Human Factors Criteria for the Design and Acquisition of ... - FAA

Keyboards June 20049.12.1 Split keyboardsThe most common alternative keyboard is the fixed splitkeyboard. Split keyboards have been shown to reducemuscular strain and tension, reduce fatigue, and promote amore neutral wrist position, reducing pronation and ulnardeviation. Some researchers have also found split keyboardsto be associated with significant pain reduction for userssuffering from carpal tunnel syndrome. [Source: Cakir, 1995;Chen, Burastero, Tittiranonda, Hollerbach, Shih & Denhoy, 1994;Gerard, Jones, Smith, Thomas & Wang, 1994; Grandjean, 1988; Mareket al., 1992; Marklin & Simoneau, 1996; Ro & Jacobs, 1997; Sommerich,1994; Strasser, Keller & Fleischer, 2000; Tittiranonda et al., 1996;Zecevic et al., 2000]9.12.1.1 Use. Fixed split keyboards should be consideredfor touch typists who type frequently as an alternative toconventional keyboards. [Source: Cakir, 1995; Chen et al.,1994; Gerard et al., 1994; Grandjean, 1988; Marek et al., 1992;Marklin & Simoneau, 1996; Ro & Jacobs, 1997; Sommerich, 1994;Strasser et al., 2000; Tittiranonda et al., 1996; Zecevic et al., 2000]Additional information. Although conclusive evidencedoes not exist that split keyboards prevent wrist injury,split keyboards have been shown to promote neutral wristposture. Carpal tunnel pressures, which are associatedwith negative physiological changes in the wrist, arelower when the wrist is in neutral positions. Althoughthere may be slight declines in initial performance withsplit keyboards, typists regain performance within 30minutes to 2 days of use. [Source: Marklin et al., 1998;Sommerich, 1994; Swanson et al., 1997; Tittiranonda et al., 1997]9.12.1.2 Location of split. Split keyboards should be splitbetween the YHN keys and the TGB keys. [Source:Grandjean, 1988]9.12.1.3 Horizontal angle of split. The horizontal splitangle between 2 halves of the split keyboard should befrom 10 to 25 degrees. [Source: Fernstrom, Ericson & Malker,1994; Grandjean, 1988; Keller, Fleischer & Strasser, 2000; Marklin& Simoneau, 1996; Nakaseko et al., 1985; Ro & Jacobs, 1997;Zecevic et al., 2000]9.12.1.4 Lateral inclination. The lateral inclination of afixed split keyboard should be 8-12 degrees. [Source: Ilg,1987; Nakaseko et al., 1985; Swanson et al., 1997; Zecevic et al.,2000]9-36