I am currently conducting research focused on evaluating biodynamic response in the human body subjected to whole-body vibration using computational human body finite element (FE) modeling. Currently, I am utilizing the THUMS human body FE model for conducting biodynamic response computations, including modal and harmonic analysis.

However, I have encountered several challenges, particularly in the modal analysis of the THUMS model. Specifically, I am experiencing abrupt deformation in the mode shapes, and I am unable to observe the initial six rigid modes in the free-free modal analysis, which is typically performed as a preliminary check.

I would greatly appreciate any insights or guidance if someone could provide to help me address these issues that help me to progress further in my research.