The need for comfortable, safe, and efficient use of interior space in the modern automobile is creating a need for anatomically and physiologically correct representations of the human body.

This thesis describes the development of a detailed geometric computer model representing the average adult male. A skeletal model capable of assuming any human posture functions as a framework to which models of other tissues are referenced. An investigation into how muscles might best be modeled leads to the use of ellipsoids to represent entire muscle groups. A non-invasive method of measuring hamstring length in vivo using sophisticated optical tracking equipment is described. The hypothesis that a limiting hamstring muscle length determines permissible combinations of knee and hip angles is investigated experimentally.

It is concluded that the methods selected for skeletal and muscle modeling produce body contours useful in seat design. It is also shown that a limiting hamstring muscle length cauSes an interdependence of knee and hip angles in certain postures.