A kinematic comparison of gait with a backpack versus a trolley for load carriage in children.

The use of a school trolley is reaching and even surpassing the use of backpacks in many countries, although a recommended load has not been studied. To accomplish this, 3D gait kinematics of the lower limbs and thorax were analysed in 49 students walking unloaded, pulling a school trolley or carrying a backpack, all with either 10%, 15%, or 20% BW. The variables obtained were the degrees of flexion/extension, adduction/abduction and internal/external rotation of the thorax, pelvis, hip, knee and ankle. Statistical parametric mapping was used to evaluate differences between conditions and loads throughout the gait cycle. In the backpack conditions, the magnitudes of the differences decreased from proximal to distal joints compared to the unloaded condition. The use of a school trolley only required minor kinematic adaptations. Therefore, from kinematic analysis, it is recommended to avoid loads above 10% BW for children using a backpack and below 20% BW for children using a trolley.