Finger motion, wrist motion and tendon travel as a function of keyboard angles

Objective. This study assessed the impact of keyboard angles tin terms of P itch, Roll and Yawl on tendon travel and wrist and finger joint kinematics for the flexor digitorum profundus and flexor digitorum superficialis. Design. A repeated measures, laboratory study was conducted. Independent va riables were three Pitch angles, three Roll angles, three Yaw angles, and t hree keyboard separation distances. Dependent variables were tendon travel, wrist deviation, wrist and finger joint kinematics, and Borg comfort ratin g. Background. The increased usage of computers and the risk of cumulative tra uma disorders have led to the development of alternate keyboards. This stud y is a biomechanical assessment of several keyboard designs. Methods. Lightweight wrist and finger goniometers were used to measure moti on of the wrist in three planes, and for three finger joints. Fifteen exper ienced typists (eight women, seven men) typed a standard text on 30 keyboar d conditions. Regression equations were used to calculate tendon travel fro m joint positions. Results. Tendon travel is sensitive to changes in Pitch, Roll and Yaw angle s with similar to 13% difference between the minimal and maximal tendon tra vel. A flat keyboard produced more tendon travel than keyboards with greate r Pitch and Roll angles. Conclusions There is a trade-off between wrist and finger positions; as the wrist extends more, the finger joints flex more to compensate. Keyboards i mposed different trade-offs between the wrist and finger positions, affecti ng the overall tendon travel. (C) 2000 Elsevier Science Ltd. All rights res erved.