The Development of Schoolchildren's Power Output in Rebound Drop Jump

Abstract

This study investigated the development of power output evaluated by the ballistic and stretch-shortening cycle (SSC) movement in the 4th, 5th and 6th graders (n=59). In order to decide on the optimal height of rebound drop jump, three kinds of stage (30cm, 25cm and 20cm) were prepared. After the optimal height of rebound drop jump was decided, the capacity of power output in the rebound drop jump [RDJindex=(1/8⋅g⋅RDJta2)/RDJtc] was calculated by using contact time (RDJtc) and air time (RDJta). Results were summarized as follows;1) There were no significant differences in the contact times among three kinds of stage. Contact times from height of 30cm were 0.189-0.211 second. This result suggests that the capacities for the ballistic and SSC movement in boys and girls of the 4th grader and upward can be evaluated by the same dropping height (30cm) as adults.2) There were no significant differences in contact times among the three grade groups. By contrast, as for the boys, air time and RDJindex of the 6th grader were significantly higher than those of the 4th and 5th graders, and as for the girls, air time and RDJindex of the 6th grader were significantly higher than those of the 5th grader.3) There were no significant sex differences in contact times of all graders. By contrast, there were significant sex differences in air times, RDJindex of the 5th and 6th graders.These results show that rebound drop jump from height of 30cm will be an effective measurement method for the 4th grader and upward since it can evaluate the characteristics of power output in jumping movement. It seems that the capacities for the ballistic and SSC movement of the boys and girls increase from the 5th to the 6th grades, and that this increase is caused by the increase of ability to jump higher. Moreover, it was shown that there were marked differences between the boys and girls in the capacities for the ballistic and SSC movement of the 5th and 6th graders.