Assessment of the elementary school students’ schoolbag weight in the urban environment in Poland: A cross-sectional study carried out as a part of the ‘Lightweight Schoolbag’ and ‘Let’s Get the Kids Moving’ projects

1 Introduction

A schoolbag is an essential items that accompany children in daily travel to their school. Pupils carry necessary textbooks, notebooks, school supplies and lunch in their schoolbags. Often schoolbags are filled with unnecessary items such as toys, electronic devices (smart phones, tablets), notebooks, and textbooks which are redundant during learning time spent in school [1–5]. All these additional accessories increase the weight of a schoolbag. An improper packing and carrying of schoolbag on one or both shoulder with too much load can cause musculoskeletal discomfort/disorder [6–11], changes in the sagittal plane of the spine [12], development of spine or reduced lung capacity [13]. The overloaded school backpacks may increase the risk of physical fatigue and decrease students’ participation in activities and assignments of school [14]. In recent years, there have been increasing interests in establishing a correlation ratio between the weight of the school bag to a child’s body weight [1, 15]. Polish Chief Sanitary Inspectorate and the American Physical Therapy Association (APTA) recommends 10–15% bodyweight as the upper limit for children’s schoolbags [16, 17]. In the United States, the American Occupational Therapy Association (AOTA) approved an upper load for school backpack reaching 10% of children’s body weight (BW) [18].

The observations presented in this study were based on the data obtained from two projects: ‘Lightweight Schoolbag’ and ‘Let’s Get the Kids Moving’. ‘Lightweight Schoolbag’ is a nationwide informational and educational campaign targeted for primary school students and their parents since 2011. It focuses on the problem of overloaded backpacks among pupils and the associated occurrence of high risk of postural defects. ‘Let’s Get the Kids Moving’ is a pro-health project created by researchers of the ‘Medical University’ and the ‘Run for Health Foundation’ and it addressed to both parents and teachers. It aims to promote a healthy lifestyle through participation in physical activity and to introduce the ideas of healthy diet. The common purpose of referring those projects in this study was to evaluate the weight of the schoolbag and to analyze whether the load depends on pupils’ age, gender, and bodyweight.

2 Method

3 Results

3.2 Schoolbags weight

The schoolbag weight ranged between 1.0 to 7.2 kg (mean 3.7±0.9 kg) among the examined primary school pupils. There was no significant difference in schoolbags load between boys and girls (p = 0.2420).

Taking into account the school grade attended by the children, there are statistical significant differences in schoolbags weight presented in Fig. 1. (F = 7.93; p = 0.0149). The 1st-grade pupils had a schoolbag weight ranged between 1.2 to 5.8 kg (mean 3.6±0.8 kg). The 2nd-grade pupils had a mean schoolbag weight ranged between 1.8 to 7 kg (mean 3.7±0.9 kg). The mean absolute schoolbag load in 3rd-grade students was 3.8±0.9 and ranged between 1 to 7.2 kg. Children attending to 1st-grade carried a lighter school backpack than pupils from 3rd-grade (p = 0.0171).

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Fig. 1

Comparison of schoolbags weight in respective school grades.

Table 3 showed that schoolbag weight was associated with the children’s bodyweight category (p = 0.0024). There was a significant difference in mean schoolbags weight between children underweight and overweight (p = 0.0223). Underweight pupils had a lighter schoolbag than overweight children (3.6±0.8 kg vs. 4.0±1.0 kg). The Statistical significant differences in mean schoolbag load were also observed between students with underweight and obesity (p = 0.0116).

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Table 3

The one-way analysis of variance (ANOVA): Comparison absolute schoolbags weight (kg) in respective Cole’s Index category

	Mean	SD	Median	Min	Max	Q1	Q3	p-value
Underweight	3.60	0.84	3.6	1.4	6.8	3	4.2
Normal body	3.73	0.89	3.6	1	6.8	3.2	4.4	0.0024
weight
Overweight	3.97	1.02	4.00	1.8	7	3.2	4.6
Obesity	4.02	1.00	4.00	1.2	7.2	3.2	4.8

Abbreviations: SD, standard deviation; Min, minimum value; Max, maximum value; Q1, lower quartile; Q3, upper quartile.

