en آسیب شناسی ورزشی و حرکات اصلاحی Sport injury and corrective exercises پژوهشي Research <div style="text-align: justify;"><strong>Purpose</strong>: Evaluating muscle activation patterns, such as co-contraction and frequency content, can help clinicians assess neuromuscular changes during gait rehabilitation in people with pronated feet (PF). This study aimed to examine the impact of double-density insoles on muscular co-activation and the frequency characteristics during gait in individuals with flat feet, in comparison to those with a neutral foot alignment.<br> <strong>Methods</strong>: Twenty males with PF and 20 controls with normal feet participated. Muscle activity was recorded using surface electromyography (sEMG) at 1000 Hz while participants walked over an 18-meter walkway with and without foot orthoses (FOs). Co-contraction was calculated as 1&ndash;(antagonist mean sEMG/agonist mean sEMG). The muscular frequency content was analyzed in the stance sub-phase.<br> <strong>Results</strong>: Group-by-condition interaction was significant for knee flexor/extensor co-contraction at mid-stance, with post hoc analysis showing increased co-contraction in the normal foot group when using orthoses. Interactions were significant for tibialis (TA) anterior, vastus lateralis (VL), rectus femoris (RF), biceps femoris, semitendinosus (ST), and gluteus medius at propulsion. Posthoc tests revealed increased activity in these muscles in the foot group when wearing orthoses.<br> <strong>Conclusion</strong>: FOs did not change knee flexor/extensor co-contraction in the PF group during mid-stance. FOs improved the muscular frequency content in the PF group while walking.</div> Flat foot, Insole, Co-activation, Gait 409 418 http://ptj.uswr.ac.ir/browse.php?a_code=A-10-639-2&slc_lang=en&sid=1 Ebrahim Piri Ebrahimm.piri@gmail.com 0000-0001-9188-9746 No Department of Sports Biomechanics, Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran Vahid Sobhani Sobhani518@gmail.com 0000-0002-4513-0488 Yes Exercise Physiology Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran AmirAli Jafarnezhadgero amiralijafarnezhad@gmail.com 0000-0002-2739-4340 No Department of Sports Biomechanics, Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran Ehsan Arabzadeh Ehsanarabzadeh@gmail.com 0000-0003-2907-9798 No Exercise Physiology Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran Alireza Shamsoddini Shamsoddini@gmail.com 0000-0001-6475-6139 No Exercise Physiology Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran