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Rossi L, Mota BI, Valadão PAC, Magalhães-Gomes MPS, Oliveira BS, Guatimosim S, Navegantes LCC, Miranda AS, Prado MAM, Prado VF, Guatimosim C. Influence of β 2-adrenergic selective agonist formoterol on the motor unit of a mouse model of a congenital myasthenic syndrome with complete VAChT deletion. Neuropharmacology 2024; 260:110116. [PMID: 39151654 DOI: 10.1016/j.neuropharm.2024.110116] [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: 05/05/2024] [Revised: 08/09/2024] [Accepted: 08/13/2024] [Indexed: 08/19/2024]
Abstract
Congenital Myasthenic Syndromes (CMS) are a set of genetic diseases that affect the neuromuscular transmission causing muscular weakness. The standard pharmacological treatment aims at ameliorating the myasthenic symptom by acetylcholinesterase inhibitors. Most patients respond well in the short and medium term, however, over time the beneficial effects rapidly fade, and the efficacy of the treatment diminishes. Increasing evidence shows that β2-adrenergic agonists can be a suitable choice for the treatment of neuromuscular disorders, including CMS, as they promote beneficial effects in the neuromuscular system. The exact mechanism on which they rely is not completely understood, although patients and animal models respond well to the treatment, especially over extended periods. Here, we report the use of the long-lasting specific β2-adrenergic agonist formoterol in a myasthenic mouse model (mnVAChT-KD), featuring deletion of VAChT (Vesicular Acetylcholine Transporter) specifically in the α-motoneurons. Our findings demonstrate that formoterol treatment (300 μg/kg/day; sc) for 30 days increased the neuromuscular junction area, induced skeletal muscle hypertrophy and altered fibre type composition in myasthenic mice. Interestingly, β2-adrenergic agonists have shown efficacy even in the absence of ACh (acetylcholine). Our data provide important evidence supporting the potential of β2-adrenergic agonists in treating neuromuscular disorders of pre-synaptic origin and characterized by disruptions in nerve-muscle communication, through a direct and beneficial action within the motor unit.
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Affiliation(s)
- Leonardo Rossi
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Bárbara I Mota
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Priscila A C Valadão
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Matheus P S Magalhães-Gomes
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil; Departamento de Ciências Básicas, Faculdade Ciências Médicas de Minas Gerais, FCMMG, Belo Horizonte, Brazil
| | - Bruna S Oliveira
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Silvia Guatimosim
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Luiz C C Navegantes
- Departamento de Fisiologia, Escola de Medicina, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Aline S Miranda
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Marco A M Prado
- Robarts Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada; Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada; Brain and Mind Institute, University of Western Ontario, London, Canada
| | - Vânia F Prado
- Robarts Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada; Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada; Brain and Mind Institute, University of Western Ontario, London, Canada
| | - Cristina Guatimosim
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
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Caillet AH, Phillips ATM, Modenese L, Farina D. NeuroMechanics: Electrophysiological and computational methods to accurately estimate the neural drive to muscles in humans in vivo. J Electromyogr Kinesiol 2024; 76:102873. [PMID: 38518426 DOI: 10.1016/j.jelekin.2024.102873] [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] [Indexed: 03/24/2024] Open
Abstract
The ultimate neural signal for muscle control is the neural drive sent from the spinal cord to muscles. This neural signal comprises the ensemble of action potentials discharged by the active spinal motoneurons, which is transmitted to the innervated muscle fibres to generate forces. Accurately estimating the neural drive to muscles in humans in vivo is challenging since it requires the identification of the activity of a sample of motor units (MUs) that is representative of the active MU population. Current electrophysiological recordings usually fail in this task by identifying small MU samples with over-representation of higher-threshold with respect to lower-threshold MUs. Here, we describe recent advances in electrophysiological methods that allow the identification of more representative samples of greater numbers of MUs than previously possible. This is obtained with large and very dense arrays of electromyographic electrodes. Moreover, recently developed computational methods of data augmentation further extend experimental MU samples to infer the activity of the full MU pool. In conclusion, the combination of new electrode technologies and computational modelling allows for an accurate estimate of the neural drive to muscles and opens new perspectives in the study of the neural control of movement and in neural interfacing.
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Affiliation(s)
| | - Andrew T M Phillips
- Department of Civil and Environmental Engineering, Imperial College London, UK
| | - Luca Modenese
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia.
| | - Dario Farina
- Department of Bioengineering, Imperial College London, UK.
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Ortega DG, Housh TJ, Smith RW, Arnett JE, Neltner TJ, Schmidt RJ, Johnson GO. The Effects of Anchoring a Fatiguing Forearm Flexion Task to a High vs. Low Rating of Perceived Exertion on Torque and Neuromuscular Responses. J Strength Cond Res 2024; 38:e219-e225. [PMID: 38662889 DOI: 10.1519/jsc.0000000000004730] [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: 05/04/2024]
Abstract
ABSTRACT Ortega, DG, Housh, TJ, Smith, RW, Arnett, JE, Neltner, TJ, Schmidt, RJ, and Johnson, GO. The effects of anchoring a fatiguing forearm flexion task to a high versus low rating of perceived exertion on torque and neuromuscular responses. J Strength Cond Res 38(5): e219-e225, 2024-This study examined the torque and neuromuscular responses following sustained, isometric, forearm flexion tasks anchored to 2 ratings of perceived exertion (RPE). Nine men (mean ± SD: age = 21.0 ± 2.4 years; height = 179.5 ± 5.1 cm; body mass = 79.6 ± 11.4 kg) completed maximal voluntary isometric contractions (MVIC) before and after sustained, isometric, forearm flexion tasks to failure anchored to RPE = 2 and RPE = 8. The amplitude (AMP) and mean power frequency (MPF) of the electromyographic (EMG) signal were recorded from the biceps brachii. Normalized torque was divided by normalized EMG AMP to calculate neuromuscular efficiency (NME). A dependent t-test was used to assess the mean difference for time to task failure (TTF). Repeated-measures analysis of variances was used to compare mean differences for MVIC and normalized neuromuscular parameters. There was no significant difference in TTF between RPE = 2 and RPE = 8 (p = 0.713). The MVIC decreased from pretest to posttest at RPE = 2 (p = 0.009) and RPE = 8 (p = 0.003), and posttest MVIC at RPE = 8 was less than that at RPE = 2 (p < 0.001). In addition, NME decreased from pretest to posttest (p = 0.008). There was no change in normalized EMG AMP or EMG MPF (p > 0.05). The current findings indicated that torque responses were intensity specific, but TTF and neuromuscular responses were not. Furthermore, normalized EMG AMP and EMG MPF remained unchanged but NME decreased, likely due to peripheral fatigue and excitation-contraction coupling failure. Thus, this study provides information regarding the neuromuscular responses and mechanisms of fatigue associated with tasks anchored to RPE, which adds to the foundational understanding of the relationship between resistance exercise and the perception of fatigue.
