The aim of this study was to assess the effect of resistance eccentric and concentric training on electromyographic (EMG) activity ratio of the vastus medilais oblique (VMO) to the vastus lateralis muscle (VL). 26 healthy men participated in this study. Training protocole contained 36 sessions of resistance eccenentric and concentric training at the level of 80 % of one repetation maximum (1RM) on leg press machine. Maximal voluntary contraction (MVC) and EMG activity of the VMO and VL muscle recorded before and after resistance eccentric and concentric training. Maxmimal voluntary contraction of quadriceps and EMG activitiy of the VMO and VL muscle significantly increased after training (P <0.05) and depended on the training type (P <0.05). Eccentric training resulted in a greater increase in maximal voluntary contraction and EMG activity of the VMO muscle as compared to concentric training (P <0.05). The increased EMG activity of the VMO to VL muscle play an important role in patella stabilization, and has commonly been used as an effective way to prevent from lateral patella tilt. Thus, it is recommended that eccentric training be included in rehabilation program for lateral patella tilt.