en عمومى General پژوهشي Research <div style="text-align: justify;"><span style="font-size:14px;"><span style="font-family:Tahoma;"><span style="line-height:2;"><strong>Purpose</strong>: Military boots mileage is a main factor that can affect the risk of running injuries. The present study aims to evaluate the effect of three types of military boots mileage on knee muscular co-contraction during running.<br> <strong>Methods</strong>: Fifteen healthy males received three pairs of new military boots. Participants wore these boots for more than 6 months. Electromyography activity of lower limb muscles during running at constant speed was recorded during pre- and post-intervention. Then, knee muscular co-contraction was calculated.<br> <strong>Results</strong>: Results showed a significant increase during loading response (P=0.030, n2p=0.157) and push-off (P=0.008, n2p=0.302) phases for general knee co-contraction at post-test compared to the pre-test. Also, directed mediolateral knee co-contraction showed a significant increment during mid-stance (P=0.028, n2p=0.040) and push-off (P=0.039, n2p=0.115) phases at post-test compared to the pre-test.&nbsp;<br> <strong>Conclusion</strong>: It can be concluded that knee joint instability while using polyurethane thermoplastic is more than polyurethane boots. Also, our results demonstrated that maintaining knee stability in the anterior-posterior direction while using polyurethane thermoplastic is better than in polyurethane boots.</span></span></span><br> <br> <strong>Coresponding author:&nbsp;</strong><span style="font-size:14px;"><span style="font-family:Tahoma;">AmirAli Jafarnezhadgero,&nbsp;E-mail: amiralijafarnezhad@gmail.com<br> <u>You can also search for this author in:</u>&nbsp; <a href="https://pubmed.ncbi.nlm.nih.gov/?term=AmirAli%20Jafarnezhadgero%20%5BAuthor%5D&page=2">P</a><a href="https://pubmed.ncbi.nlm.nih.gov/?term=%28AmirAli+Jafarnezhadgero%5BAuthor%5D%29+AND+%28University+of+Mohaghegh+Ardabili%5BAffiliation%5D%29">ubMed</a>, <a href="https://scholar.google.com/citations?hl=en&user=em_L-vQAAAAJ">Google Scholar</a></span></span></div> Co-contraction, Military boots, Rubber, Polyurethane, Polyurethane thermoplastic, Knee joint 159 164 http://ptj.uswr.ac.ir/browse.php?a_code=A-10-348-7&slc_lang=en&sid=1 Milad Piran Hamlabadi miladpiran75@gmail.com 0000-0001-9247-2563 No Department of Sports Management, Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran. AmirAli Jafarnezhadgero amiralijafarnezhad@gmail.com 0000-0002-2739-4340 Yes Department of Sport Biomechanics, Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran. Iman Bakhshodeh Nia iman.b1364@yahoo.com 0000-0002-5700-5799 No Department of Sports Management, Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran. Hamid Hassannejad hamidhasannejad08@gmail.com 0000-0002-9302-6255 No Department of Industrial Engineering, Faculty of Engineering, Science and Technology University, Tehran, Iran.