Study On Sports Biomechanics Of Continuous Vertical Jumping In Situ

With the development of athletic sports fleetly, many sports item demand preferable physical fitness of athletes for great competition and difficulties technical movement in match. They demand not only a good jumping ability but also several times, continuous and rapid take-off ability (bouncing endurance), it requires that athletes should pay special attention to develop bouncing endurance quality in training. At the same time, movement rhythm is different in different sports items and different technologies of same sports, vertical jump effect of athletes also produce certain differences in different movement rhythm. The study of continuous vertical jump was paid attention to by many experts in the industry. However, the study on continuous vertical jump at home and abroad is very rare, and systematic, comprehensive analysis of structural characteristics of continuous vertical jump movements, in-depth revelation on internal mechanisms was almost of a theory blank. Therefore, human sports biomechanics characteristics was investigated to reveal comprehensively various biomechanical factors of influencing take-off effects in the process of continuous vertical jumping in situ.In this paper, biomechanics characteristics of 20 subjects in continuous vertical jumping in situ were studied and analyzed in kinematics, kinetics and muscle mechanics. The kinematics study showed the buffer extent of lower limb joints were lesser in 60 times/min frequency, inadequately stretch of major muscles in buffer phase, the stored elastic energy was less, the energy was relatively less to utilize in thrust phase. It led to the take-off height significantly lower than the other two frequencies. In addition, the support time, the displacement and velocity of body gravity center, lower limb joint angular displacement and the peak velocity in extension phase were decreased with increase of frequency in continuous vertical jumping in situ. Time parameter was the important factors influencing the jumping effect in continuous vertical jump in situ. The take-off height was decreased obviously with increasing of time. From kinematics analyses, the main factors of influencing it had three aspects. The first factor was time parameter, support time was gradually increased with human movement time, it led to the conversion speed of lower limbs was too slowly from buffer to thrust, muscle produced relaxation and the utilization rate of stored elastic potential energy of lower limb muscle groups and rapid contraction of the muscles was decreased. Thus, it influenced the take-off effects. The second factor was displacement parameter. With human movement time increasing, vertical displacement of human gravity center and angular displacement of lower limb joints was gradually decreased. The decrease of displacement led to the main muscle group were not adequately stretch in buffer phase, the stored elastic energy was less, the available energy was relatively small in thrust phase, thus it led to the take-off height was relatively small. In addition, considering the displacement factors influencing the take-off effect, you must paid attention to the relationship of muscle tension– length and the work ability of muscles. The third factor was velocity parameter. The touchdown velocity and take-off velocity of human gravity center and the peak value of lower limb joints angular velocity in thrust phase were gradually decreased with time increasing. These factors led to movement time in buffer and thrust phase were increased, the loss of energy was larger, thus influenced the take-off effect. Otherwise, with movement time increasing, the lower limb segments patterns produced change after human fatigue; the segment movement did not produce the best combination model. It was also an important reason for influencing take-off effect.The study found that the instantaneous force at end of buffering, peak jumping force, impulse parameter and average jumping power were the important kinetics factors influencing the take-off effect of continuously vertical jumping in situ by means of 3D force measurement. The kinetics parameter produced some difference in-situ continuous vertical jump at different frequency, it mainly showed the instantaneous force at end of buffering and peak jumping force were significantly higher than the other two kinds of frequency, and impulse parameter and average jumping power were less than the other two kinds of frequency. At same frequency, the kinetics parameter diminished with the elapse of the time of continuously vertical jumping in situ, it was the main kinetics factor that the take-off height diminished with the elapse of the time of continuously vertical jumping in situ.From the analysis of muscle mechanics, median frequency (MF) of main muscle of lower limb diminished with the elapse of the time of continuously vertical jumping in situ, it showed the degree of fatigue was gradually increasing. Average EMG was studied to show that the level of muscle doing work gradually diminished with the elapse of the time of continuously vertical jumping in situ, and the work was more, the diminishing extent of AEMG was more obvious. And MF and AEMG showed the different change at different muscle of same frequency and at same muscle of different frequency. The main reason of coordination disorder of limb movement was that the change of the muscle activation order, inactivation order and muscle activity time led to change of joint muscle force at latter part of movement. The take-off effect of continuously vertical jumping in situ was different at different frequency and movement time, it should improve and select scientific training means and methods to formulate a scientific training program to strengthen the ability of athletes continuous vertical jump training and improve endurance athletes bounce according to the change of biomechanics characteristics at different condition.