Engineering anthropometry

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ENGINEERING ANTHROPOMETRY
Engineering Anthropometry-Definition
Variability in body shapes and sizes
Sources of anthropometric variability
Abstract:
Anthropometry is a fundamental branch of physical anthropology. It represents the quantitative aspect. A
wide system of theories and practice is devoted to defining methods and variables to relate the aims in the
different fields of application. In the fields of occupational health, safety and ergonomics anthropometric
systems are mainly concerned with body build, composition and constitution, and with the dimensions of the
human body’s interrelation to workplace dimensions, machines, the industrial environment and clothing. It is
used to improve the human fit in the workplace or to determine problems existing between facilities or
equipment and the employees using them.
Engineering Anthropometry
Anthropometry = Anthro(human) + metry (measurement
Definition: Anthropometry – the study of human body dimensions)
Anthropometry is the scientific measurement and collection of data about human physical
characteristics and the application (engineering anthropometry) of these data in the design and
evaluation of systems, equipment, manufactured products, human environments, and facilities.
Anthropometric variables
An anthropometric variable is a measurable characteristic of the body that can be defined,
standardized and referred to a unit of measurement. Linear variables are generally defined by
landmarks that can be precisely traced on the body. Landmarks are generally of two types:
skeletal-anatomical, which maybe found and traced by feeling bony prominences through the skin,
and virtual landmarks that are simply found as maximum or minimum distances using the branches
of a caliper.
Anthropometric variables have both genetic and environmental components and may be used to
define individual and population variability. The choice of variables must be related to the
specific research purpose and standardized with other research in the same field, as the number of
variables described in the literature is extremely large, up to 2,200 having been described for the
human body.
Anthropometric variables are mainly linear measures, such as heights, distances from landmarks
with subject standing or seated in standardized posture; diameters, such as distances between
bilateral landmarks; lengths, such as distances between two different landmarks; curved measures,
namely arcs, such as distances on the body surface between two landmarks; and girths, such as
closed all-around measures on body surfaces, generally positioned at at least one landmark or at a
defined height.
Other variables may require special methods and instruments. For instance skinfold thickness is
measured by means of special constant pressure calipers. Volumes are measured by calculation or
by immersion in water. To obtain full information on body surface characteristics, a computer
matrix of surface points may be plotted using biostereometric techniques.
Instruments
Although sophisticated anthropometric instruments have been described and used with a view to
automated data collection, basic anthropometric instruments are quite simple and easy to use.
Much care must be taken to avoid common errors resulting from misinterpretation of landmarks
and incorrect postures of subjects.

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The standard anthropometric instrument is the anthropometer—a rigid rod 2 metres long, with two
counter-reading scales, with which vertical body dimensions, such as heights of landmarks from
floor or seat, and transverse dimensions, such as diameters, can be taken.
Commonly the rod can be split into 3 or 4 sections which fit into one another. A sliding branch with
a straight or curved claw makes it possible to measure distances from the floor for heights, or from
a fixed branch for diameters. More elaborate anthropometers have a single scale for heights and
diameters to avoid scale errors, or are fitted with digital mechanical or electronic reading devices
(figure 1).
A stadiometer is a fixed anthropometer, generally used only
for stature and frequently associated with a weight beam
scale.
For transverse diameters a series of calipers may be used:
the pelvimeter for measures up to 600 mm and the
cephalometer up to 300 mm. The latter is particularly
suitable for head measurements when used together with a
sliding compass (figure 2).

Systems of variables
A system of anthropometric variables is a coherent set of
body measurements to solve some specific problem.
In the field of ergonomics and safety the main problem is
fitting equipment and work space to humans and tailoring
clothes to the right size.
Equipment and work space require mainly linear measures of
limbs and body segments that can easily be calculated from
landmark heights and diameters, whereas tailoring sizes are
based mainly on arcs, girths and flexible tape lengths. Both systems may be combined according to
need.
In any case it is absolutely necessary to have a precise space reference for each measurement. The
landmarks must therefore be linked by heights and diameters and every arc or girth must have a
defined landmark reference. Heights and slopes must be indicated.
In a particular survey the number of variables has to be limited to the minimum so as to avoid
undue stress on the subject and operator
Sources of human variability
Biological anthropologists distinguish four types of human adaptation. Over many lifetimes, genetic
changes may occur as a result of natural selection. Over the course of a lifetime, organisms exhibit
plasticity (literally the capability of being moulded). Over the short term, organisms can exhibit
acclimatisation, and over the very short term behavioural adaptation. Only the last two of these
forms of adaptation are reversible. Plasticity is an intermediate form of adaptation that takes
place over the course of a lifetime.
Figure 1
Figure 2

