BackgroundIn the state of the art finite element AHBMs for car crash analysis in the LS-DYNA software material named *MAT_MUSCLE (*MAT_156) is used for active muscles modeling. It has three elements in parallel configuration, which has several major drawbacks: restraint approximation of the physical reality, complicated parameterization and absence of the integrated activation dynamics. This study presents implementation of the extended four element Hill-type muscle model with serial damping and eccentric force–velocity relation including dependent activation dynamics and internal method for physiological muscle routing.ResultsProposed model was implemented into the general-purpose finite element (FE) simulation software LSDYNA as a user material for truss elements. This material model is verified and validated with three different sets of mammalian experimental data, taken from the literature. It is compared to the *MAT_MUSCLE (*MAT_156) Hill-type muscle model already existing in LS-DYNA, which is currently used in finite element human body models (HBMs). An application example with an arm model extracted from the FE ViVA OpenHBM is given, taking into account physiological muscle paths.ConclusionThe simulation results show better material model accuracy, calculation robustness and improved muscle routing capability compared to *MAT_156. The FORTRAN source code for the user material subroutine dyn21.f and the muscle parameters for all simulations, conducted in the study, are given at https://zenodo.org/record/826209 under an open source license. This enables a quick application of the proposed material model in LS-DYNA, especially in active human body models (AHBMs) for applications in automotive safety.

Whiplash associated disorder (WAD) is a type of injury caused by rear-end impacts. It is a painful long-term injury of the soft tissue in the neck, which women suffer from 1.5 to 3 times more often compared to men. Progress in WAD research is difficult, as (i) it occurs at a loading level where muscle activity can no longer be neglected, (ii) as soft tissue characteristics play an essential role in WAD and (iii) there is no consensus on the injury mechanism causing WAD. Therefore, computational models of the human body are the most promising method to advance the understanding of WAD. Here, improvements of boundary and initial conditions are presented together with a discussion of its effects on the head kinematics and neck load.

Among the most challenging problems in present day mechanics is the realistic simulation of the human kinetic behavior which requires correct modeling of the muscles – the human actuators. We are, therefore, implementing and validating a 1‐D massless Hill‐type muscle model in the program Neweul‐M2. As a part of this effort, various anatomical and physiological parameters need to be chosen prior to the simulation. These parameters are always subject to natural variability or scatter. Therefore, it is important to consider those parameters as uncertain fuzzy parameters and then determine the sensitivity measures of the parameters involved in various simulation scenarios using the program Famous. The applied sensitivity analysis quantifies the influence of individual parameters or subsets of parameters on the output quantity of interest. Thus, this analysis identifies those parameters with large influence on the simulation response of muscles which, therefore, needs to be chosen very carefully. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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