The research aims to identify the effect of cluster exercises on the development of rapid strength of the legs and the proportion of lactic acid in the blood of athletes, by identifying: 1- The effect of cluster exercises on developing the rapid strength of the legs for athletes. 2- The effect of cluster exercises on the level of lactic acid in the blood of athletes. The researcher used the experimental method, and the research sample was chosen in a deliberate way, and it included (20) players from the teams of sports activities (jumping in athletics - handball - basketball - volleyball) at Zagazig University. She prepared and designed a cluster training program that aims to develop strength Quick for the legs and identification of the proportion of lactic in the blood of the athletes, and the most important results were: 1- Cluster training has a positive effect on improving the rapid strength of the legs in favor of the dimensional measurements from the tribal ones. 2- The cluster training contributed to lowering the lactic acid ratio, which is represented in my tests (step 30 s after effort), (step 60 s after effort) in the research sample. 3- There are statistically significant differences between the percentages of lactic acid after (60 s) after the effort, compared to after (30 s) after the effort, whether in the pre or post measurements. 4- The highest percentages of differences in lactic ratios were achieved after (60 s) after exertion, than after (30 s) after effort in the dimensional measurements with a percentage of (75.40%), while it reached (71.63%) in the tribal measurements.