不同質量訓練用排球之反彈力學特性分析

Kinetic analysis of training volleyballs of different mass during rebounding

緒論：本研究旨在探討不同重量與結構的排球在碰撞時的力學特性變化。方法：在研究中採用兩種系列（Conti-3000 vs. Conti-7000）並搭配三種不同重量的排球（230±10克、270±10克、340±10克）。以發球機離地三公尺垂直發射至測力板上測量球體的動態力學特徵（接觸時間、平均力量、力量峰值、總衝量、球速、初始動能、入射衝量、損失動能）。以組內相關係數（intraclass correlation coefficients；ICC）考驗所獲資料之信賴度，並以二因子變異數分析考驗球種與質量的交互作用。再以趨勢分析（trend analysis）檢驗三種重量球體的差異性。結果：結果顯示，資料信賴度介於0.997－0.999之間。在組別x重量因子下，所有的力學參數皆無顯著的交互作用（p＞0.05）。在Conti-3000與Conti-7000的比較下，除了總衝量未達顯著差異外，其他參數皆達顯著差異（p＜0.05）。Conti-3000在接觸時間，力量峰值，球速和初始動能方面顯著高於Conti-7000。而Conti-7000在平均力量，入射衝量和損失動能方面明顯高於Conti-3000。且所有力學參數，皆會受到球體質量改變的影響，並呈現顯著的線性改變（p＜0.05）。除球速以外，所有參數均隨球重量增加而提升，飛行速度隨球重量減少而減緩。皮爾森相關係數的結果表明，接觸時間與球速之間存在顯著的負相關（r＝-0.957，p＜.001）。結論：從速度的因子可知，採用發泡彈性體作為球體結構（Conti-7000）可使得球體在動態過程中增加彈性與活性，但同時也會增加能量的喪失。而透過增加中胎厚度可使力量特質顯著的上升，但也會增加能量喪失的程度。因此，藉由不同質量與結構的組合，可以造成顯著並有趨勢的球體力學特性變化。

Introduction: This study aimed to explore changes in the mechanical properties of volleyballs having different weights and structures. Methods: In this study, we used two series of volleyballs (the Conti-3000 and Conti-7000) weighing 230 ± 10 g, 270 ± 10 g, and 340 ± 10 g to measure their dynamic mechanical properties (contact time, mean force, peak force, total impulse, flight velocity, initial momentum, incident impulse, and lost momentum) after they were served onto a force plate by a serving machine installed three meters above the ground. The obtained data were then examined with intraclass correlation coefficients (ICC) to determine their reliability, and the interaction effects of ball type and mass were also analysed with two-way ANOVA. Trend Analysis was then used to examine the differences in volleyballs of different weights. Results: The results revealed that the data reliability was between 0.997 and 0.999. Despite the differences in weight, none of the mechanical parameters of group × weight had significant interaction effects (p > 0.05). A comparison of the Conti-3000 and Conti-7000 indicated that, other than total impulse, all parameters had significance differences (p < 0.05). The Conti-3000 results were significantly higher than those of the Conti-7000 in contact time, peak force, flight velocity, and initial momentum. Moreover, the Conti-7000 results were significantly higher than those of the Conti-3000 in mean force, incident impulse, and lost momentum. All the mechanical parameters were affected by the changes in ball mass and showed an obvious linear change (p < 0.05). Other than flight velocity, which was decreased by the higher ball mass, all parameters were increased by it. The Pearson's correlation coefficient revealed a significantly negative relationship between contact time and flight velocity (r = -0.957, p < 0.001). Conclusion: From the flight velocity factor, it was found that, although the use of foamed elastomer padding in the ball structure (Conti-7000) can increase the bounce and liveliness of a ball, it also increases the level of energy loss. Furthermore, by increasing the thickness of the cloth wrap carcass (cloth wrapped around the center), the power of a volleyball can also be increased. However, doing so also increases the speed of energy loss. Therefore, significant trends in the kinetic parameters of volleyballs can be manipulated through different combinations of ball mass and structure.