The aim of the paper was to determine a correlation between the weight of a child’s backpack, their body weight, and certain features of their body posture.
The problem of bad posture in children and adolescents is still a current issue, frequently addressed in scientific publications [
Children at this age are exposed to a number of factors that predispose them to the occurrence of bad posture. One of these factors is carrying a backpack that is too heavy for them. According to the literature, this problem affects between 40% and 70% of children in developed countries [
Recommendations concerning the weight of school backpacks in relation to body weight diverge depending on the organization. In 2009, the American Occupational Therapy Association (AOTA) and the American Physical Therapy Association (APTA) recommended not carrying a backpack heavier than 15% (or between 10% and 20%) of the student’s body weight; in 2012, this was changed to 10% of their body weight [
The weight of backpacks carried as part of everyday activity may be related to the shape of curvatures of the spine, in particular when the activity requires taking a specific, forced posture. A child carrying a heavy backpack will tend to lean forward to balance their centre of gravity, which results in a reduction of lumbar lordosis and increased thoracic kyphosis [
The following hypotheses were set up: does the weight of the backpack constitute the recommended 10% of the body weight of a seven-year-old child? Does curvature of the spine change in children who carry a backpack heavier than 10% of their body weight?
The aim of the paper was to describe the relationship between the load of a child’s school backpack and the occurrence of changes in the parameters of their body posture in the sagittal plane.
The study was conducted at the end of the first year of primary school at Wincenty Pol Primary School in Lesko, Poland. The study group included 109 children, all aged seven years: 58 girls and 51 boys. The children had not attended a reception class before. The children in the study group were carrying their backpacks on their way to school and back and going from one classroom to another during breaks, for an average total time of 50 minutes a day. The anthropometric data of the children are summarized in Table
Basic biometric parameters characterizing the study group (
Mean | Range | SD | |
---|---|---|---|
Body weight (kg) | 25.55 | 19.02–38.00 | 4.7 |
Body height (m) | 1.25 | 1.13–1.39 | 0.1 |
SD: standard deviation.
The study was conducted after obtaining consent from the school principal, parents, and the subjects themselves and as part of a larger research project which had been approved by the local Bioethics Committee at the Faculty of Medicine, University of Rzeszów.
Inclusion criteria were as follows: only school children who were seven years of age; lack of comorbidities; only traditional school backpacks (i.e., the children’s own backpacks which they carried to school every day, designed to be carried on both shoulders).
Exclusion criteria were as follows: children aged younger than seven or over eight years (e.g., children from the reception class and Year 2); lack of consent to participate in research; musculoskeletal, vision, and neurological disorders.
The parameters of body posture were determined using the Zebris Ultrasonic System with WinSpine 2.3 software. This system enables three-dimensional analysis of body posture. It consists of a sensor with a stand, the basic CMS-HS unit, and a single marker with a belt to be attached to the hips of the subject. Tests using the ultrasonic spot indicator function by identifying the anatomical landmarks on the subject’s skeleton, which are precisely displayed on a monitor connected to the computer [
Subject’s position during the examination.
The subject was positioned 80 cm from the receiver and equipped with the transmitter belt. The position of the subject was habitual, with the upper limbs along the trunk and the lower limbs extended in the knee and hip joints. The following instructions were given: “stand in a comfortable manner”; “do not bend your knees”; and “look straight.” The children were not instructed to straighten up. When the subject corrected their body posture, the measurement was repeated so that functional defects were also noted [
The following parameters of the subjects’ posture were measured: ThS (mm): total length of the spine; THL (mm): length of the thoracic spine; LS (mm): length of the lumbar spine; KKP (degrees): thoracic kyphosis angle, calculated from the intersection of the tangents extending between the spinous processes of Th1 and Th2 and Th11 and Th12 (Figure
Analysed parameters.
Analysed parameters.
As a next step, the child’s body height, body weight, and school backpack weight (along with its contents) were measured. These measurements were made using the seca 213 portable stadiometer height rod (digital scale with 0.1 kg accuracy). The group was examined in the morning, during school hours, that is, during an ordinary school day according to the school timetable.
