(17) THE ACUTE EFFECT OF ACCENTUATED ECCENTRIC LOADING ON VERTICAL JUMP PERFORMANCE: A PRELIMINARY ANALYSIS

Purpose: To determine the acute effect of an accentuated eccentric loaded (AEL) countermovement jump (CMJ) on vertical jump force-time characteristics.

Methods: Resistance-trained men (n = 7, body mass = 82.5 ± 11.0 kg, height = 176.9 ± 7.4 cm, relative one repetition maximum (1RM) back squat strength = 1.97 ± 0.38 kg·kg^-1) and women (n = 7, body mass = 69.9 ± 8.2 kg, height = 169.4 ± 7.0 cm, relative 1RM back squat strength = 1.41 ± 0.24 kg·kg^-1) participated in two separate testing sessions. During the first testing session, the subjects completed 1RM back squat testing and familiarization with the AEL CMJ and subsequent rebound jumps (RJ). The following testing session required subjects to perform two trials of a baseline CMJ with four RJs following a dynamic warm-up. The potentiation protocol required the subjects to perform one set each of an AEL CMJ followed by four RJs using loads equated to 10, 20, and 30% of the subject’s body weight using dumbbells that were released at the bottom of the initial CMJ. The subjects performed the countermovement to a self-selected depth before dropping the dumbbells and performing a maximal CMJ and four RJs with the subject’s body weight only while standing on a force platform. The force-time data were used to calculate CMJ and RJ braking mean force (BMF) and duration (BDur) and propulsion mean force (PMF) and duration (PDur). A series of paired sampled t-tests were used to determine the differences between baseline jump performance and the performance using 30% of the subject’s body weight. Hedge’s g effect sizes were used to examine the magnitude of the differences between conditions.

Results: Baseline and 30% AEL CMJ and RJ force-time data are shown in Table 1. There was a statistically significant difference between conditions for CMJ BDur (p = 0.01), PMF (p < 0.001), PDur (p < 0.001) and BMF (p < 0.001). In addition, there was a significant difference between conditions for RJ BMF (p = 0.012) but not for BDur (p = 0.171), PMF (p = 0.088), or PDur (p = 0.165).

Conclusions: There were large increases in CMJ BMF and PDur during the loaded condition compared to the baseline performance. In contrast, there were moderate decreases in CMJ PMF and PDur during the loaded condition. Specific to subsequent RJ performance, only small differences for each variable existed between the baseline and loaded conditions. Practical Applications: Strength and conditioning practitioners should be wary when adding heavier loads to AEL CMJ if they are seeking a potentiation effect as the current results suggest that heavier loads may increase the amount of force and the duration during the braking phase but may fail to enhance the propulsion phase of the CMJ. Furthermore, additional load may negatively impact subsequent RJ performance; however, further research using the current potentiation stimulus is needed to confirm these results.


Acknowledgements: None