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Nardon M, Ferri U, Caffi G, Bartesaghi M, Perin C, Zaza A, Alessandro C. Kinematics but not kinetics alterations to single-leg drop jump movements following a subject-tailored fatiguing protocol suggest an increased risk of ACL injury. Front Sports Act Living 2024; 6:1418598. [PMID: 38832309 PMCID: PMC11144872 DOI: 10.3389/fspor.2024.1418598] [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: 04/16/2024] [Accepted: 05/08/2024] [Indexed: 06/05/2024] Open
Abstract
Introduction Neuromuscular fatigue causes a transient reduction of muscle force, and alters the mechanisms of motor control. Whether these alterations increase the risk of anterior cruciate ligament (ACL) injury is still debated. Here we compare the biomechanics of single-leg drop jumps before and after the execution of a fatiguing exercise, evaluating whether this exercise causes biomechanical alterations typically associated with an increased risk of ACL lesion. The intensity of the fatiguing protocol was tailored to the aerobic capacity of each participant, minimizing potential differential effects due to inter-individual variability in fitness. Methods Twenty-four healthy male volunteers performed single leg drop jumps, before and after a single-set fatiguing session on a cycle ergometer until exhaustion (cadence: 65-70 revolutions per minute). For each participant, the intensity of the fatiguing exercise was set to 110% of the power achieved at their anaerobic threshold, previously identified by means of a cardiopulmonary exercise test. Joint angles and moments, as well as ground reaction forces (GRF) before and after the fatiguing exercise were compared for both the dominant and the non-dominant leg. Results Following the fatiguing exercise, the hip joint was more extended (landing: Δ=-2.17°, p = 0.005; propulsion: Δ=-1.83°, p = 0.032) and more abducted (landing: Δ=-0.72°, p = 0.01; propulsion: Δ=-1.12°, p = 0.009). Similarly, the knee joint was more extended at landing (non-dominant leg: Δ=-2.67°, p < 0.001; dominant: Δ=-1.4°, p = 0.023), and more abducted at propulsion (both legs: Δ=-0.99°, p < 0.001) and stabilization (both legs: Δ=-1.71°, p < 0.001) hence increasing knee valgus. Fatigue also caused a significant reduction of vertical GRF upon landing (Δ=-0.21 N/kg, p = 0.003), but not during propulsion. Fatigue did not affect joint moments significantly. Conclusion The increased hip and knee extension, as well as the increased knee abduction we observed after the execution of the fatiguing exercise have been previously identified as risk factors for ACL injury. These results therefore suggest an increased risk of ACL injury after the execution of the participant-tailored fatiguing protocol proposed here. However, the reduced vertical GRF upon landing and the preservation of joint moments are intriguing, as they may suggest the adoption of protective strategies in the fatigued condition to be evaluated in future studied.
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Affiliation(s)
- Mauro Nardon
- School of Medicine and Surgery/Sport and Exercise Medicine, University of Milano-Bicocca, Milan, Italy
| | - Umberto Ferri
- School of Medicine and Surgery/Sport and Exercise Medicine, University of Milano-Bicocca, Milan, Italy
| | - Giovanni Caffi
- School of Medicine and Surgery/Sport and Exercise Medicine, University of Milano-Bicocca, Milan, Italy
| | - Manuela Bartesaghi
- School of Medicine and Surgery/Sport and Exercise Medicine, University of Milano-Bicocca, Milan, Italy
| | - Cecilia Perin
- School of Medicine and Surgery/Physical and Rehabilitative Medicine, University of Milano-Bicocca, Milan, Italy
- Istituti Clinici Zucchi - GDS, Carate Brianza, Monza e Brianza, Italy
| | - Antonio Zaza
- Department of Biotechnology and Biosciences/Sport and Exercise Medicine, University of Milano-Bicocca, Milan, Italy
| | - Cristiano Alessandro
- School of Medicine and Surgery/Sport and Exercise Medicine, University of Milano-Bicocca, Milan, Italy
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Mulla DM, Keir PJ. Neuromuscular control: from a biomechanist's perspective. Front Sports Act Living 2023; 5:1217009. [PMID: 37476161 PMCID: PMC10355330 DOI: 10.3389/fspor.2023.1217009] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 06/21/2023] [Indexed: 07/22/2023] Open
Abstract
Understanding neural control of movement necessitates a collaborative approach between many disciplines, including biomechanics, neuroscience, and motor control. Biomechanics grounds us to the laws of physics that our musculoskeletal system must obey. Neuroscience reveals the inner workings of our nervous system that functions to control our body. Motor control investigates the coordinated motor behaviours we display when interacting with our environment. The combined efforts across the many disciplines aimed at understanding human movement has resulted in a rich and rapidly growing body of literature overflowing with theories, models, and experimental paradigms. As a result, gathering knowledge and drawing connections between the overlapping but seemingly disparate fields can be an overwhelming endeavour. This review paper evolved as a need for us to learn of the diverse perspectives underlying current understanding of neuromuscular control. The purpose of our review paper is to integrate ideas from biomechanics, neuroscience, and motor control to better understand how we voluntarily control our muscles. As biomechanists, we approach this paper starting from a biomechanical modelling framework. We first define the theoretical solutions (i.e., muscle activity patterns) that an individual could feasibly use to complete a motor task. The theoretical solutions will be compared to experimental findings and reveal that individuals display structured muscle activity patterns that do not span the entire theoretical solution space. Prevalent neuromuscular control theories will be discussed in length, highlighting optimality, probabilistic principles, and neuromechanical constraints, that may guide individuals to families of muscle activity solutions within what is theoretically possible. Our intention is for this paper to serve as a primer for the neuromuscular control scientific community by introducing and integrating many of the ideas common across disciplines today, as well as inspire future work to improve the representation of neural control in biomechanical models.
