(31) FORCE-TIME CHARACTERISTICS DURING ACCENTUATED ECCENTRIC DUMBBELL JUMPS USING PERCENT SQUAT LOADS IN MULTI-SET CONDITIONS-PRELIMINARY FINDINGS

Purpose: To examine differences in force-time characteristics across multiple sets of accentuated eccentric loaded (AEL) countermovement (CMJ) and rebound jumps (RJ) with a prescribed load of 20% one repetition maximum (1RM) back squat.

Methods: Six resistance-trained men (age: 27.3±5.4 years, body mass: 81.7±13.3 kg, height: 176.0±8.4 cm, 1RM back squat: 2.0±0.5 kg·kg^-1) and eight resistance-trained women (age: 22.3±2.2 years, body mass: 70.1±8.7 kg, height: 169.4±7.5 cm, relative 1RM back squat: 1.4 ± 0.3) participated in two testing sessions. The first session included a 1RM back squat and familiarization with AEL CMJ followed by RJ. During the following session, subjects performed three sets of an AEL CMJ with dumbbells equating to 20% of the subject’s 1RM back squat followed by four RJ. Jumps were performed on a force platform and 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). The CMJ and averaged RJ performances were used for statistical comparison. A series of one-way repeated measures ANOVA tests were used to compare the braking and propulsion force-time characteristics and Hedge’s g effect sizes were calculated to determine the magnitude of the differences across each set. RESULTS: AEL CMJ and RJ force-time characteristics are shown in Table 1. There were significant differences in CMJ BMF (p=0.042), RJ PDur (p=0.045), and RJ PMF (p=0.010); however, post hoc analysis showed no differences between sets for CMJ BMF or RJ PDur (p>0.05). In addition, there were no significant differences between sets for CMJ BDur (p=0.148), PMF (p=0.396), or PDur (p=0.388) or for RJ BMF (p=0.066) and BDur (p=0.194). Trivial to small effect sizes existed across sets for all the examined variables.

Conclusions: CMJ and RJ braking and propulsion force-time characteristics were maintained across three sets of AEL CMJ using 20% of the subject’s 1RM back squat followed by four RJ. RJ PMF dropped significantly during set 2, but the performance during the final set showed no differences compared to set 1 indicating that the level of performance was maintained. Furthermore, there were no practically meaningful differences for any variable across sets as indicated by the effect sizes. PRACTICAL APPLICATIONS: AEL jumps may provide a unique training stimulus compared to traditional CMJ and RJ due to the additional load used during the CMJ. The current results suggest that practitioners may prescribe 20% of one’s 1RM back squat during AEL-loaded jumps for multiple sets with resistance-trained men and women. Despite the additional load, prescribing jumps in this manner may allow individuals to maintain their force-time characteristics during the initial CMJ and subsequent RJs. Future research should consider examining the impact of loading AEL jumps with different percentages of an individual’s 1RM back squat to improve training practices.

Acknowledgements: None