Anthropometry of Iranian Guidance School Students with Different Ethnicities: A Comparative Study

Objective. We measured some anthropometric dimensions of Iranian guidance school students selected from different ethnicities. Background. Anthropometric dimensions are used for design of equipment, furniture, and clothing. Furniture with inappropriate design not fulfilling the users' anthropometric dimensions may have a negative effect on health. Method. A total of 7400 Iranian guidance school students aged 12–14 years entered the study and their static anthropometric dimensions were measured. Descriptive statistics such as mean, standard deviation, and key percentiles were calculated. All dimensions were compared among different ethnicities and different genders. Results. This study showed significant differences in a set of 22 anthropometric dimensions regarding gender, age, and ethnicity. Conclusion. According to the results of this study, difference between genders and among different ethnicities should be taken into account by designers and manufacturers of guidance school furniture. Application. This study has prepared a data bank of anthropometric dimensions of 12–14-year-old students which can be used as basic information to find appropriate dimensions of school furniture.

Inappropriate dimensions of furniture and other products which do not match the users' body dimensions may lead to many adverse effects [3,5,[8][9][10][11][12]. Students are among the populations at risk for musculoskeletal disorders as a result of incorrect posture, frequently caused by inappropriate school furniture [6,11].
Appropriate design according to the target user groups and identification of the most important body dimensions are key issues in the design process [7]. There is a high prevalence of mismatch between anthropometric data and school furniture which is a factor implicated in causing low back pain [13].
Race refers to grouping of people according to biological characteristics, while ethnicity also encompasses additional cultural factors [25]. Some races consist of different ethnicities with probably different cultural, geographical, economic, and nutritional properties which may eventually create different anthropometric dimensions [5,24,[26][27][28][29]. Anthropometric dimensions in a population may change continuously [14]. Smith and Norris have shown a significant change in body size of the UK children during the past thirty years [30].
There are six ethnicities in different parts of Iran (i.e., Arab, Baluch, Fars, Kurd, Lor, and Turk) with different cultural, economic, nutritional, and geographical characteristics. Turk and Kurd population live in a naturally rich area with cold and damp weather in west and northwest of Iran, and Baluch population live in a deprived area with a hot and dry weather in southeast of Iran. It is said that Kurd and Turk population are naturally larger in body size than other ethnicities. The authors have found these differences in their previous study on primary school children in different Iranian ethnicities [24].
Anthropometric studies on Iranian population are few and most of them with small sample size [31,32]. To the best of our knowledge the only large studies for measurement of anthropometric dimensions of students were our previous studies on Iranian primary school children and university students [24,33].
1.1. Purpose. Lack of national anthropometric data leads to the design of clothing, shoes, and furniture based upon anthropometric dimensions of other populations, which may not represent the body sizes of the real population. This study was designed to measure some static anthropometric dimensions in Iranian guidance school children considering ethnic differences.

Material and Methods
This was a cross-sectional study conducted on 7400 guidance school students aged 12-14 years from different ethnicities in Iran. The students were assigned in each age category according to the information of their identity card; for example, a student was considered to be 12 years old when he (she) was born in the year 1377 Anno Persico (between 21.3.1998 and20.3.1999 AD).
The dimensions which were measured included the following: weight, standing vertical dimensions (height, eye height, shoulder height, and elbow height), sitting vertical dimensions (popliteal height, knee height, sitting height, eye height, and elbow height), horizontal dimensions (arm length, forearm length, forearm-forearm distance, elbowelbow distance, shoulder width, buttock width, buttockknee length, and buttock-popliteal length), depths (chest and abdomen), and thicknesses (one-thigh and two-thigh) [24]. Figure 1 shows the measured dimensions.
The subjects stood and sat in standard postures for measurement of standing and sitting dimensions (27,28). Six groups of technicians who were trained for measurements in a planned course performed the measurements using similar techniques. The groups consisted of an observer and two recorders. The dimensions were repeated for 7% of subjects by two other observers blinded to the previous measurements. Subjects entered the study wearing home clothing without shoes ( Figure 2  We obtained an informed written consent from parents and oral consent from students after explanation of the procedure.

Analysis.
Descriptive statistics (mean, standard deviation, and 5, 50, and 95 percentiles) were measured for each dimension regarding gender, age, and ethnicity. The dimensions were compared between two genders and among six ethnicities in each age group. Student's -test and one-way ANOVA were used for the comparison of means between two genders and among six ethnicities, respectively.

