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Barker Street: Everybody Deserves A Good Chair

For almost 100 years now, researchers have been trying to answer the question – what is a good chair? This research summary examines their work and tries to establish whether they have reached any significant conclusions.

So What?

You may be asking yourself what difference it makes: A chair is a chair, right? Well, not quite. First, people who sit down to work for long periods of time run a high risk of low-back injury, second only to those who lift heavy weights, and the risks increase with age. Also, the total number of lost work days and the cost of each back injury are increasing.

Second, as economies worldwide shift over to knowledge work, more people are sitting down on the job than ever before. In fact, you are probably reading this summary at work, and you’re likely to be sitting down. In a recent study, Herman Miller researchers observed and cataloged movements of 40 office workers for a combined total of 160 hours. As a group, these workers spent 93 percent of their time sitting in an office chair.

Finally, people in every office are doing work that has been radically influenced by the computer. They don’t have to get up often, because all the information they need is one keystroke away. And with much of the information “processed” on screen, they have less variety in their work and fewer reasons to work away from the computer.

Three Research Models

There are literally reams of research on seating. To approach it systematically, the material has been broken into models. (It is important to remember that the models are simplified ways of categorizing the inferences drawn from the material and were not models actually used by the researchers.).

THE STATIC MODEL
This model covers research that assumed there was a proper way to sit at work. Since the 1700s, designers have designed chairs that will support or even enforce correct posture.

THE DYNAMIC MODEL
The Dynamic Model covers research recognizing that people move a lot as they work sitting down and that they get up a lot to move around between bursts of work. Chairs put into this model are those that support, and even encourage, motion.

THE HOLISTIC MODEL
This model covers research that examines the chair in the context of its use. Research in this area is not limited to seating, but includes information valuable to furniture and computer manufacturers, to architects and designers, and to companies and their employees as well. The holistic model covers research that examines the chair in the context of its use. Research in this area is not limited to seating, but includes information valuable to furniture and computer manufacturers, to architects and designers, and to companies and their employees as well.

The three models are not bound by a strict chronology, with the most discredited ideas appearing earliest. In fact, influential researchers from 1924 on have articulated holistic principles, and researchers started writing about dynamic seating in the late 1950s. What the passage of time has revealed is that some early research is no longer relevant because knowledge work has been changed so dramatically by the computer.

The Spine

There is little disagreement about this basic fact: The human spine and muscular/skeletal system are two areas most vulnerable to the stresses of sitting.

The spine looks like a long, bony centipede, tapering at the neck and pelvis, and is composed of 32 individual vertebrae linked together by ligaments. Pads of fluid-filled cartilage, called discs, maintain the correct vertical spacing between the vertebrae and cushion the bones, which may otherwise grate on each other or pinch nerves as the spine flexes. The base of the spine is called the sacrum. The spine works well when a person stands, curving gently inward at the lower back and neck and outward at the shoulder blades and at the pelvis. When a person stands, the disc pressures are lower than when the person sits upright.

Numerous studies of the discs—by A. Nachemson, D. Chaffin, G. Andersson, and K.H.E. Kroemer, among others—show that a slow and subtle pumping action occurs when we are in motion. Nutrients are drawn in through the disc walls and waste products forced out. When we are immobilized, as when we sit for long periods of time, this pumping action is severely reduced and may weaken the disc walls. This weakness may lead to disc rupture—a serious, painful, and frequently disabling event.

Most office work is done sitting down since it permits a high degree of hand-eye coordination and upper-body stability. When a person sits, the inward (lordotic) curve of the lower back can straighten or even begin to curve outward (kyphotic)—something you can feel in your own lower back by placing your hand there as you sit down. It’s the rotation (or tilt) of the pelvis that influences spinal alignment, because the base of the spine, the sacrum, is rigidly attached to the pelvis.

Such reversed spinal curve puts higher pressure on the discs and may contribute to their deterioration and herniation. For this reason, some researchers say the spine is not “well designed” for sitting. They believe people are evolving too quickly from a standing being (Homo Erectus) to a sitting being (Homo Sedens).

Now the good news: When a person sits in a chair and uses its reclining backrest, disc pressure drops by as much as 20 percent. And when someone sits upright and uses the chair’s armrests, muscle activity is also reduced. These phenomena are described variously by numerous researchers in this field.

The Muscles

All physical actions involve both static and dynamic muscle activity. When a person works on a keyboard, for example, the arms are held still, but the fingers move dynamically. All activity is fatiguing, but fatigue can be delayed in onset and intensity if the activity is rhythmic and dynamic.

Dynamic activity is characterized by the alternate contraction and relaxation of muscle fibers, pumping oxygen-rich blood in and forcing out waste products like carbon dioxide and lactic acid. Dynamic activities include walking, running, and swimming. Because these activities are rhythmic, it takes less muscular effort to keep them up for long periods of time.

On the other hand, static activity is very difficult to keep up, even for brief periods of time, without feeling fatigue or pain. Static activity is characterized by the constant contraction of muscle fibers, which causes congestion, traps waste products, and prevents the flow of oxygen and nutrients into the tissue. Static activities include holding any posture for a period of time—standing still, bending one’s head forward, holding one’s arm out from the body, for example.

When people feel fatigue, they intuitively do a number of things to relieve the affected muscles. They may shift positions to come at tasks from a new angle, find ways to support their hands or arms, use the other hand for the same task, take short rest breaks, or switch to another activity for a while.

Research supports the benefits of intuitive responses to fatigue. One experiment showed that people tend to use several muscle groups to accomplish a single task, shifting from one group to the other long before the activity becomes painful. Other research showed the benefits of providing arm or elbow support, especially for work done at shoulder level or higher. Finally, research also showed that rest breaks of as little as 10 seconds increase the ability of a fatigued group of muscles to continue working.

If you want to find out more information about this important study and how to choose the right chair for you, visit Barker Street and read the complete article HERE.

 


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