Cornell University Ergonomics Web


Sitting and Chair Design

1. Introduction - An estimated 50% of people in the industrialized world suffer some form of back complaint and many of these are related to poor seat design. How we sit and what we sit on affects the health of the spine. The lumbar region is the most frequently damaged (L4 and L5). The vertebrae in the lumbar region are the largest in the spine.

2. Posture - the relative orientation of parts of the body in space.

3. Biomechanics of Sitting - depending on chair and posture, some proportion of total body weight is transferred to the floor via the seat pan and feet, armrests, and backrests.

4. Sitting Postures - Sitting with the knees and hips flexed, pelvis rotated backward leads to minimize lordosis, flat, or even kyphotic lumbar spine. Three types of sitting postures normally distinguished:

5. Factors Influencing Posture -

6. Preferred Sitting Angle - Sitting leads to 40 - 90% more stress on the back (disc pressure) than standing posture.

7. Seat Design Criteria

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