Impact of overweight on spatiotemporal gait parameters and lower-limb biomechanics in functional ankle instability

Background: Ankle sprains are common in physically active populations and may progress to functional ankle instability, which can impair gait. Excess body mass increases lower-limb loading and may further compromise walking function in this population. Objective: To examine whether overweight status influences spatiotemporal gait parameters, gait deviation/variability indices, and sagittal-plane hip, knee, and ankle biomechanics during level walking in individuals with functional ankle instability. Methods: In this cross-sectional comparative analysis, forty-four adults with functional ankle instability were enrolled (22 normal-weight and 22 overweight). Three-dimensional motion analysis was used during self-selected speed walking to quantify spatiotemporal parameters, gait deviation/variability indices, and sagittal-plane hip, knee, and ankle kinematics and kinetics. Multiple comparisons across gait outcomes were controlled using a Holm-Bonferroni correction (family-wise error rate 0.05). Results: After Holm-Bonferroni correction, spatiotemporal parameters did not differ significantly between groups. For gait deviation/variability indices, several measures showed nominal (unadjusted) between-group differences, but none remained significant after correction. For discrete sagittal-plane biomechanics, the overweight group demonstrated lower peak hip flexion after correction (P_adj < 0.05), whereas hip flexion at toe-off showed a nominal difference but did not remain significant after correction (P_adj ≥ 0.05). Conclusion: After multiplicity control, overweight status was mainly associated with reduced hip flexion-related mechanics rather than consistent spatiotemporal or deviation/variability alterations in adults with functional ankle instability.