Ankle Exoskeleton Assistance Can Affect Step Regulation During Self-Paced Walking

Area of Science:

• Biomechanics
• Human-robot interaction
• Assistive technology

Background:

• Exoskeleton assistance offers potential benefits for walking but shows high individual variability in outcomes.
• Assistance may alter gait parameters such as variability, energetic cost, and balance control through step regulation.

Purpose of the Study:

• To investigate the effects of a powered ankle exoskeleton on step regulation.
• To examine the relationship between exoskeleton-induced changes in step regulation, walking speed, cost of transport (COT), and gait variability.

Main Methods:

• Twelve unimpaired adults walked in shoes, with a zero-torque exoskeleton, and with two proportional myoelectric control settings.
• Measurements included preferred walking speed, COT, gait parameters (step length, time, width), and long-term correlations using detrended fluctuation analysis (DFA).

Main Results:

• Subjects walked slower with the exoskeleton, but COT was equivalent to normal walking.
• Medio-lateral balance control was enhanced by increased step width and reduced variability/autocorrelation, though this returned to baseline in one condition.
• Associations between step width regulation, walking speed, and COT were present without assistance but not with it.

Conclusions:

• Exoskeleton assistance influences step regulation and balance control strategies.
• The adaptability of stepping strategies, particularly during early learning phases, is crucial for understanding individual responses to powered assistance.