Ergonomics - How to Select a Chair
What do you need to look for in Ergonomic Seating?
In order to help make sure you choose a chair with all the necessary adjustments, we will break the chair down into its components.
Casters and Base
Use a chair with casters and a 5-point base to ease movement and minimize possible tipping. Generally, nylon carpet casters are standard, but soft wheel casters are available for hard surfaces such as linoleum. Rubber locking casters are useful on stools to prevent tipping.
Almost all task chairs come with a hydraulic seat height adjustment. This is probably the single most important adjustment mechanism on a chair. It allows the user to adjust the chair so their feet can rest properly on the floor or footrest and the upper body is properly aligned with the computer monitor and input devices such as the keyboard and mouse.
For optimal flexibility, the height range of the seat should include heights both slightly lower and slightly higher than your ideal setting. Many chairs offer a choice of height cylinders so the chair can be ordered with the correct height range for the individual.
Adjust your seat height so that your hips are level with or
slightly higher than your knees.
Seatpan Size: The seatpan is the component of the chair that supports the majority of the user's weight. It is important to purchase a chair which uses dense, small-cell foam padding or spring coils to retain its support and cushioning (this usually involves purchasing a chair over $250.00).Seatpan Depth:
The front part of the seat should slope down slightly (waterfall design) and allow a fist size
gap (2-4 fingers) between the back of the knees and the front edge of the seatpan to reduce pressure at the back of the thighs. Some chairs feature adjustable seatpan depths in the form of a back depth adjuster or a sliding seatpan mechanism. This adjustment allows small and tall users to adjust the distance of the seat from the backrest. Sometimes an extended seatpan slider is necessary for best fit.
Adjust your seatpan depth so that you can place 2 to 4 between the front edge
of the seat and the back of your knees.
The width of the seat should be at least one inch wider than your hips. Conversely it should not be so wide that the user cannot rest his arms on the armrests without stretching them out to the side.
Tilt adjustments are preferred to allow a forward working posture to be attained or a reclined posture. This feature is not always present.
If present, adjust the seatpan tilt for forward or reclined seating.
Adequate lumbar support is the most crucial element of a backrest. The backrest should either be small enough to fit into the small of the back, clearing the pelvis and back of the rib cage, or curved to provide adequate support. Inadequate lumbar support places excess pressure on the spine.
The backrest should also have angle, in-out, and height adjustments
to achieve proper spinal alignment. The angle adjustment
allows the user to adjust the angle of the back rest relative to the seatpan, as opposed to the tilt mechanism,
which moves the seatpan with the backrest. When you change the tilt, the angle between the seatpan and the backrest stays the same. A chair in a tilted/reclined position transfers some of the upper body weight to the backrest of the chair. You can also rock back and forth in chair. Use the tension knob (generally located directly centered under the seatpan) to control the ease with which to rock. It is also important that the user change body positioning throughout the day.
Sometimes, a lumbar support cushion properly placed behind the small of the back can help to accentuate lumbar support. However, keep in mind that such use may lend itself to the need to make other adjustments (e.g., seatpan depth).
Adjustable height and width armrests are absolutely necessary when purchasing a chair with armrests. Armrests heights should be adjusted such that the shoulders are fully relaxed. The widths should able you to sit with your arms in close to your body.
The armrests should be made of a soft material and should be at least 2" wide to provide adequate surface area for the forearms.
|Height adjustable armrests
||Width adjustable armrests
A headrest provides support for your head and can reduce the weight your neck must support. If you have neck issues, strongly consider buying a chair with a headrest.
Once you know what chair features to look for, it is very important that you be fitted to a chair or trial a chair PRIOR to purchase to ensure you are able to adjust the chair to your anthropometrics. Upon completion of this process, you are ready to purchase a chair. View the list of approved chairs
or contact the APHIS Ergonomics Program for assistance at: 301-436-3175.