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

PURPOSE: To compare the propulsion 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 required the subjects to complete a 1RM back squat protocol and familiarization trials of the AEL CMJ with RJ. The following three testing sessions required each subject to perform three sets of a single AEL CMJ with dumbbells equating to either 20% body weight or 1RM back squat or with no load followed immediately by four RJ. The jumps were performed on a force platform and the force-time data were used to calculate CMJ and RJ propulsion mean force (PMF) and duration (PD). 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 CMJ and RJ PMF and PD. In addition, Hedge’s g effect sizes were calculated to examine the magnitude of the differences for each variable.

Results: There were no significant condition x set interaction effects for CMJ PMF (p=0.361), CMJ PD (p=0.490), RJ PMF (p=0.113), or RJ PD (p=0.221). However, there were significant condition main effects for CMJ PMF (p=0.025) and PD (p< 0.001) but not for RJ PMF (p=0.190) or PD (p=0.155). 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 the CMJ PMF and PD were small-large (g=0.49-1.24) and moderate-large (g=0.67-1.44), respectively. There were trivial-small differences for both RJ PMF (g=0.05-0.21) and PD (g=0.18-0.44).

Conclusions: Greater CMJ PMF and PD magnitudes were produced during the % body weight and control conditions compared to the % back squat condition; however, there were no differences in RJ PMF or PD between conditions. PRACTICAL APPLICATIONS: CMJ with no load can provide an increased propulsive stimulus via greater PMF and PD compared to AEL CMJ. However, the braking portion of the CMJ should not be discounted as most sporting actions involve the stretch-shortening cycle. A similar training stimulus can be provided across multiple sets using either 20% of an individual’s body weight or 1RM back squat for AEL CMJ. Because a similar RJ propulsive stimulus was shown following a CMJ appeared across loading conditions, practitioners may consider splitting these exercises as no additional performance benefit was provided.

Acknowledgements: None