Impact of New Input Technology on Design of Chair Armrests: Investigation on Keyboard and Mouse

Abstract

This study investigated the effects of addition of a mouse input device on the design of chair armrests. Eleven subjects performed a VDT task for four hours sitting in a chair under three armrest conditions: 1) no armrests, 2) height adjustable armrests, and 3) height and rotation adjustable armrests. The VDT task consisted of 90 minutes of graphics work using a mouse and 60 minutes of keying. The three experimental conditions were performed on three separate days in a random sequence. Muscle fatigue in the forearm (flexor and extensor) and neck-shoulder(trapezius) muscles was measured using surface electromyography. Subjects' working posture was measured using a SVHS camera and postural analysis was conducted using the Ariel Digitizing System. Discomfort and subjective preferences were recorded using the Corlett Scale and other questionnaires. The results suggest that height-adjustable armrests did not provide effective forearm support during mouse use; while the height and rotation adjustable armrests provided superior arm support. For keyboard work, both armrests reduced neck and shoulder fatigue measured in terms of the frequency shift. These results highlight the need for proactive research to tailor workplace design to match the demands imposed by new office technologies.