(12) THE ACUTE EFFECTS OF ACCENTUATED ECCENTRIC LOADING ON SUBSEQUENT REBOUND JUMP PERFORMANCE USING PERCENTAGES OF BODY WEIGHT AND BACK SQUAT

Purpose: To examine the effects of accentuated eccentric loaded (AEL) countermovement jumps on subsequent rebound jump (RJ) performance after using different body weight or back squat one repetition maximum (1RM) percentages.

Methods: Resistance-trained men (n=11, body mass=78.9 ± 10.5 kg, hheight=174.6 ± 7.7 cm, relative 1RM back squat strength=1.96 ± 0.35 kg/kg), and women (n=8, body mass=69.7 ± 8.6 kg, hheight=166.3 ± 6.7 cm, relative 1RM back squat strength=1.39 ± 0.26 kg/kg) participated in three separate testing sessions. During the first testing session, the 1RM back squat for each subject was assessed before they were familiarized with AEL countermovement jumps and RJ. During the second and third testing sessions, the subjects performed an AEL countermovement jump using 10, 20, and 30% of their body weight or 10, 20, and 30% of their 1RM back squat distributed between two dumbbells followed by four unweighted RJ. The subjects completed the AEL CMJ by performing a countermovement to a self-selected depth, dropping the dumbbells at the lowest point, and then performing a maximal effort jump. The RJs were performed with the cues of jumping as high as possible while minimizing the time on the ground. Each jump was performed on a force platform and the force-time data were used to calculate RJ mean braking force (MBF) and duration (BD) as well as mean propulsive force (MPF)and duration (PD). The average RJ performance following the AEL countermovement jumps performed with each load was used for statistical comparison. A series of 2 (condition) x 3 (load) repeated measures ANOVA were used to compare the differences in RJ MBF, BD, MPF, and PD between conditions. In addition, Hedge’s g effect sizes were calculated to examine the magnitude of the differences between each loading method.

Results: The AEL RJ force-time descriptive statistics and post hoc differences are displayed in Table 1. There was a significant mode x load interaction effect for PDur (p=0.011) but not for MBF, BD, or MPF (p >0.05). A significant condition main effect existed for RJ MBF (p=0.013) and MPF (p=0.005) but not for BD (p=0.059) or PD (p=0.071). There were significant load main effects for MBF (p=0.042) but not for any other variable (p >0.05). The differences between conditions for all variables were trivial-small.

Conclusions: AEL CMJ performed with back squat percentages may increase MBF and MPF during subsequent RJ compared to body weight percentages. In contrast, BD and PD may not be impacted by the AEL CMJ loading condition. PRACTICAL APPLICATIONS: While the loading condition may impact MBF or MPF to a small extent, RJ performance does not appear to be altered significantly. Thus, practitioners may consider implementing AEL CMJ and RJ as individual exercises rather than pairing them together within a training program.


Acknowledgements: None