A Prediction Model of Human Torso Volitional Mobility

Empirical models are presented which predict the threespace position of the torso when responding to reaches with the right arm. Models were derived which specify torso position in terms of the spacial location of 10 surface markers. These markers were positioned over palpable skeletal points of the spine and shoulder girdle. The necessary data were obtained through photogrammetric procedures utilizing four orthogonal cameras. The independent (input) variables to these models are the coordinates of the reach target. A supplementary, slightly more accurate, set of models was also derived in which the set of independent variables was enlarged to include the anthropometric dimensions of the subject.

The second, concurrent phase of the analysis resulted in the derivation of a set of models which describes the configuration of the internal, torso skeletal system. The vector distances and angles between external surface markers and internal bone articulations points can be calculated from these models. A radiographic procedure using orthogonal or oblique x-ray photographs was used to generate the required data. The relative advantages of the present empirical models over the traditional heuristic, hard-link biomechanical models are discussed.