Differential effects of intrinsic- versus extrinsic-first corrective exercise programs on morphometric outcomes and navicular drop in pediatric flatfoot

Although the connection between muscular strength and flatfoot condition is well-established, the impact of corrective exercises on these muscles remains inadequately explored. This study aimed to assess the impact of intrinsic- versus extrinsic-first corrective exercise programs on muscle morphometry and navicular drop in boys with flexible flatfoot. Twenty-five boys aged 10-12 with flexible flatfoot participated, undergoing a 12-week corrective exercise program, with a shift in focus at six weeks. Ultrasound imaging measured muscle thickness and cross-sectional area (CSA), and the navicular drop test assessed flatfoot severity. The results demonstrated a significant interaction between exercise type and sequencing on muscle morphometry. Initiating with intrinsic exercises led to sustained improvement, even after transitioning to extrinsic exercises, while extrinsic-first exercises caused deterioration in intrinsic muscle morphometry, which was recovered after transitioning to intrinsic exercises. Statistical analysis revealed significant improvements in muscle thickness and CSA over time, particularly when initiating intrinsic exercises first. The intrinsic-first group also exhibited a more pronounced reduction in navicular drop. In conclusion, initiating corrective exercises with intrinsic muscles proved more effective in improving foot muscle morphometry and reducing navicular drop in boys with flatfoot. Therefore, commencing correction with intrinsic muscle exercises is recommended before progressing to extrinsic muscle exercises.