Age at spermarche and comparison of growth and performance of pre- and post-spermarcheal Chinese boys.

The prevalence of first ejaculation emission (spermarche) in Chinese Han boys in 1995 was considered. The subjects were 86,744 Han boys 9 through 18 years randomly selected from 28 provinces. Median spermarcheal ages (MSAs) were 14.4 and 14.6 years for urban and rural boys, respectively, and 14.3, 14.6, and 14.7 years for the boys of 1st, 2nd, and 3rd socioeconomic classes, respectively. Two environmental factors, ecological and socioeconomic, had strong influence upon MSAs. Eight indicators of somatic growth and motor ability were compared between pre- and post-spermarcheal boys of the same age. Post-spermarcheal boys were advanced in body size, shape, and physiological function during early and middle puberty, but most of the difference disappeared by 16 years. Pre-spermarcheal boys in a given age group were more linear and had more potential for increasing leg length into late adolescence. Within an age group, post-spermarcheal boys had advanced performances in several tasks requiring endurance, strength, and power around the age of maximum growth, 13-15 years. At older ages, the groups did not differ.

The geographic clustering of body size of Chinese children aged 7 years.

We studied the morphological differences and similarities among Chinese Han children aged 7 years by using PCA-Q mode cluster analysis. The data were drawn from 17,119 boys and 17,084 girls who came from 28 provinces and participated in the 1985 National Survey on Students Constitution and Health. The children were divided into urban and rural subgroups in each province. First, the values of six measures of body size (stature, sitting height, body weight, chest girth, biacromial diameter and biiliocristal diameter) were normalized into principal component scores; and then clustering was performed among subgroups according to the distances determined by the component scores. The results show significant variations in children's body size exist not only between north and south China, but also between developed and under-developed districts and between urban and rural areas. The geographic and socio-economic factors causing these variations were investigated. The practical use of PCA-Q cluster analysis and its merits in studying Chinese children's growth variations are discussed.