Normal horizontal working area: The concept of inner boundary

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