Ergonomics: How to choose the right chair

FM Alexander, an actor known for overcoming the traditional limits on bodily movement, said this in 1910:

"Give a [person] the ability to adapt himself within reasonable limits to his environment, and he will not suffer discomfort, nor develop bad physical habits, whatever chair or form you give him to sit upon. I say, “within reasonable limits,” for it is obviously absurd to expect a Brobdingnagian [person] to use a Lilliputian chair. But let us waste no valuable time, thought, or invention in designing furniture, when by a smaller expenditure of those three gifts we may train [a person] to win [his] own conscious control, and rise superior to any probable limitations imposed by ordinary …. fittings".

In short, Alexander thought ergonomics is silly.

There was once a time when the average person, by and large, didn’t sit down all that much over the course of a day, and perhaps then ergonomics wasn’t so important. But computers have changed all that – we’re largely sedentary, and as a result we’re often afflicted by pain, lumbar issues in particular. Ergonomics is the science of fixing all that, but it’s not well understood.

Even without understanding much about ergonomics, we should be able to relatively easily pick a chair that will maximize comfort and minimize posture problems (and ultimately joint pain and medical problems).

PICKING A CHAIR

Armrests

Armrests shouldn’t be a barrier between the person sitting in it and the desk. You should be able to (on models with wheels) turn naturally without the armrests hitting other pieces of furniture, and armrests shouldn’t block your own natural movements either. That’s one reason it’s important to purchase chairs that have adjustable armrests. Soft is best (to avoid stressing your elbows). There are commercially available gel wraps to soften too-hard armrests.

Back support

Adjust the height of the back (while sitting) so the lumbar pad supports the natural curve of your lumbar curve (your lower back). You should be sitting slightly reclined (several ergonomics sources recommend a 110-degree angle).

Chair height

While standing, adjust the height of the chair so the highest point of the seat is just below your kneecap. This should allow your feet to rest firmly on the floor when seated. If you feel pressure near the back of the seat, raise your chair. If you feel pressure near the front of the seat, lower your chair. The goal is to evenly distribute your weight. Office chair seat height should be easily adjustable. A pneumatic adjustment lever is the easiest way to do this. A seat height that ranges from about 40 to 52 cm off the floor should work for most people. This allows the user to have his or her feet flat on the floor, with thighs horizontal and arms even with the height of the desk.

Seat tilt

Seat tilt can be adjusted to improve your comfort. This will also affect your weight distribution. A tilt of five degrees is usually recommended.

Seat Pan

Depth: Usually 42-50 cm wide is the standard. The depth (from front to back of the seat) needs to be enough so that the user can sit with his or her back against the backrest of the ergonomic office chair while leaving approximately 5 to 10 cm between the back of the knees and the seat of the chair. The forward or backward tilt of the seat should be adjustable. When sitting, the seat pan (part of the chair you sit on) should allow you to use the back support without the front of the seat pressing against the back of your knees. If the seat is too deep, try a back support (lumbar pillow) to reduce the size of the seat pan. Some chairs have adjustable seat pans. The adjustment lever is usually located under the front of the chair, much like the lever that moves the seat forward and backward in a car. The seat should have enough width and depth to support any user comfortably.

Width: The seat pan should be wide enough so it does not apply pressure to your thighs. Conversely, the seat should be narrow enough to be able to reach the armrests when they are properly adjusted.