Long-Term Use of Anti-Pronation Insoles Enhances Inter-Joint Coordination in Individuals With Flat Feet.

BACKGROUND: Flatfoot alters lower limb biomechanics and can negatively affect interjoint coordination during gait. Antipronation insoles are commonly prescribed to correct excessive foot pronation, yet their long-term effects on interjoint coordination remain unclear. This study aimed to examine whether prolonged use of antipronation insoles improves interjoint coordination in individuals with flat feet. METHODS: Twenty-four participants (12 with flat feet and 12 with normal arches) were included. Spatiotemporal and interjoint coordination parameters were evaluated under four gait conditions: normal gait (NG), posttest normal gait (PNG), walking with shoes (SH), and posttest walking with shoes (PSH). Gait kinematics and kinetics were recorded using a motion capture system and force plates. All participants completed a baseline gait assessment, after which the flat foot group (FFG) underwent a 6-week intervention with antipronation insoles. A follow-up gait assessment was conducted for both groups to determine the long-term effects of insole use. Interjoint coordination was analyzed using the vector coding technique. RESULTS: Following 6 weeks of insole use, the flat-foot group showed phase-dependent changes in ankle-hip coordination, with lower coupling angles than controls during loading response and swing and higher angles during push-off under the normal-gait condition (p ≤ 0.01 and η2p = 0.28-0.33). Changes in ankle-knee and knee-hip coordination were smaller and generally limited to specific gait phases. Insoles produced an overall increase in coupling angles across conditions, reflecting these phase-specific effects. Spatiotemporal analysis showed longer single-support times in controls, longer double-support times in the flat-foot group with insoles, greater baseline stride length in controls, and no between-group difference in walking speed. CONCLUSION: Long-term use of antipronation insoles improves interjoint coordination in distal lower limb joints and may contribute to a more conservative or steadier gait pattern in individuals with flat feet as reflected by phase-specific changes in spatiotemporal parameters. However, their limited influence on proximal joints underscores the need for complementary interventions, such as targeted rehabilitation exercises.