Abstract
BACKGROUND: Impaired neuromuscular control is a feature for people with chronic ankle instability and could be restored by the destabilising footwear, yet there is a lack of destabilisation insole design targeting medial-lateral neuromuscular control. This study investigated whether a medial-lateral destabilising insole (medial-lateral density gradient + heel lift) acutely enhances peroneus longus (PL) activation, ankle inversion control during gait, and postural stability during single-leg standing in CAI. METHODS: The study followed the randomised crossover laboratory design. Twenty CAI participants and twenty healthy controls performed walking trials at self-selected speeds and eyes-closed single-leg standing under two conditions (destabilising vs. flat insole) randomly. Joint angle, electromyography of lower extremity during gait and centre-of-pressure (COP) parameters during stance were analysed using two-way repeated statistical parametric mapping and ANOVA. RESULTS: Compared to the flat insole, the destabilising insole significantly increased ankle inversion angle (mean differences = 2.7°; −56 to + 100 milliseconds relative to heel strike; P = 0.041) and normalised PL activation (mean differences = 20.1%; −100 to + 80 milliseconds; P < 0.001) exclusively in the CAI group during gait. During standing, destabilising insoles reduced time-to-boundary minima in the medial-lateral direction (η² = 0.487; P < 0.001) in CAI and increased medial-lateral (η² = 0.213, P = 0.036) and anterior-posterior COP velocity (η² = 0.170, P = 0.012) in both groups. CONCLUSION: The destabilising insole acutely enhanced ankle inversion control and PL activity during gait in CAI individuals while challenging postural stability during standing for healthy and CAI individuals. These findings support its potential as a supervised intervention to augment sensorimotor training during weight-bearing tasks. TRIAL REGISTRATION: Chinese Clinical Trial Registration, ChiCTR2100046146. May 5(th) 2021.