Effects of a Fixed-Angle, Split Keyboard with Center Trackball on Performance, Posture and Comfort Compared with a Conventional Keyboard and Mouse

Results of a laboratory experiment designed to compare performance, posture and comfort for a fixedangle, split keyboard (FASK) with center trackball, and a conventional 101-key keyboard (CK) and mouse are described. The FASK keyboard was 20.5" wide and 9.12" deep, and the alphanumeric keys were split centrally at a total angle of 20'. Each side of the keyboard was sloped to a central peak, 3.15" above the base, at an angle of 10". Both keyboards had a QWERTY key layout. Both keyboards were used on a conventional 29" office desktop. Twelve female trained typists served as subjects. Each attended two experimental sessions on separate days in counterbalanced order. Each session comprised two 5 minute practice trials for each keyboard and a 3 minute cursor positioning trial for either trackball or mouse use. Following practice, each subject performed 3 ten minute typing trials, then another 3 minute cursor positioning trial. The order of trials was counterbalanced for subjects. vp ing speed and errors were measured for all trials. Following these trials each subject donned a wrist exoskeleton (Exos GripMaster system) that dynamically measured wrist posture (extensionhlexion and ulnarhadial deviation were measured simultaneously at 5Hz). Then the subject performed another typing trial and cursor positioning trial. At the end of each session subjects completed questionnaires on musculoskeletal discomfort and on keyboard comfort. At the end of the final session subjects also completed a keyboard preference questionnaire. Results showed that the FASK did not improve typing speed, accuracy, or wrist posture compared with the CK. No performance differences were seen between use of a center trackball and a conventional mouse, and there were no significant differences in wrist posture between these devices. Seven of the subjects expressed a preference for the FASK and rated it as more comfortable, but the other 5 preferred the CK. These results suggest that, even though advertised as "ergonomic", a FASK design does not necessarily improve typing posture or typing performance.