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Modelling the control of interceptive actions.

Beek, P J; Dessing, J C; Peper, C E; Bullock, D
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 29/09/2003 EN
Relevância na Pesquisa
26.09%
In recent years, several phenomenological dynamical models have been formulated that describe how perceptual variables are incorporated in the control of motor variables. We call these short-route models as they do not address how perception-action patterns might be constrained by the dynamical properties of the sensory, neural and musculoskeletal subsystems of the human action system. As an alternative, we advocate a long-route modelling approach in which the dynamics of these subsystems are explicitly addressed and integrated to reproduce interceptive actions. The approach is exemplified through a discussion of a recently developed model for interceptive actions consisting of a neural network architecture for the online generation of motor outflow commands, based on time-to-contact information and information about the relative positions and velocities of hand and ball. This network is shown to be consistent with both behavioural and neurophysiological data. Finally, some problems are discussed with regard to the question of how the motor outflow commands (i.e. the intended movement) might be modulated in view of the musculoskeletal dynamics.

Visual and musculoskeletal underpinnings of anchoring in rhythmic visuo-motor tracking

Roerdink, Melvyn; Ophoff, Ellen D.; (Lieke) E. Peper, C.; Beek, Peter J.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.15%
Anchoring, that is, a local reduction in kinematic (i.e., spatio-temporal) variability, is commonly observed in cyclical movements, often at or around reversal points. Two kinds of underpinnings of anchoring have been identified—visual and musculoskeletal—yet their relative contributions and interrelations are largely unknown. We conducted an experiment to delineate the effects of visual and musculoskeletal factors on anchoring behavior in visuo-motor tracking. Thirteen participants (reduced to 12 in the analyses) tracked a sinusoidally moving visual target signal by making flexion–extension movements about the wrist, while both visual (i.e., gaze direction) and musculoskeletal (i.e., wrist posture) factors were manipulated in a fully crossed (3 × 3) design. Anchoring was affected by both factors in the absence of any significant interactions, implying that their contributions were independent. When gaze was directed to one of the target turning points, spatial endpoint variability at this point was reduced, but not temporal endpoint variability. With the wrist in a flexed posture, spatial and temporal endpoint variability were both smaller for the flexion endpoint than for the extension endpoint, while the converse was true for tracking with the wrist extended. Differential anchoring effects were absent for a neutral wrist posture and when gaze was fixated in between the two target turning points. Detailed analyses of the tracking trajectories in terms of velocity profiles and Hooke’s portraits showed that the tracking dynamics were affected more by wrist posture than by gaze direction. The discussion focuses on the processes underlying the observed independent effects of gaze direction and wrist posture on anchoring as well as their implications for the notion of anchoring as a generic feature of sensorimotor coordination.

Robust passive dynamics of the musculoskeletal system compensate for unexpected surface changes during human hopping

van der Krogt, Marjolein M.; de Graaf, Wendy W.; Farley, Claire T.; Moritz, Chet T.; Richard Casius, L. J.; Bobbert, Maarten F.
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.19%
When human hoppers are surprised by a change in surface stiffness, they adapt almost instantly by changing leg stiffness, implying that neural feedback is not necessary. The goal of this simulation study was first to investigate whether leg stiffness can change without neural control adjustment when landing on an unexpected hard or unexpected compliant (soft) surface, and second to determine what underlying mechanisms are responsible for this change in leg stiffness. The muscle stimulation pattern of a forward dynamic musculoskeletal model was optimized to make the model match experimental hopping kinematics on hard and soft surfaces. Next, only surface stiffness was changed to determine how the mechanical interaction of the musculoskeletal model with the unexpected surface affected leg stiffness. It was found that leg stiffness adapted passively to both unexpected surfaces. On the unexpected hard surface, leg stiffness was lower than on the soft surface, resulting in close-to-normal center of mass displacement. This reduction in leg stiffness was a result of reduced joint stiffness caused by lower effective muscle stiffness. Faster flexion of the joints due to the interaction with the hard surface led to larger changes in muscle length...

