The purpose of this study was to investigate the effect of weighted jump squat training with and without eccentric braking. Twenty male subjects were divided into two groups (n = 10 per group), Non-Braking Group and Braking Group. The subjects were physically active, but not highly trained. The program for Non-Braking Group consisted of 6 sets of 6 repetitions of weighted jump squats without reduction of eccentric load for 8 weeks. The training program for the Braking Group consisted of the same sets and repetitions, but eccentric load was reduced by using an electromagnetic braking mechanism. Jump and reach, countermovement jump, static jump, drop jump, one repetition maximum half squat, weighted jump squat, and isometric/isokinetic knee extension/flexion at several different positions/angular velocities were tested pre- and posttraining intervention. The Non-Braking Group exhibited greater improvement in peak torque during isokinetic concentric knee flexion at 300°/s [Non-Braking Group: (mean ± SD) 124.0 ± 22.6 Nm at pre- and 134.1 ± 18.4 Nm at posttraining, and Braking Group: 118.5 ± 32.7 Nm at pre- and 113.2 ± 26.7 Nm at posttraining]. Braking Group exhibited superior adaptations in peak power relative to body mass during weighted jump squat [Non-Braking Group: (mean ± SD) 49.1 ± 8.6 W/kg at pre- and 50.9 ± 6.2 W/kg at posttraining, and Braking Group: 47.9 ± 6.9 W/kg at pre- and 53.7 ± 7.3 W/kg at posttraining]. It appears that power output in relatively slow movement (weighted jump squat) was improved more in the Braking Group, however strength in high velocity movements (isokinetic knee flexion at 300°/s) was improved more in Non-Braking Group. This study supports load and velocity specific effects of weighted jump squat training.