The determination of optimum working surface heights by electromyographic and other psycho-physiological techniques with particular reference to interior domestic design

Optimum working heights were determined for domestic kitchen tasks carried out at a sink, worktop and cooker by 24 subjects drawn from each of the 2.5th. 50th and 97.5th percentile stature groups representative of British women. Four independent assessments of working posture were made permitting fine discrimination between the effect of different work levels upon subjects. They were:- (a) electromyography (b) dynamic anthropometry (c) centre of weight displacement. and (d) subjective preferences. All four were statistically significantly correlated with one another. (a) Electromyography The normal comfortable stand at ease posture wes not symmetrical or well balanced. The current British Standard recommended sink height of ,36 inches (914 mm.) was found suitable only for the 2.5th percentile group, invoking maximum muscle activity values in certain muscles in subjects from the 50th and 97.5th percentile groups. A flexion-relaxation posture wes recorded for the 50th and 97.5th percentile groups when working at low sink heights. This may be a contributory factor leading to low back disorders. Methods of postural adjustment adopted in aceommodating the various tasks and working heights were identified and evaluated. (b) Dynamic Anthropometric assessments of working postures were derived from photographs of the angular displacement of the main body segments identified by markers superimposed on bony landmarks on each subject. (c) Centre of Weight Displacements were recorded from a stability platform on which the subjects stood during the task performance. Assessments were based on both area and proximity of centre ot weight locations found relative to the position during normal standing at ease. (d) Subjective Preferences for working heights were recorded on the completion of each task at all workstations. General Conclusions No single working height was found suitable for all sections of the female population. A range of appropriate heights is recommended. The four parameters were in complete agreement in the evaluation of tasks undertaken at the sink and showed significant correlation for the other two workstations. The application of these findings is discussed.