A Preliminary Study of Acceptable Load Carriage for Primary School Children

Abstract

This study investigated the changes in Ground Reaction Forces, GRFs and trunk inclination among primary students when carrying heavy backpacks. A randomised controlled experimental study was conducted on seven boys aged between 9 and 11 years old with similar Body Mass Index. Observations were done when the boys were carrying school bags of 0 (as control), 10, 15 and 20% of their own body weight whilst normal walking. Data acquisition was carried out using force platforms and 3-D motion analysis system. A significant difference in Ground Reaction Forces at load of 20% of body weight was found. The vertical GRF increased almost three times when loads increased up to 20% of body weight compared to 10% of body weight. The anterior-posterior GRFs were asymmetrical when loads were increased. When carrying load of 15% of body weight, the subjects adopted a compensatory trunk inclination. If Ground Reaction Forces and trunk inclination are important as the criteria to determine the acceptable backpack loads for children, those loads should not exceed 15% of body weight.