Nondiscriminatory design

Anthropometrically, it ought to be more inclusive than its predecessors. It should do more than accommodate small or large people; it should really fit them.

Work chair size is typically based on what ergonomists call the 'middle-out' model. The designer proportions the chair to fit the anatomical dimensions of the 50th-percentile male - the hypothetical average man at the centre of the anthropometric spectrum - then makes it adjust to fit people within a certain range to either side of the middle. Typically, the goal is to accommodate people from the 5th-percentile female to the 95th-percentile male.

All shapes and sizes

One size does not fit all. The amazing diversity of human form requires a chair that can adapt to different shapes and proportions as well as different heights and weights.

While this would seem to indicate that these chairs should fit 90 per cent of the adult population, it doesn't work out that way. Most people are not perfectly proportioned: a person might be at the 50th-percentile mark for height, but have a 40th-percentile lower-leg length or a 65th-percentile upper-arm length. Even people who are proportioned the same may be shaped quite differently - rounder or bonier, with higher or lower lumbar regions, and with greater or lesser upper body weight. Add in the growing diversity of the work force and the common practice of providing size-related chair features - a high back, for example - only on chairs designated for people who have achieved a certain status within their organisation, and it's easy to see why so many people sit in office chairs that don't fit them well.

Sizes diagram

The result of applying an ends-to-the-middle model to work chair design: one chair in three sizes to fit comfortably people from the 1st-percentile female through the 99th-percentile male. The B-size chair fits the large group of people who fall in the centre of the anthropometric spectrum. The A-size chair, which adjusts lower than the other two, and the C-size chair, with its more generously sized seat and backrest, suit the smaller and the larger people at either end of the bell curve.

Based on an 'ends-to-the-middle' design approach, the Aeron chair comes in three sizes, to provide a fit that is inclusive rather than exclusive. When the designers analysed the dimensional requirements of people at the edges of the anthropometric bell curve, it became clear that a 'one-size-fits-all' office chair cannot be made to provide the personal fit required by today's work patterns. Proportioning the chair in three sizes extends the range of people who can comfortably use an Aeron chair. It also provides people who are only marginally accommodated by chairs designed for 5th-to-95th-percentile users with the custom fit enjoyed by those at the height of the curve.

Middle Out diagram Middle In diagram
'Middle-out' anthropometric design favours the 'average' person, fitting people within a certain range to either side of the 50th-percentile mark. An 'ends-to-the-middle' design approach optimises fit for people at the outskirts of the anthropometric curve as well as those at the peak.

The Aeron chair's inclusive anthropometric approach makes it a truly global chair that complies with all major international standards and guidelines for office seating.

Besides the topographically neutral Pellicle material that conforms to each person's body contours, the Aeron chair has several features that enable it to adapt to individual idiosyncrasies in shape and proportion. Optional armrests adjust for height and width, and an optional lumbar support adjusts for height and depth. Tilt-tension and tilt-limiting adjustments accommodate a wide range of sizes and personal preferences. In the Aeron chair, small people experience effortless full recline for the first time. Large people can maintain an upright posture securely.

For information about how to adjust your Aeron chair, please see the Aeron User Information (pdf format).

Aeron, Pellicle and Herman Miller are registered trademarks of Herman Miller, Inc.