자연과학편 : 배구 스파이크의 도움닫기와 발구름 동작이 도약높이에 미치는 영향 = The Effect of the Approach and Take - off Motion on the Jump - Height in Volleyball Spike

다국어 초록 (Multilingual Abstract)

A kinematic analysis of the approach and take-off motion in volleyball spike was done using three-dimensional high speed cinematography. Twelve high-class collegiate male volleyball players were involved in the data gathering process. Two cameras were utilized for filming three trials of each subject’s spike movements with the filming rate of 100 frames per second. Digitized raw data were smoothed using the digital filtering method with 8 Hz of cut-off frequency. DLT(Direct Linear Transformation) method were applied to convert the two-dimensional data to three-dimensional ones. An interpolation method of Cubic Spline Function was also used to synchronize the two separate two-dimensional data. The calculated kinematic variables of volleyball spike were descriptively analyzed. The correlation between those variables and jumping height and vertical velocity of the total body center of gravity(CG) were analyzed.
Based on the results and discussion presented in the preceding chapter, the following conclusions were drawn :
1) The stride before the take-off was found to be shorter than that in the high jump motion, and this is thought to be due to the ‘power flop’ action which is important in the vertical jump.
2) The displacement of the CG during the volleyball spike was similar to that of the high jump.
3) It is essential to practice concentric contraction training to maximize the efficiency of converting the horizontal running momentum to the vertical jumping velocity.
4) The angular displacement of the left knee joint was continuously increased from touch down to take-off, while that of the right knee joint increased just before the take-off moment. This might indicate that the concentric contraction of the left leg more critically affects the jumping speed and the height.
5) Since the contribution of the upper extremities to the vertical velocity is pretty high, the skill of controlling upper arms in the volleyball spike movement is very important.
6) It is thought that the decrease in the horizontal velocity during the take-off is mainly due to the concentric contraction of the left leg.
7) The short take-off time, and the smaller right foot angle and the angle of the knee joint in touch down seem to increase the jumping height.
For the letter and sound results, the following factors are recommended to the further researches: more subjects, actual competing situation, kinetic data.