Abstract
The countermovement jump (CMJ) is an integral part of force and velocity profiling. A movement that is regularly implemented in training protocols and testing of athletic performance. Loaded CMJs have an added benefit for testing increased power and in turn, monitoring its progressive development. On the other hand, these loads can displace the centre of mass (CoM) of individuals, which may produce undesirable effects. The purpose of this study is to understand the effects of CoM displacement on the body when performing jumping movements using three different modes of loading (barbell, trapezius barbell and dumbbell CMJs), at standardized increments of weighted resistance. (20 kg, 40 kg, and 60 kg). The aim of this study was to evaluate and assess kinetics across various incremental modes of loading (including barbell, trapezius barbell, and dumbbell CMJs. As a result, a greater understanding of the CMJ mechanics would be realised which would lead to more benefits when utilizing the movement during training and testing procedures. A quantitative cross-over design was employed on a sample of 32 male athletes (26 rugby and six basketball players). The average age of the population was 19.2±1.8 years, the average height 1.86±0.06 m, and the average recorded weight was 90.42±5.28 kg. The use of repeated measures on the same sample, with multiple different tests on each participant were conducted. The results of the study found that the mode of jumping that produced the most significantly (p<0.001) powerful movements across peak and mean metrics was the dumbbell CMJ (peak: 4861.37±1631.56 W and mean: 2510.39±887.61 W), whereas the trapezius barbell consistently produced significantly (p<0.001) high velocity (peak: 2.52±.44 m/s and mean: 1.43±.27 m/s) and acceleration metrics (peak: 12.59±4.49 m/s² and mean: 8.47±2.86 m/s²), with the barbell never producing exceedingly high results for any metrics. The CoM displacement did not play as much of a role as previously perceived. The degrees of freedom (DoF) and comfort levels of athletes during the CMJ were more influential as factors affecting vertical jump output metrics. As the jump with the highest DoF during the movement (dumbbell CMJ) reliably produced the highest power metrics throughout the study.
Keywords: countermovement jump, force velocity profiling, power, jump testing, modes of loading.