The aim of this research : The effect of Accentuated Eccentric Training on Reactive Strength Index (horizontal - vertical) And the effectiveness Fastbreak of the handball junior The researcher used the experimental method by using the experimental design for the tribal and remote measurement of two groups, one experimental and the other a control, due to its suitability to the nature of this study. The research community included handball juniors born in 2004 in clubs and youth centers affiliated to the Sharkia region for handball and registered with the Egyptian Handball Federation Among the most important results: The training program using of Accentuated Eccentric Training to the development of physical variables and the effectiveness of the Fastbreak for handball juniors. There were statistically significant differences between the tribal and remote measurements of the experimental group (Accentuated Eccentric Training) on the rebound force index (horizontal - vertical) and the effectiveness of the Fastbreak . For the handball junior under research and in favor of the dimensional measurement. The presence of improvement ratios between the tribal and remote measurements of the research sample and the experimental group in the results of the physical variables under research ranged between (5.77-17.12%), and in the results of the reversal force index (vertical - horizontal) under research ranged from Between (4.50 - 22.32%) in the vertical strength index and (8.44 - 22.8%) in the horizontal rebound strength index, and in the results of the effectiveness of the blitzkrieg under study, which ranged between (13.39 - 44.82%) in favor of the dimensional measurement of the members of the research sample.