Keying Force Applied
David A. Thompson Professor of Industrial Engineering, Emeritus Stanford University1
Keyboards are the primary communication medium for entering information into computers, and as such are extremely important in the information age. However, they have also become the primary source of physical injury to computer users. Other sources outline the nature and extent of these keyboard injuries ( Bammer and Blignault 1987; Maedaet al. 1982; Rosignolet al. 1987; Guggenbuhl and Krueger 1990, Thompson 1995, and Matias and Salvendy 1998); and they will not be repeated here.
Force has been discussed as one of the primary causes of musculoskeletal injuries to the upper extremities of the sort experienced by computer keyboarders ( Putz-Anderson 1998). Excessive keying force has also been implicated in operator injuries by Rose, 1991' Loricchio, 1992, Hargreaves, 1992, Feuerstein et al. 1997 and Radwin, 1999.
The present investigation has evaluated one aspect of the effect of keyboard design on the forces that keyboarders apply in the normal performance of their work. Clearly, the amount of force required per key should be minimized, because of the high repetition rate of the work. Text and data entry operators typically enter 12,000 to 15,000 keystrokes per hour (84,000 to 105,000 keystrokes per 7-hour day.
This study focuses on one of the keyboard design characteristics that directly influences the "feel" of the keyboard, tactile feedback, defined by a force-
____________________-157-
