Cross-Education Effects of Hip Strengthening in Individuals with Chronic Ankle Instability

Abstract

ABSTRACT Introduction/Purpose Chronic ankle instability (CAI) is associated with reduced balance, lumbopelvic stability, and hip strength. Accordingly, hip strengthening is an effective intervention for individuals with CAI. Cross-education through unilateral exercise is also beneficial to individuals with CAI, but cross-education effects of hip strengthening remain unknown. The purpose of this study was to determine cross-education effects of hip strengthening in individuals with CAI. Methods Thirty individuals with CAI were randomized into control (CON) and hip strengthening (HIP) groups. Baseline and postintervention tests of the uninvolved limb included lumbopelvic stability (unilateral hip bridge), handheld dynamometry (isometric hip extension, abduction, and external rotation strength), and balance (Star Excursion Balance Test (SEBT) in anterior, posterolateral (PL), and posteromedial directions). After baseline testing, HIP completed progressive hip strengthening of the involved limb three times per week for 8 wk, and CON did not. Repeated-measures analyses of variance assessed the effects of group and time on each outcome. Each group’s mean changes from baseline to postintervention were assessed via effect sizes. Statistical significance was set a priori at P < 0.05. Results Of the 30 participants enrolled, 10 did not complete the postintervention data collection. Multiple imputations estimated missing data, and an intention-to-treat analysis was conducted. There were no significant group-by-time interactions for hip strength, balance, or lumbopelvic stability. HIP exhibited moderate effect sizes for SEBT-PL and hip bridge. All other effect sizes were small or negligible. Conclusions We did not identify a clear cross-education effect following unilateral hip strengthening in a cohort with CAI. Examination of baseline to postintervention effect sizes indicate a potential trend toward improved balance and lumbopelvic stability of the HIP group.