You don't have to pay too much for the right chair — experts in ergonomics agree that the $1,000-plus models with all the bells and whistles are excessive. But pay some attention to your own specialized seating needs. If you don't, more than comfort will be compromised.

A chair that doesn't fit properly can "affect the shoulders, wrists, neck and even cognitive functioning," says Paul Linden, author of "Comfort at Your Computer: Body Awareness Training for Pain-Free Computer Use" and founder of the Columbus Center for Movement Studies in Columbus, Ohio.

Linden, by his own admission, is somewhat outside the mainstream of thinking when it comes to seating theory. He says too often office chair design has been driven by the assumption that the "body is incapable of self-support."

To the contrary, he says, people are inherently capable of "glorious upright posture," of the sort displayed when 3-year-olds sit on a floor and play with their toys. Trouble is, the subsequently learned notion that thrown-back shoulders and an arched back are synonymous with good posture takes out of play the deep pelvic muscles that really are responsible for supporting the torso.

So, conceding the need for back and arm rests and the ability to make a few basic but necessary adjustments, how do you go about picking a chair that's best for you?

The first step is to analyze the working context in which the chair will be used.

"A chair doesn't exist in a vacuum," says Gary Allread, program director of The Institute for Ergonomics at Ohio State University. "I can't emphasize enough that you need to fit your chair in with how you're doing your work and where your keyboard and computer and monitor are located."

Ilene Zackowitz, senior associate with the Carlsbad, Calif.-based ergonomics consulting firm of Vredenburgh & Associates, agrees. "It's like a puzzle," she says. "Once you change one part of the puzzle, a lot of different components have to be adjusted accordingly."

Things to consider when buying a chair include the nature of the work being done — typing at a computer keyboard versus other desk work, for example — the height of the work surface and, perhaps most important, the stature of the worker.

To accommodate these variables, professional ergonomists generally agree, a chair needs to incorporate at least four key features:

• Adjustable height. The chair should be raised or lowered until the body is in a proper work attitude: upper arms hanging straight down, elbows bent at a 90-degree angle, feet flat on the floor. To achieve this posture, a taller person might have to raise the work surface, while a shorter one may need a foot rest.
• An adjustable seat pan. The goal here is to avoid having the front edge of the seat cut into the backs of the calves and interrupt blood flow. Also, the seat should have a "waterfall" edge that slopes in a downward direction, thus avoiding undue pressure on the undersides of the thighs.
• Adjustable armrests. The real purpose of armrests is to help the worker fully relax during the "micro breaks" that everyone should take. That purpose is defeated if can't be raised or lowered to provide comfortable support. Armrests also can be a hindrance in getting close the work surface, so rests that either swing out of the way or are removable might be worth investigating.
• Sufficient back support. Two common failings are chair backs that either fail to provide good coverage of the worker's back, or provide no lumbar support at all. Adjustable backs can take care of the first problem, while responding to the second one may require the purchase of an inexpensive accessory. Zackowitz favors an inflatable back-support pillow made by Medic Air and readily available online; Linden recommends rolling up a towel and positioning it under the tailbone.

An important thing to keep in mind that buying for an office full of workers is not the same as buying for an individual. Trying to meet the needs of different-sized workers — one 5-foot tall, the other 6-foot-3 — may not be possible with the same chair, no matter how adjustable.

In such cases, Zackowitz recommends, look for manufacturers who offer chairs with different cylinder heights and seating-pan depths in the same style. Don't make the mistake of thinking one size will fit all.

So what should you plan of spending for your ideal chair? According to Allread, there is no one-to-one correspondence between price and ergonomic correctness. "I wouldn't buy a $39 chair and expect it to satisfy my needs," he says. "But I've talked to a lot of people who have bought expensive chairs and they fall apart."

Zackowitz says it's possible to find "a good quality adjustable chair" for no more than $300. She adds, "Some office chairs that are so-called ergonomic designs cost upward of $1,000 or more. It's not necessary to pay that much at all."

However much you pay, you would probably be wise to heed a bit of advice from Linden: "You can't simply throw a good chair at employees and say, 'Here they are.' You have to invest in a little education.