[Changes in body proportion as indicators of biological age].
Modifications in body proportionality translates into the different stages of development during the growing years of one's life. The lack of more direct and applied information on the topic, originated the current study, where already-published somatometric material was used. Two internationally accepted forms to measure the upper and lower portions of the body were analyzed: measuring height while in the sitting position (TS) or calculating height by using the difference in height minus that found in the sitting position (T-TS), or by measuring the lower segment (SI) or by subtracting and obtaining the value for the upper segment (SS). Since TS includes the muscular and fatty thickness of the gluteus, the value for T-TS is always lesser than that for the upper part of the body and therefore these are variables which do not clearly illustrate changes in linear proportionality. On the other hand, the SS is greater than the SI during infancy and the pre-school years. This relationship is later inverted (the only time during which both values are the same), a finding which occurs in small girls aged 4 years and 10 months, and little boys at the age of 6 years and 3 months. Therefore, these values and the point at which they intersect, constitute an excellent development age marker in an age for which, until now, no indicators with a practical application exists besides that of "bone age".