Evaluating Energy Consumption of Rigidly Controlled Exoskeleton-Assisted Gait in Healthy and Spinal Cord Injury Participants: Pilot study

Abstract

Exoskeleton robotics have been developed for neuro-recovery, with user engagement being a crucial factor for achieving effective rehabilitation outcomes. This study investigates the impact of rigid motion control on user engagement and examines whether the energy expended by users is due to active participation or movement restrictions imposed by the predefined motion trajectory. To evaluate effort expenditure, oxygen consumption (VO₂) was measured in both healthy and spinal cord injury (SCI) subjects during independent walking and exoskeleton-assisted walking. The results indicate that VO₂ in the healthy subject significantly increased (p < 0.01) from 8.73 ± 1.77 to 12.51 ± 4.71 ml/kg/min during exoskeleton-assisted walking, accompanied by a significant deviation in lower limb Kinematics trajectories. This suggests that the rigid control's movement restriction contributed to the increased metabolic cost. Conversely, in the SCI subject, VO₂ consumption significantly decreased (p < 0.01) from 11.74 ± 4.05 to 8.4 ± 3.31 ml/kg/min. However, VO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> consumption of the SCI subject assisted by exoskeleton revealed no significant difference from the VO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> consumed during a normal human gait for healthy subject, indicating that the SCI subject was actively engaged in movement rather than being passively assisted. These findings highlight the impact of rigid control on energy expenditure and user engagement.