scholarly journals Integration of neural architecture within a finite element framework for improved neuromusculoskeletal modeling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Victoria L. Volk ◽  
Landon D. Hamilton ◽  
Donald R. Hume ◽  
Kevin B. Shelburne ◽  
Clare K. Fitzpatrick
Keyword(s):  
Finite Element ◽  
Motor Unit ◽  
Muscle Activation ◽  
Computational Models ◽  
Integrated Model ◽  
Motor Unit Recruitment ◽  
Average Error ◽  
Neural Architecture ◽  
Rate Coding ◽  
Musculoskeletal Systems

AbstractNeuromusculoskeletal (NMS) models can aid in studying the impacts of the nervous and musculoskeletal systems on one another. These computational models facilitate studies investigating mechanisms and treatment of musculoskeletal and neurodegenerative conditions. In this study, we present a predictive NMS model that uses an embedded neural architecture within a finite element (FE) framework to simulate muscle activation. A previously developed neuromuscular model of a motor neuron was embedded into a simple FE musculoskeletal model. Input stimulation profiles from literature were simulated in the FE NMS model to verify effective integration of the software platforms. Motor unit recruitment and rate coding capabilities of the model were evaluated. The integrated model reproduced previously published output muscle forces with an average error of 0.0435 N. The integrated model effectively demonstrated motor unit recruitment and rate coding in the physiological range based upon motor unit discharge rates and muscle force output. The combined capability of a predictive NMS model within a FE framework can aid in improving our understanding of how the nervous and musculoskeletal systems work together. While this study focused on a simple FE application, the framework presented here easily accommodates increased complexity in the neuromuscular model, the FE simulation, or both.

Noninvasive In Vivo Characterization of Pediatric Human Spine: 3-D Finite Element Study

2011 ◽  
Author(s):  
Elizabeth S. Doughty ◽  
Nesrin Sarigul-Klijn
Keyword(s):  
Finite Element ◽  
Computational Model ◽  
Muscle Activation ◽  
Computational Models ◽  
Three Dimensional ◽  
Pediatric Spine ◽  
Element Analysis ◽  
Spine Stabilization ◽  
Surgical Tool

There are no full three-dimensional computational models of the pediatric spine to study the many diseases and disorders that afflict the immature spine using finite element analysis. To fully characterize the pediatric spine, we created a pediatric specific computational model of C1-L5 using noninvasive in vivo techniques to incorporate the differences between the adult and pediatric spines: un-fused vertebrae, lax ligaments, and higher water content in the intervertebral discs. Muscle follower loads were included in the model to simulate muscle activation for five muscles involved in spine stabilization. This paper is the first pediatric three-dimensional model developed to date. Due to a lack of experimental pediatric spinal studies, this 3-D computational model has the potential to become a surgical tool to ensure that the most appropriate technique is chosen for treating pediatric spinal dysfunctions such as congenital abnormalities, idiopathic scoliosis, and vertebral fractures.

scholarly journals Physiological recruitment of motor units by high-frequency electrical stimulation of afferent pathways

2015 ◽  
Vol 118 (3) ◽  
pp. 365-376 ◽  
Author(s):  
Jakob L. Dideriksen ◽  
Silvia Muceli ◽  
Strahinja Dosen ◽  
Christopher M. Laine ◽  
Dario Farina
Keyword(s):  
Electrical Stimulation ◽  
Motor Unit ◽  
High Frequency ◽  
Muscle Activation ◽  
Motor Units ◽  
H Reflex ◽  
Motor Unit Recruitment ◽  
Afferent Stimulation ◽  
Reflex Responses ◽  
Stimulation Of

Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation, but electrically evoked muscle activation is in several ways different from voluntary muscle contractions. These differences lead to challenges in the use of NMES for restoring muscle function. We investigated the use of low-current, high-frequency nerve stimulation to activate the muscle via the spinal motoneuron (MN) pool to achieve more natural activation patterns. Using a novel stimulation protocol, the H-reflex responses to individual stimuli in a train of stimulation pulses at 100 Hz were reliably estimated with surface EMG during low-level contractions. Furthermore, single motor unit recruitment by afferent stimulation was analyzed with intramuscular EMG. The results showed that substantially elevated H-reflex responses were obtained during 100-Hz stimulation with respect to a lower stimulation frequency. Furthermore, motor unit recruitment using 100-Hz stimulation was not fully synchronized, as it occurs in classic NMES, and the discharge rates differed among motor units because each unit was activated only after a specific number of stimuli. The most likely mechanism behind these observations is the temporal summation of subthreshold excitatory postsynaptic potentials from Ia fibers to the MNs. These findings and their interpretation were also verified by a realistic simulation model of afferent stimulation of a MN population. These results suggest that the proposed stimulation strategy may allow generation of considerable levels of muscle activation by motor unit recruitment that resembles the physiological conditions.

