From The Ergoweb® Learning Center

Seating “The Unseatables” – A Look at a Growing Trend

A comfortable, well-fitted office chair enhances employee productivity and safety. It’s a truism of ergonomics, and the top manufacturers have embraced it. Some have gone one step farther, building into their product lines the special needs of employees who are far wider, thinner, shorter or taller than their peers.

In October The Ergonomics Report™ talked to several manufacturers to see how they meet the challenge of seating “the unseatables” – employees whose size or proportions turn any standard chair into a torment.

“Unseatable” isn’t in the lexicon of most of these companies. They offer product lines for most body types, and customization services for the rest.

Special Needs and Risks
People outside the 5’1″-6’3″ range and over 275 pounds – some 95 percent of the population – need more than the effective system of adjustments that are now standard on quality ergonomic chairs. The The Ergonomics Report™ asked Jerome J. Congleton, PhD PE CPE, the inventor of Neutral Posture® chairs, manufactured by a Texas company of the same name, about the special design considerations for this group.

Dr. Congleton, a professor in the Safety Engineering Program at Texas A&M University and Co-Director of the National Science Foundation Industry/University Cooperative Research Center in Ergonomics, suggested it can be dangerous as well as unhealthy for obese people to work in the wrong chair. “Most of the times, what we have heard from other companies or people we sell to, is that the back broke and they fell backwards and hit their head.” Unsuitable chairs can break when overweight people use the arm rests to get in and out of the chair, he said. “When a 500-pound person flops down in a chair and pushes on the armrests to get out of the chair, that’s when (the chairs) usually fail.”

People at the other end of the spectrum are also vulnerable, he explained. “Because they are small, they have to kind of perch themselves on the front of the chair, so they can’t use the back rest … If they sit back in the chair, they put pressure on the soft tissue area behind the knee, and that causes them to lose circulation to the feet and lower legs … so they are usually perched on the front of the chair like a praying mantis.”

The Midpoint Range of Motion
Dr. Congleton introduced the neutral posture concept to office seating in 1983, he said, and at that time it was revolutionary: “Previously everyone was recommending a 90 degree trunk/thigh-erect seated military posture.”

The concept is now standard on many ergonomically-designed office chairs, and the major manufacturers have patented variations.

The professor described it as the posture of an astronaut in a weightless environment. “When the body is in space and there are no forces acting on it, (it) automatically goes to the neutral posture position. And that’s simply the midpoint of range of motion for the different joints. … very similar to the dead man’s float (face down and arms stretched forward) in water, a partial G (gravity) environment.” The midpoint range of motion “also happens to be our maximum strength posture.” He said the likelihood of being injured in this posture is low. Generally, if you are going to get injured, he said, “it’s the result of being at the end of range of motion as opposed to being in the middle or where you have your max strength.”

The company web site describes Neutral Posture® chairs are “the most adjustable you can buy.” The basic model accommodates 94-95 percent of the population, said Dr. Congleton. In this age of obesity, it is clear that the range won’t cover everybody. Two other models and the company’s customization service take care of the 2.5 percent of people at either end of the spectrum.

Inside and outside the spectrum, some body shapes present a particular challenge. “If the person is very short and heavy,” Dr. Congelton explained, “we bend the backrest post so as to go around the buttock spillage at the back and use a shorter cylinder. This is a special order and I don’t believe any other company does it. For the very tall and thin person we use a 10 inch cylinder and long/slimmer seat pan. This again is special order. We have the advantage of three certified professional ergonomists working with (the company)”

ErgoGenesis, LLC, also bases its designs on “the astronaut” posture. Its adjustment system is patented as BodyBilt® 10-Point Posture Control™. The Big and Tall chair is designed for people who weigh 250-500 pounds. The S-T-R-E-T-C-H chair accommodates users over 6’3″ who weigh under 300 pounds. Petite users have their own design and the option of a short cylinder if they are extra short. The Texas company’s customization service accommodates the other body types.

The Canadian company, Ergo Industrial Seating Systems of Ontario, offers plus sizes as well as mix-and-match customization of its eCentric Seating system.