The differences in posture between the groups (Group 1, weight of backpack less than 10% of child’s body weight, and Group 2, backpack heavier than 10% of child’s body weight) were determined using the Mann-Whitney
The number of children carrying school backpacks in accordance with recommendations (i.e., weighing less than 10% of their body weight) was 44 subjects (40.37%).
The weight analysis of the school backpacks and their relation to the body weight of the children showed that the weight of the carried load often exceeded the 10% recommended in the literature. Detailed results are shown in Table
The weight of the school backpacks carried by the subjects.
Mean | Range | SD | |
---|---|---|---|
Weight of school backpack (kg) | 2.87 | 1.64–4.10 | 0.50 |
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Weight of school backpack in relation to child’s body weight (%) | 10.90 | 6.78–17.47 | 3.14 |
SD: standard deviation.
The parameters describing the spinal shapes of the two groups (Group 1, with backpacks weighing less than 10% of the children’s body weight, and Group 2, with backpacks heavier than 10% of the children’s body weight) are shown in Table
Summary of the parameters characterizing the children’s body postures.
Backpacks lighter than 10% of body weight | Backpacks heavier than 10% of body weight | Mann-Whitney |
||||||
---|---|---|---|---|---|---|---|---|
Mean | Range | SD | Mean | Range | SD |
|
| |
ThS (mm) | 375.4 | 350.3–400.5 | 25.1 | 357.0 | 320.7–393.3 | 36.3 | 2.223 | 0.026 |
THL (mm) | 230.4 | 212.5–248.3 | 17.9 | 223.4 | 203.7–243.1 | 19.7 | 1.252 | 0.211 |
LS (mm) | 107.0 | 90.6–123.4 | 16.4 | 98.4 | 77.7–119.1 | 20.7 | 1.454 | 0.146 |
KKP (deg.) | 47.4 | 33.8–61.0 | 13.6 | 43.8 | 31.1–56.5 | 12.7 | 1.414 | 0.157 |
KKL (deg.) | 26.6 | 12.3–40.9 | 14.3 | 23.9 | 12.2–35.6 | 11.7 | 1.112 | 0.266 |
TTI (deg.) | 4.2 | 2.3–6.1 | 1.9 | 3.4 | 1.4–5.4 | 2.0 | 1.345 | 0.179 |
SCR (deg.) | 24.5 | 14.7–34.3 | 9.8 | 19.5 | 9.3–29.7 | 10.2 | 1.927 | 0.054 |
ThS (mm): total length of the spine.
THL (mm): length of the thoracic spine.
LS (mm): length of the lumbar spine.
KKP (degrees): thoracic kyphosis angle, calculated from the intersection of the tangents extending between the spinous processes of Th1 and Th2 and Th11 and Th12.
KKL (degrees): angle of lumbar lordosis, calculated from the intersection of the tangents extending between the spinous processes of L1 and L2 and L5 and S1.
TTI (degrees): total angle of anterior trunk inclination.
SCR (degrees): sacral angle in the study group (sacral angle is defined as the angle between the line connecting the spinous processes S1 and S3 and the frontal plane).
SD: standard deviation;
A statistically significant relationship was revealed between the load of the school backpack and the total length of the spine, the length of the lumbar lordosis, the lumbar lordosis angle, and the angle of sacrum inclination. With the increase in the weight of the backpack, the measured parameters decreased. No statistically significant differences were found for the following parameters: THL (length of the thoracic spine), KKP (angle of thoracic kyphosis), and TTI (total angle of anterior trunk inclination). Details are shown in Table
The relationship between the child’s school backpack load and the occurrence of changes in the parameters of the child’s body posture in the sagittal plane, using Spearman’s correlation coefficient.