3.3 Schoolbags weight as a percentage of children’s bodyweight

A tendency to carry a heavier backpack in correlation to % of BW was negatively correlated with children’s school grades (rho = –0.20; p < 0.05). There was no statistical difference between boys and girls in relative schoolbag weight (p = 0.1624). The statistical significant differences between pupils’ grade in school and relative schoolbags weight (p < 0.001) is shown in Fig. 2. The 1st-grade pupils had schoolbag weight ranging between 3.2 to 25.3% BW (mean 14.0±3.9% BW). The 2nd-grade pupils had a mean schoolbags weight % of BW ranging between 6.2 to 20.5% BW (mean 13.2±3.3% BW). The mean relative schoolbag weight in 3rd-grade students was 12.3±3.7% BW (ranging between 3.2 to 27.4% BW). Children from third grade had a lighter schoolbag in respect to % BW than pupils from second grade (p = 0.023) and first grade (<0.001), respectively. A statistically significant difference between Cole’s Index category and different schoolbag weight levels was presented in Table 4. Relative schoolbags weight more than 20% BW was observed in twenty-five (3.85%) underweight and normal body weight children. Pupils with obesity and overweight did not carry a backpack that exceeds 20% of their BW. In the examined group of children, schoolbags weight below 10% BW had 8.52% of underweight pupils, 20.06% of normal body weight, 33.78% of overweight, and 56.06% of obese pupils. The decrease in relative schoolbag weight was significantly associated with an increased in Cole’s Index (rho = –0.44; p < 0.01).

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Fig. 2

Comparison of schoolbags weight as a percentage of pupils’ body weight in respective school grades.

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Table 4

Pearson’s Chi squared test: Comparison of schoolbags weight levels in respective Cole’s Index category

% of BW	Underweight	Normal body weight	Overweight	Obesity	Total	p-value
	N = 176 (28.08)	N = 334 (51.39)	N = 74 (11.38)	N = 66 (10.15)	N = 650 (100)
<10%	15 (8.52)	67 (20.06)	25 (33.78)	37 (56.06)	144 (22.15)
10 –15 %	85 (48.30)	172 (51.50)	43 (58.11)	25 (37.88)	325 (50.00)	<0.0001
15.1 –20 %	63 (35.80)	83 (24.85)	6 (8.11)	4 (6.06)	156 (24.00)
>20%	13 (7.38)	12 (3.59)	0 (0)	0 (0)	25 (3.85)

We found a statistically significant difference between grade and schoolbag weight level (p < 0.001) (Table 5). The obtained results suggested that the first grade pupils were more often exposed to carry an overloaded backpack (more than 20% of their BW) than pupils in second and third grade (p < 0.01).

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Table 5

Pearson’s Chi squared test: Comparison of schoolbags weight levels in respective grade levels

% of BW	First grade students	Second grade students	Third grade students	p-value
	N = 187	N = 125	N = 338
<10%	29 (15.51)	21 (16.80)	91 (26.92)
10–15%	86 (45.99)	67 (53.60)	174 (51.48)	<0.001
15.1–20%	58 (31.02)	35 (28.00)	63 (18.64)
>20%	14 (7.48)	2 (1.60)	10 (2.96)

This study was designed to assess whether the weight of schoolbags is associated with primary school children’s gender, grade, bodyweight category, and carrying the type of schoolbags. The main aim of the study was to verify what percentage of children from primary schools in Wrocław, Poland were carrying overloaded schoolbags and to determine the factors that contributed the health problem. The results obtained in our study revealed that 77.9% of pupils had schoolbag whose weight exceeded 10% of children’s BW. The results of different studies revealed high prevalence of overloaded schoolbags among school-age children. Spiteri et al. [22] in a cross- sectional study conducted on 3852 Maltese children aged 8–13 years observed that 71% of pupils had a backpack weighing more than 10% of their BW. A study carried out on 813 primary school children in Nigeria showed that 79.1% of students had school bags weighing at least 10% of their BW [23]. Dockell el at. [15] studied 462 primary school children and revealed that 31% of pupils had a schoolbag weighing less or equal to 10% of their BW. In a study with 155 pupils between 7 and 9 years old in Poland, it was observed that 79% of boys and 64% of girls had a schoolbag weighted more than the recommended limit [24]. Mohammadi et al. [11] presented that 28.3% of elementary school students in Teheran were carrying a backpack that weighed less than 10% of BW. The findings from a study performed in India showed that 40.9% of pupils between 8–10 years old were carrying schoolbags over 25% BW [3]. These results suggested that heavy schoolbags in school age children are an international problem.

Kasović et al. [25] in a study among 127 first grade primary school pupils from the Czech Republic observed that the mean schoolbag weight was 4.2 kg. Pupils in the first-grade in Croatia carried a schoolbag with a mean load of 4.5 kg [26]. In our study, the average weight of the backpack of first-grade students was 3.6 kg. It indicated that Polish pupils of the first- grade tended to carry lighter schoolbags than their counterparts in other countries. In another study among 462 Ireland children aged 9–11-year-olds the average schoolbags load was 4.7 kg [15]. The mean backpack weight in elementary school pupils from South West of Iran was 3.5 kg [10]. In our study, the average weight of the backpack of primary school pupils was 3.7 kg. Compared to our results, Spiteri et al. [22] and Brzęk et al. [24] showed that pupils in older grades had a heavier school backpack than pupils in younger grades. In this study, individual schoolbag weight was varied (between 1 to 7.2 kg), mean schoolbag weight was 3.74 kg and SD 0.92. This could be related to the different weight of the empty backpack (its frame), the amount of lunch carried, the way it was packed, the amount of drinks, the school supplies of pencil case and the other toys or electronic devices brought by children to school.