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Affiliation(s)
- Dolores G Ortega
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska; and
| | - Terry J Housh
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska; and
| | - Robert W Smith
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska; and
| | - Jocelyn E Arnett
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska; and
| | - Tyler J Neltner
- Department of Health and Human Performance, University of Wisconsin-Platteville, Platteville, Wisconsin
| | - Richard J Schmidt
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska; and
| | - Glen O Johnson
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska; and
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Ogalo E, Linde LD, Ro H, Ortiz O, Kramer JLK, Berger MJ. Evaluating peripheral neuromuscular function with brief movement-evoked pain. J Neurophysiol 2024; 131:789-796. [PMID: 38353653 PMCID: PMC11383610 DOI: 10.1152/jn.00472.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 02/01/2024] [Accepted: 02/11/2024] [Indexed: 04/24/2024] Open
Abstract
Movement-evoked pain is an understudied manifestation of musculoskeletal conditions that contributes to disability, yet little is known about how the neuromuscular system responds to movement-evoked pain. The present study examined whether movement-evoked pain impacts force production, electromyographic (EMG) muscle activity, and the rate of force development (RFD) during submaximal muscle contractions. Fifteen healthy adults (9 males; age = 30.3 ± 10.2 yr, range = 22-59 yr) performed submaximal isometric first finger abduction contractions without pain (baseline) and with movement-evoked pain induced by laser stimulation to the dorsum of the hand. Normalized force (% maximal voluntary contraction) and RFD decreased by 11% (P < 0.001) and 15% (P = 0.003), respectively, with movement-evoked pain, without any change in normalized peak EMG (P = 0.77). Early contractile RFD, force impulse, and corresponding EMG amplitude computed within time segments of 50, 100, 150, and 200 ms relative to the onset of movement were also unaffected by movement-evoked pain (P > 0.05). Our results demonstrate that movement-evoked pain impairs peak characteristics and not early measures of submaximal force production and RFD, without affecting EMG activity (peak and early). Possible explanations for the stability in EMG with reduced force include antagonist coactivation and a reorganization of motoneuronal activation strategy, which is discussed here.NEW & NOTEWORTHY We provide neurophysiological evidence to indicate that peak force and rate of force development are reduced by movement-evoked pain despite a lack of change in EMG and early rapid force development in the first dorsal interosseous muscle. Additional evidence suggests that these findings may coexist with a reorganization in motoneuronal activation strategy.
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Affiliation(s)
- Emmanuel Ogalo
- International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Lukas D Linde
- International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada
| | - Hannah Ro
- International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada
| | - Oscar Ortiz
- International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada
| | - John L K Kramer
- International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael J Berger
- International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada
- Division of Physical Medicine and Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Marsala MJ, Christie AD. Neuromuscular behaviour in the first dorsal interosseus following mental fatigue. Exp Physiol 2024; 109:416-426. [PMID: 38130030 PMCID: PMC10988746 DOI: 10.1113/ep091349] [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: 06/13/2023] [Accepted: 11/28/2023] [Indexed: 12/23/2023]
Abstract
We examined sex-specific changes to neuromuscular function in response to mental fatigue. Twenty-five young, healthy adults (13 F, 12 M) performed a mentally fatiguing task and control condition for 30 min on two separate days. Neuromuscular function was assessed in the first dorsal interosseous before and after each condition. Reaction time decreased after the mentally fatiguing task (P < 0.001, η2 = 0.47). Males and females reported higher levels of subjective fatigue after the mentally fatiguing task (P < 0.02, η2 = 0.07). Motor unit firing rate increased over time at 10% maximal voluntary contraction (MVC; P < 0.04, η2 = 0.16), and decreased over time at 50% MVC (P < 0.01, η2 = 0.14); however, this was not unique to either sex. During a variable force contraction, error decreased in females over time and increased in males (P < 0.05, η2 = 0.13), although changes were not unique to mental fatigue. Physiological function of the neuromuscular system was not specifically affected by mental fatigue in males or females.
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Affiliation(s)
- Michael J. Marsala
- School of Kinesiology, Faculty of Health SciencesThe University of Western OntarioOntarioCanada
| | - Anita D. Christie
- School of Kinesiology, Faculty of Health SciencesThe University of Western OntarioOntarioCanada
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Heskamp L, Birkbeck MG, Baxter-Beard D, Hall J, Schofield IS, Elameer M, Whittaker RG, Blamire AM. Motor Unit Magnetic Resonance Imaging (MUMRI) In Skeletal Muscle. J Magn Reson Imaging 2024. [PMID: 38216545 DOI: 10.1002/jmri.29218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 12/19/2023] [Accepted: 12/20/2023] [Indexed: 01/14/2024] Open
Abstract
Magnetic resonance imaging (MRI) is routinely used in the musculoskeletal system to measure skeletal muscle structure and pathology in health and disease. Recently, it has been shown that MRI also has promise for detecting the functional changes, which occur in muscles, commonly associated with a range of neuromuscular disorders. This review focuses on novel adaptations of MRI, which can detect the activity of the functional sub-units of skeletal muscle, the motor units, referred to as "motor unit MRI (MUMRI)." MUMRI utilizes pulsed gradient spin echo, pulsed gradient stimulated echo and phase contrast MRI sequences and has, so far, been used to investigate spontaneous motor unit activity (fasciculation) and used in combination with electrical nerve stimulation to study motor unit morphology and muscle twitch dynamics. Through detection of disease driven changes in motor unit activity, MUMRI shows promise as a tool to aid in both earlier diagnosis of neuromuscular disorders and to help in furthering our understanding of the underlying mechanisms, which proceed gross structural and anatomical changes within diseased muscle. Here, we summarize evidence for the use of MUMRI in neuromuscular disorders and discuss what future research is required to translate MUMRI toward clinical practice. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 3.
