The Effect of Split and Vertically-Inclined Computer Keyboards on Wrist and Forearm Posture

Abstract

The significant findings from this study of 90 clerical subjects, whose forearm and wrist posture were measured while they typed on three alternative QWERTY computer keyboard designs, are the following: 1) when setup correctly, commercially-available split QWERTY keyboards reduced mean ulnar deviation of the right and left wrists from approximately 12 deg. to within 5 deg. of a neutral position compared to a conventional QWERTY keyboard. 2) with at least a 30 deg. tilt of the keyboard halves, a commercially-available vertically-inclined QWERTY keyboard reduced mean pronation of the forearm by approximately 20 deg. compared to a conventional QWERTY computer keyboard (60 to 40 deg.) The finding that split keyboards place the wrist closer to a neutral posture in the radial/ulnar plane substantially reduces one occupational risk factor of work-related musculoskeletal disorders (WMSDs), namely ulnar deviation of the wrist. The finding that vertically-inclined keyboards reduce forearm pronation substantially is advantageous, at least theoretically, to the keyboard user. However, since the origins of WMSDs, which include carpal tunnel syndrome (CTS) and tenosynovitis, tend to be multifactorial, the extent to which split keyboards or vertically-inclined keyboards could reduce the frequency or severity of WMSDs is unknown.