Task-Agnostic Exoskeleton Control Supports Elderly Joint Energetics during Hip-Intensive Tasks

TL;DR

This study demonstrates that a task-agnostic hip exoskeleton can accurately support various mobility tasks in older adults, reducing biological effort and augmenting total power to potentially improve mobility and endurance.

Contribution

The paper introduces a novel task-agnostic control strategy for hip exoskeletons that adapts to joint power, validated across multiple activities in older adults.

Findings

Exoskeleton matched biological power profiles with high accuracy (mean cosine similarity 0.89).

Assistance reduced biological positive work at the hip by 24.7%.

Total hip power was augmented, indicating potential for endurance and mobility support.

Abstract

Age-related mobility decline is frequently accompanied by a redistribution of joint kinetics, where older adults compensate for reduced ankle function by increasing demand on the hip. Paradoxically, this compensatory shift typically coincides with age-related reductions in maximal hip power. Although robotic exoskeletons can provide immediate energetic benefits, conventional control strategies have limited previous studies in this population to specific tasks such as steady-state walking, which do not fully reflect mobility demands in the home and community. Here, we implement a task-agnostic hip exoskeleton controller that is inherently sensitive to joint power and validate its efficacy in eight older adults. Across a battery of hip-intensive activities that included level walking, ramp ascent, stair climbing, and sit-to-stand transitions, the exoskeleton matched biological power profiles with high accuracy (mean cosine similarity 0.89). Assistance significantly reduced sagittal plane biological positive work by 24.7% at the hip and by 9.3% for the lower limb, while simultaneously augmenting peak total (biological + exoskeleton) hip power and reducing peak biological hip power. These results suggest that hip exoskeletons can potentially enhance endurance through biological work reduction, and increase functional reserve through total power augmentation, serving as a promising biomechanical intervention to support older adults' mobility.