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Affiliation(s)
- Linda Heskamp
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle Upon Tyne, UK
- Department of Radiology, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Matthew G Birkbeck
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle Upon Tyne, UK
- Newcastle Biomedical Research Centre (BRC), Newcastle University, Newcastle upon Tyne, UK
- Northern Medical Physics and Clinical Engineering, Freeman Hospital, Newcastle upon Tyne NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Daniel Baxter-Beard
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle Upon Tyne, UK
| | - Julie Hall
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle Upon Tyne, UK
- Department of Neuroradiology, Royal Victoria Infirmary, Newcastle upon Tyne NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Ian S Schofield
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle Upon Tyne, UK
| | - Mathew Elameer
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle Upon Tyne, UK
- Department of Neuroradiology, Royal Victoria Infirmary, Newcastle upon Tyne NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Roger G Whittaker
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle Upon Tyne, UK
- Directorate of Clinical Neurosciences, Royal Victoria Infirmary, Newcastle upon Tyne NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Andrew M Blamire
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle Upon Tyne, UK
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Schmid L, Klotz T, Röhrle O, Powers RK, Negro F, Yavuz UŞ. Postinhibitory excitation in motoneurons can be facilitated by hyperpolarization-activated inward currents: A simulation study. PLoS Comput Biol 2024; 20:e1011487. [PMID: 38241412 PMCID: PMC10843122 DOI: 10.1371/journal.pcbi.1011487] [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] [Received: 09/05/2023] [Revised: 02/05/2024] [Accepted: 01/09/2024] [Indexed: 01/21/2024] Open
Abstract
Postinhibitory excitation is a transient overshoot of a neuron's baseline firing rate following an inhibitory stimulus and can be observed in vivo in human motoneurons. However, the biophysical origin of this phenomenon is still unknown and both reflex pathways and intrinsic motoneuron properties have been proposed. We hypothesized that postinhibitory excitation in motoneurons can be facilitated by hyperpolarization-activated inward currents (h-currents). Using an electrical circuit model, we investigated how h-currents can modulate the postinhibitory response of motoneurons. Further, we analyzed the spike trains of human motor units from the tibialis anterior muscle during reciprocal inhibition. The simulations revealed that the activation of h-currents by an inhibitory postsynaptic potential can cause a short-term increase in a motoneuron's firing probability. This result suggests that the neuron can be excited by an inhibitory stimulus. In detail, the modulation of the firing probability depends on the time delay between the inhibitory stimulus and the previous action potential. Further, the postinhibitory excitation's strength correlates with the inhibitory stimulus's amplitude and is negatively correlated with the baseline firing rate as well as the level of input noise. Hallmarks of h-current activity, as identified from the modeling study, were found in 50% of the human motor units that showed postinhibitory excitation. This study suggests that h-currents can facilitate postinhibitory excitation and act as a modulatory system to increase motoneuron excitability after a strong inhibition.
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Affiliation(s)
- Laura Schmid
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany
| | - Thomas Klotz
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany
| | - Oliver Röhrle
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany
- Stuttgart Center for Simulation Sciences (SC SimTech), University of Stuttgart, Stuttgart, Germany
| | - Randall K. Powers
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
| | - Utku Ş. Yavuz
- Department of Biomedical Signals and Systems, Faculty of Electrical Engineering, Mathematics and Computer Sciences, University of Twente, Enschede, Netherlands
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8
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Rubin N, Hinson R, Saul K, Hu X, Huang H. Ankle Torque Estimation With Motor Unit Discharges in Residual Muscles Following Lower-Limb Amputation. IEEE Trans Neural Syst Rehabil Eng 2023; 31:4821-4830. [PMID: 38015668 PMCID: PMC10752569 DOI: 10.1109/tnsre.2023.3336543] [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] [Indexed: 11/30/2023]
Abstract
There has been increased interest in using residual muscle activity for neural control of powered lower-limb prostheses. However, only surface electromyography (EMG)-based decoders have been investigated. This study aims to investigate the potential of using motor unit (MU)-based decoding methods as an alternative to EMG-based intent recognition for ankle torque estimation. Eight people without amputation (NON) and seven people with amputation (AMP) participated in the experiments. Subjects conducted isometric dorsi- and plantarflexion with their intact limb by tracing desired muscle activity of the tibialis anterior (TA) and gastrocnemius (GA) while ankle torque was recorded. To match phantom limb and intact limb activity, AMP mirrored muscle activation with their residual TA and GA. We compared neuromuscular decoders (linear regression) for ankle joint torque estimation based on 1) EMG amplitude (aEMG), 2) MU firing frequencies representing neural drive (ND), and 3) MU firings convolved with modeled twitch forces (MUDrive). In addition, sensitivity analysis and dimensionality reduction of optimization were performed on the MUDrive method to further improve its practical value. Our results suggest MUDrive significantly outperforms (lower root-mean-square error) EMG and ND methods in muscles of NON, as well as both intact and residual muscles of AMP. Reducing the number of optimized MUDrive parameters degraded performance. Even so, optimization computational time was reduced and MUDrive still outperformed aEMG. Our outcomes indicate integrating MU discharges with modeled biomechanical outputs may provide a more accurate torque control signal than direct EMG control of assistive, lower-limb devices, such as exoskeletons and powered prostheses.
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Caillet AH, Phillips ATM, Farina D, Modenese L. Motoneuron-driven computational muscle modelling with motor unit resolution and subject-specific musculoskeletal anatomy. PLoS Comput Biol 2023; 19:e1011606. [PMID: 38060619 PMCID: PMC10729998 DOI: 10.1371/journal.pcbi.1011606] [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] [Received: 06/26/2023] [Revised: 12/19/2023] [Accepted: 10/16/2023] [Indexed: 12/20/2023] Open
Abstract
The computational simulation of human voluntary muscle contraction is possible with EMG-driven Hill-type models of whole muscles. Despite impactful applications in numerous fields, the neuromechanical information and the physiological accuracy such models provide remain limited because of multiscale simplifications that limit comprehensive description of muscle internal dynamics during contraction. We addressed this limitation by developing a novel motoneuron-driven neuromuscular model, that describes the force-generating dynamics of a population of individual motor units, each of which was described with a Hill-type actuator and controlled by a dedicated experimentally derived motoneuronal control. In forward simulation of human voluntary muscle contraction, the model transforms a vector of motoneuron spike trains decoded from high-density EMG signals into a vector of motor unit forces that sum into the predicted whole muscle force. The motoneuronal control provides comprehensive and separate descriptions of the dynamics of motor unit recruitment and discharge and decodes the subject's intention. The neuromuscular model is subject-specific, muscle-specific, includes an advanced and physiological description of motor unit activation dynamics, and is validated against an experimental muscle force. Accurate force predictions were obtained when the vector of experimental neural controls was representative of the discharge activity of the complete motor unit pool. This was achieved with large and dense grids of EMG electrodes during medium-force contractions or with computational methods that physiologically estimate the discharge activity of the motor units that were not identified experimentally. This neuromuscular model advances the state-of-the-art of neuromuscular modelling, bringing together the fields of motor control and musculoskeletal modelling, and finding applications in neuromuscular control and human-machine interfacing research.