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Crouzier M, Hug F, Sheehan FT, Collins NJ, Crossley K, Tucker K. Neuromechanical Properties of the Vastus Medialis and Vastus Lateralis in Adolescents With Patellofemoral Pain. Orthop J Sports Med 2023; 11:23259671231155894. [PMID: 37435588 PMCID: PMC10331778 DOI: 10.1177/23259671231155894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 12/08/2022] [Indexed: 07/13/2023] Open
Abstract
Background An alteration in the force distribution among quadriceps heads is one possible underlying mechanism of patellofemoral pain. However, this hypothesis cannot be directly tested as there are currently no noninvasive experimental techniques to measure individual muscle force or torque in vivo in humans. In this study, the authors considered a combination of biomechanical and muscle activation measures, which enabled us to estimate the mechanical impact of the vastus medialis (VM) and vastus lateralis (VL) on the patella. Purpose/Hypothesis The purpose of this study was to determine whether the relative index of torque distribution for the VM and VL differs between adolescents with and without patellofemoral pain. It was hypothesized that, relative to the VL, the VM would contribute less to knee extension torque in adolescents with patellofemoral pain compared with controls. Study Design Cross-sectional study; Level of evidence, 3. Methods Twenty adolescents with patellofemoral pain and 20 matched control participants were included (38 female; age, 15.3 ± 1.8 years; weight, 58 ± 13 kg; height, 164 ± 8 cm). Muscle volumes and resting moment arms were quantified from magnetic resonance images, and fascicle lengths were obtained from panoramic B-mode ultrasonography. Muscle activation was estimated using surface electromyography during submaximal isometric tasks (wall-squat and seated tasks). Muscle torque was estimated as the product of muscle physiological cross-sectional area (ie, muscle volume/fascicle length), muscle activation (normalized to maximal activation), and moment arm. Results Across tasks and force levels, the relative contribution of the VM to the overall medial and lateral vastii torque was 31.0% ± 8.6% for controls and 31.5 ± 7.6% for adolescents with patellofemoral pain (group effect, P > .34). Conclusion For the tasks and positions investigated in this study, the authors found no evidence of lower VM torque generation (relative to the VL) in adolescents with patellofemoral pain compared with controls.
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Affiliation(s)
- Marion Crouzier
- Laboratory “Movement, Interactions, Performance” (UR 4334), University of Nantes, Nantes, France
| | | | - Frances T. Sheehan
- Rehabilitation Medicine Department, National Institutes of Health Clinical Center, Bethesda, Maryland, USA
| | - Natalie J. Collins
- School of Health and Rehabilitation Sciences: Physiotherapy, Faculty of Health and Behavioural Sciences, The University of Queensland, St. Lucia, Queensland, Australia
| | - Kay Crossley
- La Trobe Sport and Exercise Medicine Research Centre, La Trobe University Melbourne, Australia
| | - Kylie Tucker
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St. Lucia, Queensland, Australia
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Del Vecchio A, Marconi Germer C, Kinfe TM, Nuccio S, Hug F, Eskofier B, Farina D, Enoka RM. The Forces Generated by Agonist Muscles during Isometric Contractions Arise from Motor Unit Synergies. J Neurosci 2023; 43:2860-2873. [PMID: 36922028 PMCID: PMC10124954 DOI: 10.1523/jneurosci.1265-22.2023] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 02/03/2023] [Accepted: 02/12/2023] [Indexed: 03/17/2023] Open
Abstract
The purpose of our study was to identify the low-dimensional latent components, defined hereafter as motor unit modes, underlying the discharge rates of the motor units in two knee extensors (vastus medialis and lateralis, eight men) and two hand muscles (first dorsal interossei and thenars, seven men and one woman) during submaximal isometric contractions. Factor analysis identified two independent motor unit modes that captured most of the covariance of the motor unit discharge rates. We found divergent distributions of the motor unit modes for the hand and vastii muscles. On average, 75% of the motor units for the thenar muscles and first dorsal interosseus were strongly correlated with the module for the muscle in which they resided. In contrast, we found a continuous distribution of motor unit modes spanning the two vastii muscle modules. The proportion of the muscle-specific motor unit modes was 60% for vastus medialis and 45% for vastus lateralis. The other motor units were either correlated with both muscle modules (shared inputs) or belonged to the module for the other muscle (15% for vastus lateralis). Moreover, coherence of the discharge rates between motor unit pools was explained by the presence of shared synaptic inputs. In simulations with 480 integrate-and-fire neurons, we demonstrate that factor analysis identifies the motor unit modes with high levels of accuracy. Our results indicate that correlated discharge rates of motor units that comprise motor unit modes arise from at least two independent sources of common input among the motor neurons innervating synergistic muscles.SIGNIFICANCE STATEMENT It has been suggested that the nervous system controls synergistic muscles by projecting common synaptic inputs to the engaged motor neurons. In our study, we reduced the dimensionality of the output produced by pools of synergistic motor neurons innervating the hand and thigh muscles during isometric contractions. We found two neural modules, each representing a different common input, that were each specific for one of the muscles. In the vastii muscles, we found a continuous distribution of motor unit modes spanning the two synergistic muscles. Some of the motor units from the homonymous vastii muscle were controlled by the dominant neural module of the other synergistic muscle. In contrast, we found two distinct neural modules for the hand muscles.
