Journal of Occupational

Students' physical health, performance, and comfort can be improved by designing equipment according to the needs of the human body dimensions. Nowadays, backache has gained public attention as an important health problem among school children [1, 2, 3, 4]. In the US, about $25 million is spent on treating students' nonspecific backaches caused by the non-appropriation of bodily dimensions to the chairs and desks used in classrooms. The use of poorly designed furniture, especially desks and tables, that fails to account for the users' anthropometric characteristics has a negative influence on human health. Students' sitting posture is influenced not only by the activities performed in the classroom but also by their anthropometric measures and school furniture designs. Therefore, one of the most important concerns of ergonomists is to design and produce instruments that match people's bodily dimensions in order to decrease the adverse effects, thus increasing work output and efficiency [5, 6, 7, 8].

According to official statistics, the student population in Iran amounts to 20 million, while it is estimated to be one billion globally. However, it seems that no serious and persistent attention has been paid to classrooms, whether nationally or globally, thus neglecting students' health. Various studies have shown that individuals' postures during childhood and adolescence deeply affect the way they sit and stand for a lifetime. Indeed, the longer these early postures are maintained, they are more difficult to be corrected later on [9, 10, 11]. Students spend a great deal of their time in classrooms in sitting positions. Static postures and sitting in a crookbacked manner for long periods can put great physical strains on muscles, tendons, and vertebrae in particular.

Anthropometric measures vary among nations and ethnic groups and change over time depending on variations in populations and environmental conditions [3, 6]. Hence, it has been recommended to use students' anthropometric data to design school supplies and equipment. In order to design the equipment for students (e.g., chairs and desks) according to technical and health principles, it is necessary to aid the designers by providing accurate data about the anthropometric dimensions of the students residing in different geographical regions [6, 7]. One of the most comprehensive anthropometric studies was conducted on students aging 11-13 years in the US in 1975, in which 87 bodily features and dimensions were measured, except for the popliteal height and the buttock-popliteal fossa length [12, 13]. In other countries in Europe and America, the necessary relevant standards have been prepared. Among the international standards approved by the World Health Organization (WHO), those provided by the US National Center for Health Statistics (NCHS) can be pointed out. This center has specified the standards of bodily dimensions for different age groups, which can be used in designing equipment [14, 15, 16]. In Iran, a survey was designed in1977 to compare the height and weight of 3270 students aging 6-14 years in urban and rural areas of Shiraz. Another anthropometric study was carried out in Mazandaran province to measure 17 bodily parameters of 1758 students aged 6-11 years; further, the means and percentiles of the anthropometric dimensions of male and female students were compared. This research objective was to provide the necessary data for designing students' chairs and desks [17, 18]. In another anthropometric survey on children less than 10 years old in Qazvin city, the height and weight of boys and girls were less than the global averages reported by WHO [19]. In another study performed on students in Kashan, emphasis was put on reliance on the necessary standards obtained from domestic anthropometric data rather than foreign standards [20].

At present, few countries have domestic anthropometric databases; thus, other countries have to use their data in case of need, which is scientifically unacceptable. The current study aims to develop a comprehensive database of the anthropometric dimensions of students from the Lor ethnic group residing in Khorramabad. Comparison of the anthropometric measures of different student populations could help design chairs, desks, and other school supplies.

Materials and Methods

This is a descriptive study conducted on Lor students in Khorramabad in primary, middle, and high schools in the public or non-profit sectors in 2018.

Given the standard variance and the coefficient of variation in similar populations, the appropriate sample size for each class, education level, and sex was determined. In the following formula, the values of z, δ, and d were equal to 1.96, 150, and 6, respectively. As a result, the sample size was estimated at 2401 people based on the variable of students' height with a standard deviation of 150 according to the formula below [21].

The following anthropometric parameters were recorded: age (years), weight (kg), stature, standing eye height, shoulder height, standing elbow height, chest depth, abdominal depth, arm length, forearm length, maximum forearm-forearm breadth, elbow-elbow breadth, shoulder breadth, hip breadth, thigh thickness, the thickness of both thighs measured together, sitting height, sitting eye height, sitting elbow height, popliteal height, knee height, buttock-popliteal length, and buttock-knee length. The anthropometric dimensions were measured (in millimeters) by male and female assistants using a digital caliper and a standardized anthropometric instrument designed by Lahmi et al. [21]. Additionally, the students were weighed by Samsung digital scales with an accuracy of ±5 grams. The accuracy and reliability of the utilized devices were assessed prior to the measurements. It should be noted that all students were wearing light clothes and were barefoot during the measurements. Besides, the data recorded for each student was the mean of three trials.

Ethics approval was obtained from the officials of Khorramabad University of Medical Sciences and Education. After entering the data into the computer, a t-test was used to compare the variables by gender at a significant level (P <0.005). Given that percentiles express the real concept of dimensional scattering within the design range, in order to use the data in the design of different percentile equipment, anthropometric dimensions of students were determined. Finally, the results were expressed in a table as averages and standard deviations.

Results

This cross-sectional study was performed on 4872 male and female students to determine the anthropometric measurements of Lor students in Khorramabad. The average weight and height of male students were 43.05 kg with a maximum of 114kg and minimum 15 kg and 1499.43 mm height with a maximum 1900 and minimum 1020 mm. The average weight and height of female students were 41.75 kg with a maximum of 97 and a minimum of 14 kg and 1458 mm height with a maximum of 1760 and a minimum of 1020 mm, respectively. Standard deviation and statistical percentages were calculated as 5% to 99%.

Table 1 provides the comparison of the mean of anthropometric variables in male and female students. As can be seen, there is a significant difference between the mean of all measured parameters except the variable of buttock-popliteal length in male and female students.

The results also show that the average anthropometric dimensions of the chest depth and abdominal depth in female students are larger than boys; these dimensions in girls were 176.89 and 172.19 mm compared to boys with 170.93 and 158.99 mm, respectively.

Table 1. Mean ± SD, min, and max of the anthropometric dimensions in the two genders (in millimeters)

Table 2 presents the different percentiles of anthropometric dimensions of male and female students. Percentiles are very important statistical indicators in developing tools and equipment and are widely used in design engineering. As can be seen, in the 95th percentile, as one of the most important percentiles in equipment design, all dimensions, except chest depth and abdominal depth, in male students have larger values than females.

Table 2. Percentile values of different anthropometric dimensions of students in the two genders (in millimeters)

 Table 3 shows the anthropometric dimensions of male and female students at different levels of education. As can be seen, the average growth of anthropometric dimensions in girls often occurs in middle school, while it occurs in high school in males. Further, the average weight and height in middle school girls are 45.93 kg and 1531.87 mm, respectively, while in boys, the values are 44.06 kg and 1528.16 mm, respectively, which are lower than the anthropometric measurements of girls

Table 3. Anthropometric estimation of body dimensions among male and female students in different education levels

Table 4 provides the different percentiles of anthropometric dimensions for students in both middle and high school. Due to the difference in the anthropometric dimensions of male and female students (Table 3), which often occurs in middle and high school, it is important for design engineers to know the percentiles of these two degrees.

Table 4. Percentile values of anthropometric dimensions among students in different education levels