Model-derived proprioceptive afferent timing during gait initiation in chronic ankle instability

Although proprioceptive deficits are reported in chronic ankle instability (CAI), their temporal organization during dynamic movement remains unclear. This cross-sectional study compared the temporal relationship between model-derived muscle spindle (MS) and Golgi tendon organ (GTO) afferent signals in the peroneus longus during gait initiation in 19 individuals with CAI and 19 healthy controls. OpenSim-derived muscle states were entered into mathematical MS and GTO models. During each original-duration anticipatory postural adjustment (APA) trial, the signed lag at the automatic maximum of an overlap-aware linear Pearson cross-correlation was calculated for the Ia–Ib and II–Ib signal pairs; positive values indicated that the spindle-derived signal led Ib. Participant-mean signed peak lags did not differ between groups in the multivariate analysis (Hotelling T² = 1.029, F(2, 35) = 0.500, p = 0.611; 50,000-permutation p = 0.614). Follow-up comparisons were also nonsignificant for Ia–Ib (CAI: 0.002 ± 0.067 s; control: 0.025 ± 0.078 s; Holm-adjusted p = 0.656) and II–Ib (CAI: −0.004 ± 0.082 s; control: 0.015 ± 0.095 s; Holm-adjusted p = 0.656). APA duration was shorter in the CAI group (0.408 ± 0.077 s) than in controls (0.493 ± 0.078 s; p = 0.002). Trial-level lag reliability was low, and the analysis did not support a between-group difference in model-derived proprioceptive afferent timing.