Keywords

1 Introduction

The design of labor and protective equipments are most concerned about the users’ head and face shapes. Helmets, protective helmets should fit for the user’s head size, the design of gas masks should combine with users’ face dimension characteristics, and eye protector design should base on the users’ facial width and distance between the eyes. For a good design of protective equipments, it should not only consider their protective functions, but also the users’ body characteristics [1]. The human head and face size is an important basis for developing head and face protective equipments. For the minors, the head sizes are also essential for children’s personal protective equipments design. For example, the design of headgear, glasses, hats, helmets, dust masks and other safety related products all need children’s head and face data. Without such data, the designs cannot fit children properly.

In different countries the anthropometric data are different [2]. It showed that most of the head and face data between the Japanese, Kenyans, South Koreans, The Netherlands, Americans and Chinese have significant difference (p < 0.05). The comparison shows that Asians’ head size can be characterized as rounder than Africans’, Americans’ and European people’s heads, and with a flatter back and forehead. So in order to design suitable personal protective equipments for Chinese people, the related body data are necessary.

In order to meet the need of protective products development, China has conducted several head and face size surveys across the whole country. In 1980, the Beijing Labor Protection Institute and the National Academy of Sciences conducted the head size survey which including 9392 samples. Based on these data, the first series of Chinese adults head standard “Head –form of adults” (GB 2428-81) [3] was published in 1981. In this standard, the head features are analyzed and 13 types of head shapes were established based on 29 measurement items. A survey including 22300 adults Chinese was conducted in 1988, which including 7 head face dimensions. The human dimensions database for Chinese adults was established [4]. In 1998, the statistical techniques were used to a small sample (393 samples) survey. Later the “adults head face dimensions” standard (GB/T 2428-1998) [5] was published, and 41 head and face items were covered in that standard. The two national standards are not covered the minors’ head and face data.

Some scholars in China also studied the Chinese head data. Li Shuyuan conducted cluster analysis to 30 population groups in China and 5 craniofacial indexes (head length breadth index, head height index, head width and height index, morphological facial index and nasal index) are covered [6]. Zhi did research on the characteristics of pilots’ heads and classification, and different classifications of pilots’ heads are achieved based on head height, head breadth and head length of Chinese male pilots according to the statistical principle [7]. Ran conducted research on the characteristics of head forms and classification of head forms of Chinese adult [8]. In this paper, the head forms have been classified according to the head height, breadth and length, two-dimensional distributions of head height-length indices and head breadth-length indices have been established. But this research are also not covered the head and face data for minors in China.

In china, a nationwide anthropometric survey project for children from 4 to 17 was completed in 2009. The head data for the children are also included in this survey. The statistical values of head length, head breadth, head height, head circumstance, face length (nasion-menton), sagittal arc and bitragion arc are presented in this paper. Estimates of mean, standard deviation (SD) are included. The differences among age groups, between boys and girls groups are discussed. The two-dimensional distribution of head length and head breadth were established.

2 Methods

2.1 Subjects

To make the anthropometric survey more representatives, a stratified cluster sampling method was used to determine the distribution of the samples. The whole country was divided into six geographical areas according to the ethnographic research result, which was in accordance with the adult anthropometric survey in 1988. The six areas included north and northeast area, central and western area, the lower reaches of the Changjiang River area, the middle reaches of the Changjiang River area, Guangdong-Guangxi-Fujian area, Yunnan-Guizhou-Sichuan area. From the ethnographic point of view, the people in the same area have similar body characteristics. The sample size in each area was determined based on the distribution of children’s population reported by China National Bureau of Statistics [9]. One or two cities in each area were selected and some kindergartens, primary schools and high schools were taken from these cities. A number of classes were taken from every selected school, and all the children in the selected classes were measured until the number of children desired in per age group was met. Based on the Report on the Second National Physical Fitness Surveillance (2000) [10], the children were subdivided into five age groups: preschool (4–6 years old), lower primary (7–10 years old), upper primary (11–12 years old), middle school (13–15 years old), high school (16–17 years old). In this survey, for example, 10 years old means ones whose age is from 9.5 to 10.5 years old.

2.2 Dimension Measurements

The 3D Scanner was adopted for head anthropometric survey, and the scan time is less than 10 s one person. The accuracy for the scanner is 3 mm and 2 mm in the horizontal and vertical direction respectively. After each scan, a view to the 3D scan results was required to prevent the scan failure caused by body position shifting. The dimension values obtained were categorized according to gender and age groups and abnormity data examination was conducted.

Before the scanning, the measurement specification and technique requirements were established. The members in the survey team were trained and evaluated to ensure the consistency and reliability of the anthropometric data.

2.3 Data Processing and Statistical Analysis

The head data were taken by Measure Software developed by CNIS. In this paper, head length, head breadth, head height, head circumstance, face length (nasion-menton), sagittal arc and bitragion arc were taken from this software. The definitions for the seven items were consistent with ISO 7250:2004 [11].

This software allows users to calculate head data interactively. The abnormity data examination was conducted. The extreme outliers and unreasonable results were identified and eliminated carefully by using 3σ test, peak value test and logical value test. The head dimensions obtained were categorized according to gender and age groups. The descriptive statistics, including arithmetic means (M), standard deviations (SD), and percentiles (5th and 95th) of the above measurements were calculated for both boys and girls.

