Changing body proportions during growth
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During normal growth body proportions
change appreciably. The skull increases comparatively little
in size. The legs grow proportionately more than the trunk.
Prader (lower figure) recorded the change in the relationship
between ratio of legs and sitting height in Swiss children
and adolescents. Sitting height represents the distance
from buttocks to cranium in a seated person; it comprises
the head, neck and abdominal area and is therefore not a simple
token for the height of the thorax.
At any rate it is obvious that during growth the legs constitute
an increasing proportion of the standing height. Not until
the adolescent growth spurt do body proportions tend to stabilize.
Conclusion
The lungs are contained in the thorax, a part of the trunc. As body proportions change during growth it should not come as a surprise that the relationship between the volume of the lungs and standing height is subject to change. Changes in body height are therefore less than ideal for scaling lung growth.
Understanding is better than plain knowledge. So let us have a look at the skeleton.
Fig. 1 modified from: Thomas A McMahon and John Tyler Bonner: On Size and Life. Scientific American Books, Inc., New York. ISBN O-7167-5000-7.
Fig. 2 modified from: Prader A, Largo R, Molinari L & Issler C (1989). Physical growth of Swiss
children from birth to 20 years of age. Helvetica Paediatrica Acta Suppl. 52, 1–
125.