Correlation Of Lower Extremity Strength And Kinematics, Kinetics During Different Vertical Jumps

Purposes: The role of vertical jump ability in sport activities is self-evident thatthe level of vertical jump ability sometimes even becomes the determinant factor ofsome sports. There are a variety of vertical jumps in physical activities. During differentform of vertical jumps, the participation degree and contraction models of lowerextremity muscle are different. The muscle involvement degree is reflected by thecontraction models, the size of muscle strength, while the important evaluatingparameters of vertical jump are the kinematics and kinetics which reflect the movementcharacteristics. Although previous researches on vertical jump have stressed theimportance of lower extremity strength, the correlation between lower limb musclestrength and vertical jump has yet to be systematically understood. This study exploredthe correlation between the muscle strength of different contraction models and theparameters of the kinematics and kinetics during vertical jump of SJ, CMJ and CJB inan effort to provide a reference for sports training and data support for the technicalevaluation of vertical jump movement.Methods: Randomly selected30healthy male subjects from the Sports departmentof Suzhou University,22.8±1.7years old, height176.2±5.2cm, weight71.6±8.5Kg; thewhole subjects with the right side dominant lower limb had no specialized strengthtraining, but vertical jump skill training. The strength test of subjects were measured bythe Con-trex multi-joint strength-testing-system, respectively testing muscle strength oflower limb hip, knee and ankle joint, recording and standardizing their peak torque ofisometric and isokinetic contraction (peak torque/body weight). The vertical jump wasdone on the infrared Vicon motion capture system and tested by static calibration with20points system of20infrared reflective ball placing on the body surface to recordkinematics data during the process of SJ, CMJ and CJB. Use Kistler force platform tosimultaneously record the maximum ground reaction force and take-off speed in aneffort to calculate the impulse based on it. Adopt correlation analysis between the strength parameters of hip, knee and ankle joint and the kinematics and kineticindicators of SJ, CMJ and CJB.Results:①The hip extensor E60(60o/s slow isokinetic eccentric strength),E240(240o/s rapid isokinetic eccentric strength),knee flexor E240and SJ center ofgravity height were positively correlated, especially knee flexor E240had a significantcorrelation with height, and hip extensor and knee flexor E240had a statisticallypositive correlation with the CMJ and CJB center of gravity height respectively. Theisometric strength of knee flexor Is90(90o/s isometric strength) was highly relevant tothe CMJ hip take-off angle, the ankle extensor C120(120o/s rapid isokinetic concentricstrength) had a high negative correlation with CJB knee take-off angle; the kneeextensor Is60and the minimum angle in the maximum hip flexed angle during verticaljump were significantly correlated, the hip extensor C240was highly correlated with theminimum angle in the maximum CJB hip and knee flexed angle; hip extensor C240washighly correlated with the maximum hip angular velocity during SJ, the hip flexor E60was highly correlated with the ankle angular velocity of the CMJ hip, the ankle flexorC60and C120were highly correlated with the maximum hip angular velocity of CMJ.In addition, the correlation between other forms of muscle strength of the lowerextremity and kinematics indicators above was in the results.③The hip extensor Is90and the CJB ground reaction force is highly positive; the hip flexor E60was negativelycorrelated with the ground reaction force of SJ, CMJ and CJB; the ankle extensor C60was highly positive with the ground action force of CJB, the ankle flexor C60and C20were highly positive with the ground action force of CJB; the knee extensor E240had apositive correlation with impulse of SJ and CJB, especially CJB impulse had a highcorrelation with it, the knee flexor C60and E240were positive with CJB impulse,E240was highly positive with it.Conclusions:①The development of rapid isokinetic eccentric strength of lowerlimb hip and knee has a significant meaning to improve the vertical jump ability withthe pre-squatting action; the improvement of the lower limb hip extensor and kneeextensor and flexor isokinetic strength is helpful to enhance the ability of SJ forathletes。②The ground reaction force has a low correlation with vertical jump and could not be used as an effective indicator for assessing the ability of vertical jump, themaximum angular velocity of joint kicking has a high correlation with the vertical jumpheight and could be used to evaluate the vertical jump ability. Moreover, the maximumangular velocity of joint kicking has a high correlation with the limb hip extensorfast-speed muscle strength and the ankle flexor fast-speed muscle strength, which couldraise the level of SJ and CMJ.③The joints muscle strength of lower limb has acorrelation with the minimum angle in the maximum angle of flexed hip, knee andankle and the taking-off angle of hip and knee, but no rules, and the jump height has nocorrelation with the minimum angle in the maximum angle of the flexed hip and ankleand the taking-off angle of hip and knee, whether it could be used as an effectiveindicator for evaluating the vertical jump still have to be further studied.