Effects of Dynamic Stability Training Using Water Inertia Load on Joint Moment Redistribution and Gait in Elderly Women: A Randomized Clinical Trial

Background: Gait decline in older adults is closely linked to reduced ankle propulsion and compensatory reliance on proximal joints, such as the hip. This study examined whether dynamic stability training using water inertia can improve gait mechanics and redistribute lower limb joint moments in elderly women. Method: Twenty-four women aged 65 years and older were randomly assigned to either an experimental group or a control group. The experimental group performed dynamic stability training using an aqua vest filled with water to provide dynamic inertia load, while the control group used a weighted vest with an equivalent external load. Both groups participated in a 12-week intervention, training two times per week. Outcome variables included spatiotemporal gait parameters (gait speed, stride length, and cadence), peak ankle plantar flexion moment, hip extension moment, and positive mechanical work at the ankle during the terminal stance phase. A two-way repeated measures ANOVA was conducted to evaluate group × time interaction effects. Results: Significant group × time interactions were found for gait speed (p < 0.001), stride length (p < 0.001), ankle plantar flexion moment (p = 0.017), and positive mechanical work at the ankle (p = 0.001). The experimental group showed the most notable improvements between weeks 6 and 12, while the control group demonstrated limited changes beyond week 6. Cadence increased significantly over time in both groups (p < 0.05), although no group × time interaction was observed. Hip extension moment showed a non-significant downward trend in the experimental group, suggesting enhanced distal propulsion and reduced reliance on proximal compensatory strategies. Conclusion: Water-inertia load training improved propulsion efficiency and joint moment distribution, favoring an ankle-dominant strategy. These findings support the use of instability-based training to enhance gait function and reduce proximal compensatory patterns in older women.