ERGONOMICS OF ERGONOMIC CHAIRS - A STUDY OF ADJUSTABILITY FEATURES

The ease of adjustability of 'ergonomic chairs' was investigated. Twen ty-six chairs were classified with respect to control features. There were 24 different types of control arrangements. Twenty subjects parti cipated in a series of three experiments. The first experiment investi gated what types of control mechanisms could be identified by naive us ers who had received no training or instruction in the use of control devices. The chairs were classified into five broad categories, and on e chair from each category was tested. Two control design features, co ntrol discernibility and control feedback, significantly improved user s' understanding of the adjustability controls. In the second experime nt controls on 20 chairs were evaluated. Subjects were first trained i n the operation of the controls for each chair; and then they performe d a chair adjustability task. Six control evaluation criteria were use d: reachability, force, ease of operation, preference, time to adjust, and number of control activations. Controls with long levers were pre ferred to controls with short levers or push buttons. The third experi ment investigated the effect of the number of adjustability features o n ratings of comfort and time for adjustment. Four chairs with differe nt levels of control complexity were evaluated. The chair with the gre atest number of adjustability controls took significantly greater time to adjust and was also judged to be the most comfortable.