In this work, a model of the seated human torso was determined through postural analysis under a broad range of seated support conditions. Utilizing optical position measurement equipment and software, posture data were collected with ten mid—size male subjects in a laboratory seat under a wide range of torso support conditions. From these data, joint locations were determined for a three segment, two joint torso linkage model, which would satisfactorily simulate seated human torso motion. The allowable angle ranges through which adjacent segments should move relative to one another were determined and the coupling between motion at one joint and the other was evaluated. This seated human torso posture linkage was developed as a necessary step toward understanding the effects of seat support geometry on human posture.