The Effect Of Passive Stretching On Vertical Jump Performance Among Middle School Athletes:a Biomechanical Study

Objective: Vertical jumping is one of the basic movements in many sports.Vertical jumping as an important index of lower limb power is paid more attention in physical education class in primary and middle schools.Current research about the effect of stretching on vertical jumping is mainly focused on the stretching types and intensity.In this study,the kinematic and kinetic data were compared between the vertical jumping before and after passive stretching.the mechanism of vertical jumping improvement after passive stretching was analysed and discussed in order to provide a more effective training method and theoretical basis for PE teacher and coaches.Method: 15 male middle school athletes,without any injury history on lower limbs within 3 months,from Jiao Chuan Academy were participated in this study.Subjects did the first vertical jumping before a passive stretching and the second one after the passive stretching.Vicon motion capture system was used to collect the kinematical data of lower limb and AMTI force platform simultaneously recorded the ground reaction force during vertical jumping.SPSS 17.0 was used to calculate the difference between the vertical jumping before lower limb stretch and the vertical jumping after stretch in terms of kinematic and kinetic data.Result.: The kinetic data showed that the peak value of ground reaction force for the vertical jumping,which was done before passive stretching,was higher than the one after passive stretching.The duration of passage through the air is significantly longer for the vertical jumping done after the passive stretching.The kinematic data showed that angles of greatest flexion for hip,knee,and ankle through take-off phase of the vertical jumping are significantly higher after passive stretching.During landing phase,the angles of greatest flexion for hip,knee of the jumping are higher before the passive stretching.Conclusion: The result shows that extra mobility of joints of hip,knee and ankle due to passive stretching could reinforce the explosive extension of lower limb during taking off which can potentially achieve higher vertical jumping.Therefore,in the warm-up session of PE class or training session,passive stretching exercise can be applied to improve the mobility of joints as well as the height of vertical jumping.