Micromechanical modelling of skeletal muscles: from the single fibre to the whole muscle

The structure of a skeletal muscle is dominated by its hierarchical architecture in which thousands of muscle fibres are arranged within a connective tissue network. The single muscle fibre consists of many force-producing cells, known as sarcomeres, which contribute to the contraction of the whole muscle. There are a lot of questions concerning the optimisation of muscle strength and agility. To answer these questions, numerical testing tools, e.g. in the form of finite element models can be an adequate alternative to standard experimental investigations. The present approach is crucially based on the use of the finite element method. The material behaviour of the muscle is additively split into a so-called active and a passive part. To describe the passive part special unit cells consisting of one tetrahedral element and six truss elements have been derived. Embedded into these unit cells are non-linear truss elements which represent bundles of muscle fibres. Besides the representation of the material model, this contribution focuses on the application to anatomically based 3D problems, as the animal soleus muscle of the rat.