INTRODUCTION
Body composition is an essential component in the description
of physical characteristics of an individual.
There are several methods available for the assessment
of body composition in field work and in laboratories
such as skinfold thickness, bioelectric impedance
analysis (BIA), densitometry, dual energy X-ray absorptiometry,
and magnetic resonance imaging. BIA
is suitable for the measurements in field studies since
it is portable and requires less technical skill. It
is also a common method in fitness clubs or health
spas. On the other hand, densitometry is a laboratory
method that requires more technical skill and subject
cooperation during the measurement. Densitometry
is nevertheless accepted as a ‘criterion method’ used
to validate other assessments 1
. To determine body
density, the body weight of a subject is measured in air
and in water with or without a direct measurement of
residual lung volume (RV), while gastrointestinal volume
is assumed to be 100 ml. To assess RV, a special
instrument such as a computerized spectrometer or a
whole body plethysmograph, not normally available
in clinics, health clubs or fitness centres, is required.
A prediction equation for RV is therefore useful when