3 The Effect of Age and Gender

3.1 The Statistical Values of Head Anthropometric Dimensions

The statistical values of head dimensions in five age groups for boys and girls are presented in Tables 1 and 2. All dimensions are reported in mm.

Table 1. The statistical values of head anthropometric dimensions for boys (mm)
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Table 2. The statistical values of head anthropometric dimensions for girls (mm)
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3.2 Differences Between Age Groups

From Tables 1 and 2, it can be found that the mean values for the seven head and face dimensions increase gradually by age. Both boys and girls show a trend for significant increase by age, and the age group 4–6 and 7–10 have relatively higher increasing rate. For example, their head circumference increased 6 mm. In the other three age groups, the increasing rates show a slow growth.

Figure 1 shows the increasing rate of head circumference for boys and girls. For boys, the difference of head circumference between age group (4–6) and (7–10) is 19 mm. From (7–10) to (11–12), the data of boys increases by 23 mm, and from (11–12) to (16–17) the increase value is 16 mm and 12 mm respectively. From (7–10) to (11–12), the head circumference of boys have a relatively high increasing speed. For girls, the increase of mean values of head circumference are 22 mm, 13 mm, 9 mm and 1 mm respectively for the age group from (4–6) to (16–17). The high increasing speed of girls’ is the age group (4–6) to (7–10). The boy’s head circumference increase very fast before 16 years old, and in the (16–17) age groups, the increasing rate also very obvious. But for girls, the increasing for their head circumference is slowing down in the (16–17) age group. It showed that for the boys in (16–17) years old and for girls in their (13–15) years old, their head and face have been basically mature. When the age continues to increase, the head size tends to be stable.

Fig. 1.
figure 1

The increasing rate for head circumference

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3.3 Gender Differences

From Tables 1 and 2, it shows that for boys and girls in the five age groups, most of the 7 item data of boys are larger than girls’ except for some individual data. Figures 2 and 3 show the difference of four data (head length, head breadth, sagittal arc, bitragion arc) between boys and girls. The differences for the head length and head breadth between boys and girls in the (4–15) years old are 3–5 mm and 1–2 mm, but for the minors in (16–17), the differences for the head length and head breadth are 9 mm and 6 mm. With the increase of age, the difference is also increasing.

Fig. 2.
figure 2

Head length and head breadth for boys and girls

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Fig. 3.
figure 3

Sagittal arc and bitragion arc for boys and girls

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The head breadth-length index is used to analyze the difference of head shape for boys and girls. The head breadth-length index = (head breadth/head length) * 100, namely, the proportion of the maximum head breadth against the maximum head length. For the five age groups, these indexes are 86.9, 87.1, 86.9, 86.7, 86.6 for boys and 87.6, 88.2, 87.8, 87.9, 87.9 for girls. For all the age groups, the indexes of girls are larger than boys. It shows that girls have relatively rounder head than the boys.

4 Two-Dimensional Distribution of Head

There are many types of head and face protective products. They need to be reasonably designed by analyzing the size of the various parts of people’s head and face. We need to select the main parameters that can represent the main features of the head and face. The main parameters should be easy to measure, to be understood and be accepted by people. Considering the characteristics of each item and the feasibility of the measurement, we choose the head length and head breadth as the main parameters for the product design.

The head type spacing should be determined according to people’s “feel domain span” and the actual background of products. For adults, the head length and breadth spacing is 10 mm. for minors, their head size are smaller than adults. If the size spacing is set to 10 mm, maybe the types would be unable to cover a certain populations. Therefore, we set 5 mm as the spacing of head length and head breadth.

After the main parameters are selected and the head size spacing is determined, we can set the head size types according to the distribution frequency of main parameters. How to match head length and head breadth need to calculate the proportion of the population under various conditions (also known as coverage). High coverage shows that products with this size can meet the large population.

The two-dimensional distribution of head length and head breadth for minors were given in Tables 3 and  4 (coverage below 0.5% are not presented). The numbers in the two tables show the size coverage, that is the proportion of the population.

Table 3. Two-dimensional distribution of head length and head breadth for boys (%)
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Table 4. Two-dimensional distribution of head length and head breadth for girls (%)
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In Table 3, the percentage of the head length in 185 mm and head breadth in 165 mm is 4.95%, it shows that for the head length in the 182.5 mm to 187.5 mm range and head breadth in the 162.5 mm to 167.5 mm range the proportion is 4.95% among the total population. For both boys and girls, the head length in 182.5 mm to 187.5 mm range and head breadth in 157.5 mm to 162.5 mm has the highest coverage. The two-dimensional distribution should be reasonable merge and to set models according to actual production needs. The distribution of the minors head in Tables 3 and 4 can guide the designers in the production of various types of head and facial products to reduce the blindness of production.

5 Conclusion

This study was conducted to provide foot anthropometric information of Chinese children from 4 to 17 years old, which could be used for the ergonomic design of workspace and products. Seven head and face dimensions extracted from 20,000 children are listed in the forms of mean, standard deviation and percentile values. The differences among five age groups are discussed, the two-dimensional distribution of head length and head breadth were established. The results could provide data support for relevant products design.