title: Human skeletal muscle behavior in vivo: Finite element implementation, experiment, and passive mechanical characterization.
abstract: In this study, useful methods for active human skeletal muscle material parameter determination are provided. First, a straightforward approach to the implementation of a transversely isotropic hyperelastic continuum mechanical material model in an invariant formulation is presented. This procedure is found to be feasible even if the strain energy is formulated in terms of invariants other than those predetermined by the software's requirements. Next, an appropriate experimental setup for the observation of activation-dependent material behavior, corresponding data acquisition, and evaluation is given. Geometry reconstruction based on magnetic resonance imaging of different deformation states is used to generate realistic, subject-specific finite element models of the upper arm. Using the deterministic SIMPLEX optimization strategy, a convenient quasi-static passive-elastic material characterization is pursued; the results of this approach used to characterize the behavior of human biceps in vivo indicate the feasibility of the illustrated methods to identify active material parameters comprising multiple loading modes. A comparison of a contact simulation incorporating the optimized parameters to a reconstructed deformed geometry of an indented upper arm shows the validity of the obtained results regarding deformation scenarios perpendicular to the effective direction of the nonactivated biceps. However, for a valid, activatable, general-purpose material characterization, the material model needs some modifications as well as a multicriteria optimization of the force-displacement data for different loading modes.
authors.affiliation: Institute for Materials Science, Faculty of Computer Science and Engineering, Frankfurt University of Applied Sciences, Nibelungenplatz 1, 60318 Frankfurt, Germany. Electronic address: c.clemen@fb2.fra-uas.de.
authors.forename: Christof B
authors.initials: CB
authors.lastname: Clemen
authors.affiliation: Institute for Materials Science, Faculty of Computer Science and Engineering, Frankfurt University of Applied Sciences, Nibelungenplatz 1, 60318 Frankfurt, Germany. Electronic address: benderoth@fb2.fra-uas.de.
authors.forename: Günther E K
authors.initials: GEK
authors.lastname: Benderoth
authors.affiliation: Institute for Materials Science, Faculty of Computer Science and Engineering, Frankfurt University of Applied Sciences, Nibelungenplatz 1, 60318 Frankfurt, Germany. Electronic address: schmidta@fb2.fra-uas.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schmidt
authors.affiliation: Department of Diagnostic and Interventional Radiology, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany. Electronic address: frank.huebner@kgu.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Hübner
authors.affiliation: Department of Diagnostic and Interventional Radiology, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany. Electronic address: t.vogl@em.uni-frankfurt.de.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
authors.affiliation: Institute for Materials Science, Faculty of Computer Science and Engineering, Frankfurt University of Applied Sciences, Nibelungenplatz 1, 60318 Frankfurt, Germany. Electronic address: silber@fb2.fra-uas.de.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Silber
mesh_terms: D001696:Biomechanical Phenomena; D003198:Computer Simulation; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000502:physiology*; D013314:Stress, Mechanical
keywords: Biomechanics; Human skeletal muscle; Inverse method