Abstract: Objective To analyze and estimate the regularity and characteristic of skinfold and body fat of students in grade one at the Huining Senior Middle School.
Method To select students through random cluster sampling and measuring their height , weight , subscapular skinfold ( SSF), triceps muscle of arm skinfold ( TSF), and navle skinfold (NSF), and then calculating BMI value, body density and body fat. Results The main problem in this sample was being underweight; 21.07 % males and 17.86 % females had BMI values lower than 18.50 kg/㎡. Weight, height and BMI of the subjects were increasing with increased age. The results of the Huining student sample were higher than that found in a Gansu Province study, but lower than the whole nation in the Physical Fitness and Health Surveillance of Chinese school students conducted in 2005. The lowest values of SSF, TSF and NSF occurred in the 16-year-old group of males and the 15-year-old group of females. These three skinfold measurements of males had a tendency to drop before the 16-year-old group and to rise after 16-year-old group. With increasing age, the body fat of all subjects increased before the 16-year-old time/period and decreased after 16-year-old time/period. The combined body fat (BF- Combined) of males calculated by the sum of SSF and TSF was lower than the body fat as determined by the SSF (BF- SS) but higher than that determined by the TSF (BF- TS). The lean body mass (LBM) of males increased with age, whereas the LBM of females did not change significantly with increased age, however, the LBM- Combined of both males and females was higher than the LBM as determined by the TSF and by the BF- SS (LBM- SS). There is a difference in the percentile of the sum of SSF and TSF in males and females of this study as compared with the Physical Fitness and Health Surveillance programme. The P3, P5 and P10 of males were higher with other slower than the percentile norms from 2005. The percentile of females aged 14 were higher than the norms in 2005 with other ages were lower. All of these results indicate that the body fat of students in Huining Senior Middle School were not high compared to other groups.
Conclusion These findings showed that physique development of Huining students was in agreement with children in puberty but that the main problem in this sample was that of being underweight. The major growth in males was mainly defined through body weight, and that of females through body fat. It is suggested that there be further education in promoting more exercise and the development of a better diet, especially an increased intake energy foods and high grade proteins. An improvement in living habit is also recommended.

Key words: Skinfold thickness; Body composition; Students; Huining