Variable Heights Influence Lower Extremity Biomechanics and Reactive Strength Index during Drop Jump: An Experimental Study of Male High Jumpers

Abstract

Introduction. This study finds the lower limbs’ reactive strength index and biomechanical parameters on variable heights. Objective. This research aims to reveal the effects of drop height on lower limbs’ reactive strength index and biomechanical parameters. Methods. Two AMTI force platforms and Vicon motion capture system were used to collect kinematic and dynamic signals of the lower limbs. Results. The drop height had significant effects on peak vertical ground reaction force and peak vertical ground reaction force in the extension phase, lower limbs’ support moment, eccentric power of the hip joint, eccentric power of the knee joint, eccentric power of the ankle joint, and concentric power of the hip joint. The drop height had no significant effects on the reactive strength index. Reactive strength index (RSI) had no significant correlations with the personal best of high jumpers. The optimal loading height for the maximum reactive strength index was 0.45 m. Conclusion. The optimal loading height for the reactive strength index can be used for explosive power training and lower extremity injury prevention.

Drop Height Impacts the Lower Limb Elastic Energy’s Utilization for Male High Jumpers: A Experimental Research from Biomechanics

“…However, the short contact time requires that the low extremity need to resist the high loading impact in the higher drop height to keep the fast muscle contraction. It is precisely that high jump training contained numerous fast takeoffs and full flexion and extension with tremendous impact [ 10 ]; it makes the muscle tendon complex absorb the elastic energy in the eccentric phase and utilize them well in the concentric phase with the excessive height (0.75 m). McBride and Snyder found that higher bounce heights were produced in the training group of sprinters and jumpers who performed drop jumps at 40 cm, 60 cm, and 80 cm.…”

“…Byrne et al [ 5 ] revealed that 0.4 m and 0.6 m are an optimal loading height reactive strength index. Zehao et al [ 9 ] found that at a height of 0.45 m, high jumper's reactive strength index and average power output reached the peak [ 10 ]. Di Giminiani and Petricola [ 11 ] suggest that athletes need to determine their individual optimal loading height for average power output, in order to control their training process.…”

Optimal Loading Height: A Practical Research of Drop Jump from Biomechanics

“…e regulation of reflex muscles such as muscle spindle will enhance the preactivation of muscle-tendon complex at the excited lower limbs, which is manifested as the higher stiffness of muscle-tendon complex and accumulation of more elastic potential energy [35]. When it exceeds the optimal loading height, due to the protection from upper spinal nerves, the muscle-tendon complex is protected from a high-load impact and the nerves are adapted to the strategy, the inhibition flow of muscle spindle will lower the preactivation of muscles [9], which is mainly manifested as lower stiffness of the muscle-tendon complex 43 , the significant extension of supporting duration and the loss of the stored elastic potential energy.…”