Choosing & Adjusting an Ergonomic Chair
The human body was not designed to keep still for long periods of time. And yet, the majority of American workers spend hours sitting in a chair while performing job activity. While sitting, the large muscles of the back, shoulders and neck contract to support the active movement of the arms and hands. This constant contraction can lead to fatigue and trigger points in the muscles. A good seating system can help alleviate this risk.
A good seating system allows for adjustability between body types. However, one size does not always fit all. A worker who is petite or larger may need to seek out special chair sizes that accommodate their body frames.
Here are some common adjustments that your office chair should be able to make.
- Height - The chair should be able to be raised and lowered easily. Height is the first adjustment that should be made. When looking at the proper height of the chair, the elbows should be slightly higher than the work surface (desk or keyboard) so that the elbow is opened slightly greater than 90 degrees. The feet should be placed flat on the floor and the work surface adjusted (such as with an adjustable keyboard tray) if possible. However, if the work surface is not adjustable then the height of the work surface dictates the height of the chair. In this case, a footrest may be necessary to support the feet.
- Depth of Seat Pan - The seat pan should slide forward and back to accommodate for differences in thigh length. If the seat pan is too shallow then body weight will not be distributed evenly through the thighs. If the seat pan is too deep or too narrow, you will be more likely to sit forward on the edge of the chair rather than taking advantage of the support of the chair back. The seat pan should also be rounded so that sharp edges do not press into the thighs and impede circulation. You should have a space of 2-3 fingers width between the edge of the chair and the back of the knee so that pressure is not placed on the nerves of the leg.
- Back Support - The back of the chair should be able to be adjusted higher or lower to accommodate for a variety of heights. Proper lumbar support will help maintain the natural curves of the back and reduce the risk of back pain.
- Seat Pan Tilt - Tilting the pan of the seat will allow you to accommodate for a variety of job tasks while still maintaining lumbar support. It will also allow you to vary working postures throughout the work day. Recent studies are now showing that a mild recline in a supported position is healthy for the back and reduces back pain. Slouching, however, reduces spinal disk height causing wear and tear on the lowest two spinal levels.
- Arm Rests - The arm rests should raise and lower so that they support the forearms without causing the shoulders to be lifted towards the ears. A good chair will also have arm rests that can swivel or be pushed out of the way if needed. Arm rests should be broad and padded so that the forearm does not press into sharp edges.
- Chair Base - Any rolling office chair should have a 5-point base of support for safety and stability.
A few more tips to help you remain pain-free while sitting at your desk or workstation -
- Visit an office supply store and take the time to sit in a variety of chairs to get the feel for one that is comfortable for you.
- Look for suppliers who have sample chairs that you can test for several weeks in the office environment.
- Learn to use the adjustments.
- Get up often and stretch frequently to increase circulation and reduce muscle fatigue.