| Research purpose:The aim of this study is to analyze the asymmetrical biomechanical characteristics of the lower limbs during single and double legged drop jumps at different heights.By analyzing the biomechanical characteristics of the hip,knee and ankle joints of the dominant and non-dominant side of the lower limb during single and double-legged deep jumps at different heights.we expect to find out the potential risk factors of lower limb injury.At the same time,the scientific design of the training program for the dominant side and the non-dominant side according to the bilateral differences of the lower limbs during the deep jump is of great significance to the scientific training of the athletes.Methods:In this study,14 high-level athletes were selected for the study,and the subjects completed the movements from 20cm,40cm and 60cm height jump boxes.The subjects were given a free fall from the box with no initial velocity,followed by a vertical jump upwards as soon as possible to the best of their ability and then fell back to the dynamometer and maintained their body balance.The experiment used a 3D infrared motion capture system and a 3D force measuring table to record the 3D kinematic signals and ground reaction force signals during the subject’s deep jump simultaneously.The calibration reflective Marker spheres were identified using Qualisys Track Manager 2019.2 data acquisition system software,and Visual 3D software（V6.01.36,C-motion,USA）was used to process the acquired signals and calculate the associated metrics.The characteristics of the changes of kinematic and kinetic indexes during the deep jump were analyzed using repeated measurement variance.Comprehensive analysis of the effect of jump depth height on the mechanical characteristics of the dominant and non-dominant sides of the lower limbs.Including the effect of jump depth height on the angle,moment,shear force and power of the hip,knee and ankle joints on the dominant side and non-dominant side of the lower limb.Results:（1）The kinematic indexes of the bilateral lower limbs showed consistent differences in the results of the three height double-legged jumping deep movements:hip abduction angle on the dominant side was significantly smaller than on the non-dominant side（P<0.05）;knee valgus angle and ankle flexion angle on the dominant side were significantly larger than on the non-dominant side（P<0.05）.Hip flexion angle,knee flexion angle,and ankle valgus angle were not significantly different between bilateral lower limbs（P>0.05）.（2）The bilateral lower extremity kinetic indexes showed consistent differences in the results of the three height double-legged jumping depth movements:hip abduction moment,knee valgus moment,ankle valgus moment,knee valgus power,and hip,knee,and ankle forward shear power were significantly greater on the dominant side than on the nondominant side（P<0.05）.There was no significant difference in hip,knee and ankle in flexion moment,flexion power,lateral shear power,hip abduction power,and ankle valgus power between bilateral lower limbs（P>0.05）.（3）With the increase of jumping depth height of both legs,hip flexion angle,flexion moment,and abduction power significantly increased（P<0.05）.With the increase of jump depth height of both legs,knee flexion angle,flexion moment,and valgus power significantly increased（P<0.05）,and knee flexion power significantly decreased（P<0.05）.With the increase of jumping depth height of both legs,ankle flexion power,external rotation power,and lateral shear power significantly increased（P<0.05）.The angle of knee valgus on the nondominant side significantly increased with the height of jumping depth of both legs over 20 cm（P<0.05）.（4）The kinematic indexes of bilateral lower limbs showed consistent differences in the results of the three height single-leg jumping deep movements:hip abduction angle and knee valgus angle were significantly smaller on the dominant side than on the nondominant side（P<0.05）;ankle flexion angle and valgus angle were significantly larger on the dominant side than on the nondominant side（P<0.05）.There was no significant difference in hip and knee flexion angles between bilateral lower limbs（P>0.05）.（5）The kinetic indexes of bilateral lower limbs showed consistent differences in the results of the three height single-leg jumping deep movements:hip abduction moment and knee valgus moment on the dominant side were significantly smaller than on the non-dominant side（P<0.05）;hip and knee forward shear force,ankle valgus moment,forward shear force,and lateral shear force on the dominant side were significantly larger than on the non-dominant side（P<0.05）.The flexion moment,flexion power and valgus power of hip,knee and ankle were not significantly different between bilateral lower limbs（P>0.05）;the lateral shear force of hip and knee were not significantly different between bilateral lower limbs（P>0.05）.（6）With the increase of single-leg jump depth height,hip flexion angle,abduction power,forward shear force,and lateral shear force significantly increased（P<0.05）.With the increase of single-leg jump depth height,knee flexion moment and valgus power significantly increased（P<0.05）.With the increase of single-leg jump depth height,ankle valgus angle,flexion power,valgus power,and lateral shear force significantly increased（P<0.05）.The hip abduction angle and knee valgus angle on the non-dominant side significantly increased with the single-leg jump depth height over 20 cm（P<0.05）.The dominant side knee anterior shear power,ankle valgus moment,and anterior shear power significantly increased with increasing jump depth height（P<0.05）.Conclusions:（1）There are asymmetrical differences between bilateral lower limbs in both double-leg and single-leg jumping deep movements,mainly manifested by differences in control strategies of the non-dominant side for landing posture,and mainly for ankle joint adjustment strategies for control in single-leg jumping deep.（2）The asymmetric difference in the deep jumping action of both legs mainly showed that the dominant side was stronger than the non-dominant side,and the three joints of the lower limb of the dominant side had greater frontal plane joint moments and sagittal plane shear forces,suggesting that there was a bilateral force difference characteristic of the dominant side dominating the work in the deep jumping action of both legs.（3）When the height of jumping depth of both legs exceeded 20 cm,the valgus angle of the non-dominant lower joint increased significantly,but at all three heights,the valgus angle of the dominant knee was significantly greater than that of the non-dominant side,showing a greater valgus angle of the dominant knee and predicting a greater risk of injury to the dominant knee.（4）Non-dominant ankle movements have a higher risk of injury in single-leg deep jump movements. |
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