Concurrent Musculoskeletal Dynamics and Finite Element Analysis Predicts Altered Gait Patterns to Reduce Foot Tissue Loading

Halloran, Jason P.; Ackermann, Marko; Erdemir, Ahmet; van den Bogert, Antonie J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.14%
Current computational methods for simulating locomotion have primarily used muscle-driven multibody dynamics, in which neuromuscular control is optimized. Such simulations generally represent joints and soft tissue as simple kinematic or elastic elements for computational efficiency. These assumptions limit application in studies such as ligament injury or osteoarthritis, where local tissue loading must be predicted. Conversely, tissue can be simulated using the finite element method with assumed or measured boundary conditions, but this does not represent the effects of whole body dynamics and neuromuscular control. Coupling the two domains would overcome these limitations and allow prediction of movement strategies guided by tissue stresses. Here we demonstrate this concept in a gait simulation where a musculoskeletal model is coupled to a finite element representation of the foot. Predictive simulations incorporated peak plantar tissue deformation into the objective of the movement optimization, as well as terms to track normative gait data and minimize fatigue. Two optimizations were performed, first without the strain minimization term and second with the term. Convergence to realistic gait patterns was achieved, with the second optimization realizing a 44% reduction in peak tissue strain energy density. The study demonstrated that it is possible to alter computationally predicted neuromuscular control to minimize tissue strain while including desired kinematic and muscular behavior. Future work should include experimental validation...

Muscle mass in musculoskeletal models

Pai, Dinesh K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.14%
Most current models of musculoskeletal dynamics lump a muscle’s mass with its body segment, and then simulate the dynamics of these body segments connected by joints. As shown here, this popular approach leads to errors in the system’s inertia matrix and hence in all aspects of the dynamics. Two sim-plified mathematical models were created to capture the relevant features of monoarticular and biarticular muscles, and the errors were analyzed. The models were also applied to two physiological examples: the triceps surae muscles that plantar flex the human ankle and the biceps femoris posterior muscle of the rat hind limb. The analysis of errors due to lumping showed that these errors can be large. Although the errors can be reduced in some postures, they cannot be easily eliminated in models that use segment lumping. Some options for addressing these errors are discussed.

Implicit methods for efficient musculoskeletal simulation and optimal control

van den Bogert, Antonie J.; Blana, Dimitra; Heinrich, Dieter
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/01/2011 EN
Relevância na Pesquisa
36.35%
The ordinary differential equations for musculoskeletal dynamics are often numerically stiff and highly nonlinear. Consequently, simulations require small time steps, and optimal control problems are slow to solve and have poor convergence. In this paper, we present an implicit formulation of musculoskeletal dynamics, which leads to new numerical methods for simulation and optimal control, with the expectation that we can mitigate some of these problems. A first order Rosenbrock method was developed for solving forward dynamic problems using the implicit formulation. It was used to perform real-time dynamic simulation of a complex shoulder arm system with extreme dynamic stiffness. Simulations had an RMS error of only 0.11 degrees in joint angles when running at real-time speed. For optimal control of musculoskeletal systems, a direct collocation method was developed for implicitly formulated models. The method was applied to predict gait with a prosthetic foot and ankle. Solutions were obtained in well under one hour of computation time and demonstrated how patients may adapt their gait to compensate for limitations of a specific prosthetic limb design. The optimal control method was also applied to a state estimation problem in sports biomechanics...

Development of a comprehensive musculoskeletal model of the shoulder and elbow

Asadi Nikooyan, A.; Veeger, H. E. J.; Chadwick, E. K. J.; Praagman, M.; van der Helm, F. C. T.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.09%
The Delft Shoulder and Elbow Model (DSEM), a musculoskeletal model of the shoulder and elbow has been extensively developed since its introduction in 1994. Extensions cover both model structures and anatomical data focusing on the addition of an elbow part and muscle architecture parameters. The model was also extended with a new inverse-dynamics optimization cost function and combined inverse-forward-dynamics models. This study is an update on the developments of the model over the last decade including a qualitative validation of the different simulation architectures available in the DSEM. To validate the model, a dynamic forward flexion motion was performed by one subject, of which the motion data and surface EMG-signals of 12 superficial muscles were measured. Patterns of the model-predicted relative muscle forces were compared with their normalized EMG-signals. Results showed relatively good agreement between forces and EMG (mean correlation coefficient of 0.66). However, for some cases, no force was predicted while EMG activity had been measured (false-negatives). The DSEM has been used and has the potential to be used in a variety of clinical and biomechanical applications.

