface EMG recordings. For a subgroup of participants, motor units were matched during control and cognitive challenge trials, so the same motor unit was analyzed across conditions. Reduced force steadiness was associated with greater oscillations in the synaptic input to motor units during both control and cognitive challenge trials ( r = 0.45-0.47, P < 0.01). Old adults and young women showed greater oscillations in the common synaptic input to motor units and decreased force steadiness when the cognitive challenge was imposed, but young men showed no change across conditions (session × age × sex, P < 0.05). Oscillations in the common synaptic input to motor units is a potential mechanism for altered force steadiness when a cognitive challenge is imposed during low-force contractions in young women and old adults. NEW & NOTEWORTHY We found that oscillations in the common synaptic input to motor units were associated with a reduction in force steadiness when a cognitive challenge was imposed during low-force contractions of the elbow flexor muscles in young women and old men and women but not young men. Age- and sex-related muscle weakness was associated with these changes.
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Affiliation(s)
- Hugo M Pereira
- Department of Health and Exercise Science, University of Oklahoma , Norman, Oklahoma
| | | | - Kevin G Keenan
- Department of Kinesiology, University of Wisconsin-Milwaukee , Milwaukee, Wisconsin
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia , Brescia , Italy
| | - Dario Farina
- Department of Bioengineering, Imperial College London, Royal School of Mines , London , United Kingdom
| | | | - Kristy A Nielson
- Department of Psychology, Marquette University , Milwaukee, Wisconsin
| | - Sandra K Hunter
- Department of Physical Therapy, Marquette University , Milwaukee, Wisconsin
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