A list of frequently asked questions and answers to them is provided below. The list should not be considered exhaustive.
Anthropometric dimensions are body dimensions measured in a standardized body posture on anatomically strictly defined measurement paths. In other words, measurement is performed in body postures that human beings seldom adopt voluntarily. This form of standardization is nevertheless necessary in order to make the dimensions of the human body comparable and reproducible. Any discrete dimension stated in a table is valid only within its more complex biological context.
Publications of anthropometric data – i.e. including standards – are collections of dimensions that should not be considered exhaustive. They represent collections of the most important absolute and functional dimensions of the human body. They can be used for a wide range of purposes; owing to the growing diversity of design, however, they fail to satisfy all purposes.
What dimensions are needed by the designer? This question is crucial to the humane design of the environment in immediate proximity to the human body. In specific cases, it may therefore be necessary for qualified experts to be tasked with measuring particular dimensions.
Safety dimensions are dimensions that are intended to ensure that factors relevant to safety and health within the person's working environment (e.g. a machine workstation), such as limits for reaches or openings, cannot be violated. As standard, the 99th and 1st percentiles of the body dimension concerned are to be observed for safety dimensions. This is also required by EN 614-11. In some standards, an allowance is added for this purpose to the relevant values derived from anthropometric data. For example, EN 547-1 (Safety of machinery – Human body measurements – Part 1: Principles for determining the dimensions required for openings for whole body access into machinery) specifies the value of the 95th/99th percentile of the elbow-elbow distance plus a safety distance y for a horizontal opening. This is just one of the allowances that must be added to the anthropometric dimensions in order to ensure safety and health during use of the access opening in accordance with EN 547-3. The allowances cannot always simply be added together, since the conditions overlap in some cases.
Safety dimensions of openings through which persons should not reach or crawl are generally geared to values for adults; children and young people may exhibit lower values, depending upon the age group.
The origin of the data is crucial to their suitability for use, particularly when a certain target group is to be considered during design. Where uncertainties exist, it is advisable for the responsible national or international standards committee to be consulted.
Owing to the continual changes in living and environmental conditions, the body dimensions of a population change from one generation to the next. Since these changes cannot be predicted, currently valid anthropometric data must be recorded at regular intervals.
Even during adulthood, human body dimensions are far from constant. For example, whereas the length dimensions of the individual long bones remain largely unchanged, the ability of a joint between two individual bones to stretch may change, as a result of which length dimensions also change. Circumferential dimensions, too, change between younger and older adulthood.
The unisex model is a form of presentation of data for both men and women. In the unisex model, all test subjects in a random sample under analysis are merged to form a single group, and analysed irrespective of sex. The percentiles stated for the individual body dimensions thus cover both women and men.
It must be taken into account that the results of unisex surveys reflect a narrower dimensional range than those of separate surveys by sex. For example, the value for the 5th percentile of a body height surveyed as a unisex random sample would be higher than the 5th percentile solely of the women in the same random sample. In the same way, the value for the 95th percentile of the unisex random sample would be lower than that for the 95th percentile solely of the men in the same random sample (see Unisex model, Figure: Percentile distribution in the unisex model and surveyed separately by sex, with reference to the example of the body height).
The skeletal dimensions (bone dimensions) are the body dimensions measured directly at bony landmarks forming part of the skeleton. Bone dimensions of the "long bones" on arms and legs and the bone dimensions on the skull remain virtually unchanged once the growth phase has been completed. Bone dimensions are variable when they include joints that lose their full ability to stretch with advancing age.
A substantial change is exhibited by bone dimensions that include the spine. With advancing age, the intervertebral discs increasingly lose their ability to store fluid, and thus also lose their resilience. An increase in physiological curvature of the spine in advanced age must also be anticipated. These length dimensions are therefore lower in older persons than when they were in young adulthood.
Circumferential dimensions are among the "obesity dimensions". They may change over the course of a lifetime. The circumferential dimensions are used to measure both the body's muscle content and its fat content. Both of these contents may vary widely over short periods of time as a consequence of personal exercise and/or dietary habits.
On average, adults become fatter with increasing age. However, the population is now also fatter on average than it was in the past, and will in future in all certainty become fatter still.
Despite the wide variation between human beings, two basic body types can broadly be distinguished. Human body typology differentiates between the comparatively slim, tall types (leptosomes) and the comparatively round, squat types (pyknics). These two types constitute the extremes of a basic spectrum, however; numerous transitional forms are encountered within the population.
