Choosing an Office Chair: An Informed Decision for Comfort and Health
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Seating as a Dynamic Activity
Because sitting should be a dynamic activity, the office task chair also needs to be dynamic to support the user's many macro and micro movements throughout the day. According to the U.S. Department of Labor Occupational Safety & Health Administration (OSHA, www.osha.gov), "A chair that is well-designed and appropriately adjusted is an essential element of a safe and productive computer workstation. A good chair provides necessary support to the back, legs, buttocks, and arms, while reducing exposures to awkward postures, contact stress, and forceful exertions. [Dynamic] adjustability ensures a better fit for the user, provides adequate support in a variety of sitting postures, and allows variability of sitting positions throughout the workday."
But supporting the user is not sufficient. The chair must support the user in the context of working, while he or she is doing different tasks such as reading documents, viewing the monitor, writing by hand or keying. Leaning back in the chair may provide optimal comfort, but it may not be possible to do if the other components such as the keyboard, mouse and monitor are not ergonomically integrated into the workstation. The office chair must be viewed as part of the workstation environment in a holistic context.
Galen Cranz, author of The Chair: Rethinking culture, body, and design, published in 1998, earned applause for her review of the chair in history, but provoked considerable criticism over her views of the chair as an ergonomic object. "Insofar as the chair stabilizes posture, it contributes actively and directly to disorders of the eye, back and wrist," she writes. "People cannot take advantage of ergonomic chairs, with some capacity for movement built in, because their eyes and hands become entrained with the keyboard and screen they are working on. In this case we cannot really blame the chair-it is simply part of an integrated complex of chair-keyboard-person-screen, which together forms a new machine."
Cranz's conclusions regarding the computer workstation as a 21st century version of Taylor's scientific management are certainly arguable. But her point that the rest of the workstation impacts seated posture as much as the chair itself is telling. Employees may have the best chairs in the world, but if they have to lean forward to use the keyboard or see the monitor, they simply won't be taking advantage of their chairs.
Recognizing the critical need for a holistic approach to the workplace, the Cornell Human Factors and Ergonomics Research Group (www.ergo.human.cornell.edu) has developed a Performance Oriented Ergonomic Checklist For Computer (VDT) Workstations. According to Hedge, the most important things for creating a healthy workplace posture are a good ergonomic chair, optimal keyboard and mouse position, and optimal monitor and document position. "Other furniture items, such as overhead storage, pedestal storage, work surface area and work surface finish, which constitute the bulk of the costs per workstation, are almost irrelevant from an ergonomic standpoint," he says. "Consequently, companies can readily cut furniture costs by minimizing the less essential items and reallocating funds to improving the immediate workspace of the seated worker, which is the micro-environment that actually affects their health and performance."
Seating Adjustments for All Sizes
Since people come in all shapes and sizes, one major challenge is identifying a chair that will fit most people comfortably. Manufacturers generally design chairs to fit the 5th percentile of women to the 95th percentile of men, which theoretically covers 90 percent of the population. This range is overly optimistic for several reasons according to one manufacturer. First, most of the data collected for anthropometric studies come from military populations, which include fewer very large and very small people-and no people with disabilities-compared with the general population. That data also focuses on skeletal dimensions, says Hedge, to the exclusion of soft tissue contours. Second, dimensions may fall below the minimum or above the maximum percentile for different people for each chair component (seat height, seat depth, lumbar support, armrest height, etc.). This means that more than five percent of women and five percent of men may find at least one chair component that doesn't quite fit.
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