Reliability and responsiveness of gait initiation profiles in those with chronic ankle instability

Individuals with chronic ankle instability (CAI) have demonstrated deviations in gait initiation (GI) compared to healthy individuals. However, the intersession reliability of GI measures remains unknown in this population. The objective of this study was to determine the reliability and responsiveness of GI measures between two testing days in those with CAI. Twelve individuals with CAI volunteered. Participants performed barefoot GI on a force plate which captured center of pressure (COP). Data was collected on two separate occasions separated by one week. The GI profile was separated into three phases (S1, S2, and S3). S1 began from the deviation of normal balanced standing to the most posterolateral displacement under the stepping limb. S2 began from the end of S1 to the maximum medial position under the stance foot. S3 began at the end of S2 and continued until the vertical ground reaction force dropped below 100N. COP displacement (cm) was calculated as the sum of resultant vectors of the medial-lateral and anterior-posterior excursions for adjacent COP data points within each phase. The averages of 5 trials were used for analyses. Intraclass correlation coefficients (ICC(2,5)), standard error of measurement, and minimum detectable change (MDC) were calculated to determine reliability and responsiveness. S1, S2, and S3 displacement values were highly reliable between days (ICC(2,5) ≥0.76) with the exception of anterior-posterior S1 and medial-lateral S3. MDC values were relatively small (0.6-2.2cm). GI can be reliably assessed in those with CAI which is important for identifying interventions to alter GI profiles in these individuals.