# Study of Force Changes Based on Orthotic Elements Under the First Ray
## 4 Discussion
The sample used in this study consisted of young individuals with a normal weight, height, and BMI, ensuring uniformity in foot size and minimizing gait-influencing factors. The foot posture index (FPI) showed a normal posture with slight pronation [26; 27], associated with limitations in first metatarasophalangeal joint dorsiflexion [47]. The correlation analysis revealed that greater foot pronation (a higher FPI) resulted in significantly lower medio-lateral forces (Fx) during the propulsion phase (L2) with the following orthoses: metatarsal elevation plus hallux, Morton's extension, proprioceptive stimulus, a cut-out, or a kinetic wedge. No significant FPI-Fx correlations were observed during mid-stance (G1/L1). This suggests that these devices modulate the pronatory forces in pronated feet. Regarding the vertical forces (Fz), significant positive correlations with the FPI occurred specifically for the orthosis with metatarsal elevation plus hallux during mid-stance (G1: r = 0.580) and propulsion (G2: r = 0.426), and for the orthosis with a cut-out during mid-stance (G1: r = 0.436). This implies that more pronated feet leverage these specific orthoses to increase the vertical loading, potentially through force redistribution from the medial to the lateral forefoot. Significant differences in the medio-lateral forces were observed, specifically during propulsion (G2 phase) between the no-orthosis (WFO) and the cut-out (E) conditions, which is consistent with the cut-out's biomechanical role in modulating supination. The kinetic wedge (F) showed no statistically supported effects during mid-stance or propulsion in the pairwise analyses. This phase-dependent behavior, with the cut-out modulating forces during propulsion and the kinetic wedge during late stance, aligns with their shared mechanism of restricting first-ray dorsiflexion, though the recorded force magnitudes were consistent with typical gait patterns. This phase-dependent control, which enhances the medial stability during late stance and the lateral stability during propulsion, suggests how targeted orthotic designs can address gait-phase-specific instability in metatarsus primus elevatus. The consistency in the antero-posterior forces (Fy) across all conditions implies neuromuscular adaptations in the sagittal plane's preserved propulsive mechanics, despite orthotic interventions. This suggests that first-ray modifications predominantly alter the frontal (Fx) and vertical (Fz) plane control. The vertical forces (Fz) showed no phase-wide orthotic effects during propulsion, though individual correlations revealed BMI- and FPI-dependent modulation. The absence of Fz changes aligns with the results of [PERSON] et al. [35], where insoles redistributed local pressures without modifying the net vertical impulse. While proprioceptive mechanisms [48] offer a theoretical rationale for force modulation, their role remains unexplored in this dataset due to non-significant D-specific outcomes. The Friedman test results showed significant differences in the medio-lateral forces during propulsion (G2), attributable to the cut-out orthosis (E) versus no orthosis. Thissuggests the kinetic wedge's effectiveness in modulating pronatory forces, particularly during propulsion. This may relate to the enhanced activation of the flexor hallucis longus, improving first-ray stability [47]. The effect size quantification was limited to the antero-posterior forces (Fy), revealing moderate impacts for the proprioceptive stimulus (D) during mid-stance and the cut-out (E) during propulsion. The pronatory force (Fx) and vertical loading (Fz) effects remain unquantified in this dataset. This study has certain limitations that should be acknowledged. One of them is that it should be interpreted primarily as a methodological contribution rather than a definitive evaluation of the clinical outcomes. The sample size was limited, which reduces the generalizability of the statistical findings and precludes subgroup analyses (e.g., by sex or first-ray mobility).