Study On The Expert Ability Test And Muscles Biomechanical Characteristic Of Long Jumpers' Take-off Leg

The athletes who engage different sports items should obviously present different expert muscles characteristic in action. Study on the muscles expert ability test of athletes has an important meaning for studying expert sports. It can provide a scientific foundation to develop expert sports level and muscles force, and it shows a more important role in coaching expert technique and muscles power training. So, it appears necessary to investigate the test measures and methods that can effectively demonstrate muscles expert ability and characteristic on their sports items. Although there were many expert exercises in long jump, they could not provide a real horizontal velocity match with competition. The main aims of this study were: 1.Depending on the trait of long jump, the long jumpers were tested in simulating the different run up velocity, so as to analyze and estimate maximal ability of long jumpers in take-off, and 2. Using the method of test study and biomechanical theory to discover the expert ability of long jumpers and expose the muscles biomechanical characteristic in action. In order to implement these purposes, a set of controlling speed test system, which can represent the expert ability of long jumpers'takeoff leg in take off, was developed by the study. Nine male long jumpers (best achievement: 7.04±0.42m, present achievement: 6.85±0.38m ) were required to perform long jump take-off (72 times) with different test velocity (6m.s^-1, 7 m.s^-1, 8 m.s^-1, 9 m.s^-1) on the test system, and to complete running long jump (7 persons, 7 times). The high-speed video, accelerometer, 3D force plate and other high science and technology measures were used for recording the entire courses of take-off. The study gained results as following: 1. The expert ability kinematics results of take-off leg ●The kinematics results of center gravity of body ●The kinematics results of lower extremity 2. The expert ability dynamics results of take-off leg ●The characteristic of vertical reaction force under foot ●The characteristic of horizontal reaction force under foot ●The joints moment of hip, knee and ankle ●The comparison in the joints moment of hip, knee and ankle with running long jump and the controlling speed test The results were investigated by the sports biomechanics principle and statistics method. There were main conclusions on the study as followings: 1. In controlling test, the vertical reaction force and horizontal reaction force under foot was calculated by using accelerometer and inverse integral tracking analysis respectively. It was reasonable and credible. This method provided a new means for using inverse dynamics to calculate the reaction force under foot. 2. With increasing velocity of controlling speed (6 m.s-1—9 m.s-1), the height of center gravity of body continually increased. So, the muscles contraction ability enhanced. The compression of take-off leg was mainly accomplished by knee in take-off. The compression period of knee lagged company with controlling speed increasing. It directed weaker muscles ability of eccentric contraction of knee. 3. With increasing velocity of controlling speed, the vertical and horizontal reaction force under foot increased. It presented the expert ability and muscles contraction enhancement of take-off leg. In different controlling speed, the period of horizontal brake phase was longer than horizontal push phase. 4. In controlling speed test, the height of center gravity of body in take-off, and the vertical reaction force under foot at knee maximal flexion and its vale could be regarded as important indexes to evaluate the muscles ability of take-off leg. 5. All joints (Hip, Knee and ankle) chiefly presented extension moment in take-off, especially, in earlier phase of take-off (within 30%). The ability of fast eccentric, concentric contraction and the switch velocity from eccentric to concentric were important to take-off. 6. In running long jump and controlling speed test, all long jumpers presented pre-support lift characteristic in take-off. It indicated the muscles ability of concentric contraction in knee extension made a very important role. 7. In running long jump, objects emerged larger peak of knee flexion moment in earlier take-off phase (within 8%). It presented that the knee flexion muscles actively contracted in this period. It must be more care by coaches and athletes in training. 8. The test system, which was developed in this study, can be used for testing expert ability of take-off leg in take-off to long jumpers of different level. It would become an effective means to increase expert ability and muscles strength in long jump.