Improved Postural Stability Using a Lightweight Semi-Active Soft Back Support Device Under Standing Perturbations

2026-06-01

AI Summary

This study addresses the challenge of postural instability in older adults, who are prone to falls due to excessive trunk flexion during standing. Existing support devices are often limited by either excessive weight that compromises balance or insufficient assistance from purely passive mechanisms. To overcome these dual limitations, this work proposes a lightweight, semi-active, compliant back-support device that innovatively combines pneumatic artificial muscles with elastic bands in parallel. Integrating minimalist design with real-time responsive semi-active control, the system rapidly delivers extension assistance upon perturbation onset. In experiments with five healthy participants, the device significantly reduced whole-body angular momentum and increased stability margins, thereby enhancing postural recovery during standing perturbations. These results demonstrate its potential to effectively mitigate fall risk while avoiding the drawbacks of conventional heavy or passive support systems.

Abstract

Older adults are particularly susceptible to falls following perturbations during standing, such as forward loss of balance. Back support devices that assist trunk extension may help mitigate fall risk by preventing excessive trunk flexion. Previous studies have investigated heavy back support devices; however, these systems often introduced adverse effects on stability due to their added mass, which shifted the body's natural center of mass unfavorably. In contrast, lightweight passive devices have shown limited benefits, as they can generate only modest assistive forces during the relatively small trunk flexion associated with forward balance loss. In this study, we evaluated the effects of a lightweight semi-active soft back support device on postural stability following standing perturbations. Our device combines an active element (a pneumatic artificial muscle) in parallel with a passive elastic band. The active element rapidly provides assistive force following a perturbation, overcoming the limitations of passive devices. Experiments conducted with five healthy individuals demonstrated that the semi-active device significantly reduced whole-body angular momentum and increased the margin of stability, indicating improved balance recovery performance. These results highlight the promise of semi-active soft wearable robots as an effective and lightweight strategy for fall prevention during standing perturbations.

Problem

• postural stability
• fall prevention
• standing perturbations
• back support device
• trunk flexion

Innovation

• semi-active
• soft wearable robot
• postural stability
• pneumatic artificial muscle
• fall prevention