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Affiliation(s)
- Alessandro Del Vecchio
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University, 91052 Erlangen, Germany
| | - Carina Marconi Germer
- Department of Bioengineering, Federal University of Pernambuco, CEP 50670-901 Recife, Brazil
| | - Thomas M Kinfe
- Division of Functional Neurosurgery and Stereotaxy, Friedrich-Alexander University, 91052 Erlangen, Germany
| | - Stefano Nuccio
- Department Human Movement Science, University of Rome Foro Italico, 00185 Rome, Italy
| | - François Hug
- Le Laboratoire Motricité Humaine Expertise Sport Santé, Université Côte d'Azur, 06103 Nice, France
| | - Bjoern Eskofier
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University, 91052 Erlangen, Germany
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado CO 80309
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Alessandro C, Prashara A, Tentler DP, Tresch MC. Inhibition of knee joint sensory afferents alters covariation across strides between quadriceps muscles during locomotion. J Appl Physiol (1985) 2023; 134:957-968. [PMID: 36759157 PMCID: PMC10069963 DOI: 10.1152/japplphysiol.00591.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 01/03/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Sport-related injuries to articular structures often alter the sensory information conveyed by joint structures to the nervous system. However, the role of joint sensory afferents in motor control is still unclear. Here, we evaluate the role of knee joint sensory afferents in the control of quadriceps muscles, hypothesizing that such sensory information modulates control strategies that limit patellofemoreal joint loading. We compared locomotor kinematics and muscle activity before and after inhibition of knee sensory afferents by injection of lidocaine into the knee capsule of rats. We evaluated whether this inhibition reduced the strength of correlation between the activity of vastus medialis (VM) and vastus lateralis (VL) both across strides and within each stride, coordination patterns that limit net mediolateral patellofemoral forces. We also evaluated whether this inhibition altered correlations among the other quadriceps muscle activity, the time-profiles of individual EMG envelopes, or movement kinematics. Neither the EMG envelopes nor limb kinematics was affected by the inhibition of knee sensory afferents. This perturbation also did not affect the correlations between VM and VL, suggesting that the regulation of patellofemoral joint loading is mediated by different mechanisms. However, inhibition of knee sensory afferents caused a significant reduction in the correlation between vastus intermedius (VI) and both VM and VL across, but not within, strides. Knee joint sensory afferents may therefore modulate the coordination between the vasti muscles but only at coarse time scales. Injuries compromising joint afferents might result in altered muscle coordination, potentially leading to persistent internal joint stresses and strains.NEW & NOTEWORTHY Sensory afferents originating from knee joint receptors provide the nervous system with information about the internal state of the joint. In this study, we show that these sensory signals are used to modulate the covariations among the activity of a subset of vasti muscles across strides of locomotion. Sport-related injuries that damage joint receptors may therefore compromise these mechanisms of muscle coordination, potentially leading to persistent internal joint stresses and strains.
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Affiliation(s)
- Cristiano Alessandro
- Department of Neuroscience, Northwestern University, Chicago, Illinois, United States
- School of Medicine and Surgery/Sport and Exercise Medicine, University of Milano-Bicocca, Milan, Italy
| | - Adarsh Prashara
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States
| | - David P Tentler
- Department of Neuroscience, Northwestern University, Chicago, Illinois, United States
| | - Matthew C Tresch
- Department of Neuroscience, Northwestern University, Chicago, Illinois, United States
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, Illinois, United States
- Shirley Ryan AbilityLab, Chicago, Illinois, United States
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Asín-Prieto G, Oliveira Barroso F, Martínez-Expósito A, Urendes E, Gonzalez-Vargas J, Moreno JC. Mechanical disturbances applied by motorized ankle foot orthosis to adapt ankle muscles activation—A validation study. Front Bioeng Biotechnol 2023; 11:1079027. [PMID: 37008040 PMCID: PMC10060880 DOI: 10.3389/fbioe.2023.1079027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 03/06/2023] [Indexed: 03/18/2023] Open
Abstract
Background: Reduced function of ankle muscles usually leads to impaired gait. Motorized ankle foot orthoses (MAFOs) have shown potential to improve neuromuscular control and increase volitional engagement of ankle muscles. In this study, we hypothesize that specific disturbances (adaptive resistance-based perturbations to the planned trajectory) applied by a MAFO can be used to adapt the activity of ankle muscles. The first goal of this exploratory study was to test and validate two different ankle disturbances based on plantarflexion and dorsiflexion resistance while training in standing still position. The second goal was to assess neuromuscular adaptation to these approaches, namely, in terms of individual muscle activation and co-activation of antagonists.Methods: Two ankle disturbances were tested in ten healthy subjects. For each subject, the dominant ankle followed a target trajectory while the contralateral leg was standing still: a) dorsiflexion torque during the first part of the trajectory (Stance Correlate disturbance—StC), and b) plantarflexion torque during the second part of the trajectory (Swing Correlate disturbance—SwC). Electromyography was recorded from the tibialis anterior (TAnt) and gastrocnemius medialis (GMed) during MAFO and treadmill (baseline) trials.Results: GMed (plantarflexor muscle) activation decreased in all subjects during the application of StC, indicating that dorsiflexion torque did not enhance GMed activity. On the other hand, TAnt (dorsiflexor muscle) activation increased when SwC was applied, indicating that plantarflexion torque succeeded in enhancing TAnt activation. For each disturbance paradigm, there was no antagonist muscle co-activation accompanying agonist muscle activity changes.Conclusion: We successfully tested novel ankle disturbance approaches that can be explored as potential resistance strategies in MAFO training. Results from SwC training warrant further investigation to promote specific motor recovery and learning of dorsiflexion in neural-impaired patients. This training can potentially be beneficial during intermediate phases of rehabilitation prior to overground exoskeleton-assisted walking. Decreased activation of GMed during StC might be attributed to the unloaded body weight in the ipsilateral side, which typically decreases activation of anti-gravity muscles. Neural adaptation to StC needs to be studied thoroughly in different postures in futures studies.
