Anthropometry for Persons with Disabilities

The Target Population

Perhaps the most difficult problem presented by this population is its diversity. Disabilities may be caused by a wide variety of diseases and injuries as well as genetic and congenital conditions. For purposes of the Access Board, we recommend that the proposed survey be limited to people who use wheelchairs. We make this recommendation for two reasons. First a modestly sized pilot study cannot adequately address the full range of anthropometric diversity, so it makes sense to focus on that portion of the range which is most different from the non-disabled population, and that portion of the range which is most challenging from the perspective of the designer or architect. The individuals who use wheelchairs fit both these criteria. Second, a major survey may well structure its sampling plan (see below) to proportionately reflect groups which use a variety of mobility aids. If this is done, wheelchair users might be statistically "outnumbered", and the result would be that reach ranges, for example, would not reflect their needs. In a concrete example of this effect, in the U.S. military, females represent about 8% of the total population. For many dimensions women represent the smaller end of the distribution. If they were measured in proportion to their representation in the military, and then the product or workspace design were created to accommodate the 5th percentile through the 95th percentile of the total population, nearly all the women would be excluded from the design because they fall disproportionately into the lowest 5 percent. What the military does instead is to measure men and women separately, and specify design targets which accommodate both men and women. This approach is likely to be effective in the present context, where people who use wheelchairs may be expected to fall at one end of the distribution of many dimensions, and where they may represent a minority of the total population of people with disabilities.

Trying to limit the scope of the pilot study, which should be exploratory in nature, we would also suggest restricting the survey group to an adult population aged 18 and over. The primary reason for this is to reduce diversity in the target population to a reasonable level. Human growth, whether or not there are disabilities involved, produces obvious and enormous anthropometric changes. Because of the anthropometric changes with age, sampling by age (see below) would require very small categories (a year or two) which would dramatically increase the sample size. In addition, methods to gain access to samples of children, measurement procedures and data analysis would all be different from the methods, procedures and analyses developed for adults. Certainly, children are candidates for future studies, and when the time is appropriate, their needs would be better served by a study targeted for their special requirements.

Recruitment of appropriate subjects must be carefully planned for, even when such subjects are widely available. In this case, appropriate subjects are not widely available. Arrangements will have to be made to seek out appropriate subjects in places where they are likely to be found in some numbers. One goal of major nationwide surveys is to maximize the diversity of the target population in the sample, not only with regard to sex, age, and racial/ethnic diversity but also with regard to geographic spread. For this preliminary study – and, perhaps even for larger future studies – geographic diversification is not likely to add anything useful to the variability of the sample. Thus, it should be possible for any qualified investigator living in or near a large city to recruit enough subjects within easy driving distance. The most likely locations would include large-hospital physical rehabilitation programs, nursing homes, and universities that enroll appreciable numbers of students with disabilities.