Erect, Neutral and Slump Sitting Postures: A Study of the Torso Linkage System from Shoulder to Hip Joint.

Sitting postures representative of a maximum erect, neutral and maximum slumped spinal curvature were defined by comparable anatomical pointmarks in three dimensional space. Nine, male, unembalmed cadavers were measured with a roentgen stereophotogrammetric system. The results describe thoracic and lumbar curvatures in three postures and the locations of specific landmarks representing the shoulder joint, spinal column, and hip joint in a three dimensional seat reference system. In addition to the three dimensional analysis of sitting posture, the range of notion for each motion segment measured in the spine was calculated. These data were used to evaluate the contribution of specific lumbar motion segments in the change of sitting posture from maximum erect to maximum slump. To evaluate the condition of each subjects musculoskeletal system, osteological, morphological and physiological procedures were used to describe the sample.