关键词: 发育期少女, 胸背部形态, 聚类分析, 三维特征

Abstract: For adolescent girls, fitted bras can provide support for the chest and help maintain body balance, while adjusting the shoulder strap to ensure its appropriate length can help maintain the vertical posture of the body and keep natural spinal curvature, so as to reduce the burden on the back and reduce the risk of kyphosis. Therefore, the design of the pattern and structure of the girls' bras relies on the study of the shape of the girls' chest and back. The measurement and analysis of the chest and back and the subdivision of the shape are particularly important.
Descriptive statistical analysis and cluster analysis of chest and back related data were carried out on the data of 55 adolescent girls collected manually. Through variable system clustering of 21 direct measurement variables and seven derivative variables, six indexes representing chest and back morphology were extracted and the samples were clustered. The best classification was divided into four categories, and the characteristics of each type of sample were described. The results showed that there were obvious differences among various types of samples, which could well distinguish the chest and back morphology of adolescent girls at different developmental stages. The reverse engineering software Geomagic studio was used to define the feature points and breast boundary of the data. At the same time, the local coordinate system of the breast was constructed. According to the local coordinate system and the ground coordinate system, the breast bottom section, cross section and sagittal section curve were extracted, and the area enclosed by each section curve was calculated for the analysis of chest shape characteristics. According to the ground coordinate system, the triangle ratio of shoulder section was defined for the analysis of back shape. Two adolescent girls and two young women were selected to compare the chest and back shapes. The results showed that although the chest circumference and chest difference of teenage girls were consistent with those of young women, the fullness of their chests was smaller than that of young women. In terms of back morphology, the adolescent girls in the sample did not show obvious kyphosis during the measurement process, but it did not mean that the group would not have kyphosis due to psychological factors during development. The study found that the chest difference of adolescent girls in the development period is small, the chest shape is mainly narrow, the breasts are relatively folded, the back shape is normal, and there are some chest protrusion and kyphosis. There are obvious differences in chest shape among the four types of chest and back shapes. For adolescent girls and young women with the same chest circumference, the fullness of each section of girls' breasts is less than that of young women. In terms of back shape, girls did not show obvious kyphosis during the measurement process.
This study analyzes the chest and back shape of girls in the development period, and clearly distinguishes the difference between the chest shape of girls and that of young women, so as to make the design of girls' underwear products more in line with the morphological characteristics of the group. The analysis of adolescent girls' back morphology mainly focuses on whether there is a significant  kyphosis phenomenon, while there is a lack of analysis of other back-related morphology. Therefore, follow-up research can refine the analysis of adolescent girls' back morphology.

Key words: girls in developmental stage, chest and back shape, cluster analysis, three-dimensional features