桌球正手擊球動作的協調與量化

The coordination and quantification of table tennis stroke

目的：為了解經驗和工作限制對少年桌球選手正手擊球動作協調的影響，本研究以主成份分析法來描述全身肢段動作協調內容。藉由分析成分型態，探討不同技術水準的球員在面臨擊快或擊準目標時的動作協調差異。方法：以少年桌球優秀選手和一般球員各4名為研究對象，分別收集他們在擊快與擊準動作要求下的擊球落點和運動學資料，計算落點成功率，並依據全身動作肢段關節和球拍標記點的三維座標計算擊球時間、擊球速度和進行主成份分析（principal component analysis，PCA）。結果：參與少年桌球選手的動作表現皆能符合擊準或擊快的動作要求。而在動作協調方面，全身動作協調可以縮減成6個成分來分析，優秀選手擊準時於描述揮拍軌跡在前後和上下軸向的控制之成份與一般球員不同，且優秀選手在擊準要求下於揮拍方向和發力有關的協調也與擊快時略有差別。結論：不同技術水準的少年桌球手之成份動作型態有所不同，而且在因應動作目標變異的情況下，只有技術水準高者能調整動作協調內容來擊球，支持Newell的限制模式的論點。Purpose: To understand the influence of experience and task constraint on movement coordination of forehand stroke of youth table tennis players, the presented study described the movement coordination from whole body segments by using principal component analysis. Further examining the pattern of components movement, the difference of movement coordination among players in vary skill level was expected as they were required to drive for accuracy or for speed. Methods: Four elite and four ordinary youth table tennis players participated. They were required to stroke under the constraints of speed and accuracy. The location of the hitting ball and the coordinates of three dimensions of markers on players' major joints and rackets were collected. For the stroke performance, the percentage of successful stroke, the stroke time and the stroke velocity were calculated. For stroke coordination, principal component analysis was performed. Results: The results showed that all the participants stroke following the constraint of speed or accuracy. Movement coordination of whole body could be described by six components. Further analysis on components showed that that the elite differed from the normal in the coordination for driving for forward and backward and that for upward and downward as they stroke under accuracy constraint. Moreover, the elite displayed different coordination for controlling the direction of stroke and for executing the force. Conclusion: It could be concluded that the pattern of component movement was different among the youth table tennis players with different skill level. Only the elite are able to adjust their movement coordination for varying task goal. The result of this study also was found to support the statement of the constraint model of Newell (1986).