The influence of stiffness in the musculotendinous complex in stretch-shortening-cycle has suggested to compare electromyografical activity in two different exercises: harmonic bench press in front of oscillatory bench press, both at high speed of movements and differents loads. Seventeen male subjects (age 22.9 \u00b1\u20090.8 years, weight 75.0\u2009\u00b1\u20099.4 kg, height 179\u2009\u00b1\u20096.5 cm, 1RM\u2009=\u2009110\u2009\u00b1\u200910,6 kg), with experience in weight training, voluntarily accepted to take part in this study. There is a difference in the execution time in single repetition and bar displacement between harmonic bench press and oscillatory bench press in most cases. The oscillatory bench press presents a lower EMG although there is not significant differences for each load and between them. There are significant differences in all registers between the activities of sternocostal and clavicular muscle portion of the pectoralis major muscle in harmonic bench press in one repetition and comparing the two phases of every movement (concentric and eccentric). Thus, in the oscillatory bench press there are significant differences between eccentric and concentric phase of sternocostal and clavicular muscle portion, but not in the whole repetition.The results suggest a different work in both type of exercise, this could mean a higher incidence of the musculotendinous complex of the non-contractile tissue.<\/p>\n\n