The Kinematics of Sitting

People who sit at their work rarely sit still. Explore how the Herman Miller Aeron Chair supports the body’s natural linkages at all points, in all positions.

Ergonomic Criteria for the Design of the Aeron Chair
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A chair should move the way the body moves. In the best of all possible worlds, the body is free to position itself spontaneously, constrained only by gravity. A person seated at work should be able to move freely and unselfconsciously from computer-related tasks to more relaxed or interactive postures. The work chair should follow along, providing optimal support whether the body is in motion or at rest.

People who sit at their work rarely sit still. Field studies of people working found them assuming a wide variety of postures even while performing a single task. Herman Miller’s own research and observations of seated behaviour in the office identified three distinct modes of sitting at work:

Forward Sitting: Used for performing work on the plane of a desk or for interacting with office equipment. Slightly Reclined Sitting: Used for conversation, telephoning, keyboarding, and mousing. Research shows that it is a preferred work posture. Deeply Reclined Sitting: used for resting, reading, and, in some cases, keyboarding.

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Experts agree that changing positions at work has important benefits for the sitter. Muscle movement serves as a pump to improve blood circulation, movement of the spine nourishes the intervertebral discs, reclining while seated pumps nutrients to the discs, and continuous movement of joints is therapeutic for joints and ligaments.

Design Solution
Provide support that nests the sacral-pelvic area and tilt action that echoes body mechanics. The design of the Herman Miller Aeron Chair bypasses current mechanical models in favour of a tilt geometry based on human body linkages. Bill Stumpf’s research with Roger Kaufman at George Washington University identified the relationship of the body’s major pivot points as it moves between the three basic seated postures. If it were possible for the body to move from an upright seated position to a reclined position without the support or constraints of a chair.

The Herman Miller Aeron Chair supports the body’s natural linkages at all points, in all positions. As the sitter moves from upright to reclined, the feet are not lifted from the floor, as in column-tilt chairs; the back support does not lose contact with the sitter’s back, as it does in many synchronous tilt chairs; the arms do not slide back on the armrests, as they do in chairs that have armrests attached to the seat pan rather than the backrest. In the Aeron Chair, the sitter pays no penalty—in terms of comfort, support, or effort expended—to achieve the benefits of seated movement.

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