The influence of specific training on the plyometric profile

Sprinting, jumping and change of direction involve the stretch-shorten cycle (SSC) and therefore plyometric training is used to improve these factors. It has been demonstrated that the jumping strategy utilized can influence the biomechanical profile of the exercise and subsequent adaptation. For example, in some cases, it is important to jump as high as possible while in other cases it is important to reduce the ground contact time. Our hypothesis is that the choice of plyometric exercise has to be matched to the desired biomechanical adaptation. Hence we investigated the influence of 8 weeks of different programs on the plyometric profile of recreational athletes. In each of five groups, very specific exercises were selected according to the training objective: ground contact time group (CT, n=9); vertical jump height group (JH, n=9); CT and JH combination group (CT-JH, n=11); JH + strength training group (JH-S, n=9); and control group (CO, n=8). The plyometric profile performed prior to and post training included measures of jump height, contact time, stiffness and reactivity at different bounding intensities. The results demonstrated that JH and JH-S programs were more effective for improving jump height performance (+7-9%; p<0.005) compared to insignificant jump height changes in the CT and CO groups. CT-JH was the most effective on the reactivity index (+14%, p<0.005) although significant increases (+8%, p<0.05) were also observed in CT, JH and JH-S groups. CT was the only group to significantly decrease short contact time (-5%, p<0.05). ANOVA analysis revealed significant groups*session effect for jump height (p<0.01) and reactivity (p<0.005) but not for short contact time. The present study confirms that the principle of specificity is fundamental in plyometric training so the exercise selection should be developed cognizant of intended adaptations. Jump height and reactivity appear to be differentially affected by specific training practices.