Purpose. Sexual dimorphism refers to diversity between females and males, which occurs in morphology, physiology and behavior. The aim of the paper was to examine sex differentiation in the development of morphological and functional features in children and youths from rural areas 7-14 years, using the results of semilongitudinal examinations from 7 to 10 and 11 to 14 years (boys n = 155 and 224, girls n = 151 and 195). Basic procedures. Body height, weight and lower limb length were measured. Percent fat and lean body mass was estimated using anthropometric methods. Body build was characterized with a modification of Sheldon`s method. Motor development variables included: right hand grip strength, shuttle run, standing long jump, 20 m run, and 1- and 2-kg ball throws. Differences in motor performance related to sex were examined using the multiple stochastic correlation method. Main findings. The pre- adolescent increase of fat tissue is associated with a greater frequency of endomorphs, while the onset of adolescence is associated with decreasing sturdiness of the body. At 11-14 years, girls show changes in somatotype that are manifested in an increase of endomorphy. In all comparisons boys feature higher mesomorphy, body weight, lean body mass and motor performance. In contrast, girls are mainly characterized by higher endomorphy and a greater per cent fat. Mesomorphy shows the largest sex difference among all somatic features. The discriminate power of the motor tests is low. Muscular strength shows the greatest differentiation between children and youth. Conclusions. It appears that the different rate of growth in both sexes had an influence on the size of sex differences in somatic features, body composition and motor tests. On the basis of the multiple stochastic correlation analysis, it is suggested that the female brain is more integrated. It is manifested in a higher frequency of generally physically fit girls, whereas in boys, in the dominance of individuals who achieve very good results in individual motor tests.
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