Previous standing long jump studies have shown that jumping with hand weights can significantly increase jumping performance. The purpose of this study was to investigate the mechanisms that enable performance improvement in the standing long jump when using hand weights and test the hypothesis that releasing the hand weights during flight can further increase jump distance. Four college-aged male subjects were chosen based on participation in athletic activities and physical ability. Each subject executed 24 jumps (six trials for each of four different standing long jump techniques:​ without weights, with weights, releasing the weights backwards near the high point of the jump, and releasing the weights just prior to landing). Joint positions were recorded using multiple high-speed cameras and reflective position markers on the body. The net joint moments were calculated using a 2D inverse dynamics analysis. An energy analysis of the system between jump initiation and takeoff was also performed. Results showed jumping with weights increased jump distance by an average of 9 cm while releasing them increased jump distance by another 7 cm. No significant difference in jump distance was found between the two release points. The mechanisms that enabled this performance improvement were a combination of increased kinetic energy stored in the hand weights before the propulsive phase, increased work performed by the muscles during the propulsive phase, and an increase in horizontal position of the center of mass at take-off. In addition performance was enhanced by releasing the weights backwards during flight due to conservation of linear momentum during the flight phase.