- Its Evaluation and Meaning
The most accurate estimation of body composition
is achieved by use of the underwater or hydrostatic weighing technique.
Obviously, this method places severe restrictions on both practicality
and convenience, and the alternative basis of skinfold thickness
measurements is therefore used in all but the most stringent of
The use of skinfold calipers in the performance
of skinfold thickness measurements (from which are derived the estimates
of body fat) has been well established and documented over the last
40 years, references to which can be found in the Bibliography section
of this manual.
These thickness measurements do not measure overall
body fat mass or its percentage directly but rely on validated equations
that describe the relationship between measures of skinfold fat
as well as other body dimensions and the measured body density.
Body fat percentage is determined from the estimate of body density.
Various experimenters have put forward equations
which are used with either skinfold thickness alone or in conjunction
with other measurements such as body circumference or limb lengths.
Two of the most common sets of equations used are attributable to
Durnin & Womersley (skinfolds alone), and to Jackson & Pollock
(skinfolds and body measurements). The result obtained from the
equations (that of body fat density) is subsequently used in the
Siri equation to calculate the body fat.
Tables are included that show the fat percentage
based on the Durnin and Womersley system. Values are shown for both
males and females across the whole age range based on the sum of
4 skinfold measurements, and the results shown for each 2 millimeter
increment of skinfold thickness.
Skinfold measurements, when properly taken, correlate
very highly (0.83 to 0.89) with hydrostatic weighing, with a standard
error of only about 3 or 4 %. In comparison, the correlation of
height and weight charts is much lower at about 0.60.
The explanation of the use of skinfold thickness
measurement in the derivation of body fat data has been simplified
enormously, and can never detract from the tremendous volume of
research and scientific ability in the fields of both nutrition
and fitness. We all owe much respect and our considerable thanks
to the specialists responsible for guiding us towards a healthier
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