Comparative Study Of Lower Limb Biomechanics Indexes In Different Vertical Jumps

ObjectiveIn sports,the common vertical jump forms are the semi-squat jump(knee flexion Angle 90～135° that is knee Angle 90～135°)and the shallow squat jump(knee flexion Angle less than 90° that is knee Angle more than 135°),which is a powerful extension of the hips,knees and ankles to push the body upward movement.Therefore,this study aims to analyze the difference of biomechanical indexes of lower limb joints in the two vertical jumping methods and their correlation with the vertical jumping height,so as to provide reference for further enriching the research system of vertical jumping training.MethodsIn this study,21 male athletes from physical education college of Jiangsu normal university were selected as research objects.Adopt half squat jump and shallow squat jump two vertical jump.The 3d motion capture system,force measuring plate and surface EMG were used to collect the kinematics data of the lower extremity of vertical jump.PSS 20.0 data processing software was used to analyze the data.The paired sample t test was used to compare the difference of vertical jump height,plantar pressure,lower limb joint Angle and angular velocity between the two groups.Pearson correlation coefficient was used to analyze the correlation between vertical jump height and plantar pressure,lower limb joint Angle and angular velocity.Results1.Half a squat jump group in hip and knee buckling Angle and ankle plantar flexion largest angular velocity is greater than the shallow squat jump group( < 0.05).2.Half a squat jump group before and after the direction of the left and right foot plantar peak pressure than shallow squat jump group,the difference was statistically significant( < 0.05).There was no significant difference between the two groups in the plantar pressure peaks in the medial and lateral and vertical directions.The height of vertical jump in the semi-squat group was highly correlated with the height of vertical jump in the vertical direction of the left and right feet.3.The shallow squat jump can better activate the muscles around the hip joint,while the semi-squat jump can activate the muscles around the knee joint more,and the rectus femoris and gastrocnemius muscles have higher EMG.4.Half squat jump group of vertical jump height and ankle varus Angle and hip height of maximum amount of spin angular velocity( < 0.05).5.Next crouching stage,half squat jump group and sagittal Angle hip and knee to knee,ankle joint maximum angular velocity between the closely linked( < 0.05).6.In the semi-squat jump,the left rectus femoris,the left and right gastrocnemius were highly correlated with the vertical jump height.Conclusion1.Increase knee flexion Angle to mobilize the muscle strength of all parts of the knee joint to achieve the goal of the highest vertical jump height.2.Since foot varus is mainly controlled by tibialis anterior and tibialis posterior muscles,in combination with the results of larger dorsiflexion in the semi-squat jumping group obtained in this study,it is believed that the semi-squat jumping mode and the shallow squat jumping mode have significantly different muscle strength modes in the tibial anterior muscle.3.In the process of vertical jump,the acceleration of the body’s center of gravity upward has been proved to be strongly correlated with the extension speed of each joint in the take-off stage,while the joint flexion with relatively large semi-squat jump mode in the squatting stage is conducive to obtaining the ideal extension speed.4.As the furthest major joint,the ankle and the supporting muscles are responsible for generating and transferring energy from the proximal segment.Therefore,powerful plantar flexion is an important part of vertical jump.The maximum plantar angular velocity of the ankle joint in the semi-squat jumping group was also beneficial to the gain of more impulse and the increase of vertical jumping height.5.Although the maximum angular velocity on the sagittal surface of the hip joint is similar to that of the shallow squats,the average value of the maximum angular velocity on the frontal surface and the horizontal surface is smaller than that of the shallow squats,indicating that the maximum torque in these two planes is relatively small when the semi-squats are performed.Strengthen the hip joint to extend the hip muscle training,such as the gluteus maximus muscle strength is very important,is conducive to improve the vertical jump height.6.When using shallow squat jump squat jump can better activate the muscles around the hip,and half a squat jump is around knee joint muscle activation degree is higher,therefore,in according to the different sports and action requirements,reasonable training,fully activate muscle,while improve the level of sports should pay attention to strengthen the synchronicity,coordination training,reduce the occurrence of sports injury.