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Affiliation(s)
- Guillermo Asín-Prieto
- Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council (CSIC), Madrid, Spain
- Gogoa Mobility Robots, Abadiño, Spain
| | - Filipe Oliveira Barroso
- Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council (CSIC), Madrid, Spain
- *Correspondence: Filipe Oliveira Barroso,
| | - Aitor Martínez-Expósito
- Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council (CSIC), Madrid, Spain
- Universidad Autónoma de Madrid, Madrid, Spain
| | - Eloy Urendes
- Departamento de Tecnologías de la Información, Escuela Politécnica Superior, Escuela Politécnica Superior, Universidad San Pablo-CEU, CEU Universities, Madrid, Spain
| | | | - Juan C. Moreno
- Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council (CSIC), Madrid, Spain
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Grillo M, Geminiani A, Alessandro C, D'Angelo E, Pedrocchi A, Casellato C. Bayesian Integration in a Spiking Neural System for Sensorimotor Control. Neural Comput 2022; 34:1893-1914. [PMID: 35896162 DOI: 10.1162/neco_a_01525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 04/30/2022] [Indexed: 11/04/2022]
Abstract
The brain continuously estimates the state of body and environment, with specific regions that are thought to act as Bayesian estimator, optimally integrating noisy and delayed sensory feedback with sensory predictions generated by the cerebellum. In control theory, Bayesian estimators are usually implemented using high-level representations. In this work, we designed a new spike-based computational model of a Bayesian estimator. The state estimator receives spiking activity from two neural populations encoding the sensory feedback and the cerebellar prediction, and it continuously computes the spike variability within each population as a reliability index of the signal these populations encode. The state estimator output encodes the current state estimate. We simulated a reaching task at different stages of cerebellar learning. The activity of the sensory feedback neurons encoded a noisy version of the trajectory after actual movement, with an almost constant intrapopulation spiking variability. Conversely, the activity of the cerebellar output neurons depended on the phase of the learning process. Before learning, they fired at their baseline not encoding any relevant information, and the variability was set to be higher than that of the sensory feedback (more reliable, albeit delayed). When learning was complete, their activity encoded the trajectory before the actual execution, providing an accurate sensory prediction; in this case, the variability was set to be lower than that of the sensory feedback. The state estimator model optimally integrated the neural activities of the afferent populations, so that the output state estimate was primarily driven by sensory feedback in prelearning and by the cerebellar prediction in postlearning. It was able to deal even with more complex scenarios, for example, by shifting the dominant source during the movement execution if information availability suddenly changed. The proposed tool will be a critical block within integrated spiking, brain-inspired control systems for simulations of sensorimotor tasks.
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Affiliation(s)
- Massimo Grillo
- Nearlab, Department of Electronics, Information and Bioengineering, Politecnico di Milano, 20133, Milan, Italy
| | - Alice Geminiani
- Department of Brain and Behavioral Sciences, University of Pavia 27100, Italy
| | - Cristiano Alessandro
- Department of Brain and Behavioral Sciences, University of Pavia 27100, Italy.,School of Medicine and Surgery/Sport and Exercise Science, University of Milano-Bicocca, 20126 Milan, Italy
| | - Egidio D'Angelo
- Department of Brain and Behavioral Sciences, University of Pavia 27100, Italy.,Brain Connectivity Center, IRCCS Mondino Foundation, Pavia 27100, Italy
| | - Alessandra Pedrocchi
- Nearlab, Department of Electronics, Information and Bioengineering, Politecnico di Milano, 20133, Milan, Italy
| | - Claudia Casellato
- Department of Brain and Behavioral Sciences, University of Pavia 27100, Italy
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KOMIYA MAKOTO, MAEDA NORIAKI, NISHIKAWA YUICHI, SASADAI JUNPEI, MORIKAWA MASANORI, TASHIRO TSUBASA, FUJISHITA HIRONORI, URABE YUKIO. SPATIAL DISTRIBUTION PATTERN OF THE ELECTROMYOGRAPHIC POTENTIAL IN THE VASTUS MEDIALIS AND LATERALIS MUSCLES FOR THREE KNEE FLEXION ANGLES DURING ISOMETRIC KNEE EXTENSION. J MECH MED BIOL 2022. [DOI: 10.1142/s0219519422500312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Understanding the function of the vastus lateralis (VL) and vastus medialis (VM) muscles is important since these muscles are essential for daily and sport activities. The association between the knee flexion angle and spatial muscle activation is controversial. This study compares the distribution patterns of multi-channel electromyographic activities of the VL and VM muscles at three knee flexion angles for three intensities of isometric contraction. Sixteen men performed isometric knee extensions at 30%, 50% and 70% maximal voluntary contraction (MVC), at [Formula: see text], [Formula: see text] and [Formula: see text] knee flexion. Alterations in the spatial electromyographic potential distribution were determined by the root mean square (RMS), modified entropy, and coefficient of variation in the spatial electromyographic potential. Modified entropy and the coefficient of variation showed differences in the VM muscle between [Formula: see text] and [Formula: see text] knee flexion. The RMS at the three angles was similar between the VL and VM muscles, with no differences in contraction intensities at 30%, 50%, or 70% MVC. The VL and VM muscle function differed among knee flexion angles, as did activity in the distal and proximal VM muscles. These findings suggest the need for functional evaluation of the VL and VM muscles at each knee flexion angle.
