Review articleSchool backpack design: A systematic review and a summary of design items
Introduction
Children in both developing and developed countries commonly carry backpacks to and from school (Whittfield et al., 2001; Jayaratne, 2012). In the developed world, 90% of schoolchildren carry a backpack (Macias, 2008). Many children use backpacks in the range of 10–20% of their body weight (BW) (Whittfield et al., 2001; Goodgold et al., 2002; Mwaka et al., 2014), with the bags disproportionately heavier relative to BW among younger students than those who are older (Goodgold et al., 2002; Mwaka et al., 2014).
Recently, the mean prevalence of low back pain (LBP) was about 39% for lifetime and 15% for point prevalence in childhood and adolescence (Calvo-Muñoz et al., 2018). Heavier backpack weight causes increased neck, shoulder, spinal and extremities pain (Moore et al., 2007), and the backpack weight has been suggested to play a pathogenic role in the causation of LBP in children (Negrini and Carabalona, 2012; Nicolet et al., 2014). The peak in pain prevalence is just before puberty (Forjuoh, 2004), so it is very important to choose a suitable backpack to mitigate the effect while the students are still pre-puberty. Girls (Forjuoh, 2004; Shamsoddini et al., 2010), shorter (Korovessis et al., 2004) and younger children, particularly for fifth and sixth grade, may be especially at risk of these injuries because they carry loads that are heavier in proportion to their BW (Goodgold et al., 2002).
For developed regions, such as Poland, England and Spain, high prevalence of back pain (BP) was generally noted in youth of 10–19 years old (Kędra et al., 2019). The risk factors were found to be the heavier weight of the schoolbag or unsatisfied perception on carrying a schoolbag (Szpalski et al., 2002; Kędra et al., 2019). Preventive activities for mitigation of related pains should be implemented (Rodríguez-Oviedo, 2012), and a good design for backpacks is certainly one of the measures.
In developing regions, children carrying heavier schoolbags and walking for long durations have about 3.5 (95% CI = 1.80–6.95) times risk of reporting pain, as compared with those who walk for similar duration but carry lighter bags (Delele et al., 2018). In Bucaramanga, Colombia, a recent cross-sectional study also indicated that carrying heavy backpacks weighted between 12% and 20% of BW increased the risk of non-specific LBP (Angarita-Fonseca, 2019). Other studies also found that a heavy backpack was associated with LBP (AlShayhan and Saadeddin, 2018; Ben Ayed et al., 2019) as well as neck and shoulder pain (Ben Ayed et al., 2019) among youth in developing countries.
In this regard, researchers have been evaluating the designs of packs, modes of carriage, and limits of load, as well as psychological, physiological, and biomechanical responses to load carriage under various pacing, gradient, and terrain conditions (Winsmann and Goldman, 1976; Legg, 1985; Legg and Mahanty, 1985; Yu and Lu, 1990; Legg et al., 1992, 1997). Chow et al., 2010, Chow et al., 2011) investigated the effects of loading, design, and carrying durations of the backpacks on the spine. Their respective findings were that spinal compression was related to carrying duration, spinal curvature was associated with spinal load conditions, and backpack design had potential effects on load carriage. However, a systematic review suggested that there is limited evidence on the effect of load positioning and various designs on the levels of perceived pain and exertion (Golriz and Walker, 2011). Another review suggested that there were conflicting results on the spine from the backpack positioning and from the shoulder strap design, but front packs and double packs provided better posture than backpacks (Golriz and Walker, 2012). A recent narrative review (Suri et al., 2019) also provided some points of view for backpack design from the biomechanical aspect and postural outcomes, but they did not review all types of carrying method (such as double-pack and backpack), different types of straps (such as hip and chest straps) and other health outcomes, such as metabolic cost or perception.
Regarding the design of studies that have investigated backpack design, researchers (Golriz and Walker, 2011) have identified limitations, including that sample size has not been adequately justified. The tasks performed and backpack usages have also varied widely, which has made meta-analysis more difficult (Golriz and Walker, 2012). Thus, we would also like to investigate whether there are improvements among the current studies that address these problems and other limitations, such as bias.
As a result, the aim of the present systematic review is to provide the up-to-date and all-round summary of items (see Table B1) of how the design of a backpack (schoolbag) could help alleviate the adverse effects on school children, adolescents and young adults in the aspect of psychological outcomes (perception), physiological outcomes (metabolic cost), and biomechanical outcomes (such as changes in posture, gait, muscle activities and foot pressure) and prevalence (such as LBP and shoulder pain). The evidence for design-oriented factors will be covered, including all strap designs (including shoulder, hip and chest), carrying methods (e.g. traditional backpack, trolley bag, the proprietary BackTpack or single strap), dimension of backpack, and biomechanical considerations (such as the positioning of the centre of gravity (CG) of the backpack).
Section snippets
Inclusion of studies
A systematic review was performed in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement (Moher et al., 2009). The protocol of this review was not registered, being not required by the journal, as was the practice for most previous studies (Golriz et al., 2011). The review was performed from September 2019 to March 2021. A single author (JL) conducted a literature search on electronic databases PubMed (Medline), Ovid (AMED, EMBASE,
Results and discussion
The intraclass correlation coefficient (ICC) value of the rater for the selection of articles was 0.93. Fig. 1 indicates the flow of our search under the framework of PRISMA. The searches yielded some articles that were not relevant to our study and were excluded. For instance, some studied parameters that were not relevant to our backpack design parameters; some recruited subjects that were not specified/within our target age or healthy; and some studied backpacks that were not schoolbags. A
Limitations of this review
When assessing the included studies, multiple reviewers were commonly used to avoid bias, especially while some assessment criteria were subjective. However, in this review, only one reviewer was deployed.
Nevertheless, in this review, the results showed that the ICC value of the rater was 0.93, indicating excellent test-retest agreement. The detailed, clear, and factual items of instruction on the checklists, RoB2 (to AHRQ standards) and STROBE(V4), account for such strong agreement. For
Conclusion
In this review, recent research related to backpack design factors and their health outcomes for school or college students, has been systematically included. Numerous factors were classified into four major elements: biomechanical consideration, strap design, dimension and carrying method. The outcomes are numerous, including postural change (e.g. spinal curvature, gait, kinematics), metabolic cost (e.g. oxygen consumption, heart rate), perception (e.g. RPE, discomfort score), muscle activity
Author statement
Joe Ching Nang Lee: Writing- Original draft preparation, Methodology, Investigation.
Simon Siu Wai Li: Conceptualization, Methodology, Writing- Reviewing and Editing.
Daniel Hung Kay Chow: Supervision, Conceptualization, Writing- Reviewing and Editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors would like to acknowledge Dr. Douglas Kei Shing Ng for his support.
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