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Affiliation(s)
- Arnault H. Caillet
- Department of Civil and Environmental Engineering, Imperial College London, London, United Kingdom
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Andrew T. M. Phillips
- Department of Civil and Environmental Engineering, Imperial College London, London, United Kingdom
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Luca Modenese
- Department of Civil and Environmental Engineering, Imperial College London, London, United Kingdom
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
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10
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Babcock CD, Volk VL, Zeng W, Hamilton LD, Shelburne KB, Fitzpatrick CK. Neural-driven activation of 3D muscle within a finite element framework: exploring applications in healthy and neurodegenerative simulations. Comput Methods Biomech Biomed Engin 2023:1-11. [PMID: 37966863 PMCID: PMC11093887 DOI: 10.1080/10255842.2023.2280772] [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: 09/14/2023] [Accepted: 11/02/2023] [Indexed: 11/16/2023]
Abstract
This paper presents a novel computational framework for neural-driven finite element muscle models, with an application to amyotrophic lateral sclerosis (ALS). The multiscale neuromusculoskeletal (NMS) model incorporates physiologically accurate motor neurons, 3D muscle geometry, and muscle fiber recruitment. It successfully predicts healthy muscle force and tendon elongation and demonstrates a progressive decline in muscle force due to ALS, dropping from 203 N (healthy) to 155 N (120 days after ALS onset). This approach represents a preliminary step towards developing integrated neural and musculoskeletal simulations to enhance our understanding of neurodegenerative and neurodevelopmental conditions through predictive NMS models.
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Affiliation(s)
- Colton D. Babcock
- Mechanical and Biomedical Engineering, Boise State University, Boise, ID
| | - Victoria L. Volk
- Mechanical and Biomedical Engineering, Boise State University, Boise, ID
| | - Wei Zeng
- Department of Mechanical Engineering, New York Institute of Technology, New York, NY
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11
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Ricotta JM, De SD, Nardon M, Benamati A, Latash ML. Effects of fatigue on intramuscle force-stabilizing synergies. J Appl Physiol (1985) 2023; 135:1023-1035. [PMID: 37732378 DOI: 10.1152/japplphysiol.00419.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/22/2023] [Accepted: 09/14/2023] [Indexed: 09/22/2023] Open
Abstract
We applied the recently introduced concept of intramuscle synergies in spaces of motor units (MUs) to quantify indexes of such synergies in the tibialis anterior during ankle dorsiflexion force production tasks and their changes with fatigue. We hypothesized that MUs would be organized into robust groups (MU modes), which would covary across trials to stabilize force magnitude, and the indexes of such synergies would drop under fatigue. Healthy, young subjects (n = 15; 8 females) produced cyclical, isometric dorsiflexion forces while surface electromyography was used to identify action potentials of individual MUs. Principal component analysis was used to define MU modes. The framework of the uncontrolled manifold (UCM) was used to analyze intercycle variance and compute the synergy index, ΔVZ. Cyclical force production tasks were repeated after a nonfatiguing exercise (control) and a fatiguing exercise. Across subjects, fatigue led, on average, to a 43% drop in maximal force and fewer identified MUs per subject (29.6 ± 2.1 vs. 32.4 ± 2.1). The first two MU modes accounted for 81.2 ± 0.08% of variance across conditions. Force-stabilizing synergies were present across all conditions and were diminished after fatiguing exercise (1.49 ± 0.40) but not control exercise (1.76 ± 0.75). Decreased stability after fatigue was caused by an increase in the amount of variance orthogonal to the UCM. These findings contrast with earlier studies of multieffector synergies demonstrating increased synergy index under fatigue. We interpret the results as reflections of a drop in the gain of spinal reflex loops under fatigue. The findings corroborate an earlier hypothesis on the spinal nature of intramuscle synergies.NEW & NOTEWORTHY Across multielement force production tasks, fatigue of an element leads to increased indexes of force stability (synergy indexes). Here, however, we show that groups of motor units in the tibialis anterior show decreased indexes of force-stabilizing synergies after fatiguing exercise. These findings align intramuscle synergies with spinal mechanisms, in contrast to the supraspinal control of multimuscle synergies.
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Affiliation(s)
- Joseph M Ricotta
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
- Clinical and Translational Science Institute, Penn State College of Medicine, Hershey, Pennsylvania, United States
| | - Sayan D De
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - Mauro Nardon
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Anna Benamati
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Mark L Latash
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
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12
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Gogeascoechea A, Ornelas-Kobayashi R, Yavuz US, Sartori M. Characterization of Motor Unit Firing and Twitch Properties for Decoding Musculoskeletal Force in the Human Ankle Joint In Vivo. IEEE Trans Neural Syst Rehabil Eng 2023; 31:4040-4050. [PMID: 37756177 DOI: 10.1109/tnsre.2023.3319959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2023]
Abstract
Understanding how motor units (MUs) contribute to skeletal mechanical force is crucial for unraveling the underlying mechanism of human movement. Alterations in MU firing, contractile and force-generating properties emerge in response to physical training, aging or injury. However, how changes in MU firing and twitch properties dictate skeletal muscle force generation in healthy and impaired individuals remains an open question. In this work, we present a MU-specific approach to identify firing and twitch properties of MU samples and employ them to decode musculoskeletal function in vivo. First, MU firing events were decomposed offline from high-density electromyography (HD-EMG) of six lower leg muscles involved in ankle plantar-dorsi flexion. We characterized their twitch responses based on the statistical distributions of their firing properties and employed them to compute MU-specific activation dynamics. Subsequently, we decoded ankle joint moments by linking our framework to a subject-specific musculoskeletal model. We validated our approach at different ankle positions and levels of activation and compared it with traditional EMG-driven models. Our proposed MU-specific formulation achieves higher generalization across conditions than the EMG-driven models, with significantly lower coefficients of variation in torque predictions. Furthermore, our approach shows distinct neural strategies across a large repertoire of contractile conditions in different muscles. Our proposed approach may open new avenues for characterizing the relationship between MU firing and twitch properties and their influence on force capacity. This can facilitate the development of targeted rehabilitation strategies tailored to individuals with specific neuromuscular conditions.
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Eisner-Janowicz I, Chen B, Sangari S, Perez MA. Corticospinal excitability across lower limb muscles in humans. J Neurophysiol 2023; 130:788-797. [PMID: 37435645 PMCID: PMC10648929 DOI: 10.1152/jn.00207.2023] [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: 05/18/2023] [Revised: 07/06/2023] [Accepted: 07/07/2023] [Indexed: 07/13/2023] Open
Abstract
Electrophysiological studies in nonhuman primates reported the existence of strong corticospinal output from the primary motor cortex to distal compared with proximal hindlimb muscles. The extent to which corticospinal output differs across muscles in the leg in humans remains poorly understood. Using transcranial magnetic stimulation over the leg representation of the primary motor cortex, we constructed motor evoked potential (MEP) recruitment curves to measure the resting motor threshold (RMT), maximum MEP amplitude (MEP-max), and slope in the biceps femoris, rectus femoris, tibialis anterior, soleus, and a foot muscle (i.e., abductor hallucis) in intact humans. We found that the RMT was lower and the MEP-max and slope were larger in the abductor hallucis compared with most other muscles tested. In contrast, the RMT was higher and the MEP-max and slope were lower in the biceps femoris compared to all other muscles tested. Corticospinal responses in the rectus femoris, tibialis anterior, and soleus were in between those obtained from other leg muscles, with the soleus having a higher RMT and lower MEP-max and slope than the rectus femoris and tibialis anterior. To examine the origin of increases in corticospinal excitability in the abductor hallucis, we compared short-interval intracortical inhibition (SICI) and F-waves between the abductor hallucis and tibialis anterior. SICI was similar across muscles while the F-wave amplitude was larger in the abductor hallucis compared with the tibialis anterior. These results support a nonuniform distribution of corticospinal output to leg muscles, highlighting that increases in corticospinal excitability in a foot muscle could be related to a spinal origin.NEW & NOTEWORTHY We provide evidence on how corticospinal output differs across muscles in the leg in intact humans. We found that corticospinal responses were larger in a distal intrinsic foot muscle and were smaller in the biceps femoris compared to all other muscles in the leg. Increases in corticospinal excitability to an intrinsic foot muscle could have a spinal origin.
