08/08/2007

Forward Sloping May Be Forward Thinking - When It Comes To Chairs!

Admittedly, the science of ergonomics is a work-in-progress, especially when it
comes to office chairs. The problem is that too much of anything, even
something as seemingly harmless as sitting in a chair, can adversely affect the
human body.

Science has worked for decades to figure out a way to relieve the back and leg
pain of workers who sit for a good portion of the workday. Even since the
advent of countless "ergonomically designed" office chairs, the number of
people suffering postural problems and back pain from sitting has not decreased.

One detail has caused much discussion: what to do about the lumbar curve of the
spine.

The majority of guidelines suggest sitting upright, with a 90 degree angle
between the torso and thighs. This flattens the lumbar curve.

Researchers are realizing, however, that a flattened lumbar curve increases
both the mechanical load on your lumbar spine as well as back muscle activity.
Sitting in this position may lead to chronic low back pain.

That's why some experts believe it's time to re-think the entire concept of
"proper" sitting and good chair design. In fact, some are going back to an
older concept, one described by A.C. Mandal in his 1985 book, The Seated Man:
Homo Sedens. Mandal believed in maintaining, above all, the lumbar curve. He
said it was absolutely essential to a healthy, pain-free back.

A New Way To Have A Seat?

One possible solution is to try using a chair with a forward-sloping seat pan
as an option. This allows the worker to maintain the angle between the torso
and thighs at about 105 degrees, while keeping the feet flat on the floor or on
a footrest.

There may be disadvantages to a sloping chair - having to constantly counteract
gravity to avoid sliding off, for one. This requires some muscular effort in
the legs, however, which can in fact be beneficial! Using the legs in this
manner improves blood flow from the lower legs.

Also, people sometimes complain that a sloping chair causes their clothing to
ride up their legs. This can be avoided on a properly designed chair with a
non-slip covering.

There seem to be more advantages, however, than disadvantages. By increasing
the activity of the lower leg muscles and improving blood flow, sitting in a
sloped position might reduce the likelihood of contracting varicose veins.

Furthermore, it's easier to rise from a sloping seat than from a horizontal
one. Most importantly, a sloping seat decreases the load on the lower back and
minimizes the risk of lower back pain. A sloping chair also gives sitters a
wider range of body positions. Experts agree that anything that reduces that
long, static position is beneficial.

Ideally, users of a sloped seat might consider using a slanted desk surface,
which would reduce bending in the neck and upper torso, thus improving postural
comfort.

Where Is Seat Science Headed?

Long periods of sitting often result in lower back pain, especially if the job
or the chair is poorly designed. It's important (but difficult) to find
alternate positions while sitting. While a forward-sloping chair might not be
the ultimate solution, it at least offers another option, with definite
benefits.

Further Information


AplusA-online.de - Source: Canadian Centre for Occupational Health and Safety