A Biomechanical Analysis of the Contributing Factors to Increases in Vertical Jump Height Following Exercise with Weighted Vests

Background: It has been shown that a bout of jumping exercise with weighted vests increases the subsequent countermovement jump height. However, it is not clear whether the improvement in jump height is due to the enhancement of joint power or due to other mechanisms such as neural adaptations. Methods: To investigate this dichotomy, we tested the acute neuromechanical changes following a preloaded exercise protocol (3 sets of 5 consecutive CMJs with a weighed vest equal to 15% of the body mass of the participant) that successfully increased the subsequent jump height. On average, jump height increased 1.52 cm (5.40%) after this exercise as compared to CMJs prior to the exercise protocol. Results:A significant decrease in the time from the start of the movement to take off (pre-take off duration) was observed. This decrease was exclusively caused by exercising with a weighted vest, since such a change was not observed in the control sessions in which participants exercised without the weighted vest. Our data showed that jumpers leave the ground with some degrees of knee flexion and upon exercising with weighted vest this amount of flexion increased and hence an increase in the jump height. However, no significant changes in peak values of lower limb joint angle, velocity, moment and power were observed. Conclusion: It is suggested that for designing weighted vest exercise protocols with the aim of increasing jump height, the idea of modifying the timing of the movement should be considered as a cause of the enhancement. This novel idea adds another mechanism for increasing the jump height following weighted vest exercise, along with the general belief of muscle potentiation.