(46) SEX DIFFERENCES IN FORCE-TIME CHARACTERISTICS DURING ACCENTUTED ECCENTRIC DUMBBELL JUMPS USING BACK SQUAT PERCENTAGES

Abstract Details:

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

Methods: Nineteen
resistance-trained subjects including 11 men (age: 25.4 ± 4.9 years, body mass: 79.0 ± 10.5 kg, height:
174.6 ± 7.7 cm, relative 1RM back squat: 1.97 ± 0.35 kg·kg -1 ) and 8 women (age: 22.3 ± 2.2 years, body
mass: 69.7 ± 8.6 kg, height: 166.3 ± 6.6, relative 1RM back squat: 1.39 ± 0.27 kg·kg -1 ) 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 10, 20, and 30% of their 1RM back squat. Subjects completed each AEL CMJ repetition by
performing a countermovement to a self-selected depth, dropping the dumbbells at the lowest point, and
then performing a maximal effort jump. Jumps were performed on a force platform and the force-time
data were used to calculate CMJ braking mean force (BMF) and duration (BDur) and propulsion mean
force (PMF) and duration (PDur). A three (load) x two (sex) repeated measures ANOVA test was used to
compare the AEL performances between sexes across each loading condition. In addition, Hedge’s g
effect sizes were calculated to examine the magnitude of the differences between the various conditions.

Results: There was a significant load by sex interaction effect for PDur (p = 0.012) but not for BMF
(p = 0.761), BDur (p = 0.320), and PMF (p = 0.325). In addition, there were significant load main effects
for each variable (p < 0.01); however, there were no significant sex main effects (p > 0.05). AEL CMJ
force-time characteristics and post hoc analyses are shown in Table 1. Small-moderate differences existed
between men and women for CMJ BMF, PMF, and PDur while trivial-moderate differences were present
for BDur.

Conclusions: Resistance-trained men generally produced larger BMF and PMF
magnitudes over similar durations compared to women; however, the differences between sexes varied
based on the loads that were examined. PRACTICAL APPLICATIONS: Both resistance-trained men
and women can receive a unique training stimulus during AEL CMJ compared to traditional CMJ due to
the additional load used during the braking phase of the movement. Practitioners working with these
populations should consider the load prescribed during AEL CMJ as heavier and lighter loads may
promote BMF and PMF adaptations, respectively. Moreover, the relative strength of each individual
should be taken into account when using this method as stronger individuals may tolerate higher BMF
and may thus be able to use heavier loads.

Acknowledgements: NONE