scholarly journals Effect of Acute Static Stretching on the Activation Patterns Using High-Density Surface Electromyography of the Gastrocnemius Muscle during Ramp-Up Task

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4841
Author(s):  
Noriaki Maeda ◽  
Makoto Komiya ◽  
Yuichi Nishikawa ◽  
Masanori Morikawa ◽  
Shogo Tsutsumi ◽  
...  
Keyword(s):  
Motor Unit ◽  
Muscle Activation ◽  
Gastrocnemius Muscle ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Motor Unit Recruitment ◽  
Static Stretching ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Before And After

This study aimed to evaluate motor unit recruitment during submaximal voluntary ramp contraction in the medial head of the gastrocnemius muscle (MG) by high-density spatial electromyography (SEMG) before and after static stretching (SS) in healthy young adults. SS for gastrocnemius was performed in 15 healthy participants for 2 min. Normalized peak torque by bodyweight of the plantar flexor, muscle activity at peak torque, and muscle activation patterns during ramp-up task were evaluated before and after SS. Motor unit recruitment during the submaximal voluntary contraction of the MG was measured using SEMG when performing submaximal ramp contractions during isometric ankle plantar flexion from 30 to 80% of the maximum voluntary contraction (MVC). To evaluate the changes in the potential distribution of SEMG, the root mean square (RMS), modified entropy, and coefficient of variation (CV) were calculated from the dense surface EMG data when 10% of the MVC force was applied. Muscle activation patterns during the 30 to 80% of MVC submaximal voluntary contraction tasks were significantly changed from 50 to 70% of MVC after SS when compared to before. The variations in motor unit recruitment after SS indicate diverse motor unit recruitments and inhomogeneous muscle activities, which may adversely affect the performance of sports activities.

scholarly journals Parallel finite-element implementation for higher-order ice-sheet models

2012 ◽  
Vol 58 (207) ◽  
pp. 76-88 ◽  
Author(s):  
Mauro Perego ◽  
Max Gunzburger ◽  
John Burkardt
Keyword(s):  
Finite Element ◽  
Computational Models ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Integrated Model ◽  
Higher Order ◽  
Order Model ◽  
Length Scales ◽  
First Order ◽  
Finite Element Approximations

AbstractHigher-order models represent a computationally less expensive alternative to the Stokes model for ice-sheet modeling. In this work, we develop linear and quadratic finite-element methods, implemented on parallel architectures, for the three-dimensional first-order model of Dukowicz and others (2010) that is based on the Blatter-Pattyn model, and for the depth-integrated model of Schoof and Hindmarsh (2010). We then apply our computational models to three of the ISMIP-HOM benchmark test cases (Pattyn and others, 2008). We compare results obtained from our models with those obtained using a reliable Stokes computational model, showing that our first-order model implementation produces reliable and accurate solutions for almost all characteristic length scales of the test geometries considered. Good agreement with the reference Stokes solution is also obtained by our depth-integrated model implementation in fast-sliding regimes and for medium to large length scales. We also provide a comprehensive comparison between results obtained from our first-order model implementation and implementations developed by ISMIP-HOM participants; this study shows that our implementation is at least as good as the previous ones. Finally, a comparison between linear and quadratic finite- element approximations is carried out, showing, as expected, the better accuracy of the quadratic finite-element method.

scholarly journals The increase in muscle force after 4 weeks of strength training is mediated by adaptations in motor unit recruitment and rate coding

2019 ◽  
Vol 597 (7) ◽  
pp. 1873-1887 ◽  
Author(s):  
Alessandro Del Vecchio ◽  
Andrea Casolo ◽  
Francesco Negro ◽  
Matteo Scorcelletti ◽  
Ilenia Bazzucchi ◽  
...  
Keyword(s):  
Strength Training ◽  
Motor Unit ◽  
Muscle Force ◽  
Motor Unit Recruitment ◽  
Rate Coding

scholarly journals Ischemic conditioning increases strength and volitional activation of paretic muscle in chronic stroke: a pilot study

