Kinematics Factors Influencing Drop Jumping

Abstract

Purpose: The aim of this study was to examine the characteristics of lower limb kinematics in drop jumping (DJ) and their relationships with ability to jump using the stretch-shortening cycle (SSC). Subjects: The subjects were 28 healthy males. Method: In a 20cm DJ the changes in lower limb joint angles and vertical and drop jump heights were measured. From the changes in joint angles in DJ, the joint angles just before landing and at the time of takeoff, and the time from the change of ankle angle at takeoff to the time of knee angle change were determined. Subjects were classified into VJ higher or lower than DJ groups, and the differences between the two groups were compared. Results: For the VJ>DJ group plantar flexion was significantly smaller. Also, the time from the change of ankle angle at takeoff to the time of knee angle change was significantly longer, and the majority of subjects changed the ankle angle earlier than the knee angle. Conclusion: The results suggests that, in addition to a smaller angle of plantar flexion on landing, adopting a takeoff action in which extension action of the ankle is earlier than the knee enables a DJ which uses SSC efficiently.