Abstract
According to the questionnaires of sitting styles in dining chairs, a large number of people were found to sit in various styles such as “agura”, “one-legged agura”, and “seiza”. The most comfortable seat surface shape for each sitting style was measured using an adjustable experimental chair, which is divided laterally into 16 rigid narrow plates. As a result, following seat-front shape was favored: concaved shape for “agura” and “one-legged agura” style, flat surface for “seiza” style, and convex shape with extended seat for “tatehiza” style. From these results, the seat was divided in two parts. A sliding/rotating frontal seat part is adjustable in its length and angle. In “agura” and “tatehiza” style, a favorable backrest shape were classified in 2 types; straight or convex lumbar shape. Also, thorax-dorsal supporting shape was favored by subjects whom lumbar vertebrae spine have contact with the backrest. Therefore, backrest is curved transversally and the bottom part is softened to bend when pushed by the lower back. Armrests were placed so as not to interfere with the leg positions during “agura”. A chair prototype was made following these conditions, and was compared with three commercially available chairs. As a result of sensory evaluation, the prototype was rated higher than the other three chairs in all sitting positions. By putting legs up on the seat, lower leg swelling was reduced, but the contact pressure has increased. By taking various sitting styles, the load of sitting is average out, and longtime sitting can be continued.
