Does your workday consist of sitting for many hours in a chair keyboarding, talking on the phone, surfing the Web, and meeting with clients and co-workers? And do your back, neck, shoulders and rear end pay the price?

Just like choosing an automobile that has adjustable seats so you can see over the steering wheel and drive safely, it important to "test drive" a new office chair before purchase so you can find one that adjusts properly for your body weight and dimensions. After all, youre going to spend a lot of time sitting in that chair!

Research by the National Institutes of Health (NIH) Division of Safety, the University of California at Berkeley's Health Service Department, and the Cornell University Human Factors and Ergonomics Research Group has indicated there are certain factors that contribute to maximum comfort and safety in office chairs.

Height: Since its important to sit comfortably with both feet flat on the floor, a chair with gas-lift height controls allows you to adjust for varying shin heights.

Seat: A chair seat has to be comfortable for a long period of time. Make sure the seat has enough resilient foam padding to reduce stress on hips and thighs. It should be wide enough to provide at least an inch of space on either side of your body. "Waterfall"-type seat contours can alleviate pressure on the back of the thighs. If your chair has seat depth controls, you can adjust the front edge of the chair so its 2-3 inches from the back of your knees. If the back of your legs touch the edge of the seat, youll be unable to lean against the chairs back support.

Backrest: Look for a chair with an adjustable back support that raises or lowers to a height that supports the curve of your back, especially the lumbar curve of the low back. Adequate lumbar support is a must to avoid stress on your spine. A chairs backrest should also be slightly curved to follow the natural contours of your spine. You should be able to adjust the tilt of the seat up and down independent of the back support. Reclining rests the back muscles, while a forward tilt encourages good back posture and takes the stress off the muscles and discs of the spine. Controlling the tilt tension also allows you to adjust for varying body weights and lets the chair rock or tilt with the correct amount of resistance.

Armrests: Well-cushioned arms that adjust in height and width can help you maintain straight wrist posture for computer work, avoiding carpal tunnel syndrome and reducing sore muscles in the neck, shoulders and back. Armrests that are too high will not allow you to relax your shoulders, while armrests that are too long can prevent you from getting close enough to your desk and may cause back discomfort. Armrests spaced too wide apart will make your elbows stick out from your body in an uncomfortable way.

Health and Safety: Always look for durable construction that has been tested and certified. The best chairs have caster wheels that let the chair move easily on the floor, and a five-point base that provides stability and minimizes the chance of tipping the chair over. Adjustment controls should be easy to operate from a seated position and not require forceful hand movements. Office chairs come in vinyl, leather, and cloth. Cloth upholstery isn't as easy to clean as vinyl, and cloth-covered foam may harbor dust mites. However, vinyl or leather coverings don't breathe as easily as cloth, which may cause discomfort after prolonged sitting.

And finally, remember to get off your butt once an hour for a good stretch. Your body will thank you!