Multiscale dynamics of single-leg standing postural control in chronic ankle instability

This study aimed to investigate postural sway complexity in chronic ankle instability (CAI) in static postural control and its relationship with the duration of ankle instability. 61 participants were recruited, including 35 CAI and 26 healthy controls (HC). Right leg standing balance was assessed in eyes open (EO) and eyes closed (EC) conditions for 20s. Multiscale entropy was used to quantify the complexity of center of pressure fluctuations in the anterior-posterior (AP) and medial-lateral (ML) directions. One-way ANOVA was used to compare the differences in postural sway complexity between the two groups. Compared with HC, the AP (F = 6.812, p = 0.012, η² = 0.133) and ML sway complexity (F = 4.164, p = 0.047, η² = 0.087) in EO condition was significantly lower in CAI group, but not in EC (ML: F = 1.229, p = 0.274, η² = 0.027; AP: F = 2.398, p = 0.129, η² = 0.052). The duration of ankle instability was correlated with ML sway complexity in EC condition in CAI group (r = -0.484, p = 0.023). This indicates that CAIs have poor adaptability to stressors, and multiscale entropy can serve as a potential indicator for identifying impaired postural control with eyes open in CAI.