Cornell University Ergonomics Web
General Problems and Recommendations
The recommendations listed below provide general guidelines for a good
ergonomic workstation arrangement based on the problems that were identified
through the three data collection methods. These guidelines alone do not cover
all complexities of their work environment, but they are a good start, providing
a base of knowledge about general ergonomic problems and their solutions in this
As the following information is reviewed, there are two points to keep in
- 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.
- there is no ďperfect posture for all timeĒ, 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
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 userís
line of sight is one to two inches below the top of the screen (not the top
of the monitor). This will reduce the userís 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 userís 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 userís legs.
Proper leg position will also help correct poor upper body posture.
Keyboard and Mouse Arrangement
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 userís hands will
de deviated because the alphanumeric keys will be to the left of the userís
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.
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
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
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.