Study of sitting posture variations using the nose and mandible as reference points.

The purpose of this study was to examine the average sitting posture in normals and to determine how clinically observed sitting posture varies as a function of the duration of relaxed sitting, patient awareness of being observed, and other situational factors. The head, neck, and upper thorax of five naive patients demonstrated increasingly anterior and inferior displacement during five minutes of relaxed sitting. These postural alternations were instantaneously reversed when the subjects were made aware that they were being observed. We conclude that sitting posture must be assessed in relationship to the patient's length of time sitting, awareness of being observed, level of instruction on how to sit, and chair style.