|
Abstract:
Cartographers were studied to determine if they were exposed to those risk
factors that may lead to a work related musculoskeletal disorder. As
part of the workstation evaluation, the investigators conducted a literature
search, observed the normal job functions of the cartographers, assessed the
layout of the cartographers' workstation, and administered a body part
discomfort diagram. The results indicated that the work
performed by cartographers has high static demands to the neck, back, and
upper extremities, and only the fingers performed repetitive work to operate
the pointing device. The cartographers operated the pointing device
once every 4-5 seconds and the required force needed to operate the device
is over twice the amount dictated in the military standard for human factors
criteria. Additionally, the results of the body part discomfort
diagram indicated that on average the cartographers suffered from discomfort
at eight different body parts with the neck, back, and shoulder being the
most prevalent.
Introduction
The ancient Egyptians, renaissance Italians, and more recently corporate
America have documented work-related musculoskeletal disorders (WMSDs).
Work related musculoskeletal disorders refer to a category of physical signs
and symptoms due to chronic musculoskeletal injuries in which the causes
appear to be related to some aspect of repetitive work. In 1936,
Klockenburg determined that the layout of the keys on a typewriter put the
wrists in non-neutral postures. Typewriter and keyboard manufacturers as
well as other researchers ignored these findings until the proliferation of
upper extremity injuries associated with use of these products surfaced
during the 1980s. These increased injury rates associated with
keyboard use has set off a flurry of studies with researchers focused on the
ergonomic evaluation of keyboard designs, among these studies are ones
performed by Chen et al; Grandjean, Nakaseko et al.; Lopez; Kroemer; and
Tittiranonda et al.
Matching the propagation
of keyboard users is a new segment of the VDT user population, the “pointing
device user.” Examples of commonly used pointing devices are
trackballs, mouses, and joysticks. The “pointing device user” is different
from the traditional computer user in that he/she uses the pointing device
the majority of the time to enter data and operate computer software.
Furthermore, the user maintains a more static upper extremity posture
whereas keyboard users perform more repetitive motions. This
difference in computer hardware choice created a new set of problems.
Unfortunately there has been little research which has documented injuries
associated with pointing device use. Telephone conversations with U.S.
Army ergonomics experts (Lopez, Rice, and Tannen), U.S. Air Force ergonomics
experts (Klingenberg and Cogburn), and others (Rempel and White) did not
yield any research evidence suggesting problems between pointing device use
and user injury. A literature search linking pointing device use to
injuries yielded two references. The first was a study performed by
Liberty Mutual Insurance Company published in the Human Factors and
Ergonomics Society Journal. The second was in the WMSD News which
used the Liberty Mutual study as its source. Currently, research
articles devoted to the mouse are dedicated to mouse design criteria and
wrist posture. Liberty Mutual's research showed mouse related injuries
jumping from zero in 1988 to 326,099 in 1993. Interestingly these
injuries only account for .58 percent of all claims and .71 percent of all
claims paid out by Liberty Mutual. Conversely, over the same period of
time injuries suffered at a computer workstation (predominately injuries
associated with keyboard use) rose from 292,359 to 15.1 million over the
same time period.
The cartographers main job
function was to digitize a map by connecting contours via computer software.
This is accomplished with the help a puck. The puck is a specially designed
pointing device that acts as a mouse. It has a viewing lens with a
cross hair on the top which aids the cartographer in properly aligning the
puck on any section of the map and to digitize the map quickly. This
job incorporated many factors associated with WSMD. Major tasks
included aligning the puck on the map and clicking on the puck once every
four to five seconds to initiate a software command. Aside from the
repetitive finger motions the task also involved static loading of the
shoulder when the puck is operated. Finally, the size of the map being
digitized and the depth of the work surface caused the worker to assume poor
upper extremity and back postures. The problems faced by mouse users
are documented but are not on as large a scale as the rest of the computer
workstation. However, it is important to note that pointing device use
has mushroomed over the past 10 years and is continuing to grow. The
increased use of window based software has ensured this. Therefore
without changes involving employee work practices and the equipment being
used by the employees, the magnitude of injuries associated with the
pointing device may equal that of today's keyboard user. It is
possible that cartographer development of WMSDs could foretell possible
trends we will see in the population of users of windows systems.
For more information about USACHPPM computer workstation assessments, contact
services@ergoworkinggroup.org |
|