(32) BRAKING FORCE-TIME CHARACTERISTICS DURING ACCENTUATED ECCENTRIC DUMBBELL COUNTERMOVEMENT AND REBOUND JUMPS USING VARIOUS LOADING SCHEMES

PURPOSE: To examine and compare the braking phase force-time characteristics of accentuated eccentric loaded (AEL) countermovement jumps (CMJ) and subsequent rebound jumps (RJ) using different loading methods across multiple sets.

Methods: Resistance-trained men (n=9, age=25.8±5.0 years, hheight=173.2±7.9 cm, body mass=76.3±9.5 kg, relative one repetition maximum [1RM] back squat=2.0±0.3 kg/kg) and women (n=9, age=22.4±2.1 years, hheight=168.0±8.1 cm, body mass=70.4±8.3 kg, relative 1RM back squat=1.4±0.3 kg/kg) participated in four total sessions. The first session included a 1RM back squat followed by familiarization with AEL CMJ followed by RJ. The three subsequent sessions required the subjects to perform three sets of a single AEL CMJ with dumbbells equating to either 20% body mass or 20% of their 1RM back squat or with no load followed immediately by four RJ. Each jump was performed on a force platform and the raw force-time data were used to calculate CMJ and RJ braking mean force (BMF) and duration (BD). The CMJ and average RJ performance within each set were used for statistical comparison. A series of 3 (condition) x 3 (set) repeated measures of ANOVA were used to compare BMF and BD for both the CMJ and RJ. In addition, Hedge’s g effect sizes were used to examine the magnitude of the differences for each variable. RESULTS: There was no significant condition x set interaction effects for CMJ BMF (p=0.520), CMJ BD (p=0.547), or RJ BD (p=0.126). While there was a significant condition x set interaction effect for RJ BMF (p=0.021), post hoc analysis revealed no significant differences (p >0.05). There were significant condition main effects for CMJ BMF (p< 0.001) and BD (p< 0.001) but not for RJ BMF (p=0.064) or BD (p=0.054). Finally, there were no significant set main effects for any variable (p >0.05). Descriptive statistics and post hoc differences are shown in Table 1. The differences between conditions for CMJ BMF and BD were small-large (g=0.49-1.72) and moderate-large (g=0.80-1.56), respectively. In contrast, differences between conditions were trivial-small for both RJ BMF (g=0.07-0.41) and BD (g=0.05-0.32).

Conclusions: Greater CMJ BMF and BD were produced during the AEL conditions compared to the control condition while there were no differences in RJ BMF or BD across conditions. In addition, there were no differences in CMJ or RJ performances between sets regardless of the condition. PRACTICAL APPLICATIONS: Based on the findings, AEL CMJ with heavier loads can provide an increased braking stimulus via greater BMF and BD compared to traditional CMJ. In addition, a similar training stimulus can be achieved across multiple sets using consistent loading with 20% of an individual’s body weight or 1RM back squat if desired. However, the braking stimulus for RJ following either AEL or traditional CMJ does not appear to be impacted; thus, these exercises may be implemented individually rather than paired together.

Acknowledgements: None