BIOMECHNICAL STRATEGY DURING PLYOMETRIC BARRIER JUMP- INFLUENCE OF DROP-JUMP HEIGHTS ON JOINT STIFFNESS

The purpose of this study was to explore the joint stiffness of lower-extremity during plyometric barrier jump. Fourteen power-oriented track and field men of collegiate and national level volunteered to participate in the study. All performed 3 maximal effort drop jumps where they landed and immediately jumped over a 60 cm barrier after dropping from 30, 60 and 90 cm. The results showed both knee and ankle joint stiffness became progressively and significantly lower with the increment of drop heights. Modulating knee and ankle joint stiffness, mainly by the joint angles during touchdown, is the biomechanical strategy to accommodate for changes in different drop heights. Our findings suggest the increment of drop heights during plyometric barrier jump diminished the benefit from stretch-shortening cycle.