ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

esearchers. The power of a finite-element muscle model rests in the fact that a muscle
is subdivided into discrete units. As skeletal muscle is composed of activatable muscle
fibres arranged within a passive matrix of connective tissues [7], a number of finite
element models based on different approaches have been developed to describe the
active behavior of the skeletal muscle.
In computer graphics, previous work by Teran et al.[8] included non-linear properties of
muscle. Simplifying assumptions for the aponeurosis properties and structure were
therefore made in the modeling of the muscle behavior (and its corresponding anatomy).
In biomechanics, Jenkyn et al.[9] proposed a non-linear finite element analysis to
simulate a two dimensional skeletal muscle. Yucesoy et al [7] described a non-linear
element analysis to simulate a three dimensional skeletal muscle using a linked fibermatrix
mesh model. Gielen et al.[10] described a planar model representing the midsagittal
plane of the muscle belly. Oomens et al.[11] Extended the mid-sagittal plane
continuum model of Gielen et al.[10] to a model with a more realistic three dimensional
geometry. According to these authors,[11] further improvements of the model are
needed in the transverse plane geometry in order to obtain the actual three-dimensional
representation of the muscle. Fernandez et al.[12] presented an anatomically based finite
element geometric model to match human specific musculoskeletal system. Blemker et
al.[13] used a nonlinear finite element analysis to simulate a three-dimensional skeletal
muscle, simplified by axial symmetry. Sheng et al. [14] introduced a nonlinear FE
model which took into account voluntary contraction of fibers and passive deformation
of muscle matrix and tendon with specifically defined geometry and boundary
conditions for evaluation of important mechanical properties of muscle. Tang et al. [15]
proposed a 3D FE model for the skeletal muscle In order to simulate concentric,
eccentric, isometric and isotonic contraction behaviors of the skeletal muscle under
either quasi-static or dynamic condition with corresponding numerical algorithm based
on the concept o f the Hill’s model to describe the active and passive properties of the
muscle fiber. In cardiac and skeletal muscles models, it has been pointed out that the
orientation of muscle fibers and activation, has a large influence on stresses and
strains.[16] Because of this, a model of skeletal muscle should have a detailed
description of the three-dimensional architecture and deformations so as to have
predictive.
The model described in this paper is simplified electromechanical modeling of muscle
based on the cellular physiological concepts. Although at this stage this physicallybased
model is a goal in itself, it is hoped that it will eventually be used for clinical
predictions and for research on the influence of deformations on the functional
properties of muscle.
3. METHOD
The finite-element method (FEM) is a well-known tool for the mechanical analysis of
stress-strain in structures and tissues. In the finite element method the domain of interest
is divided in to a number of non-overlapping but contiguous subdomains called
elements. In order to find the approximated solutions, continuities between neighboring
elements at selected points (nodes) have to be respected, and appropriate boundary
conditions have to be applied. The most attractive feature of the finite element method