Wrist and forearm posture of typists using alternative keyboards.
Marklin-R; Simoneau-G; Monroe-J
American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas. Fairfax, VA: American Industrial Hygiene Association, 1997 May; :55
Hand and wrist cumulative trauma disorders (CTDs), such as carpal tunnel syndrome, have been troublesome in the clerical service sector in the U.S., which has an employment U.S., 1992). Many clerical workers exert 50,000 to 100,000 key strokes per day. While the exact cause of occupationally induced CTDs in computer keyboard users is not known, the deviated wrist posture and forearm posture (ulnar deviation and pronation, respectively) dictated by the design of the conventional, flat keyboard is often implicated in the etiology of hand and wrist CTDs. In response to this problem, several new alternative keyboard designs have entered the market. However, little quantitative data are available as to whether the fundamental designs of these keyboards actually reduce deviated wrist and forearm posture. The specific aim of this NIOSH sponsored study is to determine whether the fundamental designs of alternative keyboards have a beneficial effect on the posture of the wrist and forearm, i.e., whether alternative keyboards impose less ulnar deviation and forearm pronation on the data entry operator than the conventional, flat keyboard. Ninety experienced clerical personnel practiced typing for at least 20 hours in their respective workplaces on one of three fundamental designs commercially available keyboards: fixed-angle split, adjustable-angle split, and vertically inclined. Each subject's wrist and forearm motions were monitored in the laboratory with electrogoniometry while he or she was typing. Results show that the conventional keyboard required 10 degrees of ulnar deviation, while the fixed-angle and adjustable angle keyboards eliminated ulnar deviation and maintained the wrist in a neutral posture. The vertically inclined keyboard reduced the pronation of the forearm by 20 deg. (from 60 deg. for a conventional keyboard to 40 deg. for the vertically inclined). The overall results show that the split and vertically inclined keyboards achieve what their manufacturers claim, i.e., that these alternative keyboards place the wrist or forearm in a more neutral posture for typing.
Cumulative-trauma-disorders; Hand-injuries; Carpal-tunnel-syndrome; Workers; Injuries; Posture; Keyboard-operators; Equipment-design; Data-processing; Humans; Men; Women; Laboratories; Ergonomics; Musculoskeletal-system-disorders
American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas