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The purpose of this study was to clarify the kinetic characteristics of the take-off leg during the take-off phase required to effectively change the direction of the center of the mass velocity vector in the running singleleg jump (RSLJ) by comparing the kinetics of jumpers and sprinters. Nine male collegiate jumpers and 9 male collegiate sprinters performed the RSLJ in 2 tasks designed to achieve as much forward and upward motion as possible, respectively, with 4 different run-up speeds. Three-dimensional coordinates of the end positions of the body segments and the ground reaction force were obtained using a motion capture and force platform system. Leg stiffness and the change in direction of the velocity of the center of mass during the second half of the takeoff phase were greater for the jumpers than for the sprinters at the same run-up speed. However, there was no significant difference in the decrease of velocity between the 2 groups. As a result, the jumpers achieved a greater jump height and jump distance. They also exhibited greater knee joint torque in the first half and greater ankle plantar torque in the second half than the sprinters. This ankle plantar flexion torque might prevent excessive forward rotation of the shank segment during the take-off phase. These results suggest that differences in the takeoff leg kinetics of jumpers may work to change the direction of the center of mass velocity more effectively. [ABSTRACT FROM AUTHOR]