The test stimuli consisted of pages of double-spaced lines of
text and five groups of five lines of seven random capital
letters (see Appendix A). The stimuli pages were placed on a
document holder located to the left side of the computer display.
The following equipment was used to present stimuli, monitor
keying performance, record hand and upper body position, and EMG
activity, and to perform data analysis. The ISO reference
(traditional) keyboard was an AST KB101 keyboard with an angle of
5 degrees, a key field angle of 8 degrees, and a home row height
of 30 mm with no palm rest; the test keyboard was the Kinesis
Ergonomic Keyboard,.Model 100.
A Precision Biometrics Inc. MyoVision 4000 instrument and
software package was used to collect and analyze EMG activity.
The software was installed on a Hewlett-Packard Vectra PC -
Two Sony DXC-930 video cameras recorded subject posture. One
was located directly above the subject and recorded the upper
body posture so that any deviation of the hands and the elbows
from a neutral position could be recorded and later measured. The
other camera, located at the side of the subject, recorded
vertical angulation of the right hand. A Panasonic WJ-MX50
Switcher allowed the superimposition of the video image from one
camera onto a section of the image from the other camera.
Subjects' keying activity was recorded onto a JVC BR-S822U
video tape deck in a S(Super)-VHS format. Time and date stamping
were incorporated on the video images, via a Panasonic WY-KBS0
Character Generator. Audio instructions ("start, stop and
break time") to subjects. comments from subjects, and
comments from test observers, were recorded via JVC MI-3000 audio
A Hewlett-Packard Vectra PC was used to analyze keying
TAB Products computer terminal tables with adjustable keyboard
trays and ergonomic chairs were used for subject's workstations.
The environmental conditions (temperature, humidity and
illumination) were set to ISO test specifications.
The study was conducted in the GET usability lab. Each subject
participated in the study for three days at the same time each
day, either in the morning or in the afternoon. At the beginning
of the first day, each subject was briefed about the test and
asked to complete Kinesis questionnaire (see Appendix B). The
subjects were asked to adjust their chairs to a preferred
comfortable position. The keyboard height was then adjusted to an
ergonomically correct position at the preferred chair height.
Electrodes were next placed on eleven of the subjects at four
locations on the forearm and at one location on the upper arm to
monitor the muscle activity levels of ulnar deviation, extension,
pronation, and arm abduction. A ground electrode was attached to
the neck of each subject. Table 1 shows the names of the muscles,
activity controlled by these muscles, and assignment of the
electrode to an EMG channel.
|extensor carpi ulnaris
||hand ulnar deviation
|extensor communis digtorium
||abduction of elbow
|pronator radii teres
||inward twist of forearm
Each subject was tested on the two keyboards at the same time on
two different days. Each subject practiced keying on the Kinesis
keyboard for seven hours the day before they were tested on it.
Keyboard assignment was altered between subjects to provide for
balanced experimental design (see Table 2).
The keying tasks consisted of typing text for four 20-minute
sessions and then typing random letters for two 20-minute
sessions on each keyboard. Each subject was given 5-minute break
at the end of each 20-minute session, and 15-minute break between
the third and fourth sessions (see Table 3). The subjects were
instructed to turn each page when they completed keying the page.
Each subject was instructed to use the left hand to turn the page
in order not to interfere with muscle activity monitoring of the
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