A new approach for the validation of skeletal muscle modelling using MRI data

Active and passive experiments on skeletal muscles are in general arranged on isolated muscles or by consideration of the whole muscle packages, such as the arm or the leg. Both methods exhibit advantages and disadvantages. By applying experiments on isolated muscles it turns out that no information about the surrounding tissues are considered what leads to insufficient specifications of the isolated muscle. Especially, the muscle shape and the fibre directions of an embedded muscle are completely different to that of the same isolated muscle. An explicit advantage, in contrast, is the possibility to study the mechanical characteristics in an unique, isolated way. On the other hand, by applying experiments on muscle packages the aforementioned pros and cons reverse. In such situation, the whole surrounding tissue is considered in the mechanical characteristics of the muscle which are much more difficult to identify. However, an embedded muscle reflects a much more realistic situation as in isolated condition. Thus, in the proposed work to our knowledge, we, for the first time, suggest a technique that allows to study characteristics of single skeletal muscles inside a muscle package without any computation of the tissue around the muscle of interest. In doing so, we use magnetic resonance imaging data of an upper arm during contraction. By applying a three-dimensional continuum constitutive muscle model we are able to study the biceps brachii inside the upper arm and validate the modelling approach by optical experiments.