Effects of a Multitouch Keyboard on Wrist Posture, Typing Performance and Comfort
The design of computer keyboards is rapidly evolving as portable computing becomes increasingly ubiquitous due to wireless networking and the increased popularity of personal digital assistants and notebook computers. However, there is a balance between mobility and productivity, in terms of text-entry accuracy and speed, which needs to be maintained as computer keyboards become smaller and slimmer through the introduction of ultra low-profile designs. In addition, the ergonomic benefits, in terms of the reduction of awkward wrist postures and user comfort, of ultra-low profile designs are unclear. <br><br> This study tests a new prototype ultra-low profile MultiTouch keyless keyboard (MTK) that uses a MultiTouch surface to create an extremely thin typing environment that requires no force to register a keystroke and allows mousing and gestural input on the same surface. In this study, the MTK was tested against a conventional keyboard (CK) for typing speed, accuracy, wrist postures and user comfort. It was hypothesized that the lack of key travel would increase speed and accuracy, while the ultra-thin design would reduce the amount of wrist extension, which could decrease the risk of a wrist injury or other hand and wrist musculoskeletal disorder. Finally, it was hypothesized that there would be a significant short-term learning effect on typing speed and accuracy for the MTK. <br><br> A laboratory experiment was conducted with 6 males and 6 females typing using two QWERTY keyboard designs: a CK and a MTK. Subjects visited the lab for 1.5 hours for 2 non-consecutive days in the same week, for a total of 3 hours. Each visit consisted of eight randomly assigned 7.5-minute typing tasks of text passages of similar difficulty and identical length. Quantitative measures of typing speed and accuracy were collected using Typing Quick and Easy 13.0 and qualitative measures of user preference and comfort were gathered by self-report questionnaires. A wrist glove electrogoniometer system was used to record right-hand wrist positioning data, which was analyzed to assess the risk of injury. The two keyboards were evaluated in a repeated measures within-subjects factorial design. <br><br> Subjects, typed slower (F1,11 = 41.86, p=0.000) and less accurately (F1,11 = 23.55, p=0.001) on the MTK during the typing tasks. Subjects preferred the CK and reported a higher level of ease (F1,11 = 49.732, p=0.00) and enjoyment (F1,11 = 51.129, p=0.00) during its use. <br><br> Mean wrist extension was lower for the MTK (F1,11= 10.205, p=0.000) while radial and ulnar deviation did not differ significantly between the two keyboards. The MTK had a lower percentage of highest-risk wrist extension (F1,11= 6.437, p=0.028), and conversely, a higher percentage of neutral wrist posture (F1,11= 12.947, p=0.004). <br><br> A significant positive linear trend was observed across the within-subjects scores for speed (F1,11= 9.308, p=0.011) and accuracy (F1,11= 11.903, p=0.005) across tasks in the MTK condition. <br><br> Limitations to this study include practice effects, due to the naive subjects' lack of training on the MTK and the limited duration of exposure to this novel keyboard. Fatigue effects may have also been a factor, even though the experimental conditions were spread out over two non-consecutive days in the same week. <br><br> Future research directions include additional testing of the unique mousing and gestural capabilities of the MTK. Other research suggests that practice and extended exposure to the MTK may raise performance to comparable levels associated with CK devices.
Alan Hedge Geri Gay
College of Human Ecology, Cornell University
gestural interface; alternative keyboard; human factors
dissertation or thesis