Simulation of Anterior Cruciate Ligament Deficiency in a Musculoskeletal Model with Anatomical Knees

Guess, Trent M; Stylianou, Antonis
Fonte: Bentham Open Publicador: Bentham Open
Tipo: Artigo de Revista Científica
Publicado em 09/03/2012 EN
Relevância na Pesquisa
26.09%
Abnormal knee kinematics and meniscus injury resulting from anterior cruciate ligament (ACL) deficiency are often implicated in joint degeneration even though changes in tibio-femoral contact location after injury are small, typically only a few millimeters. Ligament reconstruction surgery does not significantly reduce the incidence of early onset osteoarthritis. Increased knowledge of knee contact mechanics would increase our understanding of the effects of ACL injury and help guide ACL reconstruction methods. Presented here is a cadaver specific computational knee model combined with a body-level musculoskeletal model from a subject of similar height and weight as the cadaver donor. The knee model was developed in the multi-body framework and includes representation of the menisci. Experimental body-level measurements provided input to the musculoskeletal model. The location of tibio-menisco-femoral contact as well as contact pressures were compared for models with an intact ACL, partial ACL transection (posterolateral bundle transection), and full ACL transection during a muscle driven forward dynamics simulation of a dual limb squat. During the squat, small changes in femur motion relative to the tibia for both partial and full ACL transection push the lateral meniscus in the posterior direction at extension. The central-anterior region of the lateral meniscus then becomes “wedged” between the tibia and femur during knee flexion. This “wedging” effect does not occur for the intact knee. Peak contact pressure and contact locations are similar for the partial tear and complete ACL transection during the deep flexion portion of the squat...

Effectiveness of Selected Fitness Exercises on Stress of Femoral Neck using Musculoskeletal Dynamics Simulations and Finite Element Model

Qian, Jing-Guang; Li, Zhaoxia; Zhang, Hong; Bian, Rong; Zhang, Songning
Fonte: Akademia Wychowania Fizycznego w Katowicach Publicador: Akademia Wychowania Fizycznego w Katowicach
Tipo: Artigo de Revista Científica
Publicado em 08/07/2014 EN
Relevância na Pesquisa
46.14%
The purpose of the study was to establish a dynamics model and a three-dimensional (3D) finite element model to analyze loading characteristics of femoral neck during walking, squat, single-leg standing, and forward and lateral lunges. One male volunteer performed three trials of the five movements. The 3D kinematic data were captured and imported into the LifeMOD to establish a musculoskeletal dynamics model to obtain joint reaction and muscle forces of iliacus, gluteus medius, gluteus maximus, psoas major and adductor magnus. The loading data LfeMOD were imported and transformed into a hip finite-element model. The results of the finite element femur model showed that stress was localized along the compression arc and the tension arc. In addition, the trabecular bone and tension lines of the Ward’s triangle also demonstrated high stress. The compact bone received the greatest peak stress in the forward lunge and the least stress in the squat. However, the spongy bone in the femoral neck region had the greatest stress during the walk and the least stress in the squat. The results from this study indicate that the forward lunge may be an effective method to prevent femoral neck fractures. Walking is another effective and simple method that may improve bone mass of the Ward’s triangle and prevent osteoporosis and femoral neck fracture.

Are Subject-Specific Musculoskeletal Models Robust to the Uncertainties in Parameter Identification?

Valente, Giordano; Pitto, Lorenzo; Testi, Debora; Seth, Ajay; Delp, Scott L.; Stagni, Rita; Viceconti, Marco; Taddei, Fulvia
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 12/11/2014 EN
Relevância na Pesquisa
26.15%
Subject-specific musculoskeletal modeling can be applied to study musculoskeletal disorders, allowing inclusion of personalized anatomy and properties. Independent of the tools used for model creation, there are unavoidable uncertainties associated with parameter identification, whose effect on model predictions is still not fully understood. The aim of the present study was to analyze the sensitivity of subject-specific model predictions (i.e., joint angles, joint moments, muscle and joint contact forces) during walking to the uncertainties in the identification of body landmark positions, maximum muscle tension and musculotendon geometry. To this aim, we created an MRI-based musculoskeletal model of the lower limbs, defined as a 7-segment, 10-degree-of-freedom articulated linkage, actuated by 84 musculotendon units. We then performed a Monte-Carlo probabilistic analysis perturbing model parameters according to their uncertainty, and solving a typical inverse dynamics and static optimization problem using 500 models that included the different sets of perturbed variable values. Model creation and gait simulations were performed by using freely available software that we developed to standardize the process of model creation, integrate with OpenSim and create probabilistic simulations of movement. The uncertainties in input variables had a moderate effect on model predictions...

