An Analysis of Drop Jump Performance of High-Level Sprinters: From the Lower-Limb Joint Biomechanics Perspective

OBJECTIVES: The purpose of the study is to compare the differences in biomechanical indices of hip, knee, and ankle joints, to explore the relationship between lower-limb joint biomechanical indices and the performance index of drop jump and to determine the lower-limb joints biomechanical factors that affect the performance index of drop jump. METHODS: Sixteen highlevel male sprinters were recruited and took a drop jump test at the height of 0.45 m, and their 3-dimensional kinematic and kinetic data were synchronously collected. RESULTS:(1) In drop jump, the differences of high-level male sprinters' hip, knee and ankle joints in torque, negative power, positive power, negative work, positive work and stiffness indices were all statistically significant(P<0.001).(2) The effects of ankle planter flexion torque and knee stiffness on ground contact time(Adjusted R²=0.801, P=0.011),the effect of knee positive work on jump height(Adjusted R²=0.677, P<0.001), the effect of ankle positive power on average power output(Adjusted R²=0.554, P=0.001), and the effects of knee stiffness and ankle positive power on reactive strength index(RSI)(Adjusted R²=0.842, P=0.004) were all statistically significant. CONCLUSIONS: In drop jumps of high-level male sprinters, knee stiffness primarily correlated to the time of the eccentric phase, whereas ankle plantar flexion torque and positive power primarily correlated to the time of the concentric phase, thus leading to the differences in drop jump completion time and reactive strength.Knee positive work and ankle positive power were the main power source to regulate the jump height and mechanical power output in drop jump.