Development of a finite-element muscle model accounting for transverse loading

Overview & Synopsis

To our knowledge, FE neck models including active 1D or 3D muscles have been mainly used for impact simulations and have yet to be used to investigate the effects of volumetric deformation, transverse loading and stiffening interactions between muscles, which may affect posture and task performance in the daily life. Muscle efficiency has been experimentally assessed under the influence of transverse loading in experiments on the rat (Siebert et al. 2014) and human (Siebert et al. 2018) gastrocnemius muscles. In these studies, the authors reported changes in transverse expansion of the muscle and a reduction of the axial contraction force with increased external transverse loading, which would seem to work adversely to the structural transverse stiffening and stabilization effects between muscles or muscles and bones that are generally associated with contraction and bulging. In order to improve the bio-fidelity of a FE neck model (Howley et al. 2014) we investigated the implementation of a continuum passive/active law to account for such transverse effects in a single FE muscle model.