## Boundary Manikins Guidelines

“Manikins” are typically two- or three-dimensional representations of the human form with external contours intended to represent human body size and shape for design. They exist as 2D templates and as 3D computerized manikins (e.g., Jack). Digital Human Modeling, or DHM, refers to the use of computerized manikins for design. A “boundary manikin” or “boundary case” refers to a body geometry that lies at the limit of acceptability. For a design problem in which only one body dimension is relevant and both “small” and “large” people must be considered, only two cases are typically considered to describe the upper and lower limits of acceptability. For example, to accommodate 95% of the population, one might use the 2.5th-percentile and 97.5th-percentile values of the measure of interest as boundary cases. Note that since the distribution of body sizes is continuous, the specific level of accommodation (95%) could be achieved by targeting any number of segments. Generally the range is selected to minimize the amount of adjustability or material and cost required (e.g., the 0th to 95th percentile or the 2.5th to 97.5th percentile portion of the distribution).

Since stature and weight data are the most easily obtained and therefore prevalent in databases, distributions of those variables are often used to determine the sizes of the “small” and “large” virtual users. To position a manikin, it is helpful to have knowledge of the length of the relevant dimension(s). This dimension may not be stature or weight, but instead might be leg length or shoulder height, for example. Therefore, in the event that the true measure of interest is something besides stature, proportionaility constants are often used. These represent the average length of a particular body segment as a proportion of stature. This approach is imprecise, however, since there is no “standard” person with all dimensions belonging to the same percentile. For example, when a manikin representing the body as a kinematic linkage is scaled so that an overall dimension, such as stature, meets some target percentile, the body dimensions that make up the aggregate dimension do not themselves define useful design limits. That is, a person who is 5th-percentile by stature has other body dimensions that vary widely from the 5th-percentile for those measures.

The ANSUR II database is a useful source of anthropometric data for configuring boundary manikins because it contains hundreds of body segment measurements collected from thousands of people. The tools on this website can help you to explore the ANSUR II data. However, caution must be exercised in the application of these data since the data were collected from a specific population that is not representative of, for example, US civilians. NHANES data are another useful source of anthropometric and demographic data. NHANES data are collected every few years, so the measures are more representative of the general US population. However useful measures for spatial design are mostly limited to stature and BMI. Proportionality constants may be used to calculate the actual measure of interest. Further details regarding sources of anthropometric data may be found in the Anthropometric Database guidelines on this site.

Boundary manikins have various limitations when used for design. Some of these limitations are addressed in the publications on this site. Examples are Garneau and Parkinson (2009, JMD) and Garneau and Parkinson (2009, JED), which provides a more general discussion of the appropriateness of several design methods.