OpenSim: a musculoskeletal modeling and simulation framework for in silico investigations and exchange

Seth, Ajay; Sherman, Michael; Reinbolt, Jeffrey A.; Delp, Scott L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
26.15%
Movement science is driven by observation, but observation alone cannot elucidate principles of human and animal movement. Biomechanical modeling and computer simulation complement observations and inform experimental design. Biological models are complex and specialized software is required for building, validating, and studying them. Furthermore, common access is needed so that investigators can contribute models to a broader community and leverage past work. We are developing OpenSim, a freely available musculoskeletal modeling and simulation application and libraries specialized for these purposes, by providing: musculoskeletal modeling elements, such as biomechanical joints, muscle actuators, ligament forces, compliant contact, and controllers; and tools for fitting generic models to subject-specific data, performing inverse kinematics and forward dynamic simulations. OpenSim performs an array of physics-based analyses to delve into the behavior of musculoskeletal models by employing Simbody, an efficient and accurate multibody system dynamics code. Models are publicly available and are often reused for multiple investigations because they provide a rich set of behaviors that enables different lines of inquiry. This report will discuss one model developed to study walking and applied to gain deeper insights into muscle function in pathological gait and during running. We then illustrate how simulations can test fundamental hypotheses and focus the aims of in vivo experiments...

The Effects of Walking Speed on Tibiofemoral Loading Estimated Via Musculoskeletal Modeling

Lerner, Zachary F.; Haight, Derek J.; DeMers, Matthew S.; Board, Wayne J.; Browning, Raymond C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.15%
Net muscle moments (NMMs) have been used as proxy measures of joint loading, but musculoskeletal models can estimate contact forces within joints. The purpose of this study was to use a musculoskeletal model to estimate tibiofemoral forces and to examine the relationship between NMMs and tibiofemoral forces across walking speeds. We collected kinematic, kinetic, and electromyographic data as ten adult participants walked on a dual-belt force-measuring treadmill at 0.75, 1.25, and 1.50 m/s. We scaled a musculoskeletal model to each participant and used OpenSim to calculate the NMMs and muscle forces through inverse dynamics and weighted static optimization, respectively. We determined tibiofemoral forces from the vector sum of intersegmental and muscle forces crossing the knee. Estimated tibiofemoral forces increased with walking speed. Peak early-stance compressive tibiofemoral forces increased 52% as walking speed increased from 0.75 to 1.50 m/s, whereas peak knee extension NMMs increased by 168%. During late stance, peak compressive tibiofemoral forces increased by 18% as speed increased. Although compressive loads at the knee did not increase in direct proportion to NMMs, faster walking resulted in greater compressive forces during weight acceptance and increased compressive and anterior/posterior tibiofemoral loading rates in addition to a greater abduction NMM.

A Probabilistic Approach to Quantify the Impact of Uncertainty Propagation in Musculoskeletal Simulations

Myers, Casey A.; Laz, Peter J.; Shelburne, Kevin B.; Davidson, Bradley S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.15%
Uncertainty that arises from measurement error and parameter estimation can significantly affect the interpretation of musculoskeletal simulations; however, these effects are rarely addressed. The objective of this study was to develop an open-source probabilistic musculoskeletal modeling framework to assess how measurement error and parameter uncertainty propagate through a gait simulation. A baseline gait simulation was performed for a male subject using OpenSim for three stages: inverse kinematics, inverse dynamics, and muscle force prediction. A series of Monte Carlo simulations were performed that considered intrarater variability in marker placement, movement artifacts in each phase of gait, variability in body segment parameters, and variability in muscle parameters calculated from cadaveric investigations. Propagation of uncertainty was performed by also using the output distributions from one stage as input distributions to subsequent stages. Confidence bounds (5–95%) and sensitivity of outputs to model input parameters were calculated throughout the gait cycle. The combined impact of uncertainty resulted in mean bounds that ranged from 2.7° to 6.4° in joint kinematics, 2.7 to 8.1 N m in joint moments, and 35.8 to 130.8 N in muscle forces. The impact of movement artifact was 1.8 times larger than any other propagated source. Sensitivity to specific body segment parameters and muscle parameters were linked to where in the gait cycle they were calculated. We anticipate that through the increased use of probabilistic tools...

