Ergonomic Tips for Computer Use

Ergonomic Keyboard Tilt Diagram

The following is an excerpt from the University of North Carolina website on Ergonomics.

Ergonomics can roughly be defined as the study of people in their working environment. More specifically, an ergonomist (pronounced like economist) designs or modifies the work to fit the worker, not the other way around. The goal is to eliminate discomfort and risk of injury due to work. In other words, the employee is our first priority in analyzing a workstation.

Officially, the definition of ergonomics is:
“Ergonomics (or human factors) is the scientific discipline concerned with the understanding of the interactions among human and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance.”
(International Ergonomics Association Executive Council, August 2000)

When evaluating a job, look for three main characteristics known as Ergonomic Stressors:

  • The force required to complete a task.
  • Any awkward or static working postures adopted in completing a task.
  • The repetitiveness of a task.

Any of these factors, or any combination of these factors, may place someone at greater risk for discomfort.

OFFICE ERGONOMICS

Many people don’t realize that a poorly designed computer workstation and/or bad work habits can result in serious health problems. Common symptoms associated with poor design or habits include discomfort in the back, neck and shoulders, hands and wrists, as well as headaches and eyestrain. Fortunately, the solution can be quite simple. Proper workstation setup and work practices can eliminate discomfort and even prevent it from occurring in the first place! Simple adjustments to office equipment can work wonders, making work more comfortable and more productive.

What to look for in a keyboard tray

The purpose of a keyboard tray is to change the height and angle of the keyboard without interfering with how the user uses the keyboard and mouse. Therefore, the tray should be easy to adjust, have enough room for the keyboard and mouse and not prevent the user from typing with the keyboard at forearm length from the body.

Height:
The tray should be height adjustable until the mouse and keyboard are at or slightly below height. Avoid keyboard trays that require unscrewing a knob every time the height is adjusted. Knob-adjust trays discourage users from making small adjustments in height and the knob, often located under the tray, may hit the user’s knee and prevent them from sitting close enough to the keyboard and mouse to use them properly. Many newer trays have lever-less mechanisms, which allow users to adjust tray height by lifting the front edge and either pulling up on or pushing down on the back edge.

Angle:
The tray should be angle adjustable to align the forearm with the keyboard. Often this will require a “negative tilt” where the front of the keyboard is higher than the back. For some users, it may be necessary to adjust the angle of the mouse surface as well to prevent the mouse from rolling off the tray.

Mouse:
The tray should have space for the mouse beside the keyboard at about the same height.

Wrist Rest:
If the tray comes with a wrist rest, it should be soft foam or gel and be removable. Not all keyboards will fit on a standard keyboard tray with the wrist rest attached.

Setting up your keyboard tray

Height:
Sit upright in the chair and bend your elbow 90°. Hold your open, palm down and raise the keyboard tray until the keyboard is just under your fingers. Keep the keyboard at this height or slightly lower it as desired. Reach to the side and check to be sure the mouse is just under your hand as well. Some keyboard trays have mouse attachments that attach to the side and below the keyboard. If this places the mouse too low, put additional mousepads under your mouse until it is at approximately the same height as the mouse.

Angle:
Hold your hand, palm open, over the keyboard. Tilt the tray to align the angle of the keyboard with the angle of the forearm. If the keyboard is below elbow height, this will require a negative slope where the spacebar edge of the keyboard is higher than the back edge. In most cases, the keyboard will be either flat or tilted at a negative slope. Do not use the feet on the back of your keyboard or tilt the tray at a positive slope unless you are seated in a reclined position. Even when reclined, start with the keyboard flat before trying a positive tilt.

Mouse:
Place the mouse beside the keyboard tray and at about the same height. On trays where there is room for the keyboard and mouse on the same tray, place the mouse beside the keyboard. On trays where there is a mouse attachment attached underneath the tray, check the mouse height in the same way as the keyboard height. If the mouse is too low, put something on the attachment under the mouse until the mouse is at the right height. Additional mousepads are a good way to raise the mouse. Some trays have a mouse attachment above the keyboard. These attachments slide or pivot to cover the numeric keypad on the right hand side of the keyboard and reduce side reaching to use the mouse. Keep these trays pivoted over the numeric keypad when not using the keypad.

Setting up your monitor

Side-to-Side Location:
The monitor should sit directly in front of the user, and in line with the ‘g h’ keys on the keyboard.

Tilt:
The monitor should be tilted back, so the bottom of the screen is slightly closer to the viewer than the top.

