Measuring and modeling force-deflection responses of human thighs in seated postures

There is great interest in automotive seat comfort. Physiological factors that affect seating comfort are related to deformations and forces within people's bodies and their seats. Deformability of soft tissues is a significant determinant of body-seat interface contours along the back of the thigh.

This thesis describes the measurements of the mechanical responses of the hamstring regions of seated human subjects. A seating fixture with load cells and electronic gauges was built to support people in a variety of seated postures that affect the length of and the tension in the hamstring muscles. While pushing a flat, rigid surface into the back of peoples' thighs, force-time and displacement-time data were collected and analyzed.

Two-dimensional, plane strain, finite element models were developed to represent the thigh compression responses. Models were created with geometries that were specific to each of ten subjects, ranging from small female to large male. The properties of the in vivo soft tissue were assumed to be isotropic, homogeneous, and hyperelastic. The same material characteristics were used for all subjects. Comparisons between computational responses and experimental measurements showed close agreement.

It is concluded that the finite element method presented in this thesis is useful in soft tissue modeling and is an effective quantitative tool which may be used for seat cushion design.