DEA 651 Graduate Project: Fall 1999
The recommendations
listed below are intended to educate the Department of Planning and Development
on general guidelines for a good ergonomic workstation arrangement. The recommendations are based on the
problems that were identified through the three data collection methods. These
guidelines alone will not be able to capture all the interactions and
complexities of their work environment, but they will be a good start in
providing a base of knowledge about general ergonomic problems and their
solutions.
As the following
information is reviewed, there are two points to keep in mind. One point is to
understand that all body parts are linked together, and consequently a
modification in one area may have significant effects in another. For example,
lowering the seat height so that someone may comfortably rest his feet on the
floor may force a stressful upper body posture if the monitor position or the
keyboard height is not adjusted in concert. Also, it is important to note that
there is no “perfect posture for all time”, and that a dynamic posture
(frequent changes in posture) is a good way to reduce stress and redistribute
pressure related to long duration static posture.
The implementation of
these recommendations will help improve the comfort, productivity and quality,
as well as the health and safety of the employees of the Department of Planning
and Development.
Poor sitting posture can result in lower back injuries and
contribute to the poor positioning of other parts of the body, such as the
arms, wrists, and legs. In a seated
position, the trunk of the body should form an angle with the base of the chair
that is between 100 and 130 degrees.
Both lumbar disc pressure and back muscle activity are lowest at this
angle of recline.
In many of the workstations, this angle was less than 90
degrees and the upper back was not in contact with the back of the chair. The back should be in contact with the chair
so that the weight of the body is evenly distributed throughout the chair.
Also, the seat pan of the chair should be angled slightly downward. This allows the user to sit comfortably and
relieve stress on the ischial tuberosities located at the base of the spine.
In some instances, a new chair should be provided for the
user. There are many features that constitute an ergonomic chair. Some of the most
important of these are upper body and lumbar support; adjustable recline angle
between 100 and 130 degrees; adjustable seat height; and adjustable seat pan angle.
In other cases, the workstation configuration should be changed so that
the user can perform his tasks while leaning against the back of the
chair.
Many of the employees were
observed leaning forward and bending the neck. The weight of the head was not
properly supported which could cause discomfort and injury to the neck and
shoulders. This poor neck posture is often caused by improper monitor
placement. If the monitor is placed to
low, the user will have to tilt his head downward to view the computer screen.
Neck discomfort can also
be a result of the employee constantly turning the neck and head to read
documents while entering data on the computer.
This constant repetition of movements can place severe stress on the
neck and shoulder muscles.
The neck and head position
can be corrected by adjusting the height of the computer monitor. The monitor should be in a position so that
the user’s line of sight is one to two inches below the top of the screen (not
the top of the monitor). This will
reduce the user’s need to lean forward and tilt his head down thus reducing the
stress placed on the muscles in the neck and shoulders.
Neck posture can also be
improved through the addition of a freestanding document holder. This device will allow the user to position
documents close to the computer monitor and reduce the movement of the head and
neck while working on the computer.
Although some workstations in the facility were equipped with document
holders, they only allowed the user to view one sheet of paper at a time. The employees should be provided with
document holders capable of supporting larger documents.
Some employees were
observed sitting with their legs not touching the floor or crossed beneath the
chair. This position can place a high
amount of stress on the popliteal arch that runs through the underside of the
thigh and knee and can result in serious discomfort and injury.
There should also be room
under the desk to extend the legs and feet comfortably. Many workstations used the space beneath the
desk for storage of files, printer paper and other office supplies. This has caused the employees to tuck their
legs and feet under the chair, which could eventually lead to the problems
mentioned above.
The user’s chair should be
height adjustable so that the feet are firmly on the floor in a position
slightly in front of the knees. This
posture will ensure that the feet and chair are comfortably supporting the
weight of the legs.
It is also important to
remove all stored items from beneath the desk to allow for sufficient room for
the user’s legs. Proper leg position
will also help correct poor upper body posture.
The keyboards at many of
the workstations were at the incorrect height for the user. The result was ulnar deviation and flexion
of the wrists. The use of the hands and
wrists in these deviated postures places a large amount of stress on the
tendons and nerves in the hands and wrists.
Improper keyboard position
can lead to such cumulative trauma disorders as tendonitis and carpal tunnel
syndrome. These disorders are caused by injury to the tendons and the median
nerve at the point where they pass through the carpel tunnel of the wrist.
In all of the
workstations, the mouse was placed too far to the right of the user. This caused a large amount of stress on the
arm, shoulder and neck. As the user reached to the side to grasp the mouse, the
arm became abducted, placing significant strain on the shoulders and neck.
Most of the problems
associated with the keyboard and mouse use can be solved with the installation
of an articulating keyboard and mouse tray at each workstation. This system
should be height adjustable, allow the user to slightly tilt the keyboard tray
away from the body for better wrist posture (negative tilt), and allow the user
to use the mouse with his upper arms relaxed and as close to his body as
possible.
Use of this system will
ensure that the user can reach the keyboard and the mouse with his wrists as
flat as possible (not bent up or down) and straight (not bent to the left or
right) and with his arm and shoulders in a more neutral position. Additionally, this system will help
facilitate the creation of an elbow angle (the angle between the inner surface
of the upper arm and the forearm) that is at or greater than 90 degrees to
avoid nerve compression at the elbow.
If an alphanumeric
keyboard is used, the user should make sure that the he is centered on the
keyboard. Most modern keyboards are asymmetrical in design (the alpha numeric
keyboard is to the left and a numeric keyboard to the right). If the outer
edges of the keyboard are used as landmarks for centering the keyboard and
monitor, the user’s hands will de deviated because the alphanumeric keys will
be to the left of the user’s midline. Therefore, the keyboard should be moved
so that the alphanumeric keys are centered with the midline of the user.
It is also possible to use a keyboard without a numeric keypad in
order to position the mouse closer to the user. This is only recommended if the user does not need the numeric
keypad for daily tasks.
Incorrect desk height was
a problem found at many of the workstations.
Desk height refers to the desk that the computer is on as well as any
desk used for writing and other activities.
The desk should be at the correct height to allow the user to position
his hands, wrists and arms in a neutral position. Improper desk height can cause arm abduction and flexion or
extension of the wrists. It is also
important that all work surfaces used by the employee are the same height. This will allow the chair to be adjusted at
a height that will promote proper sitting posture at both desks.
Recommendations:
The recommended height for
a desk used in a computer workstation setting is 28 inches. This height will allow the user to
comfortably perform activities such as reading and writing on the
worksurface. This height is also
appropriate for a computer workstation with an articulating keyboard and mouse
tray.
Screen glare was a
significant problem for many of the users in this facility. This glare can cause eyestrain and
headaches. To reduce glare, the monitor
should be placed so that the screen is flat (not tilted) and directly in front
of the user. Tilting the screen up or
down can increase the glare on the screen and can also contribute to improper
head and neck posture.
Placing an optical glass filter
over the monitor can reduce screen glare.
This type of filter will reduce reflections from nearby windows and
overhead lights. However, it is
important to note that the brightness of the monitor must be increased when a
filter is used.
Glare can also be reduced
by keeping the monitor flat and facing the user. If the monitor is tilted up or down, it will reflect light from
surrounding windows and lights and increase the amount of glare on the screen.
Title Page · Purpose/Data
Collection · General Recommendations
Individual Recommendations · Summary of Recommendations · Slideshow