Anthropometric |
|
Interpretation |
---|---|---|
ThS | −0.3999, (0.017) | The heavier the backpack, the lower the total length of the spine |
|
||
THL | −0.2313, (0.181) | Not significant |
|
||
LS | −0.3352, (0.049) | The heavier the backpack, the lower the length of the lumbar lordosis |
|
||
KKP | −0.2695, (0.117) | Not significant |
|
||
KKL | −0.5065, (0.002) | The heavier the backpack, the smaller the lumbar lordosis angle |
|
||
TTI | −0.0537, (0.759) | Not significant |
|
||
SCR | −0.4279, (0.010) | The heavier the backpack, the smaller the sacral angle |
ThS (mm): total length of the spine.
THL (mm): length of the thoracic spine.
LS (mm): length of the lumbar spine.
KKP (degrees): thoracic kyphosis angle.
KKL (degrees): lumbar lordosis angle.
TTI (degrees): total angle of anterior trunk inclination.
SCR (degrees): sacral angle.
The issue of school backpack load is still a valid one [
Children usually carry their backpacks for a relatively short period every day. Nevertheless, the relationship between backpack load and spine shape in the sagittal plane observed in the study arouses a certain interest. In our study, the school backpacks filled with books weighed on average 2.87 kg. The backpacks were weighed once during the study, assuming that the backpack weight would be similar every day, based on the number of daily lessons; these data correspond with the findings of other researchers. Nevertheless, the issue should be taken into account when analysing the obtained results. It has already been mentioned that the results are consistent with the results of other researchers, for example, those of Al-Hazzaa regarding similarly aged children. In this study, the mean weight of the backpack was 2.77 kg, but higher values were accepted for school backpack weight as a percentage of mean body weight (12.5%) compared to in our study (10.9%) [
A study by Kułaga and Grajda found that a backpack weight exceeding 10–15% of the child’s body weight forces the child to compensate for the excessive load by tilting their torso forward. However, according to the authors, a greater impact on the children’s posture was produced by the wrong position of the body, rather than the weight of the backpack [
Relationships between a child’s school backpack load and the total length of their spine, the size of their lumbar lordosis, and their sacrum inclination were all found in our study. When the school backpack weight was higher, greater decrease of the lumbar lordosis was observed, and the sacrum inclination was smaller. Such a situation may lead to a reduction in the natural curvature of the lumbar spine and related adverse consequences, such as reduced amortization properties of the spine, and asymmetric loading of intervertebral discs, which can lead to overloading and degenerative changes in the spine.
There was no relationship observed between backpack load and the length of the thoracic spine, the angle of thoracic kyphosis, or the anterior inclination of the trunk. The lack of correlation with the angle of thoracic kyphosis in our study may be due to the fact that over 40% of the children wore backpacks according to the standard, that is, weighing less than 10% of the weight of the child. The habitual posture during rest and learning should be controlled, and the weight of the school backpacks should also be checked by parents and representatives of the educational institutions. Continuous monitoring and systematic screening tests to detect abnormalities in body posture are also justified.
Studies evaluating the incidence of abnormal behaviour, such as children wearing heavy backpacks and the relationship between this and their posture, are important in the prevention of back pain. The observed reduction and shortening of the lumbar spine as the weight of the carried backpack increases may indicate a primary cause of subsequent future overloading and degenerative changes in the spine. It can also help explain the occurrence of lower back pain in school children, discussed widely in the literature [
The weight of the backpacks without content (which would have indicated the actual weight of the school books and notebooks) was not examined, as the weight was checked only once. In addition, the study was not a longitudinal study conducted over a longer period, for example, at the beginning and the end of the school year.
Wearing a backpack heavier than 10% of one’s body weight can cause shallowing of the lumbar lordosis and a tendency towards a vertical position of the sacrum. Monitoring the weight of children’s school backpacks by parents and teachers, as well as children themselves, and enabling them to leave books and notebooks at school would probably be beneficial in reducing the daily burden put on children’s spines.
The authors declare that there is no conflict of interests regarding the publication of this paper. The study was funded using the authors’ own resources.