The Effect Of Change Of Hamstring And Quadriceps Femoris Strength Of Knee On Continuous Vertical Jump

Objectives : The parameterof kinematics and kineticsof continuous counter movement jump were me asured pre and posttraining. The purpose of this study was toinve stigate the influence of vertical jump from changed strength of quadriceps femoris and biceps muscles.to guide training and prevent injury.Method : Twenty-four male Non-professional sports students voluntarily participated in this study. Mainly throughthe six-week strength training,Measured parameter of kinematics and kinetics of continuous countermovement jump pre,mid and post training. Force plates were used to capture ground reaction force and Mega Speed motion-captureand Simi Motion2D analysis systemwere used to capture kinematics data.A pair t-testwas usedto evaluate the difference betweenpre and post training and ANOVAwas used to evaluate the difference in groupsusing SPSS. Allvalues are expressed as mean±standard deviation .Result:1 After 6 weeks extensor strength training, quadriceps strength increase significantly, biceps musclesstrength has no obviously changed ; The complete time of continuous countermovement jump was shorter with same intensity, the height of center of gravitylargened; The stretch and buffering capacity were increased; The useless power was increased.2 After 6weeks flexorstrength training, the strength of knee extensors and flexors were significantly increased; the time to complete a same intensity of continuous longitudinal jump shortened; the heightof center of gravitylargened; The stretch and buffering capacity enhanced. Besides, the strength which the subjects used horizontally shrank and the level component ratio decreased. 3 The extensor strength before training was no influence to trend of parameter of kinematics and kinetics after training, however, the flexors training before extensors training was no influence to trend of parameter of kinematics and kinetics.4 After flexor and extensor muscle strength come to"high level", ,the subjects persist doing flexor strength trainin. Both of their flexor and extensor muscle strength increase observably. The rangeability of flexor and extensor muscle strength is not evidently. It's cost more time to finish counter movement jump and the peak height of gravity centre become lower. It's enhancing buffer ability but not jump ability. The ineffective force or proportion of ineffective force has no obvious changes.5 Trained these common people 12 weeks for different types. (extensor training,flexor training,extensor and flexor muscle alternately training,each of types training persist for 6 weeks.) the subjects'extensor muscle strength increase observably. It's cost shorter time to finish counter movement jump and the peak height of gravity centre become higher. It's enhancing buffer ability and jump ability. During the process of initial time landing to peak flexor value, the phenomenon of"second jump"disappeared.6 Flexor and extensor muscle strength increased can significantly reduce horizontal force and improved ground reaction in longitudinal jump aspects utilization. After flexor and extensor muscle strength come to"high level"the subjects persist flexor strength training. Training on the influence of flexion than is not obvious, but for continuous countermovement jump related index effects obviously.Conclusion:1 After knee flexion strength training, knee extensor and flexor muscles strength can be improved, but knee extensor muscle strength increased more than flexor muscle. The value of flexor muscle strength/ extensor is increased can decreased horizontal force in pedal stretch period. And then ground reaction force in vertical component increased, which results in increased continuous vertical jump for use. After flexor and extensor muscle strength come to"high level"continue training can reduced continuous vertical jump, But can't influenced ground reaction force for use.2 After knee extensor strength training, knee extensor and flexor muscles strength can be improved, but knee extensor muscle strength increased less than flexor muscle. The value of flexor muscle strength/ extensor is increased can increased horizontal force in pedal stretch period. And then ground reaction force in vertical component decreased, which results in reduced continuous vertical jump for use.