Researchers identify the maximum weight that children should carry in their school backpacks

Scientists from the University of Granada and Liverpool John Moores University (UK) 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 identify the maximum weight that children should carry in their school backpacks. Photo: Eva Orantes González/Department of Physical Education and Sports, University of Granada

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.

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. (University of Granada)

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