The Body Composition, Somatotype Feature And The Comparison Research On The Body Fat Percentage Speculate Methods In The 12 To 15 Years Old Of Different Developmental Types

Because of the gap between living age and physical age, there are different types of development during puberty. There are obvious differences in the age of puberty beginning, ending and growth speed and development degree. That makes the individual in body composition and somatotype well different. Mid-puberty is the critical in the whole development, so their body fat content, fat-free mass, fat content in different parts of the ratio of total body fat content and distribution are totally different and various according to the different development types of children, so does the gender difference. This study discussed the changes in body composition, the distribution and somatotype regularity. We took the body shape method, skin fold thickness method (ST), bioelectrical impedance analysis (BIA), dual energy X ray absorptiometry ( DEXA) to test on the same subject simultaneously, and the result of DEXA as gold standard. We compared, analysed and evaluated the rest methods in a systematic and objective way, in order to establish body composition testing methods which are suitable for the physical characteristics of Chinese mid-puberty people. And then, that is useful to assess the students'physical fitness for future of the country, and to lay the theory and practice foundation for constructing for different groups of body fat composition measurement system.In this research we selected 150 healthy students from Beijing NO.71 middle school (male life aged 13 to 15 year-old, female 12 to 14 year-old), including 69 males and 74 females. X-ray pictures of wrist bone were taken for students, according to China 05 to determine the bone age. In the same living age of the same gender, the three development types are distinguished by bone age minusing living age. When the value is greater than or equal to 1,it means early development group, when between -0.5 to 0.5, it refers to normal development group; late development group is below or equal to -1.We measured the skin folds thickness at eight different positions for each student,and also measured the body fat percentage through bioelectrical impedance analysis and dual energy X-ray absorptiometry. We analyzed the changes of body composition, distribution regularity and Heath-Carter somatotype regularity, by comparing the results from three different methods, we concluded as follows:1, During mid-puberty, boys and girls of different developmental types are significantly different in the morphological index, body composition, skinfold thickness in the eight parts of body, and fat distribution. And also the differences change according to the levels of maturity completely by the same rate.2, The body fat in mid-puberty boys of different developmental types is mainly distributed in the lower extremities and trunk. The trunk fat in early development group is greater than the lower extremity fat, while the normal and the late developmental group are totally oppisite. For girls, body fat is mainly distributed in the lower extremities and trunk, otherwise in three different types the trunk fat content is larger than lower extremity fat.3, The mid-puberty boys of different development types, early development group tends to mesomorphic- endomorphy: normal development group are apt to balanced-ectomorph, and the late development group tends to balancedectomorph.Of the girls, early development group tends to mesomorphic-endomorphy; while the ectomorphic endomorph and endomorphic-ectomorph is with the normal development group and late development group.4, Mid-puberty boys of different development types feature as follows: In the endomorphic factor and medial factor , early development group is the highest, followed by normal development group, and the late development group is the lest. On the contrary, the highest ectomorphic factor is in late development group, the second and the third is normal and early development group.5, The huge differences in somatotype of the mid-puberty boys and girls is about the endomorphic and medial factors. Endomorphic factor of early development group is well larger than late development group, but ectomorphic factor is on the contrary.6, The somatotype differences of mid-puberty boys of different developmental types are mainly due to the changes of the supraspinale skinfold, fixed upper arm girth and HWR index. FOR girls, the differences are mainly due to the changes of the subscapular skinfold, fixed upper arm girth, fixed calf girth, breadth of the distal ends of femora, HWR index.7, By comparing and analyzing the result of body fat percentage deduced from the bioelectrical impedance analysis and skinfold thickness method, we can find that both are feasible. But the skinfold thickness method has a huge gap with measured fat percentage. While the InBodyJ20 equipment(exclusive for children and adolescent) are more accurate than them.8 In this research, a reliable and accurate formula by skinfold thickness method to assess the mid-puberty body fat percentage is as follows: Boy Fat% = 0.812 +0.749Ñ…Triceps +0.393Ñ…Abdominal -0.555Ñ…Biceps+0.337Ñ…ThighGirl Fat% = 14.191 +0.421Ñ…Suprailiac +0.399Ñ…Chest...