A study conducted in Czech Republic revealed that 96.6% of first grade pupils carried a backpack weighing more than 10% BW [25]. Overloaded school backpacks, especially in children from the youngest school grades, who are in the phase of developing bone, muscle joint and neural tissues, may negatively affect the development of their musculoskeletal system. Another study among 108 pupils in Poland showed that 78.3% of 1st grades students, 43.3% of 2nd grades children and 40.0% of 3rd grades pupils carry schoolbags weighted more than 10% of BW [4]. In our study, 84.5% of children in first grades, 83.2% of children in second grades, 73.1% of third grades children carried school backpacks that were over 10% of their BW. Our results indicated that pupils in the youngest grades were more likely to be affected by overloaded schoolbags (>10% of BW) than pupils in older grades in primary schools. Contrary to our study Spiteri et al. [22] stated that relative schoolbag weight was higher in children of higher grades.

Numerous studies from different countries indicated that schoolbags load above 10% of students BW was resulted in biomechanical abnormalities and musculoskeletal discomfort [6–8, 27]. Overloaded school bags might impact changes in body posture, gait, and muscle activity [26, 27]. Other studies emphasized that school bags’ type, its duration of carrying also influenced the occurrence of musculoskeletal abnormalities [8, 28]. Recent biomechanical studies presented that pupils might experience musculoskeletal discomfort and changes in body posture due to carrying the overloaded schoolbags. [25, 29–32] Chen et al. [29] revealed that schoolbags weighing 15% of BW changed a spine position in the sagittal plane. Drzał-Grabiec et al. [32] observed that asymmetrical carrying of schoolbags has an impact on evaluating body posture parameters in the sagittal plane. Vieira et al. [33] studied 37 primary school students in Portugal and showed that carrying backpack type (on both shoulders or over one shoulder) with load 15% of the students BW had a key influence on expiratory muscle strength. In contrast, Gelalis et al. [28] observed a lack of differences in kinematic parameters during walking with symmetrical or asymmetrical school backpacks between children causes mild idiopathic scoliosis compared to the control group. Pau et al. [31] stated that overweighed school backpacks increased the risk of foot discomfort in elementary school children. Overloaded school bags in children caused a shift in the center of pressure towards the forefoot [34]. Ornates-Gonzales et al. [30] showed that 53 assessed pupils had kinematic gait parameters without a backpack with wheels compared to those pulling a schoolbag with wheels having school bags 10%, 15%, and 20% of their BW. The obtained results showed that the asymmetrical load of school bags with wheels caused changes in the thorax position in the transverse plane. However, the above-mentioned adaptations in body posture were minimal so the authors [30] suggested that school backpacks on wheels can be used by pupils.

Observations of gender differences in the weight of the schoolbags are inconsistent. Some studies showed that boys were carrying heavier schoolbag than girls [24, 35]. In contrast, Barbosa et al. [36], Kellis et al. [37] and Al Salem et al. [38] revealed that girls used to carry heavier schoolbags than boys. Lasota et al. [4] and Bryant et al. [39] observed no differences in schoolbag weight between girls and boys.

In previous studies girls more frequently reported severe muscle pain and fatigue symptoms related to carrying overloaded schoolbags [37, 41]. Aprile et al. [40] suggested that anatomical, physiological and environmental factors might influence pain perception in children. Data obtained in a systematic review with meta-analysis did not confirm the association between overloaded schoolbags (>10% of BW) and lower back pain in children [42]. Similar results were obtained by Yamato et al. [43] in a systematic review of five prospective longitudinal studies. The researchers claimed that the schoolbag weight and method of its carrying did not have an impact on developing back pain in pupils [43].

Limitations of the study include schoolbags weight measurements on one day only, lack of specified duration of carrying a school bag, lack of data on musculoskeletal symptoms among examined pupils. A further limitation was the limited school grades of pupils taking part in the study. In our study, we analyzed the weight of the schoolbag of children in the 1st, 2nd, and 3rd grades in elementary schools (7–10 years old students). Further studies on this matter should include children from all grades in primary and secondary schools. The next study should also take into account the re-examination after conducting educational classes with children and teachers regarding the correct way of school bags’ packing and carrying. Further studies are needed to assess the levels of the schoolbags lower or higher than the lumbar level to see how it effects height levels of schoolbags on musculoskeletal pain. To the best of our knowledge, this is one of the biggest studies on schoolbag weight in the primary school pupils in Poland.

5 Conclusions

The results of this study indicate that children’s BW category is significantly associated with relative schoolbag weight. In the future recommendations for schoolbag weight limits for primary school, pupils should consider incorporating children’s bodyweight category. We highlight the importance of monitoring the weight of the schoolbag, especially in the youngest grade of pupils. Daily checking of the schoolbag content should prevent from taking unnecessary items to school by children. It is advisable to conduct prospective studies assessing the long-term asymmetrical use of backpacks with wheels exceeding the recommended 10% of BW on children’s body posture.