THE ANALYSIS OF ELASTIC STIFFNESS BETWEEN THE SHORT-STRETCH AND LONG-STRETCH DROP JUMPS

Abstract

This experiment is to investigate the elastic stiffness of drop jumps (DJ) in order to understand capacity of elastic energy between the short-stretch DJ and long-stretch DJ. Force-platform and electrical goniometer were used to record ground reaction forces and angular displacements of the 11 subjects. The phenomenon of stiffness discovered on the individual muscle of animal also existed in this experiment with the human being implementing the explosive SSC movement, because: 1) The short-range stiffness was significantly larger than eccentric stiffness, 2) Eccentric stiffness was larger than concentric stiffness. When comparing with long-stretch DJ, short-stretch DJ had better capacity of utilizing elastic energy by inducing larger eccentric stiffness and produced larger power by taking a jump of faster concentric average velocity. if the purpose is to induce the capacity of utilizing elastic energy and produce larger power, the short-stretch DJ is recommended.