| Summary: | 碩士 === 國立體育學院 === 教練研究所 === 89 === Abstract
This experiment used methods of sport biomechanics to investigate the kinematic, dynamic and neuromuscular characteristics of drop jumps（DJ）in order to understand the differences on elasticity energy, stretch reflex and sport performance between two different stretch amplitudes of SSC jumps.
There were 11 subjects in this experiment including jumpers and sprinters. Their ages are 23.18±2.64, heights are 173.0±4.03 and weights are 64.31±5.97. AMIT forceplatform, Penny electrical goniometer and Biovision electromyographic system were used to record the ground reaction forces, knee angular displacement and the EMG-signals of soleus and rectus femoris. SPSS software was adopted to calculate the average values of the parameters and repeated measures t-test was used to test the difference between short and long stretch DJ. The significance level was set at.05.
From three different heights of 20, 40 and 60 centimeter, we adopted the short stretch DJ and long stretch DJ at each height. After treating the data and discussion, the results of different SSC mechanism and performance between the two DJ were obtained. The two main mechanisms affecting SSC movements are elastic energy and stretch reflex. In the aspect of elastic energy, the higher force developed at the end of prestretch and the shorter coupling time indicated that small stretch DJ could store more elastic energy and can efficiently utilize elasticity energy. As for neuromuscular innervation, the higher average amplitude EMG of supporting and eccentric／supporting phase demonstrate that the small stretch DJ activates higher innervation of the neuromuscular system and stretch reflex activity. The ratio of concentric／supporting phase IEMG magnitude of short stretch is smaller than that of long-stretch DJ, which implied that short-stretch DJ had better capacity of utilizing elastic energy. Under the influence of higher elasticity energy, stretch reflex and innervation activity, short stretch DJ produce larger eccentric and concentric average force. Therefore, it is recommended to adopt the method of short stretch DJ to have a better training effect on the SSC mechanism.
Although the method of large stretch DJ did not have the advantage of inducing elasticity energy, stretch reflex and larger force, it ended up with the higher flight height because of its larger momentum.
The short stretch DJ had better capacity of elastic energy, stimulated higher stretch reflex activity, innervated higher activity of neuromuscular, and produced larger concentric force. These facts demonstrated that short stretch DJ was a better training method for inducing SSC mechanism, innervation activity and larger force. On the other hand, although the short stretch DJ could produce larger eccentric and concentric force, it couldn’t decide the flight height. Flight height is determined by momentum, and long stretch DJ had larger momentum and jumped higher. The purpose of jump is to jump higher altitude, so we should use the way of long stretch DJ to obtain the better performance.
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