Biomedical Engineering Reference
In-Depth Information
is just over 1.0, fat is less than 1.0, and the lungs contain light respiratory
gases. The average density is a function of body build, called
somatotype.
Drillis and Contini (1966) developed an expression for body density
d
as a
function of ponderal index
c
h/w
1
/
3
, where
w
is body weight (pounds)
=
and
h
is body height (inches):
d
=
0
.
69
+
0
.
0297
c
kg/1
(4.1)
The equivalent expression in metric units, where body mass is expressed
in kilograms and height in meters, is:
d
=
0
.
69
+
0
.
9
c
kg/1
(4.2)
It can be seen that a short fat person has a lower ponderal index than a
tall skinny person and, therefore, has a lower body density.
Example 4.1.
Using Equations (4.1) and (4.2), calculate the whole-body
density of an adult whose height is 5
10
and who weighs 170 lb,
h/w
1
/
3
70
/
170
1
/
3
c
=
=
=
12
.
64
Using Equation (4.1),
d
=
0
.
69
+
0
.
0297
c
=
0
.
69
+
0
.
0297
×
12
.
64
=
1
.
065 kg/1
In metric units,
h
=
70
/
39
.
4
=
1
.
78 m,
w
=
170
/
2
.
2
=
77
.
3 kg,
and
1
.
78
/
77
.
3
1
/
3
c
=
=
0
.
418
Using Equation (4.2),
d
=
0
.
69
+
0
.
9
c
=
0
.
69
+
0
.
9
×
0
.
418
=
1
.
066 kg/1
4.1.2 Segment Densities
Each body segment has a unique combination of bone, muscle, fat, and other
tissue, and the density within a given segment is not uniform. Generally,
because of the higher proportion of bone, the density of distal segments is
greater than that of proximal segments, and individual segments increase their
densities as the average body density increases. Figure 4.2 shows these trends
for six limb segments as a function of whole-body density, as calculated by
Equations (4.1) or (4.2) or as measured directly (Drillis and Contini, 1966;
Contini, 1972).
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