Ergonomics evaluation of school bags in Tehran female primary school children

Abstract

BACKGROUND: More than 90% of the elementary school students in the world and most of the Iranian students use backpacks. Heavy school bags, failure to apply ergonomics standards in student’s backpacks, and also mismatch between anthropometrics dimensions and schoolbag size are important issues for children’s health.

OBJECTIVE: The purpose of this study was to gather baseline information on the average weight carried by female primary students. It also aimed to evaluate ergonomics standards for student backpacks.

METHODS: A cross-sectional study was conducted on 212 Iranian girl students aged 6– 11 years. Body weight and bag weight were measured with electronic scales and body mass index calculated with WHO software 2007. A questionnaire was constructed to gather information about the backpacks. Body dimensions were measured with VICON motion Analyze system (460). Ergonomics factors were recorded using a checklist.

RESULTS: 80.8% of the students used a backpack at a higher weight than recommended by the standards of 10% of body weight. The most common type of schoolbag used was double strap packs (92.5%). The majority of the students carried packs on their backs; however, most of them did not make any adjustments (79.8%). The results have shown a mismatch between the anthropometric measures and the student’s backpack dimensions.

CONCLUSIONS: Parents, students and school staff should be informed about these critical issues as well as suitable controls should be implemented in buying and using the bags.

Keywords

Anthropometry backpack student weight

1 Introduction

Internationally, there have been many studies on the use of backpacks in children which mainly looked at backpack weight and musculoskeletal problems [1 –17]. To date, these studies have focused on European, Australian and American children, but there have been limited studies on Middle Eastern children. It has been demonstrated that 90% of school-age children use backpacks to carry their books and school supplies [13 , 19].

Previous studies have found that backpacks are the most suitable tool for carrying daily school equipment, that, when used properly, distribute the load symmetrically [4 , 16] but poorly designed and improper usages results in serious physical injuries to the users [3 , 20].

Since school-age children are in a critical stage of their physical development, lifting, carrying and handling a heavy backpack may result in the child leaning forward, adversely affecting balance and making it easier to fall [6, 21]. According to Bauer and Al Qalaf, heavy backpacks can distort the natural curves in the middle and lower spine, causing muscle strain, irritation to the spinal joints and result in rounding of the shoulders. These effects can lead to excess load on the spine, as well as pain and discomfort in the neck, shoulders and back [5 , 21].

Some studies have shown that other factors like the student’s sitting posture and school furniture can contribute to causing back pain therfore it seems that the use of a backpack is not the only reason for back pain in school-age children. Schulze reported that backpack weight has a significant impact on stress and pressure on the shoulder [22]. AlQallaf, Chow, Dolphens and Rice reported that there is concern among health professionals regarding the long-term effects of heavy backpack use [7 , 24].

The mismatch between the size of the child and the weight of their backpack is an important issue for school-age children’s health. Currently, the recommended backpack weight varies from between 5 and 15% of their body weight (BW) [5 , 25– 28]. Evidence has been shown that a backpack weight of more than 20% of BW results in back pain [27], an increased deviation angle of upper body [29] as well as cardio-respiratory changes [22, 30]. However, even 10% of BW is frequently considered harmful for children [9–13 , 31–33] therefore health-related literature has focused on a school backpack weight limit of 10% of the individual’s body weight [6 , 31]. Poor design and poor fitting of backpacks can also cause health problems for children such as low back pain, shoulder and neck pain [13 , 28].

Researchers recommended that school backpacks should be designed with pads in the back and shoulder area and the strap of the backpacks should be adjustable to children’s anthropometric dimensions [7 , 33–35].

The purpose of this study was to gather baseline information on the average weight carried by female primary school students in Iran as well as to evaluate the ergonomics features of their bags.

2 Material and method

A cross-sectional study was conducted on 212 elementary school girl students aged six to eleven years between January and February 2011 in Tehran, Iran. A multistage random sampling technique was used to first select schools and then children. Tehran city was divided into four geographical areas, with one public school randomly selected from each one and then one class was chosen randomly in each grade so that a total of five classes were sampled in each school. This study was approved by the Ergonomics department of University of Social Welfare and Rehabilitation Sciences (USWR). The children’s participation was voluntary with consent-given in writing by their parents. Standing height was measured in barefoot condition using a Seca portable stadiometer (Design No. 1013522) and body weight and school bag weight were measured with electronic scales (Sahand Model BSR85) with 50 g accuracy. The weight of students with and without backpack was measured on three separate days to account for difference of loads children may carry on different days with the students in their uniform and shoes. Relative Weight of the backpack was calculated by dividing the weight of backpack by the weight of the students. Finally, the average value from the three measurements was calculated and subsequently the body mass index was calculated with WHO software 2007. A 10% of body weight limit line was compared with the student backpack weight [5 , 30].

