ABSTRACT
A special chair for microscopic surgery was developed from studies on Zen sitting to facilitate long hours of surgery operations on a comfortable seat. This paper describes design principle for the chair along with a proposal for its manufacture. The chair development places an emphasis on 3-dimensional contours formed on an interface between muscles, especially those on lumbar, buttock, and thigh parts, and a sitting tool. The design principle includes 1) maximization of contact surface area formed when a person sits on a seat and 2) adjustment of peak body pressures. The essential point of the chair manufacture is creation of a shell emulating a 3D shape of primary user's buttocks. Evaluation experiments were conducted in an operation room to compare the prototype chair with a conventional chair. The evaluated items were pelvis tilt angles, body pressure distributions, physical measurements, and subjective ratings. Of the results, the pelvis tilt angles measured on the prototype chair demonstrated the backward inclination of pelvis being prevented by the sacral support as seen in zazen. The transitional variations of statistical figures from areas identified by palpation on the regionally-differentiated pressure maps (RDPM) along with changes in pelvis tilt angles served to objectively gauge levels of seating
comfort. Accordingly, the newly developed chair was proved to provide improved seating comfort and stability to facilitate easier long duration work as compared with a conventional chair. It could be said as a conclusion that this research has justified the effectiveness of a concave-shaped chair that was made up in accordance with individual's buttocks size following the method adopted in the Zen sitting.
