Condition-specific role of ankle proprioception in postural control in older adults: a stabilogram diffusion analysis approach.

This study examined whether Stabilogram Diffusion Analysis (SDA) parameters differ between younger and older adults across sensory conditions, and whether reduced ankle proprioceptive acuity correlates with SDA parameters in older adults, specifically when standing on a foam surface with and without visual input. Fifty-three healthy adults (25 older) participated. Ankle proprioception was evaluated through Kinesthesia Threshold (KT) and Joint Repositioning Error (JRE), and static postural control was measured with a pressure platform under four conditions (foam/firm × eyes open/closed). SDA quantified short- and long-term diffusion coefficients (Ds, Dl) and critical time interval (Δtc) to characterize open- and closed-loop control. Older adults showed higher KT (dorsiflexion: 1.4° vs. 0.9°) and greater JRE at 6° plantarflexion (1.8° vs. 0.9°). A two-way mixed-design ANOVA revealed significant condition effects on Ds and Dl (ηp2 = 0.47, ηp2 = 0.44), while group and interaction effects were non-significant. Proprioceptive errors correlated with SDA parameters in older adults exclusively under foam standing conditions. The condition-specific link between ankle proprioceptive deficits and SDA parameters indicates that the proprioceptive contribution to postural control depends on the sensory context in which it is assessed, and that surface condition should be considered when ankle proprioception is evaluated in older adults.