(4) THE EFFECT OF LOAD ON ACCENTUATED ECCENTRIC LOADED COUNTERMOVEMENT AND REBOUND JUMPS: A PRELIMINARY ANALYSIS

Purpose: To examine the effect of load on force-time characteristics during an accentuated eccentric loaded (AEL) countermovement jump (CMJ) followed by four rebound jumps (RJ).

Methods: Resistance-trained men (n = 6, body mass = 82.5 ± 11.0 kg, height = 176.9 ± 7.4 cm, relative one repetition maximum (1RM) back squat strength = 1.97 ± 0.38 kg·kg^-1) and women (n = 7, body mass = 69.9 ± 8.2 kg, height = 169.4 ± 7.0 cm, relative 1RM back squat strength = 1.41 ± 0.24 kg·kg^-1) participated in two separate testing sessions. The first session consisted of a 1RM back squat and familiarization with an AEL CMJ and repeated RJ. The following testing session required the subjects to perform an AEL CMJ followed by four consecutive RJ with the lowering phase of the CMJ performed with 10, 20, or 30% of their 1RM back squat. The additional load during the AEL CMJ was added by using dumbbells that were released at the bottom of the initial CMJ. The AEL CMJ and subsequent RJ repetitions were performed on a force platform and the force-time data were used to determine CMJ and RJ braking mean force (BMF) and duration (BDur) and propulsion mean force (PMF) and duration (PDur). The CMJ and average RJ performances were compared between loads using a series of one-way repeated measures ANOVA. In addition, Hedge’s g effect sizes were used to examine the magnitude of the differences between loads.

Results: AEL CMJ and RJ force-time data are shown in Table 1. There were statistically significant differences between loads for CMJ BDur (p = 0.006), PDur (p = 0.001), and PMF (p = 0.001). In contrast, there were no statistically significant differences between loads for CMJ BMF (p = 0.282) or RJ BMF (p = 0.324) or BDur (p = 0.117). Post hoc analysis did not show any significance between the examined loads for RJ PMF (p > 0.05). Trivial to small effects existed between loads for CMJ BMF and all the RJ force-time variables. However, moderate, small to moderate, and moderate to very large effects existed across loads for CMJ BDur, PMF, and PDur, respectively.

Conclusions: Heavier loads during the AEL CMJ increased CMJ BDur but decreased both CMJ PMF and PDur. In contrast, heavier loads did not seem to impact subsequent RJ braking and propulsion performance as only trivial to small effects existed between loads. PRACTICAL APPLICATIONS: Practitioners may be able to prescribe a spectrum of loads during AEL CMJ to emphasize individual characteristics. However, as load increases, CMJ performance may be altered whereas RJ performance may not be affected to a meaningful extent. Thus, strength and conditioning practitioners should determine the appropriate loading of AEL CMJ to provide an effective stimulus to achieve the training goals of each individual.


Acknowledgements: None