Wrist Posture in Office Work - Fundamentals and Assessment Tools for Occupational Ergonomics - page 770

FIGURE 39.3 The keyboards that have been used in the experiment: (a) conventional; (b) maltron; (c) prosper
street technologies; and (d) goldtouch.

force, and performance were measured during a standardized typing task. Four different keyboards
(one conventional and three alternative) were used in this study (Figure 39.3). The conventional key-
board was a Fujitsu 105-keys traditional QWERTY layout with 5 positive slope. The alternative key-

boards were: Maltron E-Type (fixed split design, tilted keys and pads, straight vertical key columns,
central number pad, and slightly modified layout such as thumb keys for Enter, Space, and Backspace),
Goldtouch Adjustable Ergonomic Keyboard (adjustable split angle and lateral slope with lacking ball
and socket latch mechanism), and Prosper Street Technologies (PST) LLC Wave Keyboard (QWERTY
slim design with row vertical curves for longer fingers). Although the Goldtouch w keyboard lateral incli-
nation could have influenced both pronation and ulnar deviation, in order to be able to assess the impact
of split angle design on typing posture, the authors chose a fixed split angle of 25

8

8 anda0 8 lateral slope.

Also, wrist motion and number of wrist repetition greater than 10 (changes in wrist movement) were

measured bilaterally using two SG 65 Biometrics Ltd electrogoniometers. The EMG forearm muscle
activity was measured using DelSys Bagnoly TM EMG system. In order to record the overall applied
typing force, an AMTI force plate was placed under the keyboards.
The results of the study indicate that for all four keyboards, the wrist was ulnarly deviated and
extended for typing. Table 39.1 presents the wrist deviation angles for extension

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/
radial deviation planes while typing on each of the four tested keyboards. When compared to conven-
tional keyboard, Maltron and Goldtouch keyboards significantly reduced the wrist ulnar deviation for

/ flexion and ulnar

TABLE 39.1 Means and Standard Deviations for Average Wrist Angles on Four Different Keyboard Designs

Extension (þ) / Flexion ( 2 ) Ulnar (þ) / Radial ( 2 ) Deviation

Keyboard Left Right Left Right

Conventional 21.80 (4.89) 21.73 (6.12) 15.67 (3.63) 16.91 (4.33)

Goldtouch 25.76 (4.67) 23.56 (5.87) 0.55 (6.44) 3.62 (5.61)

Maltron 15.01 (5.55) 13.29 (5.45) 4.69 (4.11) 7.00 (4.80)

PST 21.00 (5.46) 21.78 (4.45) 14.04 (4.81) 15.58 (3.32)