Effects of excess bodyweight and flexible Flatfoot on female stance-phase lower-limb biomechanics assessed by statistical non-parametric mapping

This study investigated the effects of excessive body weight and flexible flatfoot (FFF) on gait patterns in females. Sixty participants were divided into four groups (overweight/obese or normal weight, each with either normal feet or FFF; 15 per group). Walking data were analyzed using two-way ANOVA and post-hoc pairwise comparisons with statistical non-parametric mapping to assess the main and interaction effects of obesity and flatfoot on lower-limb biomechanics. Results indicated that overweight/obesity was the primary factor influencing lower-limb biomechanics (p = 0.049), with no significant interaction between overweight/obesity and FFF. Overweight/obese females showed reduced hip extension (~ 7°) and increased knee flexion (~ 9°), effects that were further amplified by FFF (p < 0.01). Both overweight/obesity and FFF decreased normalized hip/knee external-rotation and ankle-eversion moments (p < 0.05). Overweight/obese females also exhibited reduced joint contact forces (knee: ~1 bodyweight; ankle: ~0.5 bodyweight) during propulsion, with greater reductions in those with FFF. Each factor independently decreased activation of key lower limb muscles. In conclusion, overweight/obesity is the main factor affecting gait patterns in females, with FFF further intensifying its impact. Weight management, exercise, and appropriate footwear are recommended, especially for overweight/obese females with FFF.