2018 ◽  
Vol 124 (5) ◽  
pp. 1140-1147 ◽  
Author(s):  
Allison S. Hyngstrom ◽  
Spencer A. Murphy ◽  
Jennifer Nguyen ◽  
Brian D. Schmit ◽  
Francesco Negro ◽  
...  
Keyword(s):  
Motor Unit ◽  
Muscle Activation ◽  
Knee Extensor ◽  
Chronic Stroke ◽  
Motor Unit Recruitment ◽  
Stroke Survivors ◽  
Single Session ◽  
Ischemic Conditioning ◽  
Leg Strength ◽  
Knee Extensor Strength

Ischemic conditioning (IC) on the arm or leg has emerged as an intervention to improve strength and performance in healthy populations, but the effects on neurological populations are unknown. The purpose of this study was to quantify the effects of a single session of IC on knee extensor strength and muscle activation in chronic stroke survivors. Maximal knee extensor torque measurements and surface EMG were quantified in 10 chronic stroke survivors (>1 yr poststroke) with hemiparesis before and after a single session of IC or sham on the paretic leg. IC consisted of 5 min of compression with a proximal thigh cuff (inflation pressure = 225 mmHg for IC or 25 mmHg for sham) followed by 5 min of rest. This was repeated five times. Maximal knee extensor strength, EMG magnitude, and motor unit firing behavior were measured before and immediately after IC or sham. IC increased paretic leg strength by 10.6 ± 8.5 Nm, whereas no difference was observed in the sham group (change in sham = 1.3 ± 2.9 Nm, P = 0.001 IC vs. sham). IC-induced increases in strength were accompanied by a 31 ± 15% increase in the magnitude of muscle EMG during maximal contractions and a 5% decrease in motor unit recruitment thresholds during submaximal contractions. Individuals who had the most asymmetry in strength between their paretic and nonparetic legs had the largest increases in strength ( r2 = 0.54). This study provides evidence that a single session of IC can increase strength through improved muscle activation in chronic stroke survivors. NEW & NOTEWORTHY Present rehabilitation strategies for chronic stroke survivors do not optimally activate paretic muscle, and this limits potential strength gains. Ischemic conditioning of a limb has emerged as an effective strategy to improve muscle performance in healthy individuals but has never been tested in neurological populations. In this study, we show that ischemic conditioning on the paretic leg of chronic stroke survivors can increase leg strength and muscle activation while reducing motor unit recruitment thresholds.

Neural control of the healthy pectoralis major from low-to-moderate isometric contractions

2021 ◽  
Author(s):  
Tea Lulic-Kuryllo ◽  
Christopher K. Thompson ◽  
ning.jiang Jiang ◽  
Francesco Negro ◽  
Clark Dickerson
Keyword(s):  
Motor Unit ◽  
Neural Control ◽  
Discharge Rate ◽  
Arm Movement ◽  
Shoulder Function ◽  
Pectoralis Major ◽  
Motor Unit Recruitment ◽  
Isometric Contractions ◽  
Motor Unit Discharge ◽  
Rate Coding

The pectoralis major critically enables arm movement in several directions. However, its neural control remains unknown. High-density electromyography (HD-sEMG) was acquired from the pectoralis major in two sets of experiments in healthy young adults. Participants performed ramp-and-hold isometric contractions in: adduction, internal rotation, flexion, and horizontal adduction at three force levels: 15%, 25%, and 50% scaled to task-specific maximal voluntary force (MVF). HD-sEMG signals were decomposed into motor unit spike trains using a convolutive blind source separation algorithm and matched across force levels using a motor unit matching algorithm. The mean discharge rate and coefficient of variation were quantified across the hold and compared between 15% and 25% MVF across all tasks, while comparisons between 25 and 50% MVF were made where available. Mean motor unit discharge rate was not significantly different between 15% and 25% MVF (all p > 0.05) across all tasks or between 25% and 50% MVF in horizontal adduction (p = 0.11), indicating an apparent saturation across force levels and the absence of rate coding. These findings suggest that the pectoralis major likely relies on motor unit recruitment to increase force, providing first-line evidence of motor unit recruitment in this muscle and paving the way for more deliberate investigations of the pectoralis major involvement in shoulder function.

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