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We used 3 psychophysics methods to determine perceptible changes in seat height, seat pan angle, and backrest angle using an experimental chair. In the method of adjustment, the chosen chair settings were affected by the initial setting. For example, a high initial setting of the seat height led to a high selected setting and a low setting led to a low value. The difference between settings was referred to as not noticeable difference (NND). The method of limits was used to determine acceptable chair settings using verbal limits such as "too high" and "too low." Using the method of constant stimuli, just noticeable differences (JNDs) were determined for chair height (1.5 cm), seat pan angle (1.2 degrees) and backrest angle (1.7 degrees). The corresponding values for NNDs and verbal limits were about twice as large: chair height (2.5 cm), seat pan angle (4 degrees) and backrest angle (3 degrees). NNDs and verbal limits are unobtrusive measures that are considered more valid than JNDs, which exaggerate the need for adjustability. The results have practical implications for the design of office chairs. [ABSTRACT FROM AUTHOR]

Investigates the possible multidimensional nature of comfort and discomfort in sitting. Solicitation of descriptors of feelings of comfort and discomfort; Treatment of comfort and discomfort as different and complementary entities in ergonomic investigations; Linking of discomfort with biomechanical factors and fatigue; Evaluation of descriptors of comfort and discomfort.

A previous study defined sitting comfort and discomfort as independent entities associated with different factors: discomfort is related to biomechanics and fatigue factors, and comfort to a sense of well-being and aesthetics. In this study a checklist for evaluation of chair comfort and discomfort was analysed in two field studies. In the first study two groups of subjects, ten secretaries and ten managers, evaluated two groups of ten chairs. Subjects assessed each chair three times during a workday using three different types of scales. The results of a factor analysis reconfirmed the factor structure of comfort and discomfort. Analysis of variance demonstrated that discomfort was related to fatigue accumulated during the workday, but it was not related to chair design. There was no significant Chair Time period interaction, which implies that the rank order of preference among a set of chairs was established during the first assessment and did not change during the day. In a second field study 37 secretaries used three different formats of a Chair Evaluation Checklist with 14 items. The results of a factor analysis again confirmed the factor structure of comfort and discomfort. Analyses of variance demonstrated that subjects can evaluate comfort and discomfort simultaneously without any halo-effect. The results have methodological implications for measurement of comfort and discomfort. The findings for comfort, as defined, carry an important message that aesthetic design matters. This could provide a unifying focus for ergonomists and designers. [ABSTRACT FROM AUTHOR]