Physiological Issues

The illustration below shows some of the factors that we deal with in seat design. The red arrows show the main gravitational forces on the body, and the green arrows show how the seat has to deliver its support.

The seat has to:

• keep the correct curvature in the spine
• stop the pelvis tilting backwards
• minimise pressure under the coccyx (tail) and buttocks
• manage high pressure under the pelvis (ischial tuberosities)
• limit pressure under the hamstring muscles
• provide good support under the pelvis and feet

To achieve this, the seat has to have an ergonomics specification, which includes dimensions, shape, geometry, adjustment ranges and cushioning.Other factors can include head and shoulder posture, armrests, footrest, and movements associated with seated tasks.


SEAT DESIGN

The working-place drive must be designed for different size of human. There are 3 ways to test whether the design of the seat is ergonomic which is :

"What-Is-It" gather cushion data

NO, it’s not a car of the future, nor the past either. The strange-looking contraption in which the young woman seems to be going for a drive is designed to gather information for engineers. Installed at the University of Michigan, at Ann Arbor, where thousands of persons have sat in it, the apparatus was built for a cushion manufacturer who hopes from countless measurements made on it to obtain an average-size automobile-seat cushion that will be comfortable for the majority of motorists. This method was used since 1940.