The characteristics of joint kinetics associated with the take-off leg during bounding while jumping in different directions

Abstract

The aim of this study was to clarify the point of attention and determine an eŠective method for the vertical single-leg rebound jump (VSJ) and horizontal single-leg bounding jump (HSJ) in plyo- metrics by investigating the diŠerences and relationship between the two jumps with respect to take-oŠ movement and joint kinetics. 11 male track and ˆeld athletes performed the VSJ, 50?HSJ, 75?HSJ, and HSJ. The kinematics and kinetics during the take-oŠ phase were recorded using a high-speed video camera (300 Hz) for movements in the sagittal plane and force platforms (1000 Hz), and then analyzed. Theresults aresummarizedbelow: 1. According to a spring-mass model, the vertical velocity of the center of gravity in the VSJ was attained by using shortening-lengthening movements. However, in the HSJ, most of the horizontal velocity of the center of gravity was due to rotational movement. This velocity increased with increasing jump distance. 2. The extension torque of the knee and hip joints during the former phase, the negative torque power of the knee, and the positive torque power of the ankle and hip joints in the HSJ were greater than thoseinthe VSJ. However, theankle jointtorque duringthe former phase and thenegativetorque power in the HSJ were smaller than those in the VSJ. 3. The jump distance for the HSJ was correlated with the RJ-index for the VSJ.Moreover, there was a correlation between the HSJ and VSJ with respect to negative joint work and joint contribution. These results suggest that there are diŠerences in take-oŠmovement and joint kinetics between the VSJ and HSJ; however, both jumps show similarities in the recruitment characteristics of the take-oŠ leg muscle during the former phase.