An upper limb musculoskeletal model using bond graphs for rotorcraft-pilot couplings analysis

TOD, Georges; MALBURET, François; GOMAND, Julien; BARRE, Pierre-Jean
Fonte: SIMBIO-M Publicador: SIMBIO-M
EN
Relevância na Pesquisa
36.09%
Under certain flight conditions, a rotorcraft fuselage motions and vibrations might interact with its pilot voluntary and involuntary actions leading to potentially dangerous dynamic instabilities known as rotorcraft-pilot couplings (RPCs). A better understanding of this phenomenon could be achieved by being able to reproduce the phenomenon during simulations. Design guidelines could be then obtained at an early stage of development of rotorcrafts improving flight safety for pilots and passengers. In this work, an upper limb musculoskeletal model using bond graphs is presented. It is then integrated in a larger aeroelastic rotorcraft bond graph model that allows simulating pilot-rotor-fuselage couplings under several flight conditions. Simulations are performed and compared to literature’s models and experimental data.; “Complex Mechanical Systems Dynamics” project - Airbus Group Foundation - Arts et Metiers Paristech

Musculoskeletal adaptation to Partial Weight Suspension : studies of Lunar and Mars loading; Musculoskeletal adaptation to PWS

Wagner, Erika Brown
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 257 p.
ENG
Relevância na Pesquisa
26.22%
As human spaceflight extends in both duration and scope, it is critical to better understand the physiologic effects of this novel environment. In the weight bearing structures of the body, bone loss and muscle atrophy far in excess of age-related declines are hallmarks of microgravity adaptation. However, while the physiological effects of such disuse unloading are well-described, the effects of partial weight bearing, such as expected on the moon (16% of Earth's gravity) and Mars (38% of Earth's gravity), have yet to be quantified. In these environments, the risks of musculoskeletal atrophy and accompanying orthopedic injury are uncertain, and a means of further investigation is needed. To address this need, we developed a novel model of Partial Weight Suspension (PWS) that supports investigation of the physiologic effects of chronically reduced quadrupedal loading in mice. Validation of the PWS system was conducted using a gait analysis treadmill and high-precision force platform. These studies showed that peak ground reaction forces were significantly reduced under conditions of partial weightbeari:ng, and changes in gait dynamics were consistent with previous studies of human locomotion. Using the PWS system, we conducted the first known studies of chronic musculoskeletal adaptation to Mars and lunar levels of weight bearing. Adult female BALB/cByJ mice underwent 21 days of partial weight bearing or control treatment. Relative to controls...

Evaluation of a Musculoskeletal Model with Prosthetic Knee through Six Experimental Gait Trials

Kia, Mohammad; Stylianou, Antonis P.; Guess, Trent M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.31%
Knowledge of the forces acting on musculoskeletal joint tissues during movement benefits tissue engineering, artificial joint replacement, and our understanding of ligament and cartilage injury. Computational models can be used to predict these internal forces, but musculoskeletal models that simultaneously calculate muscle force and the resulting loading on joint structures are rare. This study used publicly available gait, skeletal geometry, and instrumented prosthetic knee loading data [1] to evaluate muscle driven forward dynamics simulations of walking. Inputs to the simulation were measured kinematics and outputs included muscle, ground reaction, ligament, and joint contact forces. A full body musculoskeletal model with subject specific lower extremity geometries was developed in the multibody framework. A compliant contact was defined between the prosthetic femoral component and tibia insert geometries. Ligament structures were modeled with a nonlinear force-strain relationship. The model included 45 muscles on the right lower leg. During forward dynamics simulations a feedback control scheme calculated muscle forces using the error signal between the current muscle lengths and the lengths recorded during inverse kinematics simulations. Predicted tibiofemoral contact force...