Nick DeJulio, Vice President of Sales and Marketing, told The Ergonomics Report™ that the company “can fit 100 percent of the people, from the very petite to the obese, from the very tall to people shorter in stature.” Their focus is on offering four seat and back sizes, from extra small to extra large. “Plus we have six various pneumatic lifts as well as a heavy duty lift which will accommodate up to 400 pounds. Therefore we can accommodate anyone depending on their height, weight and size.”

Their customization service includes cutting special size seats and tailoring “seat foam if people have specific issues and have altered arms to meet the needs of people who have had strokes.”

Quantifying the truism
Steelcase, a Michigan company, is another of the makers striving to fit all shapes and sizes. Its chairs were used in a recent study that quantified the improvement in productivity and health when an office worker is ergonomically seated.

Researchers at The University of Texas School of Public Health at Houston published the 15-month study involving 200 state employees in the journal, Spine, in December 1993. Billed as the first of its kind, the study examined “the effect of using a highly adjustable office chair to reduce musculoskeletal symptoms such as loss of function, pain or stiffness.”

Ken Tameling, Seating Marketing Manager for Steelcase Inc., told the The Ergonomics Report™ that the Criterion Plus is an example of a specialized product for the right fit. It is warranted for users up to 500 lbs, he said, and is also 5 inches wider in the seat than the average office chair. The “increasing percentage of Americans who are overweight” is boosting sales of the model, he added.

Part of their approach is to make their standard products fit a wide range of individuals. “For example,” he explained, “our Leap chair has a high back that is 26 inches high, 3 inches taller than the typical office chair … and is an inch wider in the seat to accommodate a broader range of torso widths.”

Arm width and seat depth adjustments round out the system. “People, even of the same height, have very different torso lengths. Some are longer from the waist up, some are longer from the waist down. We are moving away from the “three-sizes-of-chair” approach because people don’t fit into nice mathematical averages of the ideal A, B and C size persons.”

Meeting the Needs of the 95th Percentile
Many other manufacturers concentrate on building comfortable and work enhancing chairs for a wide variety of body types within the 95 per cent range. One of the best known is the venerable Herman Miller company, which calls its patented system of adjustability PostureFit®. One its classic ergonomic chairs, the Ergon chair designed by Bill Stumpf, has been on the market for almost 30 years.

Haworth Inc., also based in Michigan, is a rival in the same global market. The design of Haworth’s new Zody office chair was based on very recent lumbar research that set out to quantify comfort. Researchers Teresa A. Bellingar, PhD AEP, Pete Beyer and Larry Wilkerson at the Human Performance Institute of the Department of Industrial & Manufacturing Engineering at Western Michigan University found that 71 percent of the subjects self-selected asymmetrical lower back support to maximize comfort. They also found a possible relationship between the location and relative magnitude of lower back contact pressures with gender, stature and weight.

The findings shaped the way Haworth provides lumbar support in the Zody chair. “We have found that the key to comfort is in the adjustments,” Julie Smith, the Senior Public Relations Administrator at Haworth, explained to The Ergonomics Report™. “The chair provides adjustable lumbar support and the support can be independently adjusted for the left and right sides of the body. We have always known that our bodies are not symmetrical – for instance, one foot can be larger than the other – but we have not designed furniture that way. We are continuing the studies to find out more about differences in human bodies and how we can further accommodate that in a chair. Zody also supports the body in a similar way to a standing position – an S curve.”

From even this small sample of companies in the ergonomic office chair market it is clear that no office workers are “unseatable” – that the right chair is available for every body type. But the conclusion begs the question of whether employers can be persuaded to go to the extra expense and trouble of buying special chairs for workers who are nowhere near average.

The Case for the Right Chair
The conclusions of the Texas researchers may be useful to make the case. “In today’s knowledge economy, in which an increasing number of people are in sedentary jobs, our findings strongly support implementing office ergonomic interventions,” said Benjamin Amick, PhD, the principal investigator. “Our research shows that with a highly adjustable office chair and appropriate office ergonomics training workers can experience reduced pain throughout the work day and be more productive. In the continued debate on ergonomic standards, this study suggests that there is also minimal cost to employers when they invest in ergonomics to improve health. It’s a win-win situation.”

Sources: Dr. Jerome Congleton, Neutral Posture, Inc.; Nick DeJulio, Ergo Industrial Seating Systems; Ken Tameling, Steelcase Inc.; Julie Smith, Haworth

This article originally appeared in The Ergonomics Report™ on 2005-10-26.