Postural adjustment and muscle activity during each phase of gait initiation in chronic ankle instability: an observational study

Background: Gait initiation (GI) can be divided into three sections according to the center of pressure (COP) trace (S1, S2, and S3). Almost all studies do not separate each phase of the GI profile in postural control assessment and muscular investigation, whereas differences in the COP and muscles are found in each phase of the GI profile in people with gait problems.

Methods: Twenty individuals with CAI and twenty healthy controls were included in the present study. A force plate synchronized with Qualisys motion analysis, MEGAWIN electromyography, and a pair of auditory cues were used for data capture. The participants carried out five trials of GI with the affected leg (dominant leg). The peak and mean COP excursions; the mean and maximum velocities of COP excursion during S1, S2,, S3, and the total phases in the mediolateral (ML) and anterior‒posterior (AP) directions; the root mean square (RMS); and the onset activity of the Tibialis Anterior (TA) and Soleus (SOL) muscles for both legs were used for statistical analysis. Independent t tests and Mann‒Whitney U tests were used for statistical analysis on the basis of a significance level of ≤ 0.05.

Results: Compared with those of healthy controls, independent t tests revealed a significant decrease in the peak COP excursion in the AP direction during S2 (P = 0.021) and in the mean velocity of COP excursion in the AP direction during S1 (P = 0.044) in the CAI group. Additionally, there was a significant increase in the duration of S1 in the GI profile (P = 0.045) in the CAI group compared with the healthy control group. There was no significant difference in the other COP variables, TA or SOL RMS or onset activity for either leg during S1, S2, or S3 between the two groups (P > 0.065).

Conclusion: Individuals with CAI exhibit increased stiffness in the AP direction in the injured ankle. This leads to a reduction in the velocity and peak of COP excursion, as well as an increase in the time required for postural control adjustment. These findings highlight the challenges individuals with CAI may face in meeting postural demands when trying to unload the affected foot.

Ethical code: IR.SBMU.RETECH.REC.1402.095, 2023-5-28.