en آسیب شناسی ورزشی و حرکات اصلاحی Sport injury and corrective exercises 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>: A proper warm-up method can be used as a strategy to improve the performance of athletes in various sports fields. The present study aimed to compare the effect of two traditional and post-activation potentiation (PAP) warm-up methods on electromyographic variables of lower limb muscles during squat jumps.<br> <strong>Methods</strong>: Fourteen trained male athletes randomly performed three different protocols: traditional warm-up method, dynamic post-activation potentiation (PD) by implementing two dynamic half-squat repetitions with 90% 1RM (one rep maximum), and static post-activation potentiation (PS) warm-up by implementing two static half-squat repetitions with 90% 1RM. Vertical jump tests were performed five minutes after implementing each protocol (recovery time). EMG activity of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semi-tendinous, medial gastrocnemius, and tibialis anterior was recorded. Also, the co-contraction index and median frequencies were calculated. Repeated measures analysis of variance (ANOVA) was used for data analysis (P<0.05).&nbsp;<br> <strong>Results</strong>: The results of this study showed that the activity level of all muscles in the concentric and flight phases, the co-contraction index of the ankle and knee joints, and also median frequencies of rectus femoris, vastus lateralis, semi-tendinous, biceps femoris, and medial gastrocnemius significantly changed in the PD and PS warm-up methods compared to the traditional warm-up method (P&ge;0.05). Also, the activity level of rectus femoris, vastus medialis, and biceps femoris muscles had a significant difference between the PD and PS compared to the traditional warm-up method in the eccentric phases (P&ge;0.05).&nbsp;<br> <strong>Conclusion</strong>: According to the study results, the PAP warm-up method can improve the performance of athletes in training and competition conditions.</span></span></span></div> Warm-up, Electromyographic variables, Post-activation potentiation, Squat jump 123 132 http://ptj.uswr.ac.ir/browse.php?a_code=A-10-510-1&slc_lang=en&sid=1 Mehrdad Anbarian anbarian@basu.ac.ir 0000-0002-3605-5586 Yes Department of Sport Biomechanics, Faculty of Sport Sciences, Bu-Ali Sina University, Hamedan, Iran. Sajad Avazzadeh Samani sajad.av.samani92@gmail.com 0000-0003-4036-2420 No Department of Sport Biomechanics, Faculty of Sport Sciences, Bu-Ali Sina University, Hamedan, Iran.