Effects of drop height and load on ground reaction force and joint kinetics of the lower extremity during the drop clean

The purpose of this study was to identify the characteristics of lower extremity joint kinetics during the drop clean based on the plyometric theory. Twelve male track-and-field athletes performed the drop clean under four conditions. Kinematic and kinetic data were collected using a Vicon motion system (250 Hz) and force platforms (1,000 Hz). The results of these analyses were as follows: (1)The peak vertical ground reaction force, joint torque of the ankle joint, and torque power of the hip and ankle joints during the drop clean were significantly greater than those during the hang power clean. (2)During the drop clean, force development was achieved mainly by the hip joint during the descending phase and by the ankle joint during the ascending phase. (3) The joint torque of the ankle in the descending phase, and the joint torque and joint torque power in the ascending phase were increased when the total mechanical energy was increased by the mass factor. The joint torque and joint torque power of the ankle in the descending phase were increased when the total mechanical energy was increased by the velocity factor. (4)Even if the magnitude of the mechanical energy was the same, the vertical ground reaction force in the descending phase during the velocity-type drop clean was larger than that during the mass-type drop clean. The ground reaction force, joint torque of the hip, and joint torque power of the hip in the ascending phase during the mass-type drop clean were larger than those during the velocity-type drop clean.