Abstract
This study aims to improve our understanding of gait initiation mechanisms and the lower-limb joint mechanical energy contributions. Healthy subjects were instructed to initiate gait on an instrumented track to reach three self-selected target velocities: slow, normal and fast. Lower-limb joint kinematics and kinetics of the first five strides were analyzed. The results show that the initial lateral weight shift is achieved by hip abduction torque on the lifting leg (leading limb). Before the take-off of the leading limb, the forward body movement is initiated by decreasing ankle plantarflexion torque, which results in an inverted pendulum-like passive forward fall. The hip flexion/extension joint has the greatest positive mechanical energy output in the first stride of the leading limb, while the ankle joint contributes the most positive mechanical energy in the first stride of the trailing limb (stance leg). Our results indicate a strong correlation between control of the frontal plane and the sagittal plane joints during gait initiation. The identified mechanisms and the related data can be used as a guideline for improving gait initiation with wearable robots such as exoskeletons and prostheses.
Highlights
This study aims to improve our understanding of gait initiation mechanisms and the lower-limb joint mechanical energy contributions
Several studies have investigated the center of mass (CoM) and center of pressure (CoP) movements during gait initiation
This work aims at further understanding gait initiation mechanism by focusing on the energy injection from the perspective of the lower-limb joints
Summary
This study aims to improve our understanding of gait initiation mechanisms and the lower-limb joint mechanical energy contributions. Before touch down of the swing foot, the CoM has already established a near steadystate trajectory[10] It remains unclear how lower-limb joints contribute to the mechanism of shifting the CoM and CoP. Lower-limb joint mechanical power and energy have been used to explain walking energetics[12,13]. Positive and negative mechanical joint power indicate energy injection and energy dissipation/ storing, respectively. For level walking the average positive and negative power of the hip, knee and ankle increase as walking velocity increases[13]. No study has shown the lower-limb joint mechanical power and energy contribution during gait initiation of different target velocities
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