Joint Torque and Power of the Takeoff Leg in the Long Jump

Abstract

The purposes of this study were to determine the joint torque (JT) and power (JP) of the takeoff leg and the relationship of the angular impulse and work done by the JTs to center of gravity (CG) velocity change during the long jump takeoff, and to identify the functions of the takeoff leg joints. The takeoff motion of eleven Japanese male long jumpers was videotaped (250 Hz) from the right side of the runway. Ground reaction forces were also recorded (1 kHz). The forward-backward component of the force platform was set parallel to the runway. The plantar-fl exors and knee extensors exerted great negative JP during the fi rst phase and positive JP during the second phase, and, thus, they functioned as great mechanical energy absorbers in the fi rst phase and as mechanical energy generators in the second phase. The hip joint exerted extension torque immediately after touchdown and supported the body against the impact force and contributed to an increase in vertical CG velocity by pivoting the body over the takeoff foot during the fi rst phase. There were no relationships of the magnitude of the peak joint torques of the takeoff leg and angular impulse and work of the takeoff leg joint torques to horizontal CG velocity at touchdown or jumping distance