Adolescent growth in main somatometric traits of Japanese boys: Ogi Longitudinal Growth Study.

Considerable information is available on peak growth velocity characteristics of various body dimensions but the age at minimal velocity (AMV) and the duration of the spurt are not that well documented. Authors applied the mathematical growth model of Preece and Baines (PBGM1) to six longitudinally followed somatometric traits [height, sitting height, iliospinal height (B-ic), upper limb length (a-da), biacromial diameter (a-a), and biiliocristal diameter (ic-ic)] of Japanese boys of Ogi Growth Study. Biological variables derived from the estimated parameters were studied with emphasis on duration and velocity characteristics of the adolescent spurt. Ages for measurements at peak velocities tend to be younger than previously reported non-Japanese ones. Spurt duration in limb measurements was significantly the shortest. Earlier AMV and later age at peak velocity (APV), thus the longest spurt duration, are the characteristic for transverse measurements (a-a, ic-ic). B-ic and a-da had the largest, while a-a and ic-ic had the smallest relative velocity at AMV. Another result for the transverse measurements is that the magnitudes of differences between relative minimal and peak velocities (RMV, RPV) are the largest. It is suggested that a high level of RMV results from early maturation of bones, thus leading to the shortest spurt duration in limb dimensions, while a low level of RMV results from late maturation of the bones, consequently leading to the longest spurt duration in transverse measurements. This tendency of reverse relation was present in the rest of the measurements as well. Transformation of velocity variables (minimal velocity -- MV, peak velocity -- PV) to relative ones, proved to be useful in observing the relation of spurts in measurements.