CONSIDERATIONS FOR LINKING SEATPAN AND BACKREST ANGLES

Modern ergonomic chairs typically have several dimensions that can be adjusted independently of one another. Finding a desirable setting for any one dimension can depend on how other dimensions are set, thereby confronting users with a significant control problem. One design stra tegy for dealing with this problem has been to link changes in seatpan and backrest angles in some ratio, such that a one-degree change in s eatpan angle is associated with a two- or three-degree change in backr est angle. However, there is no evidence to justify the choice of a pa rticular ratio. This article presents data that addresses this issue. Subjects, performing either an entry or verification task, could adjus t the chair to any position. Backrest and seatpan angles were plotted over time and analyzed using both graphical and statistical methods. T he resulting scatter plots do not support the industry standard, 1:2 o r 1:3 ratio, of changes in seatpan to backrest angles. The possibility of a variable linkage is discussed; however, problems associated with such a solution raise the possibility that control issues might be be st addressed through training and exploration.