ANATOMICAL AND PHYSIOLOGICAL PRINCIPLES IN CHAIR AND TABLE DESIGN

Abstract

General principles derived from anatomical, physiological and clinical studies of movement and posture may be applied to the design of furniture. The paper is concerned with this problem in relation to dimensions and shape of chairs and tables for office and general domestic use. From a study of the literature and consideration of the authors' own investigations the following conclusions emerge.: 1. In sitting, changes of posture are important. A good chair should permit this. 2. In sitting, the weight of the trunk should be borne mainly by the ischial tuberosities. This probably maximises comfort. The thighs are anatomically and physiologically unsuited for supporting the body weight. 3. Therefore, the height of a chair seat should be no more than the length of the lower leg of the shortest person who will use the chair. There is however some conflict between the need for a seat height low enough to accommodate shorter persons and the need to avoid too great hip flexion, and the lumbar convexity which accompanies it, in the taller person sitting on a low seat. More than one seat height may be required to cover the range from the tallest male to the shortest female 4. The maximum goat depth for comfort is determined by the length of the thighs of the shorter persons using the seat. Seat width is adequately measured by trochanteric width. 5. A substantially piano seat is preferable to one shaped or moulded to fit the backside. A backward slope of up to 5° may be suitable for some purposes. 6. The mechanics of rising from a seat require that no horizontal struts or other obstructions be placed between the front legs of a chair. 7. Trunk muscle activity in sitting is diminished by the use of a backrest, which should not however restrict the movement of the spinal column or of the arms. Support in the lumbar region within the limits of the 2nd to 5th lumbar vertebrae allows adequate free movement. A saddleshaped backrest like that recommended by Akerblom gives satisfactory support. Dimensions and angles of slope are considered in the paper. 8. Table and chair form a single anthropometric unit. Table height is closely correlated with elbow height. Elbows should be about the level of the working piano. The space between the under-surface of the table and the chair scat should be slightly greater than thigh thickness.