Effects of negatively sloped keyboard wedges on user performance and perceptions

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Virginia Tech


Of the studies that considered negatively sloped keyboards, results showed improved comfort and postural effects while typing on keyboards; however, few studies of negatively sloped keyboard angles and their resulting effects on objective physiological measures, psychological measures, and performance have been performed. The objective of this study was to quantify the effects of negative keyboard slopes on forearm muscle activity, wrist posture, key strike force, perceived discomfort, and performance to identify a negative keyboard angle or range of keyboard angles that minimizes exposure to hypothesized risk factors for hand/wrist work related musculoskeletal disorders.

Ten experienced typists (4 males and 6 females) participated in a laboratory study to compare keyboard slopes ranging from 7° to -30°, at 10° increments from 0° to -30°, using an experimental wedge designed for use with QWERTY keyboards. Repeatability was examined by requiring participants to complete the experiment in two test sessions one week apart. Dependent variable data was collected during 10 minute test sessions.

Wrist posture data revealed postural benefits for negative angles of 0° or greater compared to 7°. Specifically, the percentage of wrist movements within a neutral zone and percentage of wrist movements within ±5° and ±10° degrees increased as keyboard angle became more negative. EMG results were mixed with some variables supporting negative keyboard angles, while other results favored the standard keyboard configuration. Net typing speed supported the -10° keyboard angle, while other negative typing angles were comparable, if not better, than the standard. These findings showed that there was strong support for improved postural changes associated with negatively sloped keyboard wedges, though user perceptions favored the standard configuration.



electromyography, discomfort, key strike force, wrist posture, CTS, negative slope