A checklist was constructed to gather information about the type of schoolbag carried, the mode of carriage, availability of lockers or storage space at school and the method of travel to and from school. The checklist was completed by one of the researchers through student observation and an interview with the student and their parents. All of the students were unobtrusively observed as to how they wore the backpack during school time. Fifty children volunteered to participate in the next stage of study including the evaluation of the ergonomics standards of their backpacks and measuring some anthropometric dimensions. All 50 participants removed the top half of their clothing and were without shoes during this trial. Body anthropometric dimensions (shoulder breadth, hip breadth, shoulder width, torso length) taken according to Pheasant were measured with VICON motion Analyze system (V460, Oxford, UK). Markers were attached by an expert anatomist on the pre-defined landmarks (top of head, right heel, acromion processes, illiac crest, spinous process of 7th cervical vertebrae and 5th lumbar vertebra and A point (Fig. 1). The static positions of each marker was tracked by the Vicon motion analysis system for approximately five seconds and then the data was exported as an excel file for further analysis and computing the anthropometrics dimensions. Anthropometric measurements of the participants were compared with their backpack dimensions as well as the backpacks’ upper width and shoulder breadth, the backpacks’ lower width and hip breadth, the backpacks’ shoulder strap width and shoulder width, the backpacks’ height and torso length were compared.

The quality of the padding in the backpacks’ handle, back panel and shoulder strap and the S shaped (anatomically curved) design of shoulder strap and the existence of waist and chest straps were recorded on a checklist.

A one way ANOVA test was used to compare the difference between the weight of different age groups and their backpack weight while a Bonfrerroni test was used to show post hoc results. A chi square and t-test was used to compare the correlation between BMI and backpack weight as a percent of body weight while an Odds Ratio was used to define the association between carrying heavy school bags and BMI, mode of travelling and the grade of school. Significance level for all of the tests was set at α≤0.05 and SPSS for windows (version 16) was used for data analysis.

3 Results

A total of 212 school girls were tested from first to fifth grade age between 6–11 years old with a mean and standard deviation of height (143.4±10.57 cm), body weight (34.9±10 kg), BMI (16.7±3.3) and backpack weight as a percent of body weight (12.54±4.22%).

Descriptive results of volunteers by their grade, backpack weight and backpack weight as a percentage of body weight are shown in Table 1.

There was a significant difference between the grade and backpack weight (F = 4.768, α= 0.001), and between the grade and backpack weight as a percent of body weight (F = 10.03, α= 0.000). The backpack weight increased in upper grades. Post hoc Bonferoni tests indicated that the backpack weight as a percent of body weight in the first, second and third grade was significantly higher than in the fourth and fifth grades.

The chi square test showed a correlation between BMI and backpack weight as a percent of body weight (p < 0.01). Since high and low BMI can act as a confounding variable, children with a BMI greater than the 85th percentile and fewer than the 15th percentile (35 students) were eliminated and a new analysis was done with the children with a normal BMI (between 15th and 85th). Figure 2 shows the percentage of students with different backpack weight as a percent of body weight.

The most commonly reported type of school bag was a double strap pack (n = 196, 92.5%) while fewer students (n = 11, 5.2%) had a roller bag (n = 3, 1.4%) or used shoulder bag and only (n = 2, 0.9%) of children carried a sling style. The mode of school bag carriage was recorded as (n = 178, 84%) wearing their pack on both shoulders, (n = 19, 9%) using one shoulder, (n = 11, 5.2%) using a roller trolley and (n = 3, 1.4%) carrying their backpacks on the side of their body and (n = 1, 0.5%) in their hand. The majority of the students carried packs on their backs however; most of the students (n = 169, 79.8%) did not make any adjustments to the straps. Only some (n = 43, 20%) adjusted the straps to properly fit their bodies. Most participants (n = 149, 70.3%) traveled to and from school by school bus or in their parent’s car.

Grade of the student and their BMI were identified as the characteristics most significantly associated with using heavy backpacks (Table 2). Students with a BMI’s percentile less than 15 were more likely to carry backpacks above the 10% body weight limit (11- fold compare with those that had a BMI 51–85 percentile and 33- fold compare with those that had a BMI more than the 85 percentile. Furthermore, students in grade one were more likely to carry heavy loads (6-fold compared with grade 4 and 4-fold compared with grade 5).

No association was found between heavy backpacks and the mode of traveling to and from school.

The t-Test results showed that there was a significant difference between the backpack dimensions and the student anthropometric measures. As shown in Fig. 3, significant differences were found between the backpack upper width and the shoulder breadth (t = 2.536, p = 0.014), the backpack lower width and the hip breadth (t = 13.574, p = 0.000), the shoulder strap width and the shoulder width (t = 11/965, p = 0.000) the backpack height and the torso length (t = 19.883, p = 0.000) (Fig. 3).

The majority of school backpacks in the study obviously were not designed ergonomically and the results were far from the ergonomics standards. Descriptive results of surveying the backpacks ergonomics factors are shown in Table 3.

4 Discussion

This is the first study examining the anthropometric and the backpack weight on Iranian females. The weight of backpacks carried by students is a key factor in the safety and health of school-aged children [36].

The average backpack weight carried in our study was 4.1 kg, which is similar to that reported by Al Qallaf [21] in secondary school girls (4.57 kg) and Barkhordari [36] which reported 4.6 kg in primary school boys. Our study also demonstrated that Iranian school girls carried heavier weights than those reported in the al Hazzaa [27] study in primary school boys of 3.2 kg and the mean weight of 2.9 kg found in the Dianat [20] study in elementary school children.