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The distributions of body sizes are known to be normal or similar to normal
Sources of variability
Age
Gender
Racial and ethnic group
Occupation
Diurnal
Secular trend
Factors influencing the change in body size of populations
Many studies indicate that better living conditions are associated with larger body size. Smallness
does not appear to be intrinsic to many groups of people but it is related to development in a
biologically stressful environment. Thus, smallness in a population may be a plastic response to
deprivation.
There is a great deal of evidence to suggest that improved living conditions are accompanied by an
increase in body size. Many countries have witnessed an increase in the size of their inhabitants
over the last 150 years since the establishment of industrialised societies. Part of this in
undoubtedly due to better diet and living conditions;- better sanitation, childhood immunisations,
refrigerated transportation making available a year-round supply of fresh food, and
supplementation of dairy products and cereals with vitamin D.
Anthropometry and its uses in ergonomics
There are two types of anthropometric dimensions useful for the study of human physiology and
its effect on workplace layout and design:
Structural or static anthropometry: The body measurements and dimensions of subjects in
fixed, standardized positions are referred to as ‘‘structural’’ or ‘‘static’’ anthropometrics.
Common structural anthropometric measurements include stature (height), sitting height,
body depth, body breadth, eye height sitting or standing, knuckle height, elbow height, elbow
to fist length, and arm reach.
Functional or dynamic anthropometry: Functional or dynamic anthropometry refers to the
body measurements and dimensions taken during physical activities. Frequently used functional
measurements include crawling height, crawling length, kneeling height, overhead reach, bent
torso height, and range of movement for upper-body extremities.
Anthropometric measurements help designers determine furniture o r workplace layout
requirements based on typical human body sizes. Prior to the utilization of ergonomics and
anthropometrics, many machines and workplaces were designed for the so-called average
employee. Unfortunately, average statistical measurements represent less than 1 percent of the
normal distribution of body measures. For example, if a standing workplace were designed for an
average American male (5’8”), it would not fit 99 percent of the American population. The
evolution of automobile interiors illustrates the value added by the application of ergonomics.
Years ago, seats could be adjusted forward and backward to accommodate the leg length and
pedal reach requirements of the driver. Height, pedal, and steering wheel adjustments were not
typically available. Cars were designed for the average

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person in the population, causing short individuals to look through the steering wheel and tall
individuals to strike their heads against the roof. Today, ergonomists use anthropometric
measurements to include at least 90 percent of the population.
Most workplace designs attempt to achieve this goal by including people dimensions between the
5th and 95th percentiles. This can usually only be accomplished by providing adjustable devices, as
they have done in automobiles by providing multidirectional power seats, moveable pedals, and
adjustable seat backs and head rests. Percentile statistics are used extensively in anthropometrics
to represent the number of people with measurements less than or equal to the dimensions of
interest. If a man has an anthropometric measurement that places him in the 95th percentile, his
measurement is as large as or larger than 95 percent of the population. In considering the height
(stature) of an American population of 50 percent males and 50 percent females, the 5th
percentile of this population comprises those of a height of 604/5 inches while the 95th percentile
includes individuals of a height of 72 inches. If someone is six feet (72 inches) tall, he or she is in
the 95th percentile. This indicates the person is as tall as or taller than 95 percent of the entire
population.
Ninety percent of this male/female population could then be accommodated for height if the
workplace is designed to be adjustable for people between these two measurements of 604/5 and
72 inches. As the size of the average American increases, these measurements increase
accordingly.
Taking anthropometric measures and adjusting the workstation may help eliminate ergonomic
problems. An example is in trying to eliminate back injuries associated with lifting boxes onto a
shelf.
According to the recommendations associated with the NIOSH lifting equation, knuckle height
standing at the start of a lift produces the least amount of stress upon a worker’s back. In addition,
if one can minimize the destination (height of the shelf) where the box has to be placed, this will
also reduce back stress. Thus, back muscle stress could be greatly reduced if the boxes could be
removed from a scissors pallet at knuckle height and stored at knuckle height.
This requires taking employee measurements or referring to anthropometric data for knuckle
height standing. Anthropometric charts state that male and female employees have knuckle
heights ranging from 259/10 inches (at the 5th percentile) to 319/10 inches (at the 95th
percentile). The solution to this ergonomic problem is adjustability! Using an adjustable scissors
pallet and providing a platform for shorter employees can meet the height requirement.