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Affiliation(s)
| | - Bing Chen
- Shirley Ryan AbilityLab, Chicago, Illinois, United States
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, Illinois, United States
- Edward Hines Jr. VA Hospital, Hines, Illinois, United States
| | - Sina Sangari
- Shirley Ryan AbilityLab, Chicago, Illinois, United States
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, Illinois, United States
| | - Monica A Perez
- Shirley Ryan AbilityLab, Chicago, Illinois, United States
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, Illinois, United States
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, Illinois, United States
- Edward Hines Jr. VA Hospital, Hines, Illinois, United States
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14
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Lloyd EM, Pinniger GJ, Murphy RM, Grounds MD. Slow or fast: Implications of myofibre type and associated differences for manifestation of neuromuscular disorders. Acta Physiol (Oxf) 2023; 238:e14012. [PMID: 37306196 DOI: 10.1111/apha.14012] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 05/30/2023] [Accepted: 06/06/2023] [Indexed: 06/13/2023]
Abstract
Many neuromuscular disorders can have a differential impact on a specific myofibre type, forming the central premise of this review. The many different skeletal muscles in mammals contain a spectrum of slow- to fast-twitch myofibres with varying levels of protein isoforms that determine their distinctive contractile, metabolic, and other properties. The variations in functional properties across the range of classic 'slow' to 'fast' myofibres are outlined, combined with exemplars of the predominantly slow-twitch soleus and fast-twitch extensor digitorum longus muscles, species comparisons, and techniques used to study these properties. Other intrinsic and extrinsic differences are discussed in the context of slow and fast myofibres. These include inherent susceptibility to damage, myonecrosis, and regeneration, plus extrinsic nerves, extracellular matrix, and vasculature, examined in the context of growth, ageing, metabolic syndrome, and sexual dimorphism. These many differences emphasise the importance of carefully considering the influence of myofibre-type composition on manifestation of various neuromuscular disorders across the lifespan for both sexes. Equally, understanding the different responses of slow and fast myofibres due to intrinsic and extrinsic factors can provide deep insight into the precise molecular mechanisms that initiate and exacerbate various neuromuscular disorders. This focus on the influence of different myofibre types is of fundamental importance to enhance translation for clinical management and therapies for many skeletal muscle disorders.
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Affiliation(s)
- Erin M Lloyd
- Department of Anatomy, Physiology and Human Biology, School of Human Sciences, The University of Western Australia, Perth, Western Australia, Australia
- Curtin Health Innovation Research Institute, Curtin Medical School, Curtin University, Bentley, Western Australia, Australia
| | - Gavin J Pinniger
- Department of Anatomy, Physiology and Human Biology, School of Human Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Robyn M Murphy
- Department of Biochemistry and Chemistry, School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Victoria, Australia
| | - Miranda D Grounds
- Department of Anatomy, Physiology and Human Biology, School of Human Sciences, The University of Western Australia, Perth, Western Australia, Australia
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15
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Joyner MJ, Wiggins CC, Baker SE, Klassen SA, Senefeld JW. Exercise and Experiments of Nature. Compr Physiol 2023; 13:4879-4907. [PMID: 37358508 PMCID: PMC10853940 DOI: 10.1002/cphy.c220027] [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: 06/27/2023]
Abstract
In this article, we highlight the contributions of passive experiments that address important exercise-related questions in integrative physiology and medicine. Passive experiments differ from active experiments in that passive experiments involve limited or no active intervention to generate observations and test hypotheses. Experiments of nature and natural experiments are two types of passive experiments. Experiments of nature include research participants with rare genetic or acquired conditions that facilitate exploration of specific physiological mechanisms. In this way, experiments of nature are parallel to classical "knockout" animal models among human research participants. Natural experiments are gleaned from data sets that allow population-based questions to be addressed. An advantage of both types of passive experiments is that more extreme and/or prolonged exposures to physiological and behavioral stimuli are possible in humans. In this article, we discuss a number of key passive experiments that have generated foundational medical knowledge or mechanistic physiological insights related to exercise. Both natural experiments and experiments of nature will be essential to generate and test hypotheses about the limits of human adaptability to stressors like exercise. © 2023 American Physiological Society. Compr Physiol 13:4879-4907, 2023.
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Affiliation(s)
- Michael J Joyner
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Chad C Wiggins
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - Sarah E Baker
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Stephen A Klassen
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Jonathon W Senefeld
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, USA
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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16
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Casolo A, Maeo S, Balshaw TG, Lanza MB, Martin NRW, Nuccio S, Moro T, Paoli A, Felici F, Maffulli N, Eskofier B, Kinfe TM, Folland JP, Farina D, Vecchio AD. Non-invasive estimation of muscle fibre size from high-density electromyography. J Physiol 2023; 601:1831-1850. [PMID: 36929484 DOI: 10.1113/jp284170] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 03/13/2023] [Indexed: 03/18/2023] Open
Abstract
Because of the biophysical relation between muscle fibre diameter and the propagation velocity of action potentials along the muscle fibres, motor unit conduction velocity could be a non-invasive index of muscle fibre size in humans. However, the relation between motor unit conduction velocity and fibre size has been only assessed indirectly in animal models and in human patients with invasive intramuscular EMG recordings, or it has been mathematically derived from computer simulations. By combining advanced non-invasive techniques to record motor unit activity in vivo, i.e. high-density surface EMG, with the gold standard technique for muscle tissue sampling, i.e. muscle biopsy, here we investigated the relation between the conduction velocity of populations of motor units identified from the biceps brachii muscle, and muscle fibre diameter. We demonstrate the possibility of predicting muscle fibre diameter (R2 = 0.66) and cross-sectional area (R2 = 0.65) from conduction velocity estimates with low systematic bias (∼2% and ∼4% respectively) and a relatively low margin of individual error (∼8% and ∼16%, respectively). The proposed neuromuscular interface opens new perspectives in the use of high-density EMG as a non-invasive tool to estimate muscle fibre size without the need of surgical biopsy sampling. The non-invasive nature of high-density surface EMG for the assessment of muscle fibre size may be useful in studies monitoring child development, ageing, space and exercise physiology, although the applicability and validity of the proposed methodology need to be more directly assessed in these specific populations by future studies. KEY POINTS: Because of the biophysical relation between muscle fibre size and the propagation velocity of action potentials along the sarcolemma, motor unit conduction velocity could represent a potential non-invasive candidate for estimating muscle fibre size in vivo. This relation has been previously assessed in animal models and humans with invasive techniques, or it has been mathematically derived from simulations. By combining high-density surface EMG with muscle biopsy, here we explored the relation between the conduction velocity of populations of motor units and muscle fibre size in healthy individuals. Our results confirmed that motor unit conduction velocity can be considered as a novel biomarker of fibre size, which can be adopted to predict muscle fibre diameter and cross-sectional area with low systematic bias and margin of individual error. The proposed neuromuscular interface opens new perspectives in the use of high-density EMG as a non-invasive tool to estimate muscle fibre size without the need of surgical biopsy sampling.
