الملخص الإنجليزي
Background Study and Aims: reactive-strength is a basic physical requirement for all individual and group sports. It is an essential element for achieving athletic achievement Drop jump is one of the most important tests that assess reactivestrength. It aims to study the effect of drop jump heights on vertical and horizontal reactive-strength index, the relationship between vertical reactive-strength index and horizontal reactive- strength index, and the relationship between horizontal, vertical reactive-strength indices and sprint with and without changing of direction.
Methods: The study sample consisted of 15 students (20.7 + 0.82 years) of the Department of Physical Education and Sports Sciences (2018/2019). Participants visited the gymnasium for nine times. The visits were assigned from 1 to 4 to get used to drop vertical and horizontal jumping tests and sprint tests, as well as two measurements for vertical and horizontal jump tests from 30-40-50-60s heights and sprint tests were made by each subject to study the reliability of tests. During the next visit, subjects were made vertical and horizontal drop jump tests of the different heights (30-40-50-60s), and sprint tests with and without changing of direction. The subjects were randomly assigned to the different tests.
Results: There was a significant effect of heights (30-40-50-60cm) of vertical and horizontal drop jumps on the reactive strength index (P = 12.3; P <0.001). Also, it was shown that there was no relationship between vertical and horizontal reactive strength indices. The results showed a significant correlation between the horizontal reactive strength indices, calculated from flight time and distance, and sprint 20ms without changing of direction, whereas (P <0.01; R = 0.70; P <0.01; R = 0.80, respectively). However, the study specified that there was no relationship observed between vertical reactive strength indices and sprint with and without changing of direction.
Conclusion: The study showed that heights of vertical and horizontal drop jump have an effect on reactive strength index. The study also concluded that there is a significant relationship between horizontal reactive strength indices and sprint 20m without changing of direction Key words: Reactive strength index, Horizontal Drop jump, Vertical Drop Jump, sprint
in straight line, sprint with change of direction.