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Affiliation(s)
- MAKOTO KOMIYA
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - NORIAKI MAEDA
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - YUICHI NISHIKAWA
- Faculty of Frontier Engineering, Institute of Science and Engineering, Kanazawa University, Kanazawa, Japan
| | - JUNPEI SASADAI
- Sports Medical Center, Japan Institute of Sports, Sciences, Tokyo, Japan
| | - MASANORI MORIKAWA
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - TSUBASA TASHIRO
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | | | - YUKIO URABE
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
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Relationship between individual forces of each quadriceps head during low-load knee extension and cartilage thickness and knee pain in women with knee osteoarthritis. Clin Biomech (Bristol, Avon) 2022; 91:105546. [PMID: 34920238 DOI: 10.1016/j.clinbiomech.2021.105546] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 11/11/2021] [Accepted: 12/07/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND This study aimed to clarify the individual forces of each quadriceps head during low-load contractions and to determine the associations between individual muscle force and cartilage thickness and symptoms in female knee osteoarthritis patients. METHODS Twenty-two women with painful knee osteoarthritis and 15 asymptomatic age-matched women (control group) participated in this cross-sectional study. Maximal knee extension strength and the cross-sectional area of each quadriceps muscle were measured. Shear modulus was calculated for each muscle during 20-Nm torque production by shear-wave elastography. Muscle force index was defined as the product of the cross-sectional area and shear modulus. Medial femur cartilage thickness was measured using an ultrasound B-mode image. Knee pain during gait was evaluated using a Numerical Rating Scale. Muscle force index, cross-sectional area, and maximal knee extension strength, which were defined as muscle functions, were compared between groups using the unpaired t-test. Correlation coefficients were calculated using muscle function, cartilage thickness, or pain. FINDINGS Maximal strength and vastus lateralis force index were smaller in the knee osteoarthritis group than in the control group (p < 0.001 and p = 0.005, respectively). In the knee osteoarthritis group, vastus medialis and vastus lateralis force indexes were positively correlated with cartilage thickness (r = 0.57 and r = 0.45, respectively), whereas the rectus femoris force index was negatively correlated with cartilage thickness (r = -0.45). The vastus lateralis force index was negatively correlated with knee pain (ρ = -0.56). INTERPRETATION Vasti force indices were positively associated with cartilage thickness; however, rectus femoris index was negatively associated in female patients with knee osteoarthritis.
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Stamenkovic A, Ting LH, Stapley PJ. Evidence for constancy in the modularity of trunk muscle activity preceding reaching: implications for the role of preparatory postural activity. J Neurophysiol 2021; 126:1465-1477. [PMID: 34587462 PMCID: PMC8782652 DOI: 10.1152/jn.00093.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 08/30/2021] [Accepted: 09/26/2021] [Indexed: 11/22/2022] Open
Abstract
Postural muscle activity precedes voluntary movements of the upper limbs. The traditional view of this activity is that it anticipates perturbations to balance caused by the movement of a limb. However, findings from reach-based paradigms have shown that postural adjustments can initiate center of mass displacement for mobility rather than minimize its displacement for stability. Within this context, altering reaching distance beyond the base of support would place increasing constraints on equilibrium during stance. If the underlying composition of anticipatory postural activity is linked to stability, coordination between muscles (i.e., motor modules) may evolve differently as equilibrium constraints increase. We analyzed the composition of motor modules in functional trunk muscles as participants performed multidirectional reaching movements to targets within and beyond the arm's length. Bilateral trunk and reaching arm muscle activity were recorded. Despite different trunk requirements necessary for successful movement, and the changing biomechanical (i.e., postural) constraints that accompany alterations in reach distance, nonnegative matrix factorization identified functional motor modules derived from preparatory trunk muscle activity that shared common features. Relative similarity in modular weightings (i.e., composition) and spatial activation profiles that reflect movement goals across tasks necessitating differing levels of trunk involvement provides evidence that preparatory postural adjustments are linked to the same task priorities (i.e., movement generation rather than stability).NEW & NOTEWORTHY Reaching within and beyond arm's length places different task constraints upon the required trunk motion necessary for successful movement execution. The identification of constant modular features, including functional muscle weightings and spatial tuning, lend support to the notion that preparatory postural adjustments of the trunk are tied to the same task priorities driving mobility, regardless of the future postural constraints.
