Age- and Fall-Risk–Related Differences in Reactive Balance Responses

Reactive balance control is critical for fall prevention. The ReBalance study examined trunk, hip, and knee range of motion (ROM) from inertial sensors (Trigno, Delsys) during anterior, posterior, right, and left tilting perturbations with triangular (TRIANG) and trapezoidal (TRAPZ) acceleration profiles, in order to reveal age- and risk-related differences in young adults (N=10, 29.4 ± 5.3 years, 40% female) and older adults at low (N=26, 73.4 ± 7.0 years, 40% female) and high (N=25, 79.7 ± 7.4 years, 60% female) fall risk. Fall risk was assessed using FRAT-up (Cattelani et al, JMIR, 2015).

For anterior TRIANG perturbations, trunk ROM increased progressively from young (4.2 ± 1.9°) to low-risk (6.4 ± 2.9°) and high-risk older adults (9.0 ± 4.3°), with a similar pattern in hip ROM. Posterior TRIANG and TRAPZ responses were comparable. Kruskal–Wallis tests indicated significant group effects for trunk and hip ROM (p ≤ 0.04). Knee ROM did not differ. High-risk older adults exhibited greater trunk ROM than young adults (p < 0.01), whereas hip ROM differences were task-dependent. Low-risk older adults showed trunk ROM lower than high-risk participants (p ≤ 0.02), while hip ROM was often comparable between groups.

These findings indicate an age- and risk-related shift in balance control strategies. Young adults predominantly relied on an ankle-dominant strategy, whereas older adults increasingly adopted proximal control mechanisms, with high-risk individuals displaying excessive trunk excursions and reduced inter-segmental coordination. Consistently, actual falls, safely arrested by a harness, occurred mainly in high-risk older adults during posterior perturbations.

The observed patterns of trunk and hip control may inform fall-risk assessment and support the design of balance-assistive exoskeletons.

This research was supported by the Italian Ministry of University and Research through PRIN project REBALANCE.