The aim of this study was to examine the effects of barbell load on countermovement vertical
jump (CMJ) power and net impulse within a theoretically valid framework, cognisant of the
underpinning force, temporal, and spatial components. Twenty-four resistance-trained rugby
union athletes (average ± SD: age: 23.1 ± 3.4 yrs; height: 1.83 ± 0.05 m; body mass: 91.3 ±
10.5 kg) performed maximal CMJ under five experimental conditions in a randomised,
counterbalanced order: unloaded, and with additional loads of 25, 50, 75 and 100% of body
mass (BM). Peak power and average power were maximised during the unloaded condition,
both decreasing significantly (p < 0.05) as load increased. Net impulse was maximised with
75% of BM, which was significantly greater (p < 0.05) than the unloaded and 100% of BM
conditions. Net mean force and mean velocity were maximised during the unloaded condition
and decreased significantly (p < 0.05) as load increased, whereas phase duration increased
significantly (p < 0.05) as load increased. As such, the interaction between barbell load and
the underpinning force, time and displacement components should be considered by strength
and conditioning coaches when prescribing barbell loads.