Kinematic patterns on the star excursion balance test and y-balance test and postural stability in individuals with chronic ankle instability
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Background: The star excursion balance test (SEBT) and Y-balance test (YBT) are similar tests that have been commonly applied to assess dynamic postural stability deficits in the Chronic Ankle Instability (CAI) population. However, they could in fact require different task performance and/or movements to assess dynamic postural stability, as they use different measuring techniques and one uses a platform. The purposes of this study were to determine if there is a significant difference in performance in the kinematic patterns of CAI and control groups on the SEBT and the YBT, and to determine if there is a significant difference in dynamic postural control stability between the groups while performing the SEBT. Methods: 70 participants (35 in the CAI and 35 in the control group) performed in the Anterior (AN), Posteromedial (PM), and Posterolateral (PL) directions of the SEBT (on the single force plate) and the YBT. Also, the kinematics of hip, knee, and ankle joint in sagittal, frontal, and transverse planes were calculated and analyzed. Center of Pressure (COP) data with a sampling rate of 180Hz were collected while performing the SEBT. Findings: Compared with the control group, the CAI group achieved significantly shorter reach distance in the AN and PM reach directions on the SEBT. On the YBT, the CAI group had significantly shorter reach distance in the PM and PL directions compared with the control group. In the CAI group, participants had significantly greater reach distance in the PL direction on the YBT compared with the SEBT. Comparing performance on the SEBT and YBT within each group, significant differences in angular displacement and joint angle at the point of maximum reach at the hip, knee, and ankle in 3 planes were observed. The CAI group had significantly lower A-P COPSD (cm) and COPA-95 (cm2) than the control group while performing the SEBT in the AN, PM, and PL reach directions. Interpretation: Clinicians and researchers should not apply these dynamic postural control tasks interchangeably or compare reach distances from one task to another. Also, clinicians may need to incorporate rehabilitation techniques to challenge COP control during dynamic balance tasks.