We found that a high percentage of female students (80.8%) carried backpacks heavier than 10% of their BW. This is higher than what Barkhordari (65.2%) [36] Hazzaa (50%) [27] and Tarhani (57.7%) [37] found in recent Middle East studies.

In the Dianat study which included both genders it was reported that girls carried bags with a greater percentage of their body weights (boys 2.8 kg, girls 3.1 kg).

Research outside of the Middle East including Sharan [15] study showed 100% of participants carry backpacks that were more than 15% of their BW in India which is more than our findings and Bryant [38] reported in his study in the United states a lower percentage (60%) than ours. The differences between the results of our study and other studies in the Middle East may have originated due to different study methodologies, age of participants, cultural and differences in gender. There is no specific reason as to why females carry heavier weights than males, and this should be explored further in other studies.

Many studies showed that the prevalence of back or other pain was due to carrying heavy backpacks [13 , 39–41]. Siambanes [32] reported that the backpack weight, measured as a percentage of body weight, was effective in predicting back pain with girls are more likely to report back pain. Some researchers concluded the same results and reported neck, shoulders and back pain were related to heavy backpacks [8 , 40]. In addition, heavy backpacks can cause changes in the lumbar discs and normal curvature, postural angles and respiratory parameters [14 , 42–45]. A number of studies have proposed that carrying weight on the back is the safest and healthiest way for students [46, 47] and wearing packs on both shoulders is necessary for good ergonomics [5]. Our finding indicated that the majority of students (92.5%) had double strap backpacks and most of them (84%) wore their backpacks on both shoulders which is similar to the findings of Barkhordari [36] and Al-Hazza [27].

Mismatching between the anthropometric characteristics and the backpack dimensions can cause other problems. Bauer has suggested that backpack breadth and shoulder breadth should be equal or backpack breadth should be smaller to provide space for arms to move freely [6]. Lindstorm found that if the backpack’s height is longer than torso length, it can cause higher risk for low back pain [28] and wearing these backpacks this way increases stress on the shoulder and back muscles [26].

A narrow shoulder strap could cause pain in shoulders and prevent normal blood circulation which could lead to tingling and numbness in the arms and hands [5, 26]. Unfortunately, in our findings none of the backpack dimensions were standard. The mean of lower backpacks’ breadth were 7.7 cm bigger than hip breadth and upper backpacks’ breadth were 1.5 cm bigger than shoulder breadth. In comparison between torso length and backpack height, backpacks’ height were 8.8 cm taller than torso length in addition the shoulder straps were 2.83 cm more narrow than the shoulder width.

It has been revealed that the form of backpack should be considered in the design process to provide better weight distribution and comfort. These factors are an S shaped (anatomically curved) shoulder strap which provides a good fit to each students body [5], padding in the handle, back panel and shoulder strap [25, 28] which decreases pain in the neck and shoulders. Providing a waist and chest strap to reduce forces on shoulders when the center of gravity moves to the rear also helps to relieve back pain [5 , 35].

In our study, 8% of the participants’ backpacks had an S shaped shoulder strap and none of the backpacks had a chest strap. Only 2% had waist straps and these were never used by the students. Not only did backpacks with suitable padding increase comfort for students but also they can decrease the risk of sharp objects jabbing into the students’ back and padded shoulder straps will absorb extra contact pressure on the shoulders [5, 26]. In our findings, the percent of padding was not desirable (8% handles, 34% back panel and 44% shoulder strap).

According to Whittfield et al. [10], placing the backpack at the level of the dorsum and adjusting the straps to fit tightly with no gaps is the best way to carry school materials. Since loose straps may lead to kyphosis and lordosis. Unfortunately, our findings indicated that the majority of participants (79.8%) were wearing their backpacks improperly without any attempt to adjust them to properly fit their bodies. Loose straps were common among participants and this can increase the risk of future injuries and pain.

Some limitations should be mentioned regarding the study results. This study was limited to primary school girls and therefore results for boys or other settings may be totally different. Additionally, in phase two of our study only 50 volunteers participated and the results may vary in larger samples. Finally, there were no rural or private school children that participated in the study.

5 Conclusion

The present study demonstrates that children in lower grades are carrying heavy backpacks that could lead to serious health problems. With a high percentage of our study participants carrying backpacks over 15% of the body weight and this is putting these students at a high risk of future injuries. It is recommended that strategies be developed to educate students, parents, schools and manufacturers to limit the weight carried. Mismatching between backpack dimensions and the anthropometry of students was also revealed in the study participants. Therefore, it is recommended that the educational system, designers and parents should pay more attention to prevent these potential health problems. This could be achieved by reducing backpack weight such as replacing textbooks by CDs or electronic books or having some books at school, making proper adjustments to the weight and fitting of the backpack and attention to ergonomic factors when purchasing or designing a backpack for children.

Conflict of interest

The authors have no conflict of interest to report.

Footnotes

Acknowledgments

Authors would like to thank the members of ergonomics laboratory from University of welfare and Rehabilitation sciences for their valuable help and cooperation.

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