Anthropometrics: Important Aspects of Users’ Bodies - Foundations for Designing User-Centered Systems - page 57

problems, such as reduced attention to the task over time, or an increase in the
number of errors. It can also lead to health issues including eye-strain, back pain,
and upper limb disorders (ULDs).
ULDs are quite common. Many people who use display screen equipment
suffer from ULDs. ULDs include conditions such as repetitive strain injuries (RSI),
cumulative trauma disorder, and occupational overuse syndrome. Although most
of these conditions are not indicative of any serious ill health, it makes sense to try
to avoid them as far as possible.
ULDs are aches, pains, tension, and disorders that involve any part of the arm
from the fingers to the shoulder, or the neck. They include problems with the soft
tissues, muscles, tendons, and ligaments, as well as with the circulatory and nerve
supply to the limbs. ULDs are often caused or exacerbated by work and particu-
larly repetitive work.
There are several risk factors that contribute to the chance of suffering from
ULDs. These include task-related aspects, such as uncomfortable working pos-
tures, continuous use of excessive force, and long tasks. Other risk factors include
organizational aspects, such as a poor working environment (lack of temperature
regulation, poor lighting, and so on) and job demands, such as time pressures, and
a lack of rest breaks or task rotation. There are suggestions that lack of control of
one's time or task exacerbates the situation, encourages reporting of the problem,
or helps accelerate the process. In addition, some people are more susceptible to
some of these risks than other people. It is now a legal requirement in most
countries to make sure that workstations are appropriately set up for people who
regularly use such equipment for extended periods of time, as shown in Fig. 3.4 .It
is important to make sure that the keyboard is placed appropriately with respect to
the hands and the wrists, that the display is positioned correctly, that the display is
appropriately illuminated, and that the angle of the head, neck, back, hips, and feet
when using the workstation are considered.
The recommended sitting posture is to be more upright and avoid pressure on
wrists, hands, and elbows. Posture will naturally change across tasks, however,
with some people leaning forward to type on a touch screen device, for example,
but leaning back to read from the screen of the same device. English and Andre
( 1999 ) identified several postures that should generally be avoided; some of the at-
risk postures observed during web browsing are shown in Fig. 3.5 .
There are situations where people deliberately choose to ignore the risks,
however. Hand-held game consoles, for example, include information about the
potential risks of extended use in their instruction manuals. In spite of this, some
people persist in playing games for excessive periods of time without a break, and
often hunched over the console.
It is most important to be aware of the risks and to take appropriate steps to
mitigate the effects of these risks. The UK's Health and Safety Executive devel-
oped the Assessment of Repetitive Tasks (ART) tool to help in this area. ART is
designed to assist health and safety inspectors in assessing those repetitive tasks