Height:
The top of the screen should be at or below eye level. If you notice that you tilt your head back while viewing the screen, think of ways you can lower the monitor. First, check to see if the CPU is underneath the monitor. Call 688-HELP and ask if the CPU can be moved to its side safely. If so, move the CPU from under the monitor and place it beside the monitor. Ask (688-HELP) if a special attachment is needed inside the computer’s CD/DVD drive to hold discs in place while the computer is on its side.

Distance:
Start by placing it at arm’s length. Adjust the monitor slightly closer or further away as your eyes dictate. If you find the monitor is only viewable extremely close or far away, consult your optometrist as you may require corrective lenses (or a change in prescription) to see the monitor properly.

Privacy screens:
If the job requires privacy while working, instead of rotating your monitor to one side, consider a privacy screen, which will allow you to keep the monitor directly in line with you and the keyboard.

Visibility:
Keep the computer screen clean by wiping it very lightly when needed with a damp paper towel or monitor cleaning solution.

COMMON SYMPTOMS OF MSDs

What is a MSD?
Musculoskeletal disorders, also called cumulative trauma disorders, are gradual-onset injuries that usually occur after repeated micro-trauma to a specific body part. They may take weeks, months or years to develop and are often ignored at first due to the slow onset of symptoms. MSDs are disorders of the muscles, nerves, tendons, ligaments, joints, cartilage and spinal discs. Some examples of MSDs include: Carpal tunnel syndrome, Rotator cuff syndrome, De Quervain’s disease, Trigger finger, Tarsal tunnel syndrome, Sciatica, Epicondylitis, and tendonitis.

How do MSDs occur?
One way to think about musculoskeletal disorders is to think of parts of your body (wrists, neck, eyes, etc) as a bucket. Micro-trauma from a variety of activities starts to fill that part of your body’s trauma bucket. At the same time, your body is healing and removing trauma from the bucket. If more trauma goes into the bucket than can be removed by healing, the result can be pain, impaired movement and/or weakness. MSDs occur based upon the duration and severity of exposure to ergonomic stressors. MSDs and MSD symptoms usually occur gradually over a long period of exposure where brief exposure would not cause harm.

How do I identify a MSD?
Unfortunately, most of the structures initially affected by MSDs do not have nerve endings to let you track how much micro-trauma your body has left to heal. In a sense, this is good because we are always experiencing some micro-trauma and we would always be in pain. On the other hand, this lack of obvious feedback means we have to pay extra attention to the MSD signs we do get.

Remember, MSDs are gradual-onset disorders, they usually take a while to occur. Therefore be on the lookout for lingering:

  • Discomfort or Pain: A tendon may not have nerve endings but if it starts to swell, becomes damaged or the muscles around it are being overworked, you may feel some discomfort or pain. If it occurs as soon as you arrive at work or start a task, if it wakes you up at night, follows you home, take notice!
  • Tingling, Numbness or Weakness: Some MSDs affect nerve function. If your hands “fall asleep” unexpectedly or wake you up in the middle of the night with that “pins and needles” feeling, this may be a sign of MSD onset. Likewise, if you experience trouble opening doors, jars, etc, this may be a sign.

Other signs include:

  • Burning
  • Swelling
  • Change in color
  • Tightness, loss of flexibility

ERGONOMIC STRESSORS

Poor workplace designs can present ergonomic risk factors called stressors. These stressors include but are not limited to repetition, force, extreme postures, static postures, quick motions, contact pressure, vibration, and cold temperatures. (Ergonomics: The Study of Work, OSHA)

  • Repetition – Is the number of motions or movements that are performed per cycle or per shift.
  • Force – Is the muscles used to produce force in order to perform necessary activities such as lifting, grasping, pinching, pushing, etc.
  • Extreme Postures – Is when muscles are required to work at a level near or at their maximum capacity.
  • Static Postures – A special type of awkward posture which occurs when a body part is not moving, but is still doing work. Examples include sitting in a chair or holding an object.
  • Contact Pressure – Is the pressure from resting part of the body against a sharp edge or corner. Resting the wrists or forearms on a edge of a desk while typing is one example.
  • Vibration – Exposure to local vibration occurs when a specific part of the body comes in contact with a vibrating object, such as a power handtool. Exposure to whole-body vibration can occur while standing or sitting in vibrating environments or objects, such as when operating heavy-duty vehicles or large machinery.
  • Cold Temperatures – Reduce the natural elasticity of the body and reduce the sensation of touch (tactile feedback). In order to get the same amount of tactile feedback, an employee may exert more force than is necessary.

Employee exposure to these stressors can cause injury or some type of MSD.

For more information about MSDs visit the UNC website at: http://www.ehs.unc.edu/workplace_safety/ergonomics/ergo/medical.shtml#identify

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