Student Research: Margaret Hughes

, Occupational & Environmental Exposure Sciences (OEES), 2010
Faculty Advisor: Peter W. Johnson

Effects of Key Displacement Distance and Key Switch Mechanism on Applied Forces During Typing


Upper extremity cumulative trauma disorders (CTDs) are the largest source of occupational injuries and illnesses in the US each year. Prior research has tied the development of upper extremity CTDs to computer use. Some keyboard characteristics, including key travel distance and switch mechanism, may affect risk factors for developing CTDs. As occupational use of laptop and short-profile keyboards become more prevalent, it is important to understand how characteristics of these keyboards may affect the risks of users developing CTDs. This study sought to identify how travel distance and switch mechanism affects three-dimensional applied forces, finger flexor and extensor muscle activity, and wrist extension and flexion.

Twenty subjects typed on four study keyboards for fifteen minutes each. Keyboards were placed atop a six degree of freedom load cell and subjects were instrumented with goniometers on their right and left wrists, and EMG over the flexor digitorum superficialis and extensor digitorum communis of their right arms. LabVIEW programs were used to collect and analyze the applied force, goniometry, and EMG data. The data was analyzed in JMP using repeated measures ANOVA with the subject included as a random effect.