Date: July 2, 2019
Source: University of Granada
Summary: Scientists have established that school children who use backpacks should avoid loads of more than 10% of their
body weight — and those who use trolleys, 20% of their body weight.
Researchers from the University of Granada (UGR) and UK-based Liverpool John Moores University
have determined for the first time the maximum weight a child should carry using a school backpack
trolley: a maximum of 20% of their body weight.
In an article published in the Applied Ergonomics journal, ranked second in the Ergonomics area of Journal Citation Reports, the
scientists describe how they have established — in a worldwide first — recommendations on the appropriate load that primary
school-age children should carry when using a backpack trolley.
To date, weight recommendations have been established for ordinary school backpacks, as they are the most widely used type in
the school context worldwide. However, in Spain, more than 40% of children use backpacks on wheeled trolleys, and until now
there have been no studies making weight recommendations for this type of backpack.
This research was conducted via a collaborative project involving researchers from the UGR (the Department of Physical
Education and Sports and the Laboratory for the Analysis of Movement and Human Behaviour, Ceuta campus, or HubemaLab)
and from Liverpool John Moores University.
Study focuses on Primary School pupils
In this study, 49 primary school pupils were assessed. A kinematic analysis of the children (posture of the trunk and lower limbs)
was conducted while (i) they walked freely, carrying no weight, (ii) carrying a traditional backpack, and finally (iii) pulling a backpack
trolley with different loads (10%, 15%, and 20% of their respective body weights).
For the analysis, a three-dimensional optical motion capture system was used, similar to those used in animation films and video
games. In collaboration with the researchers from Liverpool John Moore University, the UGR researchers used statistical
techniques to analyse the full kinematics curves, based on tracing point trajectories.
The main findings of the study indicate that the greatest alterations when using trolleys or backpacks are produced in the proximal
extremities (hip and trunk), while there is little difference in the kinematics of the distal extremities (knee and ankle). However,
pulling the backpack trolley produces fewer changes in the child’s kinematics and, therefore, resembles more closely their
movement when walking free of any load, compared to carrying the backpack, even when it weighs very little.
As an overall conclusion, the study corroborates that schoolchildren who use backpacks should avoid carrying loads greater than
10% of their body weight. Furthermore, in a new finding, when pulling a school backpack trolley, the child should avoid carrying any
load greater than 20% of their body weight.
Story Source: https://www.sciencedaily.com/releases/2019/07/190702112708.htm
Materials provided by University of Granada. Note: Content may be edited for style and length.