Describe the three design standards based on anthropometry G

Describe the three design standards based on anthropometry. Give an example of something you would design based on each standard.

Solution

There are three principles for applying anthropometric data to specific design problems; each applies to a different type of situation.

1- Design for Extreme Individuals: In some circumstances a specific design dimension or feature is a limiting factor that might restrict the use of the facility for some people; that limiting factor can dictate either a maximum or minimum value of the population variable or characteristic in question. Designing for the maximum population Value is the appropriate strategy when high value of some design feature should accommodate all (or virtually all) people. In turn, designing for the minimum population value is the appropriate strategy if a given minimum low value of some design feature has to accommodate all (or virtually all) people. Sometimes there may be reasons for accommodating most, but not 100 percent of the population (e.g. it is not reasonable to have all doorways 9 ft (2.7 m) high to accommodate circus giants). Thus, it frequently is the practice to use the 95th and 5th percentiles of the distributions of relevant population characteristics as the maximum and minimum design parameters.

2- Designing for Adjustable Range: Certain features of \'equipment or facilities can be designed so they can be adjusted to the individuals who use them. Some examples are automobile seats, office chairs, etc... In The design of such equipment, it frequently is the practice to provide for adjustments to cover the range from the 5th to the 95th percentile of the relevant population characteristic (sitting height, arm reach, etc.).

3- Designing for—the Average: - The human factors literature is strewn with pronouncements that there are very few (or not) individuals who are \"average.\" Indeed, there are few, if any, individuals who are average on each of many anthropometric characteristics. The use of average values in the design of certain types of equipment or facilities, is appropriate specifically when, for legitimate reasons, it is not appropriate to pitch the design at an extreme value (minimum or maximum) or feasible to provide for an adjustable range. As an example, the checkout counter of a supermarket built tor the average customer probably would discommode customers less in general than one built either for the circus midget or for Goliath. This is not to say that it would be optimum for all people, but that, collectively, it would cause less inconvenience and difficulty than one might be lower or higher.

Factors to be considered in the design of seating It is the requirement of good seating that the person sitting in a seat should be able to maintain a good posture which will not cause any strain of any particular group of muscles. It has already been\" explained that continual- strain on one particular group of muscles can cause fatigue and therefore it would seem that a good seat should enable the user to change posture at intervals so that different muscle groups may be called into play. At the same time the use of a well designed and positioned back-rest may relieve the back muscles of a good deal of a postural work. Any seat which maintains the body in a rigid, position is likely to be unsatisfactory, especially if it causes bad postural habits which may result in the development of the postural abnormalities. Some writers have suggested that a satisfactory posture is achieved only when there is a lumbar concavity but this may well be too rigid an interpretation. A second important factor is that the seat should not press unduly on the tissue of the thigh which is not designed to withstand pressure as is the tissue of the buttocks. Thus if the thighs are pressed into the front edge of a hard seat of the type so often found in many factories, they may be compressed by a quarter or even a third of their full thickness before the weight is taken by the femur. This pressure will restrict the blood flow and may cause pressure on the nerve trunk which runs on the under -side of the thigh and will cause discomfort and may cause the limb to “go to sleep” [Murrell]. The parts of the body which are intended to be sat upon are two bony protuberances of the pelvis known as the ischial tuberosities and the tissue in the vicinity is adapted to withstand pressure without restriction if the blood supply, in fact after the feet and the hands it is probably the part of the body best adapted to the bearing of weight. A well designed seat should therefore bear the weight of the body in a good posture on the buttocks and not on the thighs, and when achieving this objective there are anatomical, physiological and anthropometric principles which have to be taken into consideration and these may impose a few restriction on the design of seats for specific purposes. The elements of good seating will depend on the length, width and shape of the seat; to a limited extent on the material of which the seat is made; on the shape and height of the back-rest and the height of the seat above the floor.