Muscle activity on head-first compression responses of a finite element neck model

Effects of muscle activation on human neck kinematic responses under compressive loads have not been un-derstood empirically due to the limitation of testing on in vivo test specimens. Advanced computational models can potentially provide information to improve our understanding of such responses. This study used a previ-ously developed ligamentous finite element (FE) neck model, further integrated with muscles, fleshy tissue, and skin of the neck to predict the influence of passive and active muscles on responses to neck compression. For validation, post-mortem human subject (PMHS) and volunteer responses in frontal sled impacts were used to compare the dynamic response of the model with passive and active muscles, respectively. An objective eval-uation of the validation responses suggested the 'fair' to 'good' biofidelity rating of the muscular system model. The compressive impacts, used to validate the ligamentous FE neck, were methodologically applied in the current study including the muscles with various activation states, flesh, and skin. The contribution of muscles (passive or active) resulted in an increase in the peak lower neck compression and shear forces and in a reduction in the upper neck forces on average; the role of active state dynamics of the muscles was crucial on the magnitude of the forces. Therefore, modeling of the muscles in a computational neck model may not be neglected to study a head-first compressive impact.