Posture of the trunk when sitting on forward inclining seats.

Changes in posture during one hour of sitting were measured by a statometric method on ten subjects. Four seats were used, one horizontal and three with forward inclinations respectively of 5 degrees, 10 degrees and 15 degrees. With increasing forward inclination of the seat, the spine moved toward lumber lordosis. A supplementary sample showed that 1/3 of the body's adaptation to the seat inclination took place in the spine and 2/3 in the hip joints. A tendency to a more vertical position of the trunk as a whole was observed on the 5 degrees chair, but the posture of the cervical spine was not influenced by the seat inclination. During the hour of sitting a slight tendency was observed for the subjects to sit with the trunk in the most vertical position at the first measurements. The back curves did not change in any systematic way during the hour. A comfort evaluation showed the 5 degrees forward inclination and the horizontal seats to be preferred.