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Affiliation(s)
- Alexander Stamenkovic
- Neural Control of Movement Laboratory, School of Medicine, Faculty of Science, Medicine & Health, University of Wollongong, Wollongong, New South Wales, Australia
- Department of Physical Therapy, College of Health Professions, Virginia Commonwealth University, Richmond, Virginia
| | - Lena H Ting
- Walter H. Coulter Department of Biomedical Engineering, Georgia Tech College of Engineering, Emory School of Medicine, Emory University, Atlanta, Georgia
- Division of Physical Therapy, Department of Rehabilitation Medicine, Emory School of Medicine, Emory University, Atlanta, Georgia
| | - Paul J Stapley
- Neural Control of Movement Laboratory, School of Medicine, Faculty of Science, Medicine & Health, University of Wollongong, Wollongong, New South Wales, Australia
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Xu Y, Poon WS, Zheng Y, Zhang S, Hu X. Evaluation of Central Fatigue in Post-stroke Rehabilitation: A Pilot Study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:6687-6690. [PMID: 34892642 DOI: 10.1109/embc46164.2021.9630323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Central fatigue induced by excessive rehabilitation training would limit motor activity or even damage the post-stroke motor function recovery. However, the central fatigue progress during training is unclear and ignored in post-stroke rehabilitation. In this study, we tried to investigate the changes in central fatigue with fractal dimension (FD) of electromyography (EMG) at different peripheral fatigue levels based on the intracerebral haemorrhage (ICH) model. Ten Sprague-Dawley rats with ICH and EMG electrodes implantation were randomly distributed into two groups: the forced training (FOR) group with exhausted peripheral fatigue level (n=5) and fatigue-controlled (FAT) group (n=5) with peripheral fatigue constrained in moderate level. A higher central fatigue level was found in the FOR group (P<0.0001), and the central fatigue could be alleviated by peripheral fatigue-based modulation in the FAT group. The FAT group with less central fatigue achieved significantly better motor function recovery (P<0.0001), and it might be related to the recovery in the ability of motor unit recruitments.
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12
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Abd AT, Singh RE, Iqbal K, White G. A Perspective on Muscle Synergies and Different Theories Related to Their Adaptation. BIOMECHANICS 2021; 1:253-263. [DOI: 10.3390/biomechanics1020021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
The human motor system is a complex neuro-musculo sensory system that needs further investigations of neuro-muscular commands and sensory-motor coupling to decode movement execution. Some researchers suggest that the central nervous system (CNS) activates a small set of modules termed muscle synergies to simplify motor control. Further, these modules form functional building blocks of movement as they can explain the neurophysiological characteristics of movements. We can identify and extract these muscle synergies from electromyographic signals (EMG) recorded in the laboratory by using linear decomposition algorithms, such as principal component analysis (PCA) and non-Negative Matrix Factorization Algorithm (NNMF). For the past three decades, the hypothesis of muscle synergies has received considerable attention as we attempt to understand and apply the concept of muscle synergies in clinical settings and rehabilitation. In this article, we first explore the concept of muscle synergies. We then present different strategies of adaptation in these synergies that the CNS employs to accomplish a movement goal.
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13
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Cruz-Montecinos C, Pérez-Alenda S, Cerda M, Maas H. Modular reorganization of gait in chronic but not in artificial knee joint constraint. J Neurophysiol 2021; 126:516-531. [PMID: 34133242 DOI: 10.1152/jn.00418.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
It is currently unknown if modular reorganization does occur if not the central nervous system, but the musculoskeletal system is affected. The aims of this study were to investigate 1) the effects of an artificial knee joint constraint on the modular organization of gait in healthy subjects; and 2) the differences in modular organization between healthy subjects with an artificial knee joint constraint and people with a similar but chronic knee joint constraint. Eleven healthy subjects and eight people with a chronic knee joint constraint walked overground at 1 m/s. The healthy subjects also walked with a constraint limiting knee joint movement to 20°. The total variance accounted (tVAF) for one to four synergies and modular organization were assessed using surface electromyography from 11 leg muscles. The distribution of number of synergies were not significantly different between groups. The tVAF and the motor modules were not significantly affected by the artificial knee constraint. A higher tVAF for one and two synergies, as well as merging of motor modules were observed in the chronic knee constraint group. We conclude that in the short-term a knee constraint does not affect the modular organization of gait, but in the long-term a knee constraint results in modular reorganization. These results indicate that merging of motor modules may also occur when changes in the mechanics of the musculoskeletal system is the primary cause of the motor impairment.NEW & NOTEWORTHY It is currently unknown if modular reorganization does occur if not the central nervous system, but the musculoskeletal system is affected. This study showed that in the short-term a knee constraint does not affect the modular organization of gait, but in the long-term a knee constraint results in modular reorganization. These results indicate that modular reorganization may also occur when changes in the mechanics of the musculoskeletal system is the primary cause of the motor impairment.
