The anthropometry of the manual work space for the seated subject.

Abstract

This paper is an exploration of the space-geometry of hand motions as they relate to young men in the seated posture. It is primarily a presentation in functional anthropometry, but the information derived should have practical use in improving the design of work areas. The pilot of an airplane, the driver of an automobile, the assembly worker or the machine operator all perform critical tasks with their hands. Controls and switches or objects upon which work is to be done must not merely be within reach, they should also be placed in the best possible spatial position relative to the operator. This ideal position has not yet been prescribed. A detailed job analysis of a specific manual operation should of course improve the work area materially, but this information has little transfer value to another situation. Our work is concerned with the general range of hand motion, and we have attempted to find principles applicable to all work situations involving the seated position. The approach is anthropometric-but in an entirely different sense from traditional anthropometry. Our measurements of the space within reach of the seated subject for all possible upper limb postures represent an approach to a dynamic anthropometry. The method of measurement is indirect, and it involves a certain novelty in anthropometric procedure; this shows up especially in the methods of gathering raw data, of making measurements, and of treating data. A study of the functional-anatomical background for limb motion paralleled this study. Relevant work (Dempster, '55a, '55b, '56) involved a study of the motions of the major limb joints and a clarification of the characteristics of the link mechanisms involved. ( A link is the straight line or core line through a body segment between adjacent joint hinge points; it is the mechanical unit of body motion.) Older sources that cannot be ignored in a functional-anatomical-anthropometric study of this type are: Fischer ('07), Fick ( ' l l ) , Strasser ('17), Braus ('21), Lanz and Wachsmuth ( ' 3 5 ) , and Mollier ('38). The Albert-Strasser globographic technique (Albert, 1876; Dempster, '56) for demonstrating the range of individual joint movement has provided useful background material. Equivalent work on living subjects is not available. Joint range studies on living subjects are typified by papers by Gilliland ('21 ) , Sinelnikoff and Grigorowitsch ('3 1 ) , Glanville and Kreezer ( '37 ) , Dempster ('55a) and Barter, Emanuel and Truett ('57). These studies are rather incomplete for certain joints and are not wholly satisfactory. Further work relating to age, sex, race, and occupation is warranted. During the past decade or so, various authors have touched on aspects of the work place. Motion and time study workers (Barnes, '49; Branson, '52), psychologists (Chapanis, Garner and Morgan, '49; Hick and Bates, '50; McFarland, '53), engineers ( Wallichs and Hulverscheidt, '35; Davis, '49; MacNeil, '54), and physiologists (Taylor and Blaschke, '51) have directed attention to spatial aspects of hand action. Dynamometric studies on hand forces by Hugh-Jones ('45) and by Darcus