The effect of subject grouping on the kinematic assessment of wheelchair propulsion

Abstract

FINGERTIP IMPACT LOADING DURING KEYBOARD USE D. Rempel, J.T. Dennerlein, C.D. Mote, Jr., and T. Armstrong Ergonomics Laboratory, University of California, San Francisco Department of Mechanical Engineering, University of California, Berkeley Department of Industrial Engineering, University of Michigan Building 112, 1301 South 46th Street, Richmond, CA 94804 Measuring the fingertip loads during keyboard use is a necessary first step to understanding the biomechanics of keying. A single keycap from a standard keyboard was instrumented with a piezoelectric load cell and fingertip motion was recorded with a high-speed video motion analysis system. Fingertip force histories were collected while four typists typed standard text for five minutes. Each keystroke force history contained three distinct phases: key switch compression (I), finger impact (II), and fingertip pulp compression and release (III). The subject mean peak forces ranged from 167.3 to 542.3 gm. Subject mean peak fingertip velocities ranged from 0.28 to 0.66 m/s. Motion analysis combined with high-speed force measurements indicate a ballistic process of finger motion during typing on a computer keyboard.