These two terms describe the different possible morphological forms taken by the human body. Two people may have identical body heights (e.g. 1,730 mm), yet differ considerably in their body types, i.e. their physical proportions. The term "seated giant" describes a person with a proportionally long trunk and short legs, the term "seated dwarf" a person with a proportionally short trunk and long legs.
Proportionally long legs do not necessarily result in great body height. Seated giants and seated dwarfs may be encountered in all percentile groups.
The terms secular acceleration and secular trend describe changes to the human body between an older generation (born earlier) and a younger generation. Besides the increase in the body dimensions, the physical changes also include earlier attainment by young people of biological maturity. For the purposes of ergonomics, the focus lies upon differences in the length dimensions. Recent observations permit the assumption that the secular increase in length dimensions for future generations is gradually coming to an end.
The obesity dimensions (circumferential and breadth dimensions) are also subject to secular development. It is more likely that these dimensions will increase in future successive generations (secular trend) than that the trend will peter out.
The (arithmetic) mean of a random sample describes the average value of all discrete values measured. The mean is calculated by division of the sum of all observations by the number of observations. The standard deviation is a measure of the scatter. It describes how the individual values of a random sample lie around the mean value. For a body dimension that is normally distributed, the single standard deviation describes 68.3% of the recorded values located around the mean, the double standard deviation 95.5% of the values, and the triple standard deviation 99.7% of the values.
The mean and the standard deviation are statistical parameters that may be used solely for normally distributed body dimensions.
Percentiles are indicators that divide the incidences of a body dimension under analysis into 100 parts according to the associated values. In other words, the values are placed in an ordered sequence. A percentile indicates what percentage of the subjects studied attain the dimension in question. The 50th percentile for example, which corresponds to the median, describes the fact that 50% of the discrete observations exhibit values that are lower than or equal to the value concerned, and 50% of the discrete observations exhibit higher values. The 5th, 50th and 95th percentiles have become established as thresholds suitable for use in practice, and cover a dimensional range encompassing 90% of the random population sample.
Percentiles state only the percentage distribution of a body dimension in a random population sample. The percentile values are very unlikely to represent an entire studied population.
Both values are statistical tools that characterize a random sample. The mean is the average value for the entire sample. If the values are normally distributed, the mean (arithmetic mean) is identical to the 50th percentile. Where present, strongly deviating outliers influence the mean. The 50th percentile, the median, is a mean incidence corresponding to the 50th component of the discrete observations. The percentile of 50 indicates that 50% of the discrete observations exhibit values that are lower than or equal to the value concerned.
Whereas the mean need not necessarily be a value that actually exists, the median is a value actually measured on a human being.
Categorically not. Percentiles are values denoting incidences; they describe a group of persons under analysis, not an individual. Whereas the summation of values for an individual is permissible, the summation of percentiles yields results that over- or under-represent the calculated value of the dimension. The use of percentiles to calculate body proportions is also not permissible.
In 2009, the Commission for Occupational Health and Safety and Standardization (KAN) published Report 44, "Anthropometric data in standards". The report underscores the importance of anthropometric data for occupational safety and health, and makes a number of recommendations for action. A key recommendation is made to DIN: that it develop a guide for users of anthropometric data to applying such data, both during design tasks and during the development of product standards.
In response, the Steering Committee of DIN Standards Committee Ergonomics issued a recommendation to the responsible committee (Anthropometry and Biomechanics) that it develop a user guide in the form of a DIN SPEC describing the correct selection and use of anthropometric data in lay persons' terms. Since the committee has requested support from KAN and KAN has considered the undertaking very beneficial for the design of ergonomic work equipment, KAN has commissioned production of a draft of such a guide.
The draft was forwarded to the responsible national standards committee with a view to it being published in a suitable form following further editing. Its publication in the form of an online guide emerged as an advantageous option in the course of the project.
During implementation of the concept, importance was attached to easily comprehensible flow charts and text being used wherever possible.
Normen
1 From DIN EN 614-1:2009 (Safety of machinery – Ergonomic design principles – Part 1: Terminology and general principles): "Where health and safety aspects are important, wider percentile ranges shall be used, according to the risk assessment, at least to the 1st and/or 99th percentiles."