RESUMO
The purpose of this study was to quantify the effect of plyometric training (PT) in changes of jump abilities and ankle joint motions on repeated-rebound-jumps exercise without buffer function of lower limb joints. Seven female collegiate runners executed 10-repeated rebound jumps training (10 RJ) on a switch mat with maximum effort. Each subject executed the training program twice a week for 5 consecutive weeks. Parameters of repeated-rebound jumps training involved jump height (m), the contact time (s), flight time (s), and rebound jumps index (=RJ-index). Three-dimensional ankle joint kinematics of each subject were captured using ten motion capture systems (250 Hz). As a result, RJ-index, jump height, and flight time were increased significantly between pre-and post-test (p<0.001). But, the contact time decreased significantly. The relationships between rebound jumps index and jump height and between rebound jumps index and the durations of contact phase were highly correlated (r=0.858, r=-0.739; p<0.001). In addition, the time (%) between start and finish phase in the dorsiflexion angle of ankle joint was reduced significantly between pre-and post-test (p<0.001). The repeated-rebound-jumps exercise was shown to have an effect on improvement in stretch-shortening cycle (SSC) performance of lower limb joints in distance runners. The RJ-index and the time between start and finish phase in the dorsiflexion angle of ankle joint was shown to be a valid evaluation index of SSC performance. Therefore, repeated-rebound-jumps exercise is a significant training protocol where ankle behavior improves and where the performance of stretch-shortening cycle is enhanced.