桌球正、反拍拉球動作之生物力學分析

Abstract

本研究以6名大專男子甲組桌球選手（年齡21±4.69歲、身高173.5±4.59公分、體重67±5.80公斤、球齡12±4.52年）為對象，分析其桌球正拍與反拍拉球技術的差異，提供對桌球訓練與教學之參考。本實驗使用10部Vicon MX13+ System (250Hz) 紅外線高速攝影機拍攝各動作的3D影像資料、兩部Kistler測力板(1500Hz) 擷取選手的動力學數據和Noraxon無線肌電系統(1500Hz)同步蒐集持拍手的表面肌電訊號，並利用Vicon Nexus 1.52計算3D的運動學及動力學資料及Noraxon軟體計算持拍手上肢肌群的表面肌電振幅。所得數據以無母數魏可遜符號檢定考驗同樣技術時正拍與反拍拉球動作間的差異，再以無母數弗里曼二因子等級變異數分析考驗正拍、反拍之不同柆球技術(拉上旋球、拉下旋球)間的差異情形，並以Excel軟體進行事後比較計算，顯著水準訂為α = .05。從結果發現正拍拉球在回擊球速、揮拍速度、重心速度都比反拍拉球來得快，正拍拉球有較大的揮拍距離及較高的擊球重心高度。在正、反拍不同的擊球技術中，兩者回擊下旋球時都有較低的重心高度以及較大的拍面角度。在地面反作用力方面，揮拍期的前、後方向的衝量與球拍前、後方向的速度達顯著相關。在肌電訊號中我們發現，正拍與反拍拉球於揮拍擊球期，肌群活化達峰值的順序先為近端肌群而後遠端。而來球的旋轉不同並不影響肌肉的作用順序，但回擊的方向不同則會影響肌肉的作用順序。在平均肌電振幅中，正拍拉球在前三角肌、胸大肌、橈側屈腕肌與尺側伸腕肌有較大的振幅，反拍則在後三角肌、肱三頭肌與尺側伸腕肌有較大的振幅。當拉球時，肱二頭肌與肱三頭肌、橈側屈腕肌與尺側伸腕肌，在正拍的擊球期時有明顯的共同收縮現象；而反拍則無共同收縮的現象，因此正、反拍拉球時有不同的肌肉作用模式。

The purpose of this study was to combine the kinematics, kinetics and surface EMG methods to analyze six elite collegiate table tennis players in Taiwan (age: 21 ±4.69 yr, height: 173.5 ±4.59 cm, weight: 67 ±5.80 kg, experience: 12 ±4.52 yr.) when they were performing the forehand and backhand drives techniques while receiving the top spin and the under spin services. Ten VICON MX13+ Motion Capture systems (250 Hz), two KISTLER Force Plates (1500 Hz) and Noraxon Wireless EMG system (1500 Hz) were used to collect the kinematics of the dominate upper limb muscle groups, which were the wrist flexor, wrist extensor, biceps brachii, triceps brachii, pectoralis major, anterior deltoid and posterior deltoid. The EMG data were analyzed by using the Acknowledge software (1000Hz)., kinetics data and surface EMG signal. The Vicon Nexus 1.52 was used to calculate the kinematics and the kinetics data, the Noraxon software was to analyze the EMG signal parameters. All the variables were tested by Friedman two-way analysis of variance nonparametric statistical test, and the post-hoc comparisons were calculated by the Excel software. The Wilcoxon matched-pairs signed-rank nonparametric statistical test was to test the different variables between forehand and backhand drives, the significant level was at α =.05. The results were as follows: there was a significant difference that the forehand drive was greater than backhand drive in the following variables, the return initial velocity of the ball, racket swing velocity, the velocity of center of gravity, racket upswing displacement and the height of center of gravity at the contact point. There was greater racket tilt angle and a lower center of mass when return backspin serve. In ground reaction forces,there was a significant correlation between anteroposterior impulse and horizontal racket anteroposterior velocity. In EMG, The anterior deltoid, pectoralis major, flexor carpi radialis and extensor carpi ulnaris in forehand drives, the posterior deltoid, triceps and extensor carpi ulnaris in back hand drives exerted the greater muscular amplitude during the swing forward phase. There were co-contractions between Biceps Brachii and Triceps Brachii, Flexor carpi radialis and Extensor carpi ulnaris in forehand drives during upswing phase, while a less co-contraction in backhand. The muscular strategy and the patterns of the forehand and backhand drives in elite table tennis players were not the same.