Effects of power and flexibility training on vertical jump technique

PURPOSE: The purpose of this study was to assess the effects of power and flexibility training on countermovement and drop jump techniques. METHOD: All jumps were executed with the goal of attaining maximum height and no restrictions were placed on the magnitude of countermovement or ground contact time. Subjects underwent initial testing followed by random allocation to one of four groups: power training to increase vertical jump height (P), stretching to increase flexibility (S), a combination of power and stretch training (PS), and a control group (C). Training lasted for 10 wk, followed by retesting. Jump height was calculated in addition to the following technique variables: eccentric lower-limb stiffness produced during the countermovement phase, magnitude of countermovement, and in the case of the drop jumps, ground contact time. RESULTS: Groups PS, P, and S all increased countermovement jump (CMJ) height, but only groups PS and P increased drop jump height (DJ30, DJ60, and DJ90 for drop jumps performed from 30-, 60-, and 90-cm drop heights). The technique changes associated with power training were increases in magnitude of countermovement (CMJ, DJ30, DJ60, and DJ90) and increases in ground contact time (DJ30 and DJ60). In addition, the eccentric lower-limb stiffness produced during the countermovement phase of the jumps increased for CMJ and decreased for DJ30, DJ60, and DJ90. Stretching appeared to have no significant effect on CMJ or drop jump technique. CONCLUSION: The results of this study show that when the training goal is maximum jump height alone, it is likely that drop jump technique will change in the direction of a lower eccentric leg stiffness, greater depth of countermovement, and a longer ground contact time, whereas for a countermovement jump eccentric leg stiffness and the depth of countermovement will both increase. It is proposed that these technique changes are a result of attempting to optimize a complex combination of factors involved in jumping (e.g., utilization of elastic energy, Golgi tendon organ inhibition, and contractile component contribution).