Characterization of the mechanical properties of backpacks and their influence on the energetics of walking

Abstract The objectives of the experiment were (i) to characterize the mechanical properties of backpacks and (ii) to study the influence of a flexible backpack on the energetics and kinematics of walking. Twelve subjects walked at different speeds on a treadmill with each of two backpacks loaded with 25% bodyweight, with either a rigid or a flexible link between the body attachment and the suspended loads. A single degree of freedom linear model of the link between the pack and the trunk was used to calculate the stiffness and damping coefficient of the two backpacks. The oxygen consumption ( V ˙ O 2 ) and the vertical acceleration of both the backpack and trunk were measured. The vertical excursion of the pack given by the model was significantly correlated with that actually measured ( R =0.87, p −1 the flexible pack induced lower acceleration peaks (respectively −22% and −8%; p V ˙ O 2 ( p =0.055 at 4.5 km h −1 ) compared with the rigid one. At 5.2 and 6 km h −1 both the accelerative forces and V ˙ O 2 increased with the flexible pack ( p