5. Dark Margins:

positioning of the keyboard and the mouse, the position of the computer screen, and whether the
worker will be sitting or standing. If the worker also has to frequently access the CPU, then placing
this closc so that the worker can reach the CPU while still in a neutral posture is important.

1. Keyboard-If most of the work being done involves typing text, then the worker should
be centered on the alphanumeric keyboard. Hedge (2004) summarizes the ergonomic con-
siderations with computer keyboards and Kroemer (2001) provides an excellent annotated
bibliography of the keyboard literature from 1878 to 1999. Rempel et al. (2008) have shown
that the wrist extension during typing can elevate carpal tunnel pressure. Most modern
keyboards are fairly flat and asymmetrical-the alphanumeric keyboard is to the left and a
numeric keypad, to the right. If the outer edges of such a keyboard are used as landmarks
for centering the keyboard and the monitor, the worker's hands, especially the right hand,
will be ulnar-deviated because the alphanumeric keys will be to the left of the user's mid-
line. Positioning such a keyboard so that the center of the alphanumeric keys, the H key,
is centered on the midline of the user will reduce the hand deviation. However, if most of
the entry work that is being done involves using the number pad, then aligning this with
the right hand with the arm relaxed by the side of the body will reduce hand deviation.
If the person is left-handed, then a left-handed keyboard or a separate number pad can be