Anthropometrics & Ergonomics
Anthropometrics & Ergonomics Anthropometrics- The study of measuring the various sizes and proportions of the human body. Data is represented in units of measurements from one point of a body part to another (e.g. elbow joint to shoulder joint is 275mm) Greek Antrho- Man Metrics- Measurement Ergonomics- The study of the relationship between man and their environment. This is more concerned with the shape and texture of the product. (e.g. groovy shaped mobile phone case and buttons to make it user friendly and comfortable to use) Greek Ergon- work
Anthropometrics & Ergonomics Using the Ergonome to estimate shape, size and proportions of chair- it is also a useful aid to visualise the comfort of the seating position of the chair
Anthropometrics & Ergonomics Seating People sit down in a number of ways and for a variety, of reasons, like writing, resting and watching TV. When sitting people change positions often to stop parts of the body getting too tired. A good chair design will allow people to move about like this. Seats can be badly designed in a number of ways. Seat A is too high. The front of the seat presses into the back of the thigh at X. The thigh is not meant to bear a lot of weight and will soon get tired. Seat B is too low. The legs either slide forward or the body has to crouch. Both positions soon become uncomfortable. Seat C is too long. Either the sitter has no back support or has to lean back too far. Both positions can cause back ache.
Anthropometrics & Ergonomics How can you decide upon seating size and shape? First you must decide exactly what the seat’s purpose is. An easy chair will have to be very different from a desk chair. (2) Then you must take measurements of the relevant parts of the body (or use anthropometric data). (3) In complex cases you should use a test rig, or prototype model, to test your design.
Anthropometrics & Ergonomics What needs to be measured? 1 Seat height depends upon the distance between the lower heel and the back of the knee. In adult men there is a range between about 370 mm and 470 mm. For women the range is 355 mm to 455 mm. Therefore, overall the range is between 355 mm and 470 mm. An ideal solution would be a seat with an adjustable height. If you cannot make this, a reasonable height for, say, a dining chair would be between 390 and 420 mm. The ideal height would be lower for an easy chair. 2 Seat width is not so critical, unless the chair has arm rests. The seat needs to be wide enough to hold the spread of the buttocks. It must also allow for small changes of position. For long periods of sitting a minimum width is 435 mm.
Anthropometrics & Ergonomics 3 Seat depth depends on the distance between the back of the knee and the buttocks. The minimum for adult women is about 405 mm and the maximum for an adult man is about 505 mm. A common work chair seat depth is 380 mm, which will be suitable angle for both men and women. 4 Seat angle usually slopes down towards the back of the chair. 5 Seat hardness needs to be soft enough for comfort but firm enough to support the body. For short periods of sitting the seat can be hard, but for longer periods some sort of padding has to be provided.
Anthropometrics & Ergonomics 6 Backrests are generally used for chairs in which a person is to be seated for more than a short time. A rest which tilts backwards is more comfortable than a perfectly upright rest. The angle of tilt varies. A leisure chair will tilt more than a work chair, for example. Why do you think this is? A good back rest will support both the lumbar region and the shoulder blades. For working chairs, the shoulders are normally free and only the lumbar region supported. Ergonomics Investigation Tasks (1) Find three different kinds of chair as you can. State their main purpose. Try them out, measure their height, depth, angle and so on and Describe how successful you think they are. (2) Find an adjustable chair, Study it until you understand how it works. How could you improve the design?