Wearable Assessment of Nonlinear Gait Stability Identifies Fall History in Older Women

Background Falls are a major cause of injury, disability, and reduced exercise participation among older women. Wearable technologies may enable scalable assessment of gait stability to support injury prevention and rehabilitation in community settings. This study examined whether a trunk-worn inertial measurement unit (IMU)–derived measure of dynamic stability, the short-term Lyapunov exponent (LyE), discriminates older women with and without a history of falls during overground (OG) and treadmill (TM) walking. Methods Thirty-four women aged ≥ 60 years (17 with and 17 without fall history) completed the Timed Up and Go (TUG) test and walked at self-selected speeds under OG and TM conditions. Trunk acceleration was recorded from a lower-back IMU. LyE was calculated in anterior–posterior (AP), medio-lateral (ML), and vertical (V) directions. Binary logistic regression models were constructed separately for each direction and condition, adjusting for age and gait speed. Between-group differences were evaluated using independent t-tests (Cohen’s d). Results Fallers walked more slowly in both conditions (p < 0.001). LyE in the AP direction was higher (indicating reduced dynamic stability) in fallers during OG (p = 0.001, d = 1.24) and TM walking (p = 0.002, d = 1.24). Higher LyE_AP was associated with greater odds of fall history in OG (OR = 1.80, 95% CI 1.09–2.97) and TM (OR = 1.90, 95% CI 1.07–3.37), independent of age and gait speed. ML and vertical LyE, gait speed, and TUG were not significant predictors. Conclusions Reduced anterior–posterior gait dynamic stability, derived from a trunk-worn IMU, discriminated fall history in older women across walking conditions. Overground assessment demonstrated comparable performance to treadmill testing, supporting its feasibility for real-world screening. These findings highlight the potential clinical application of nonlinear biomechanical metrics to enhance fall-risk assessment, support injury-prevention strategies, and inform exercise-based rehabilitation in ageing populations.