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Affiliation(s)
- Andrea Casolo
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Sumiaki Maeo
- Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
| | - Thomas G Balshaw
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
- Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, UK
| | - Marcel B Lanza
- Department of Physical Therapy and Rehabilitation Science, University of Maryland, Baltimore, MD, USA
| | - Neil R W Martin
- Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, UK
| | - Stefano Nuccio
- Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Tatiana Moro
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Antonio Paoli
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Francesco Felici
- Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Nicola Maffulli
- Department of Trauma and Orthopaedic Surgery, School Medicine, Surgery and Dentistry, University of Salerno, Salerno, Italy
- School of Pharmacy and Bioengineering, Keele University School of Medicine, Stoke on Trent, UK
- Queen Mary University of London, Barts and the London School of Medicine and Dentistry, Centre for Sports and Exercise Medicine, Mile End Hospital, London, UK
| | - Bjoern Eskofier
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Thomas M Kinfe
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Jonathan P Folland
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
- Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, UK
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, UK
| | - Alessandro Del Vecchio
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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Smith RW, Housh TJ, Arnett JE, Anders JPV, Neltner TJ, Ortega DG, Schmidt RJ, Johnson GO. The Effects of Anchor Schemes on Performance Fatigability, Neuromuscular Responses and the Perceived Sensations That Contributed to Task Termination. J Funct Morphol Kinesiol 2023; 8:jfmk8020049. [PMID: 37218845 DOI: 10.3390/jfmk8020049] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/18/2023] [Accepted: 04/20/2023] [Indexed: 05/24/2023] Open
Abstract
The present study examined the effect of anchor schemes on the time to task failure (TTF), performance fatigability, neuromuscular responses, and the perceived sensations that contributed to task termination following the sustained, isometric forearm flexion tasks. Eight women completed sustained, isometric forearm flexion tasks anchored to RPE = 8 (RPEFT) and the torque (TRQFT) that corresponded to RPE = 8. The subjects performed pre-test and post-test maximal isometric contractions to quantify performance fatigability and changes in electromyographic amplitude (EMG AMP) and neuromuscular efficiency (NME). In addition, the subjects completed a post-test questionnaire (PTQ) to quantify the contributions of perceived sensations to task termination. Repeated measure ANOVAs were used to assess the mean differences for TTF, performance fatigability, and neuromuscular responses. Wilcoxon Signed Rank Tests were used to assess the differences between anchor schemes for the average values from the PTQ item scores. For TTF, the RPEFT was longer than the TRQFT (174.9 ± 85.6 vs. 65.6 ± 68.0 s; p = 0.006). Collapsed across the anchor scheme, there were decreases in torque (23.7 ± 5.5 Nm vs. 19.6 ± 4.9 Nm; p < 0.001) and NME (1.00 ± 0.00 vs. 0.76 ± 0.15; p = 0.003). There were no significant (p > 0.577) changes for EMG AMP. For the PTQ, there were no differences (p > 0.05) between anchor schemes. There were, however, inter-individual differences in the response scores. The current findings indicated that performance fatigability was likely due to peripheral fatigue (based on NME), not central fatigue (based on EMG AMP). Furthermore, the use of a PTQ may serve as a simple tool to assess the contributions of perceived sensations to task termination.
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Affiliation(s)
- Robert W Smith
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68510, USA
| | - Terry J Housh
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68510, USA
| | - Jocelyn E Arnett
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68510, USA
| | - John Paul V Anders
- The Exercise Science Program, Department of Human Sciences, The Ohio State University, Columbus, OH 43017, USA
| | - Tyler J Neltner
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68510, USA
| | - Dolores G Ortega
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68510, USA
| | - Richard J Schmidt
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68510, USA
| | - Glen O Johnson
- Exercise Physiology Laboratory, Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68510, USA
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18
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Chung JW, Knight CA, Bower AE, Martello JP, Jeka JJ, Burciu RG. Rate control deficits during pinch grip and ankle dorsiflexion in early-stage Parkinson's disease. PLoS One 2023; 18:e0282203. [PMID: 36867628 PMCID: PMC9983837 DOI: 10.1371/journal.pone.0282203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 02/10/2023] [Indexed: 03/04/2023] Open
Abstract
BACKGROUND Much of our understanding of the deficits in force control in Parkinson's disease (PD) relies on findings in the upper extremity. Currently, there is a paucity of data pertaining to the effect of PD on lower limb force control. OBJECTIVE The purpose of this study was to concurrently evaluate upper- and lower-limb force control in early-stage PD and a group of age- and gender-matched healthy controls. METHODS Twenty individuals with PD and twenty-one healthy older adults participated in this study. Participants performed two visually guided, submaximal (15% of maximum voluntary contractions) isometric force tasks: a pinch grip task and an ankle dorsiflexion task. PD were tested on their more affected side and after overnight withdrawal from antiparkinsonian medication. The tested side in controls was randomized. Differences in force control capacity were assessed by manipulating speed-based and variability-based task parameters. RESULTS Compared with controls, PD demonstrated slower rates of force development and force relaxation during the foot task, and a slower rate of relaxation during the hand task. Force variability was similar across groups but greater in the foot than in the hand in both PD and controls. Lower limb rate control deficits were greater in PD with more severe symptoms based on the Hoehn and Yahr stage. CONCLUSIONS Together, these results provide quantitative evidence of an impaired capacity in PD to produce submaximal and rapid force across multiple effectors. Moreover, results suggest that force control deficits in the lower limb may become more severe with disease progression.