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Affiliation(s)
- Carlos Cruz-Montecinos
- Physiotherapy in Motion Multispeciality Research Group (PTinMOTION), Department of Physiotherapy, University of Valencia, Valencia, Spain.,Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands.,Laboratory of Clinical Biomechanics, Department of Physical Therapy, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Sofía Pérez-Alenda
- Physiotherapy in Motion Multispeciality Research Group (PTinMOTION), Department of Physiotherapy, University of Valencia, Valencia, Spain
| | - Mauricio Cerda
- Integrative Biology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Center for Medical Informatics and Telemedicine, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Santiago, Chile
| | - Huub Maas
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
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14
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Bornstein B, Konstantin N, Alessandro C, Tresch MC, Zelzer E. More than movement: the proprioceptive system as a new regulator of musculoskeletal biology. CURRENT OPINION IN PHYSIOLOGY 2021. [DOI: 10.1016/j.cophys.2021.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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15
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Serrancolí G, Alessandro C, Tresch MC. The Effects of Mechanical Scale on Neural Control and the Regulation of Joint Stability. Int J Mol Sci 2021; 22:ijms22042018. [PMID: 33670603 PMCID: PMC7922058 DOI: 10.3390/ijms22042018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 02/02/2021] [Accepted: 02/04/2021] [Indexed: 11/17/2022] Open
Abstract
Recent work has demonstrated how the size of an animal can affect neural control strategies, showing that passive viscoelastic limb properties have a significant role in determining limb movements in small animals but are less important in large animals. We extend that work to consider effects of mechanical scaling on the maintenance of joint integrity; i.e., the prevention of aberrant contact forces within joints that might lead to joint dislocation or cartilage degradation. We first performed a literature review to evaluate how properties of ligaments responsible for joint integrity scale with animal size. Although we found that the cross-sectional area of the anterior cruciate ligament generally scaled with animal size, as expected, the effects of scale on the ligament’s mechanical properties were less clear, suggesting potential adaptations in passive contributions to the maintenance of joint integrity across species. We then analyzed how the neural control of joint stability is altered by body scale. We show how neural control strategies change across mechanical scales, how this scaling is affected by passive muscle properties and the cost function used to specify muscle activations, and the consequences of scaling on internal joint contact forces. This work provides insights into how scale affects the regulation of joint integrity by both passive and active processes and provides directions for studies examining how this regulation might be accomplished by neural systems.
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Affiliation(s)
- Gil Serrancolí
- Department of Mechanical Engineering, Universitat Politècnica de Catalunya, 08019 Barcelona, Spain
- Correspondence:
| | - Cristiano Alessandro
- Department of Brain and Behavioral Sciences, Università degli Studi di Pavia, 27100 Pavia, Italy;
- Department of Physiology, Northwestern University, Chicago, IL 60611, USA;
| | - Matthew C. Tresch
- Department of Physiology, Northwestern University, Chicago, IL 60611, USA;
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL 60208, USA
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL 60611, USA
- Shirley Ryan AbilityLab, Chicago, IL 60611, USA
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16
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Botzheim L, Laczko J, Torricelli D, Mravcsik M, Pons JL, Oliveira Barroso F. Effects of gravity and kinematic constraints on muscle synergies in arm cycling. J Neurophysiol 2021; 125:1367-1381. [PMID: 33534650 DOI: 10.1152/jn.00415.2020] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Arm cycling is a bimanual motor task used in medical rehabilitation and in sports training. Understanding how muscle coordination changes across different biomechanical constraints in arm cycling is a step toward improved rehabilitation approaches. This exploratory study aims to get new insights on motor control during arm cycling. To achieve our main goal, we used the muscle synergies analysis to test three hypotheses: 1) body position with respect to gravity (sitting and supine) has an effect on muscle synergies; 2) the movement size (crank length) has an effect on the synergistic behavior; 3) the bimanual cranking mode (asynchronous and synchronous) requires different synergistic control. Thirteen able-bodied volunteers performed arm cranking on a custom-made device with unconnected cranks, which allowed testing three different conditions: body position (sitting vs. supine), crank length (10 cm vs. 15 cm), and cranking mode (synchronous vs. asynchronous). For each of the eight possible combinations, subjects cycled for 30 s while electromyography of eight muscles (four from each arm) were recorded: biceps brachii, triceps brachii, anterior deltoid, and posterior deltoid. Muscle synergies in this eight-dimensional muscle space were extracted by nonnegative matrix factorization. Four synergies accounted for over 90% of muscle activation variances in all conditions. Results showed that synergies were affected by body position and cranking mode but practically unaffected by movement size. These results suggest that the central nervous system may employ different motor control strategies in response to external constraints such as cranking mode and body position during arm cycling.NEW & NOTEWORTHY Recent studies analyzed muscle synergies in lower limb cycling. Here, we examine upper limb cycling and specifically the effect of body position with respect to gravity, movement size, and cranking mode on muscle coordination during arm cranking tasks. We show that altered body position and cranking mode affects modular organization of muscle activities. To our knowledge, this is the first study assessing motor control through muscle synergies framework during upper limb cycling with different constraints.
