Background and Aim: Whole Body Vibration (WBV) is more attended as a new exercise modality helping improvement in neuro-muscular performance, but so far, its immediate effect indirectly concurrent with different external load (EL) on maximum voluntary CONTRACTION (MVC) and upper limb electromyography (EMG) in not known. The purpose of the spresent study was to investigate the immediate effect of WBV on maximumisometric CONTRACTION and upper limb EMG indifferent CONTRACTION forces.Materials and Methods: In 15 young healthy men, dominant biceps randomly underwent isometric contaction with supination of forearm and 90 degrees of elbow flexion while receiving no WBV or WBV with a frequency of 50 Hz and low amplitude (4 mm) for 60 seconds (i.e. two thirty-second phase with an interval of 20-second-rest) in three different modes: without EL, with an EL of 10% of primary MVC, and finally with an EL of 20% of primary MVC. In the meantime, EMG activity of the muscle was recorded and once the whole exercise protocol was terminated, MVC was measured and its EMG activity was recorded simultaneously with MVC.Results: WBV without EL showed a significant increase in biceps MVC compared with no WBV and no EL (P=0.006), wheras in WBV the comparison of an EL of 10% of primary MVC and that of 20%, despite rendering higher rate of MVC, is not statistically significant. On the other hand, WBV without EL revealed a significant improvement in biceps RMS (P=0.001). The same was true in WBV with an EL of 20% of MVC (P=0.032). The rate of ΔFMED with WBV or without WBV, and with an EL of 20%, was statistically more significant than without WBV, with an external load of 10%, and this significancy with vibration was P=0.011 and without vibration was P=0.016. Meanwhile, ΔFMED was significant with WBV and with an external load of 20% of MVC compared with WBV and 10% of MVC (P=0.023).Conclusion: It seems that a single session of WBV reults in an immediate increase of MVC and EMG of biceps bracheiand applying ELs of 10% and 20% of MVC with WBV did not significantly increase in the present study, but it leadsto more increase of MVC and EMG. Also, the effect of an EL of 20% of MVC in this increase is more tangible than 10% of MVC.