Typing for a long period of time on a touch-screen keyboard on tablet computers could lead to chronic shoulder problems, suggests a study in the
November issue of Applied Ergonomics that compared the musculo-skeletal
impact of three types of keyboards, The Wall Street Journal reported.
The small study found touch screen, or virtual, keyboards, which lack
a feedback mechanism indicating a key has been pressed, require less
typing force and finger-muscle activity than conventional keyboards. But
tablet users must keep their fingers hovering above the keyboard to
avoid accidentally activating the keys. That can lead to prolonged
static loading in the shoulders, a form of muscle exertion caused by not
moving, the study suggests.
Researchers at Northern Illinois University in DeKalb, Ill.,
recruited 19 experienced virtual-keyboard users—10 men and nine women in
their mid-20s. The subjects typed passages from Grimm’s Fairy Tales
during five-minute typing tests on touch-screen, desktop and notebook
keyboards. The tests were done twice on each keyboard, while electrodes
recorded muscle activity in the forearms and shoulders. A force platform
under the keyboards measured keystroke force.
The average typing speed on the desktop and notebook keyboards was 63
words a minute compared with 25 words on the touch screen. Accuracy was
also higher on the conventional keyboards. Although muscle activity in
the forearms was lowest when the subjects were typing on a virtual
keyboard, it was higher in the trapezius muscles in the upper back,
which support the shoulders and arms. That may be due to hand and
forearm floating while typing, researchers said. The differences in
trapezius activity were small but could be important if they accumulate
over time, they said.
Caveat: The virtual keyboard screen wobbled slightly during typing, which
may have resulted in an underestimation of the typing forces and
keystroke duration, researchers said. The study was partially funded by
computer company Hewlett-Packard Co.
References & Further Reading:
1.The Wall Street Journal
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