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Affiliation(s)
- Lilla Botzheim
- Department of Information Technology and Biorobotics, Institute of Mathematics and Informatics, Faculty of Sciences, University of Pecs, Pecs, Hungary.,Neurorehabilitation and Motor Control Research Group, Department of Computational Sciences, Wigner Research Centre for Physics, Budapest, Hungary
| | - Jozsef Laczko
- Department of Information Technology and Biorobotics, Institute of Mathematics and Informatics, Faculty of Sciences, University of Pecs, Pecs, Hungary.,Neurorehabilitation and Motor Control Research Group, Department of Computational Sciences, Wigner Research Centre for Physics, Budapest, Hungary.,Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Diego Torricelli
- Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council, Madrid, Spain
| | - Mariann Mravcsik
- Department of Information Technology and Biorobotics, Institute of Mathematics and Informatics, Faculty of Sciences, University of Pecs, Pecs, Hungary.,Neurorehabilitation and Motor Control Research Group, Department of Computational Sciences, Wigner Research Centre for Physics, Budapest, Hungary
| | - Jose L Pons
- Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council, Madrid, Spain.,Legs & Walking AbilityLab, Shirley Ryan AbilityLab, Chicago, Illinois.,Department of Biomedical Engineering and Mechanical Engineering, McCormick School of Engineering, Northwestern University, Chicago, Illinois.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Filipe Oliveira Barroso
- Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council, Madrid, Spain
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17
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Xu Y, Yao Y, Lyu H, Ng S, Xu Y, Poon WS, Zheng Y, Zhang S, Hu X. Rehabilitation Effects of Fatigue-Controlled Treadmill Training After Stroke: A Rat Model Study. Front Bioeng Biotechnol 2020; 8:590013. [PMID: 33330421 PMCID: PMC7734251 DOI: 10.3389/fbioe.2020.590013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 10/28/2020] [Indexed: 11/13/2022] Open
Abstract
Background: Traditional rehabilitation with uniformed intensity would ignore individual tolerance and introduce the second injury to stroke survivors due to overloaded training. However, effective control of the training intensity of different stroke survivors is still lacking. The purpose of the study was to investigate the rehabilitative effects of electromyography (EMG)-based fatigue-controlled treadmill training on rat stroke model. Methods: Sprague-Dawley rats after intracerebral hemorrhage and EMG electrode implantation surgeries were randomly distributed into three groups: the control group (CTRL, n = 11), forced training group (FOR-T, n = 11), and fatigue-controlled training group (FAT-C, n = 11). The rehabilitation interventions were delivered every day from day 2 to day 14 post-stroke. No training was delivered to the CTRL group. The rats in the FOR-T group were forced to run on the treadmill without rest. The fatigue level was monitored in the FAT-C group through the drop rate of EMG mean power frequency, and rest was applied to the rats when the fatigue level exceeded the moderate fatigue threshold. The speed and accumulated running duration were comparable in the FAT-C and the FOR-T groups. Daily evaluation of the motor functions was performed using the modified Neurological Severity Score. Running symmetry was investigated by the symmetry index of EMG bursts collected from both hind limbs during training. The expression level of neurofilament-light in the striatum was measured to evaluate the neuroplasticity. Results: The FAT-C group showed significantly lower modified Neurological Severity Score compared with the FOR-T (P ≤ 0.003) and CTRL (P ≤ 0.003) groups. The FAT-C group showed a significant increase in the symmetry of hind limbs since day 7 (P = 0.000), whereas the FOR-T group did not (P = 0.349). The FAT-C group showed a higher concentration of neurofilament-light compared to the CTRL group (P = 0.005) in the unaffected striatum and the FOR-T group (P = 0.021) in the affected striatum. Conclusion: The treadmill training with moderate fatigue level controlled was more effective in motor restoration than forced training. The fatigue-controlled physical training also demonstrated positive effects in the striatum neuroplasticity. This study indicated that protocol with individual fatigue-controlled training should be considered in both animal and clinical studies for better stroke rehabilitation.
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Affiliation(s)
- Yuchen Xu
- Qiushi Academy for Advanced Studies, Zhejiang University, Hangzhou, China.,Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Yuanfa Yao
- Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China.,Department of Endocrinology, The Affiliated Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Hao Lyu
- Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, ShaTin, Hong Kong
| | - Stephanie Ng
- Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, ShaTin, Hong Kong
| | - Yingke Xu
- Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China.,Department of Endocrinology, The Affiliated Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Wai Sang Poon
- Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, ShaTin, Hong Kong
| | - Yongping Zheng
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
| | - Shaomin Zhang
- Qiushi Academy for Advanced Studies, Zhejiang University, Hangzhou, China.,Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Xiaoling Hu
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
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18
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Coordination amongst quadriceps muscles suggests neural regulation of internal joint stresses, not simplification of task performance. Proc Natl Acad Sci U S A 2020; 117:8135-8142. [PMID: 32205442 DOI: 10.1073/pnas.1916578117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Many studies have demonstrated covariation between muscle activations during behavior, suggesting that muscles are not controlled independently. According to one common proposal, this covariation reflects simplification of task performance by the nervous system so that muscles with similar contributions to task variables are controlled together. Alternatively, this covariation might reflect regulation of low-level aspects of movements that are common across tasks, such as stresses within joints. We examined these issues by analyzing covariation patterns in quadriceps muscle activity during locomotion in rats. The three monoarticular quadriceps muscles (vastus medialis [VM], vastus lateralis [VL], and vastus intermedius [VI]) produce knee extension and so have identical contributions to task performance; the biarticular rectus femoris (RF) produces an additional hip flexion. Consistent with the proposal that muscle covariation is related to similarity of muscle actions on task variables, we found that the covariation between VM and VL was stronger than their covariations with RF. However, covariation between VM and VL was also stronger than their covariations with VI. Since all vastii have identical actions on task variables, this finding suggests that covariation between muscle activity is not solely driven by simplification of overt task performance. Instead, the preferentially strong covariation between VM and VL is consistent with the control of internal joint stresses: Since VM and VL produce opposing mediolateral forces on the patella, the high positive correlation between their activation minimizes the net mediolateral patellar force. These results provide important insights into the interpretation of muscle covariations and their role in movement control.
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