Normal horizontal working area: the concept of inner boundary

A model was developed to determine the inner boundary of the normal horizon tal working area based on the concept that the elbow and forearm-hand shoul d move on the table surface while describing the area. The proposed model w as applied to determine the normal horizontal working areas for the 5th per centile female and 95th percentile male. It was shown that the conventional models that had disregarded the concept of the inner boundary overestimate d the area on the average by 26%. The proposed model is more realistic and accurate than the conventional models.