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Affiliation(s)
- Jae Woo Chung
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States of America
| | - Christopher A. Knight
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States of America
- Interdisciplinary Neuroscience Graduate Program, University of Delaware, Newark, DE, United States of America
| | - Abigail E. Bower
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States of America
| | - Justin P. Martello
- Department of Neurosciences, Christiana Care Health System, Newark, DE, United States of America
| | - John J. Jeka
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States of America
- Interdisciplinary Neuroscience Graduate Program, University of Delaware, Newark, DE, United States of America
| | - Roxana G. Burciu
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States of America
- Interdisciplinary Neuroscience Graduate Program, University of Delaware, Newark, DE, United States of America
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19
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Preservation of functional descending input to paralyzed upper extremity muscles in motor complete cervical spinal cord injury. Clin Neurophysiol 2023; 150:56-68. [PMID: 37004296 DOI: 10.1016/j.clinph.2023.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 02/13/2023] [Accepted: 03/01/2023] [Indexed: 03/18/2023]
Abstract
OBJECTIVE Spinal cord injury (SCI) is classified as complete or incomplete depending on the extent of sensorimotor preservation below the injury level. However, individuals with complete SCIs can voluntarily activate paralyzed lower limb muscles alone or by engaging non-paralyzed muscles during neurophysiological assessments, indicating presence of residual pathways across the injury. However, similar phenomena have not been explored for the upper extremity (UE) muscles following cervical SCIs. METHODS Eighteen individuals with motor complete cervical SCI (AIS A or B) and five age-matched non-injured (NI) individuals performed various UE events against manual resistance during functional neurophysiological assessment (FNPA), and electromyographic (EMG) activity was recorded from UE muscles. RESULTS Our findings demonstrated i) voluntary activation of clinically paralyzed muscles as evident from EMG readouts, ii) increased activity in these muscles during events engaging muscles above the injury level, iii) reduced spectral properties of paralyzed muscles in SCI compared to NI participants. CONCLUSIONS Functional EMG activity in clinically paralyzed muscles indicate presence of residual pathways across the injury establishing supralesional control over the sublesional neural circuitry. SIGNIFICANCE The findings may help explain the neurophysiological basis for UE recovery and can be exploited in designing rehabilitation techniques to facilitate UE recovery following cervical SCIs.
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20
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Lanza MB, Lacerda LT, Gurgel Simões M, Martins-Costa HC, Diniz RC, Chagas MH, Lima FV. Normalization of the electromyography amplitude during a multiple-set resistance training protocol: Reliability and differences between approaches. J Electromyogr Kinesiol 2023; 68:102724. [PMID: 36399915 DOI: 10.1016/j.jelekin.2022.102724] [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: 09/01/2022] [Revised: 10/26/2022] [Accepted: 11/02/2022] [Indexed: 11/14/2022] Open
Abstract
The first aim was to investigate the impact of different electromyography (EMG) parameters as a reference to normalize the EMG amplitude of the superficial quadriceps femoris muscles across different sets of a knee extension exercise. The second aim is to examine the reliability between days of the EMG parameters used as a reference. Eleven young males attended the laboratory on 4 different days and performed one repetition maximum test, maximumvoluntary isometric contractions, and a resistance training protocol until failure. Surface EMG was placed over the rectus femoris, vastus lateralis, and vastus medialis muscles. Seven EMG parameters were calculated from the tasks and used to normalize EMG amplitude measured during the resistance training protocol. A repeated-measures two-way ANOVA was used (normalized EMG amplitude × set) to compare normalized EMG across sets, while an intraclass correlation coefficient, coefficient of variation, and Bland-Altman plots were used to calculate the intra-day reliability of the EMG parameters. The present investigation showed that normalized EMG amplitude of the superficial muscles of the quadriceps measured during a knee extension exercise is influenced by the EMG parameter and depends on the muscle. While rectus femoris and vastus lateralis normalized EMG amplitude presented one parameter among seven showing similar value to the other parameters, VM showed two. Lastly, all EMG parameters for all muscles presented an overall excellent reliability and agreement between days.
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Affiliation(s)
- Marcel B Lanza
- Department of Physical Therapy and Rehabilitation, School of Medicine, University of Maryland, Baltimore, United States.
| | - Lucas T Lacerda
- Weight Training Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Federal University of Minas Gerais, Belo Horizonte, Brazil; Department of Physical Education, State University of Minas Gerais, Divinópolis, Brazil
| | - Marina Gurgel Simões
- Weight Training Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Hugo C Martins-Costa
- Department of Physical Education, Pontifical Catholic University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Rodrigo C Diniz
- Weight Training Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Mauro H Chagas
- Weight Training Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Fernando V Lima
- Weight Training Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Federal University of Minas Gerais, Belo Horizonte, Brazil
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21
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Dideriksen J, Del Vecchio A. Adaptations in motor unit properties underlying changes in recruitment, rate coding, and maximum force. J Neurophysiol 2023; 129:235-246. [PMID: 36515411 DOI: 10.1152/jn.00222.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Changes in the discharge characteristics of motor units as well as in the maximum force-producing capacity of the muscle are observed following training, aging, and fatiguability. The ability to measure the adaptations in the neuromuscular properties underlying these changes experimentally, however, is limited. In this study we used a computational model to systematically investigate the effects of various neural and muscular adaptations on motor unit recruitment thresholds, average motor unit discharge rates in submaximal contractions, and maximum force. The primary focus was to identify candidate adaptations that can explain experimentally observed changes in motor unit discharge characteristics after 4 wk of strength training (Del Vecchio A, Casolo A, Negro F, Scorcelletti M, Bazzucchi I, Enoka R, Felici F, Farina D. J Physiol 597: 1873-1887, 2019). The simulation results indicated that multiple combinations of adaptations, likely involving an increase in maximum discharge rate across motor units, may occur after such training. On a more general level, we found that the magnitude of the adaptations scales linearly with the change in recruitment thresholds, discharge rates, and maximum force. In addition, the combination of multiple adaptations can be predicted as the linear sum of their individual effects. Together, this implies that the outcomes of the simulations can be generalized to predict the effect of any combination of neural and muscular adaptations. In this way, the study provides a tool for estimating potential underlying adaptations in neural and muscular properties to explain any change in commonly used measures of rate coding, recruitment, and maximum force.NEW & NOTEWORTHY Our ability to measure adaptations in neuromuscular properties in vivo is limited. Using a computational model, we quantify the effect of multiple neuromuscular adaptations on common measures of motor unit recruitment, rate coding, and force-producing capacity. Scaling and combining adaptations had a near-linear effect on these measures, indicating that the results can explain and predict neuromuscular adaptations in a wide range of conditions, including, but not limited to, strength training.
