Everyone knows heavy school bags are a serious threat to the health and wellbeing of the children which makes knowing how much weight shall children carry a vital aspect. 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 reported a recent study published in the Journal of Applied Ergonomics. 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