(26) THE FORCE-TIME CHARACTERISTICS OF ACCENTUATED ECCENTRIC LOADED COUNTERMOVEMENT JUMPS DURING DIFFERENT LOADING CONDITIONS

Purpose: To examine the braking and propulsion force-time characteristics of accentuated eccentric (AEL) loaded countermovement jumps (CMJ) that used percentages of body weight (BW) or percentages of a one repetition maximum (1RM) back squat.

Methods: Resistance-trained men (n=11, body mass = 78.9 ± 10.5 kg, height = 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, height = 166.3 ± 6.7 cm, relative 1RM back squat strength = 1.39 ± 0.26 kg/kg) participated in three separate testing sessions. The first session required the subjects to perform a 1RM back squat and complete familiarization trials of the AEL CMJ. The second and third sessions required the subjects to perform three single AEL CMJ using 10, 20 and 30% BW or 10, 20, and 30% of their 1RM back squat. The subjects performed the AEL CMJ by performing a countermovement to a self-selected depth, dropping dumbbells at the lowest point, and the performing a maximal effort jump. Each AEL CMJ was performed on a force platform and the force-time data were used to calculate mean braking force (MBF), braking duration (BDur), mean propulsive force (MPF), and propulsive duration (PDur). A series of 2 (condition) x 3 (load) repeated measures ANOVA were used to compare each variable between conditions. Hedge’s g effect sizes were used to examine the magnitude of the differences. RESULTS: The AEL CMJ force-time characteristics and post hoc comparisons are displayed in Table 1. There was a significant condition x load interaction effect for CMJ BDur (p=0.002), MPF (p=0.032), and PDur (p=0.037) but not for BMF (p=0.065). There was however a significant main effect for condition (p=0.007) and load (p< 0.001) for MBF. The differences between conditions were trivial-moderate for both BMF and BD, trivial-small for MPF, and small-moderate for PD.

Conclusions: Larger MBF and BDur were produced during the % 1RM loading condition compared to the % BW. In contrast, the MPF and PDur magnitudes were greater during the % BW condition compared to % 1RM. In general, heavier loads increased BMF and BD but decreased PMF and PD. PRACTICAL APPLICATIONS: AEL CMJ may provide a novel stimulus compared to traditional CMJ for training braking and propulsive characteristics. Using heavier loads during an AEL CMJ may provide greater braking force characteristics, whereas using lighter loads may promote greater propulsive characteristics.

 

Acknowledgements: None