Proposal for a universal measurement system for school chairs and desks for children from 6 to 10 years old
Introduction
Growth is defined as the measurable physical changes of the body (Newman and Newman, 2012) that occur from birth to around 18–23 years old (Gonçalves, 2012, Ribeiro, 2012). Although growth depends on genetic potential, its pace and quality can, at any point, be disturbed by extrinsic factors (Ministério da Saúde do Brasil, 2002), such as bad posture during school years.
The constraints related to a sitting posture are considered more harmful for the human body than standing, therefore the design of the furniture used has a significant influence. Poorly designed school furniture may lead to bad posture habits which may have a direct impact on the growth process because they are likely to remain unchanged into adolescence or adulthood (Gonçalves, 2012, Gouvali and Boudolos, 2006, Panagiotopoulou et al., 2004, Parcells et al., 1999). Accordingly with Molenbroek et al. (2003) and Parcells et al. (1999) bad posture may lead to back, leg, arm, neck, shoulder and feet pain in school age children.
There are however contradictions about the direct relationship between poor posture and ergonomic school furniture. Troussier (1999) concludes that there is no modification of back pain prevalence in 8–11 year old schoolchildren using ergonomically designed furniture.
Despite these contradictory findings between studies and in a prevention perspective we considered important to take account of the hypothesis described by Molenbroek et al. (2003) and Parcells et al. (1999).
Chairs are the largest contributors to incorrect posture among children because they are not appropriate for the anthropometric and biomechanical characteristics of their users. Despite the fact that stature differences at the same age can reach 200 mm, it is nonetheless common to use the same seat size for all students in the same class.
School furniture along with good posture training could address this issue. The primary goal of school furniture, in particular chairs and desks, is to promote comfort and good posture and thus enhance school performance (Castellucci et al., 2014b, Domljan et al., 2010, Gonçalves, 2012, Guat-Lin, 1984, Moro, 2005, Parcells et al., 1999). In their consideration of child anthropometry, many authors (Castellucci et al., 2015, Gonçalves, 2012, Molenbroek et al., 2003, Panagiotopoulou et al., 2004, Parcells et al., 1999) have commented that school furniture should be adapted to the anthropometric changes that take place during growth.
The design of school furniture is guided by national and regularity standards. The countries in the European Union follow the Normative EN 1729-1, while in Brazil the NBR-14006 and NBR 14007 (Reis, 2003, Reis et al., 2005), and in the USA the ISO 5970 (Poston, 2002). Unfortunately, these standards do not always comply with the anthropometric reality of the users. For example, Gonçalves (2012) and Molenbroek et al. (2003) show that the European Standard does not fit the anthropometric reality of European children, demonstrating sizing gaps. For its part, Reis et al. (2005) shows that the Brazilian Standard is not fully implemented in terms of its practical application, revealing that Brazilian schools only use a single size of chairs and school desks for 7–17 years old leading to inadequate postures and musculoskeletal pathologies. Parcells et al. (1999) concludes that the furniture used in some North American schools is unsuitable with less than 20% of the students having a chair and desk compatible with their anthropometric dimensions. It can be seen, therefore, that there is a poor relationship between the actual anthropometric measures of each country and the dimensioning considered by their particular standards.
As demonstrated in the studies of Castellucci et al., 2015, Molenbroek et al., 2003, Gouvali and Boudolos, 2006, among others, the anthropometric measures are directly related to the dimensions of the chair and desk. When the (mis)match equations are applied it is possible to obtain the optimal values for the considered sample.
Given the need of global manufacturing and the inherent diversity in the global market, it becomes a priority to develop an adaptable chair and desk for primary school children. A methodology of sizing, able to support the design of this adaptable chair and desk set and having as a prescribed criteria the popliteal height (PH), as advocated by Molenbroek et al. (2003) and Castellucci et al. (2015), which when compared with stature presents a “better cumulative fit or match”.
This methodology can be an important instrument to justify the designer’s decision during the conceptual and development phases. An adjustable chair can be adapted to children with different statures from different countries. For the industry this is a very convenient solution, with one chair is possible to respond to the needs of different markets, enhancing responsiveness in production efficiency, environmental impact, market management and economic sustainability of the product.
Section snippets
Material and methods
The criteria of age selection in this study, between 6 and 10 years old, correspond to the school ages according to ISCED 1 – International Standard Classification of Education 2011 (UNESCO, 2012). The popliteal height (PH) was taken as prescription criteria for the selection of the proper size of the chair and desk, as recommended by Molenbroek et al. (2003) and Castellucci et al. (2015). The (mis)match equations presented by Castellucci et al. (2014b) were taken in to account for sizing the
Calculation
The proposed methodology is based on two assumptions defined by Molenbroek et al. (2003) and Castellucci et al. (2015):
- 1.
The sizes of the chair and desk set should be prescribed having as reference the popliteal height (PH) instead of the stature. This can only serve as a secondary reference but never, in any case, as a primary reference running the risk of choosing the wrong size.
- 2.
The starting point for the sizing of the chair and desk set is the seat height (SH), this being defined by the
Results
The calculations performed for each dimension indicated that 5 sizes were needed to accommodate the population studied. For each of these sizes, the recommended dimensions are described in the following table (Table 7). Although all calculations have been made based on the popliteal height (PH), it is given for each size the corresponding stature range only as a secondary reference.
Discussion
From this study, a set of universal measures can be defined for school furniture, chair and desk set, for children from 6 to 10 years old. With the popliteal height (PH) as a prescription measurement it is possible to have all the children properly seated without overlapping sizes (Fig. 17). It is also noted that popliteal height (PH) corresponds only to one chair and desk size, which does not happen with stature.
It is recommended that these sizes are used in adjustable chairs and desks,
Conclusion
For companies wishing to compete in international markets, their product ranges must be competitive and fit the market they are being designed for.
In the school furniture industry, the chair and desk sets have a major role to ensure comfort within the classroom. From the age of 6, all children spend much of their time in this space. If the furniture they use does not correspond with their anthropometry, it will lead to discomfort, physiological problems, the adoption of bad postures and
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