---

Background and Objective: The asymmetry index during walking can be used for clinical treatment. This study was done to determine the immediate and long-term effects of foot orthoses on asymmetry of ground reaction forces frequency spectrum in male children with flat foot during walking.
Methods: This clinical trial study was done on fifteen children with flat foot. Subjects were randomly divided into without foot orthoses, immediate and long term usage of foot orthoses groups. The kinematic and kinetic data during three without foot orthoses, immediate and long term use of foot orthoses conditions were recorded by the motion analysis and force platform systems, respectively.
Results: Asymmetry index of medio-lateral frequency spectrum component during walking without foot orthoses, immediate and long term use of orthoses in median frequency and band width were greater than 4 percent. There were not any significant differences in asymmetry index of ground reaction force frequency spectrum components, asymmetry index of essential harmony numbers, asymmetry index of essential harmony total powers, and asymmetry index of fundamental harmony number in vertical, anterior-posterior,  and medio-lateral axes between without foot orthoses, immediate and long term use of foot orthoses conditions. However, asymmetry index of essential harmony total power in medio-lateral axis during immediate use of foot orthoses tend to be reduced than that walking without foot orthoses. However, this difference was not significant.
Conclusion: Despite the high asymmetry index of the ground reaction force frequency spectrum in the medio-lateral component during walking without foot orthoses, immediate and long-term effects of foot orthoses in the median and bandwidth frequency variables, the acute or long term use of foot orthoses did not show any significant effect on improvement of asymmetry index of ground reaction force frequency spectrum components.

---

Foot pronation, as one of the prevalent foot abnormalities, can influence the biomechanics of the lower limbs. The use of various foot orthoses, including insoles and braces, is very common in eliminating this problem. The results obtained regarding the effect of orthoses on pain and biomechanics of individuals with foot pronation are different. The present review study was conducted to evaluate the effects of foot orthoses and shoes on the biomechanics of the lower limbs and balance in individuals with foot pronation. The articles were searched in Persian and Latin languages during 2004-22 in the databases of PubMed, Web of Science (WOS), Scopus, Islamic Science Citation (ISC), and Google Scholar search engine. Moreover, the types of the searched studies were original research, review studies, and clinical trials. Using keywords of Foot pronation, Foot orthoses, Medical soles, and Motion-control shoes, 52 relevant articles were selected, and 22 articles regarding the effects of orthoses and shoes on foot pronation were finally analyzed. Eight articles also reported that reducing forces imposed on the joints, absorbing shock, preventing pronation-related running injuries, and improving muscle activity occurred when using orthosis. Furthermore, 4 articles reported improving sports performance in athletes, reducing the ground reaction forces, and changing the frequency of muscle activity. Finally, 2 articles showed that motion-control shoes prevented intensifying the injury due to increased fatigue and subsequently increased mechanical loading during running. The results of the present study demonstrated that foot orthoses and motion-control shoes could have positive effects on balance, improving the activities of the lower limbs and reducing foot pronation and force imposed on the foot and lower limb joints.