Effects of frailty and walking speed on gait variability in older adults.

Background: Gait variability is crucial for predicting frailty. This study aims to explore the effects of frailty and speed on endpoint variability and coordination variability (CV) during walking. Methods: Forty-seven adults (≥60 years; 18 males, 29 females) participated in this study. Gait kinematics were captured using Xsens MVN inertial sensors at three speeds (preferred, fast, and slow). Endpoint variability was evaluated using standard deviations (SD) of support times (total, single, and double). The coordination of the lower limb during braking phase and propulsive phase was quantified by continuous relative phase (CRP) analysis for interlimb (hip-hip, knee-knee, ankle-ankle) and intralimb (hip-knee, knee-ankle), and then CV was assessed through SD of interlimb CRP and intralimb CRP. Effect sizes were calculated using partial eta squared (η Results: The results revealed an interaction between frailty and speed on total support time variability ( Conclusion: Frail elders exhibited greater endpoint variability but smaller CV, especially interlimb CV. During preferred speed walking, frail and pre-frail elders may demonstrate more flexible distal joint coordination, while rigid distal joint coordination during braking phase may increase instability risks during fast walking. This study used a cross-sectional design with a limited sample; future longitudinal studies are needed for verification, and more gait parameters and population differences should be explored.