Results
In this study, 7400 subjects (3560 boys and 3840 girls) aged 12 to 14 years in six ethnicities were assessed. Table 2 shows means of 22 anthropometric dimensions of guidance school children in 6 different Iranian ethnicities. Table 3 shows key percentiles (i.e., 5, 50, and 95) for 6 most important anthropometric dimensions (i.e., weight, body height, standing eye height, standing shoulder height, standing elbow height, and buttock-popliteal length) in different ethnicities. There was a significant difference between males and females in most dimensions. Table 4 shows the key percentiles of six more important anthropometric dimensions and Table 5 shows the comparison of dimensions regarding gender.
There was a significant difference between ethnicities in all anthropometric dimensions. values for difference among ethnicities were less than 0.001 for all dimensions except for

Discussion
Today, it is important to measure anthropometric dimensions as a key step for design process. Such variables as age, gender, and ethnicity affect these dimensions, so it is critical to consider these variables for preparation of anthropometric databases.
In this study we measured the anthropometric dimensions of students aged 12 to 14 years from different ethnicities in Iran. The results showed a significant difference between two genders in all age groups and among all ethnicities for most of the dimensions.
In this study, 12-and 13-year-old girls' weight was significantly more than boys which was opposite in 14-year-old subjects. In 12-year-old subjects, girls had larger heights and upper extremity lengths, although boys showed larger lower extremity heights and lengths. In 13-and 14-year-old subjects, most anthropometric dimensions were significantly larger in boys except for depths and dimensions related to buttocks which is explainable by the size of breasts and buttocks in girls due to puberty.
In this study, Turk boys had the largest dimensions in most of the measured dimensions except for abdominal depth, upper extremity distances and widths, lower extremity, and sitting heights which were larger in Fars ethnicity, although in some of them such as forearm-forearm distance the difference was negligible. Most dimensions were smaller in Baluch boys than other ethnicities except for most upper extremity dimensions and some lower extremity heights.
In about one-third of dimensions Arab girls had the largest measures and in other dimensions Kurds and Turks showed larger dimensions.
There is a considerable difference among different Iranian ethnicities regarding genetic characteristics, climate, geographical area, and socioeconomic characteristics which may affect anthropometric dimensions. For example, Turks and Kurds live in a naturally rich area, but Baluchis live in a province which is naturally deprived, so some differences are probably due to these issues.
There are some studies in different populations for measurement of anthropometric dimensions. Mokdad and Al-Ansari measured 44 anthropometric dimensions of Bahraini children aged 6-12 years. They found significant difference between two genders in many dimensions [34]. A total of 50 anthropometric dimensions were measured among Mexican children and a significant difference among different populations was found [16].  The difference between races or ethnicities regarding anthropometric dimensions has also been identified in some studies. Rosnah et al. found a significant difference between Malays and non-Malays which is in agreement with the results of current study [35]. Jahanshahi et al. found that ethnicity affects facial anthropometric dimensions in an Iranian population [27]. Lin et al. also found a significant difference among four East Asian populations [5].
Although climatic, nutritional, and economic factors are significantly different in different populations and countries, one of the important factors contributing to anthropometric differences is race or ethnicity.
Anthropometric dimensions of the study children were different from other populations. Anthropometric dimensions of Greek, American, and Mexican children were more than Iranian children [16,17,19] and these dimensions in Vietnamese children were less than Iranian children [9].
The anthropometric dimensions we measured in this study can be used to design school furniture matched to our population. It is recommended that the number of anthropometric dimensions be increased to create databases used to design clothing, shoes, and other products. It is also recommended that these measurements be repeated to seek for temporal trends.
This study had some limitations. We tried to select real native students in each ethnicity, but some hybrid students may have entered the study and we might not have detected these subjects.

Conclusions
In this study we found significantly different anthropometric dimensions in different Iranian ethnicities. This makes it necessary to pay attention to these differences when school furniture is designed. The results of this study showed that students need furniture specifically designed and manufactured considering their ethnicity, gender, and age. It is obvious that designing school furniture separately for each ethnicity is very difficult, so a practical approach is to design adjustable furniture using the anthropometric dimension measured in this study.

Key Points
(i) Anthropometric dimensions of the users should be put in mind when determining the dimensions of school furniture. (ii) This study showed a significant gender difference in all anthropometric dimensions.
(iii) This study showed a significant difference among different ethnicities in most anthropometric dimensions.