The purpose of the study was to determine velocity changes in relation to the load lifted along with their muscular activity. Twenty athletes representing different sport disciplines, familiar with the flat bench press took part in the research project. The ANOVA analysis revealed a significantly higher effect on range of mean velocity (F = 128.34; η2 = 1.22 with p = 0.001) and maximal velocity (F = 7 3.31; η 2 = 0 .81 w ith p = 0 .001) t o m easured l oads ( 70÷100% 1-RM) i n a scending p hase. Tukey’s p ost-hoc t ests revealed a statistically significant difference between 70% and 100% 1-RM loads, in mean velocity with p = 0.001 and maximal velocity with p = 0.001. Similarly the results revealed a statistically significant difference between 80% and 100% 1-RM loads in mean velocity (p = 0,012) and maximal velocity (p = 0,021) during the ascending phase. Relationship between velocity and the muscles activity indicates that the anterior deltoid and latissimus dorsi muscles show synergy and a significant relationship for loads 90 and 100% 1-RM. The triceps brachii muscle shows a higher relationship with velocity of the barbell for loads 70% and 80%, then the relationship of the pectoralis major muscle with velocity only for 90% 1-RM.