The Effects of a Lower Body Exoskeleton Load Carriage Assistive Device on Oxygen Consumption and Kinematics during Walking with Loads

The purpose of this study was to investigate the metabolic cost of wearing a prototype exoskeleton (EXO) while walking with a range of heavy loads, and to analyze the associated gait biomechanics. Ten Army enlisted men participated in the study. Oxygen consumption (VO2) and gait biomechanics were measured while Soldiers walked at 4.83 km/h and 0% grade under three realistic load weight configurations that were comprised of Army clothing and equipment: fighting load (20 kg), approach march load (40 kg), and emergency approach march load (55 kg). The volunteers were tested under all load configurations with and without wearing the EXO prototype. Mean VO2 significantly increased while wearing the EXO compared to not wearing the EXO across all conditions. Mean VO2 scaled to body mass and scaled to total mass also significantly increased while wearing the EXO. Mean VO2 and mean VO2 scaled to body mass significantly increased with load, however, there were no significant EXO by load interaction effects for both the non-scaled and scaled VO2. The kinematic and kinetic data revealed significant changes when wearing EXO compared to not wearing EXO. In summary, volunteers walked with shorter and faster strides; maintained a more flexed posture with reduced movement at the individual leg joints; braked with higher ground reaction forces at heel strike; and pushed off with lower force at toe off. This study demonstrated that use of an exoskeleton prototype increases users’ metabolic cost while carrying various loads and alters their gait biomechanics compared to conventional load carriage using a backpack.