title: The influence of biophysical muscle properties on simulating fast human arm movements.
abstract: Computational modeling provides a framework to understand human movement control. For this approach, physiologically motivated and experimentally validated models are required to predict the dynamic interplay of the neuronal controller with the musculoskeletal biophysics. Previous studies show, that an adequate model of arm movements should consider muscle fiber contraction dynamics, parallel and serial elasticities, and activation dynamics. Numerous validated macroscopic model representations of these structures and processes exist. In this study, the influence of these structures and processes on maximum movement velocity of goal-directed arm movements was investigated by varying their mathematical model descriptions. It was found that the movement velocity strongly depends on the pre-activation of the muscles (differences up to 91.6%) and the model representing activation dynamics (differences up to 43.3%). Looking at the influence of the active muscle fibers (contractile element), the simulations reveal that velocities systematically differ depending on the width of the force-length relation (differences up to 17.4%). The series elasticity of the tendon influences the arm velocity up to 7.6%. In conclusion, in fast goal-directed arm movements from an equilibrium position, the modeling of the biophysical muscle properties influences the simulation results. To reliably distinguish between mathematical formulations by experimental validation, the initial muscular activity and the activation dynamics have to be modeled validly, as their influence excels. To this end, further experiments systematically varying the initial muscular activity would be needed.
authors.affiliation: a Institut für Sport- und Bewegungswissenschaft , Universität Stuttgart , Stuttgart , Germany .|b Stuttgart Research Centre for Simulation Technology , Universität Stuttgart , Stuttgart , Germany .
authors.forename: A
authors.initials: A
authors.lastname: Bayer
authors.affiliation: a Institut für Sport- und Bewegungswissenschaft , Universität Stuttgart , Stuttgart , Germany .|b Stuttgart Research Centre for Simulation Technology , Universität Stuttgart , Stuttgart , Germany .
authors.forename: S
authors.initials: S
authors.lastname: Schmitt
authors.affiliation: a Institut für Sport- und Bewegungswissenschaft , Universität Stuttgart , Stuttgart , Germany .|c Institut für Sportwissenschaft , Friedrich-Schiller-Universität , Jena , Germany .
authors.forename: M
authors.initials: M
authors.lastname: Günther
authors.affiliation: b Stuttgart Research Centre for Simulation Technology , Universität Stuttgart , Stuttgart , Germany .|d Multi-level Modeling in Motor Control and Rehabilitation Robotics , Hertie Institute for Clinical Brain Research, Eberhard Karls Universität , Tübingen , Germany .
authors.forename: D F B
authors.initials: DFB
authors.lastname: Haeufle
mesh_terms: D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D055592:Biophysical Phenomena; D003198:Computer Simulation; D004548:Elasticity; D004550:Elbow / Q000502:physiology; D056966:Excitation Contraction Coupling; D006801:Humans; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D016059:Range of Motion, Articular; D013997:Time Factors
keywords: Biomechanics; Hill-type muscle model; activation dynamics; neuromechanics