Simplified and effective motor control based on muscle synergies to exploit musculoskeletal dynamics

Berniker, Max; Jarc, Anthony; Bizzi, Emilio; Tresch, Matthew C.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
35.89%
The basic hypothesis of producing a range of behaviors using a small set of motor commands has been proposed in various forms to explain motor behaviors ranging from basic reflexes to complex voluntary movements. Yet many fundamental questions regarding this long-standing hypothesis remain unanswered. Indeed, given the prominent nonlinearities and high dimensionality inherent in the control of biological limbs, the basic feasibility of a low-dimensional controller and an underlying principle for its creation has remained elusive. We propose a principle for the design of such a controller, that it endeavors to control the natural dynamics of the limb, taking into account the nature of the task being performed. Using this principle, we obtained a low-dimensional model of the hindlimb and a set of muscle synergies to command it. We demonstrate that this set of synergies was capable of producing effective control, establishing the viability of this muscle synergy hypothesis. Finally, by combining the low-dimensional model and the muscle synergies we were able to build a relatively simple controller whose overall performance was close to that of the system's full-dimensional nonlinear controller. Taken together, the results of this study establish that a low-dimensional controller is capable of simplifying control without degrading performance.

Cortical Spiking Network Interfaced with Virtual Musculoskeletal Arm and Robotic Arm

Dura-Bernal, Salvador; Zhou, Xianlian; Neymotin, Samuel A.; Przekwas, Andrzej; Francis, Joseph T.; Lytton, William W.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 25/11/2015 EN
Relevância na Pesquisa
26.15%
Embedding computational models in the physical world is a critical step towards constraining their behavior and building practical applications. Here we aim to drive a realistic musculoskeletal arm model using a biomimetic cortical spiking model, and make a robot arm reproduce the same trajectories in real time. Our cortical model consisted of a 3-layered cortex, composed of several hundred spiking model-neurons, which display physiologically realistic dynamics. We interconnected the cortical model to a two-joint musculoskeletal model of a human arm, with realistic anatomical and biomechanical properties. The virtual arm received muscle excitations from the neuronal model, and fed back proprioceptive information, forming a closed-loop system. The cortical model was trained using spike timing-dependent reinforcement learning to drive the virtual arm in a 2D reaching task. Limb position was used to simultaneously control a robot arm using an improved network interface. Virtual arm muscle activations responded to motoneuron firing rates, with virtual arm muscles lengths encoded via population coding in the proprioceptive population. After training, the virtual arm performed reaching movements which were smoother and more realistic than those obtained using a simplistic arm model. This system provided access to both spiking network properties and to arm biophysical properties...

Using subject-specific muscle parameters to compare muscle forces and activation between an EMF-driven and OpenSim musculoskeletal model

Olchowski, David
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
36.15%
Buchanan, Thomas S.; Higginson, Jill S.; Experimental gait analysis was developed to analyze and calculate mechanical aspects such as joint kinetics and kinematics to understand the characteristics that lead to human walking. Unfortunately, gait analysis is limited because it alone cannot determine individual, in vivo muscle function. Redundant systems are created from multiple muscles spanning one joint, thus eliminating the possibility to directly calculate muscle activity. The recent use of musculoskeletal modeling has allowed researchers to extend the functionality of gait analysis, predict individual muscle activity and forces, and gain insight to the underlying neuromuscular function. Many different optimization approaches with varying degrees of complexity exist to estimate individual muscle forces and activation. Previous studies have used electromyograms (EMG) to derive subject-specific muscle parameters that match inverse dynamics, while others use a generic model and redistribute muscle forces across synergistic muscles based on a particular cost function. Because generic musculoskeletal models are limited by their lack of specificity, we hoped to include subject-specific muscle parameters that would lead to improved force predictions. Prior sensitivity studies have determined the effect of altering one parameter within a specified range and calculating the difference in forces. However...

Estimation of joint contact forces using a real-time forward dynamics EMG-driven musculoskeletal model

Hume, Donald
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
36.28%
Buchanan, Thomas S.; Gait research is an important part of gaining a better understanding of the onset and progression of many debilitating diseases. There are many different tools used in this field, but one of significance is forward dynamics modeling. This technique has allowed researchers to gain insight into the force generation of different muscles during gait. A shortcoming to this modeling technique is that all data must be collected before it can be analyzed and processed offline. This provides no significant returns until several hours after the data has been collected. In academic gait research this is not a problem, but more often than ever we are seeing an effort to create a more synergistic relationship between the clinic and the laboratory setting. Researchers are working hand in hand with clinicians to help bring their findings into immediate practice. It is for this reason that a real-time paradigm is the next logical application of such modeling practices. Real-time modeling of joint forces would allow clinicians to step from a largely qualitative rehabilitation regime, to a more quantitative understanding of patient specific kinetics thus allowing them to increase their therapeutic efficacy. The goal of this project is to implement a model which will calculate the forces that the muscles exert on the joint...