Dynamic stability in sit-to-walk transition: A quantitative analysis based on age-related momentum distribution and lower extremity kinematics

PURPOSE: The sit-to-walk (STW) transition serves not merely as a highly prevalent functional movement in activities of daily living but also as a pivotal task paradigm for elucidating overall motor control strategies. The objective of this study was to comparatively evaluate the stability control characteristics between two groups during STW transitions and to explore the underlying mechanisms associated with potential fall risks. METHODS: Lower-limb differences between the two groups were assessed using independent samples t-tests, statistical parametric mapping, and phase-average comparisons, supplemented by correlation analyses. RESULTS: Peak horizontal momentum (HM) showed significant differences between the two groups across the entire phase (p < 0.05). The anteroposterior margin of stability (MOS) differed significantly during the extension and swing phases (p < 0.03), whereas knee range of motion and center of pressure excursion velocity exhibited significant differences only in the unloading phase (p < 0.05). In the young group, the MOS, HM, and joint kinematics demonstrated significant strong negative correlations (r < -0.5, p < 0.05), whereas these correlations were generally attenuated in the older adult group. CONCLUSIONS: Older adults tend to adopt a conservative postural control strategy during STW transitions, prioritizing enhanced stability by restricting forward HM and prolonging movement duration. These findings elucidate the characteristics underlying fall risks during STW in older adults, providing a scientific rationale for the design of targeted biomechanical interventions.