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Affiliation(s)
- Jakob Dideriksen
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Alessandro Del Vecchio
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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22
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Muceli S, Poppendieck W, Holobar A, Gandevia S, Liebetanz D, Farina D. Blind identification of the spinal cord output in humans with high-density electrode arrays implanted in muscles. SCIENCE ADVANCES 2022; 8:eabo5040. [PMID: 36383647 PMCID: PMC9668292 DOI: 10.1126/sciadv.abo5040] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 10/20/2022] [Indexed: 06/16/2023]
Abstract
Invasive electromyography opened a new window to explore motoneuron behavior in vivo. However, the technique is limited by the small fraction of active motoneurons that can be concurrently detected, precluding a population analysis in natural tasks. Here, we developed a high-density intramuscular electrode for in vivo human recordings along with a fully automatic methodology that could detect the discharges of action potentials of up to 67 concurrently active motoneurons with 99% accuracy. These data revealed that motoneurons of the same pool receive common synaptic input at frequencies up to 75 Hz and that late-recruited motoneurons inhibit the discharges of those recruited earlier. These results constitute an important step in the population coding analysis of the human motor system in vivo.
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Affiliation(s)
- Silvia Muceli
- Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | | | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Simon Gandevia
- Neuroscience Research Australia and University of New South Wales, Randwick, Sydney, New South Wales, Australia
| | - David Liebetanz
- Department of Neurology, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, UK
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Petrovic I, Amiridis IG, Holobar A, Trypidakis G, Kellis E, Enoka RM. Leg Dominance Does Not Influence Maximal Force, Force Steadiness, or Motor Unit Discharge Characteristics. Med Sci Sports Exerc 2022; 54:1278-1287. [PMID: 35324535 DOI: 10.1249/mss.0000000000002921] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE The aim of our study was to compare maximal force, force steadiness, and discharge characteristics of motor units in tibialis anterior during contractions with the dorsiflexors of the dominant and nondominant legs at low-to-moderate target forces and three ankle angles. METHODS Twenty young adults performed maximal and submaximal isometric contractions (5%, 10%, 20%, 40%, and 60% of maximal voluntary contraction (MVC)) with the dorsiflexors of the dominant and nondominant legs at three ankle angles (75°, short length; 90°, intermediate length; 105°, long length). High-density EMG signals from the tibialis anterior muscle of each leg were recorded. RESULTS Maximal force (average dominant, 182.9 ± 64.5 N; nondominant, 179.0 ± 58.8 N) and the fluctuations in force, quantified as absolute (SD) and normalized amplitudes (coefficient of variation (CoV)), were similar between the two legs across the three ankle angles (average CoV for dominant, 1.5% ± 1.0%; nondominant, 1.7% ± 1.3%). The CoV for force for both legs decreased from 5% to 20% MVC force, and then it plateaued at 40% and 60% MVC force. EMG amplitude, mean discharge rate of motor units, discharge variability (interspike interval), and the variability in neural drive (filtered cumulative spike train) were similar between the two legs across the submaximal contractions. CONCLUSIONS MVC force and force steadiness were similar across ankle angles and target forces between the dominant and nondominant legs. The attributes that underlie the self-reported identification of a dominant leg were not associated with the force capacity or the control of force for the dorsiflexor muscles, at least during isometric contractions.
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Affiliation(s)
| | - Ioannis G Amiridis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, GREECE
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, SLOVENIA
| | - Georgios Trypidakis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, GREECE
| | - Eleftherios Kellis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, GREECE
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO
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Škarabot J, Folland JP, Holobar A, Baker SN, Del Vecchio A. Startling stimuli increase maximal motor unit discharge rate and rate of force development in humans. J Neurophysiol 2022; 128:455-469. [PMID: 35829632 PMCID: PMC9423775 DOI: 10.1152/jn.00115.2022] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Maximal rate of force development in adult humans is determined by the maximal motor unit discharge rate, however the origin of the underlying synaptic inputs remains unclear. Here, we tested a hypothesis that the maximal motor unit discharge rate will increase in response to a startling cue, a stimulus that purportedly activates the pontomedullary reticular formation neurons that make mono- and disynaptic connections to motoneurons via fast-conducting axons. Twenty-two men were required to produce isometric knee extensor forces "as fast and as hard" as possible from rest to 75% of maximal voluntary force, in response to visual (VC), visual-auditory (VAC; 80 dB), or visual-startling cue (VSC; 110 dB). Motoneuron activity was estimated via decomposition of high-density surface electromyogram recordings over the vastus lateralis and medialis muscles. Reaction time was significantly shorter in response to VSC compared to VAC and VC. The VSC further elicited faster neuromechanical responses including a greater number of discharges per motor unit per second and greater maximal rate of force development, with no differences between VAC and VC. We provide evidence, for the first time, that the synaptic input to motoneurons increases in response to a startling cue, suggesting a contribution of subcortical pathways to maximal motoneuron output in humans.
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Affiliation(s)
- Jakob Škarabot
- School of Sport, Exercise and Health Sciences, grid.6571.5Loughborough University, Loughborough, United Kingdom
| | - Jonathan P Folland
- School of Sport, Exercise and Health Sciences, grid.6571.5Loughborough University, Loughborough, United Kingdom.,Versus Arthritis Centre for Sport, Exercise and Osteoarthritis, Loughborough University, Loughborough, United Kingdom
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Stuart N Baker
- Medical Faculty, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Alessandro Del Vecchio
- Department of Artificial Intelligence in Biomedical Engineering, University of Erlangen-Nuremberg, Erlangen, Bavaria, Germany
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Heskamp L, Miller AR, Birkbeck MG, Hall J, Schofield I, Blamire AM, Whittaker RG. In vivo 3D imaging of human motor units in upper and lower limb muscles. Clin Neurophysiol 2022; 141:91-100. [PMID: 35853787 DOI: 10.1016/j.clinph.2022.05.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 05/17/2022] [Accepted: 05/30/2022] [Indexed: 11/24/2022]
Abstract
OBJECTIVE To assess in-vivo cross-sectional and 3D morphology of human motor units in hand, forearm and lower leg muscles using magnetic resonance imaging (MRI). METHODS Diffusion weighted MRI was used with in-scanner electrical stimulation in healthy controls to image motor units at a single slice in lower leg, forearm and hand muscles (n = 6) and multiple slices in the lower leg for 3D assessment (n = 7). RESULTS Motor unit cross-sectional area (CSA) and maximum Feret diameter (FDmax) did not differ between the lower leg (CSA: 22.4 ± 8.4 mm2; FDmax: 8.7 ± 2.4 mm), forearm (CSA: 23.6 ± 14.1 mm2; FDmax: 9.0 ± 3.3 mm) and hand (CSA: 26.8 ± 12.8 mm2 and FDmax: 9.6 ± 2.7 mm) (ANOVA; p = 0.487 and p = 0.587, respectively). Lower leg motor units were 8.0 ± 3.8 cm long with largest CSA in the motor unit's middle section. 3D motor unit imaging revealed a complex structure with several units splitting and re-forming along their length. CONCLUSIONS Motor unit MRI (MUMRI) can be applied to upper limb muscles, and can reveal the 3D structure of human motor units in-vivo. SIGNIFICANCE MUMRI provides the first in-vivo 2D images of upper limb motor units and 3D images of lower leg motor units. 3D imaging suggest a more complex human motor unit structure than previously thought.
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