以行動本位量數檢證網球底線擊球之行動特定效應

Action-based measures examining action-specific effect in tennis ground strokes

緒論：本研究探討不同球速、擊球目標大小、以及正拍與反拍等情境下，網球底線擊球表現與球速知覺的行動特定效應。方法：參與者為19 名網球選手，於底線以正拍與反拍將發球機所發出不同球速的球，回擊至大或小目標區，擊球後口語評估球速度。以高速攝影拍攝擊球動作，分析動作啟動時間、準備期啟動時間、加速期啟動時間、拍-球觸擊時間，以及動作時間、準備期時間、加速期時間，解析球速知覺的行動本位量數，並比較回擊成功與失敗時的球速知覺。結果：一、不同球速、目標大小、正拍與反拍的擊球成功率沒有顯著差異。二、球速越快則越早啟動加速期；正拍與反拍動作時間沒有差異，但正拍準備期較短且加速期較長。三、不同球速的口語球速評估達顯著差異，擊球落點目標大小、正拍與反拍皆不影響口語球速評估。四、將加速期啟動時間視為球速知覺的行動本位量數，發現擊球成功與失敗時，口語球速知覺沒有差異，但高球速與小目標要求下，成功試作的加速期啟動時間顯著較晚。結論：一、網球選手正拍及反拍擊球成功率相同，且不受球速及目標大小影響。二、選手因應不同球速，會維持相同的動作啟動時間，並隨球速加快而提早啟動加速期，減少動作時間以及準備期與加速期時間；正拍加速期較早啟動且時間較長。三、球員能辨認各球速差異並予以評估，口語球速評估不受目標大小與正反拍影響。四、成功與失敗時的口語球速評估沒有差異，但行動本位量數顯示，在小目標要求且較快球速的情境下，回擊成功時知覺球速較慢。本研究之行動本位量數結果支持行動特定效應。

Introduction: This study aimed to examine the influence of ball speed, target size, and forehandbackhand on tennis groundstroke performance and action-specific effect on ball speed perception. Methods: Nineteen tennis players served as participants. They performed forehand and backhand ground stroke to return tennis balls to small and large targets. Tennis balls were shot by a ball machine in different speed. Ball-speed judgments were made verbally after every stroke. High-speed cameras were used to capture stroke movements and further analysis of movement initiation time (MIT), preparation initiation time (PIT), acceleration initiation time (AIT), racket-ball contact time, movement time (MT), preparation time (PT), and acceleration time (AT). We figured out what is the action-based measure for ball-speed perception in tennis ground strokes and compared ball-speed perceptions in success returns and faults. Results: 1. There was no significant difference among performances in different ball speed, target size, forehand and backhand. 2. AIT was significant earlier in higher ball speed. There was no significant difference between movement time of forehand and backhand, but AIT was earlier in forehand stroke. 3. Verbal ball-speed judgments were significant differed in different ball-speed. There were no significant effect of target size and forehand-backhand on ball-speed judgments. 4. AIT was regarded as action-based measures for ball-speed perception in tennis ground strokes. When compared success returns and faults, there was not difference in verbal judgments, but AIT occurred later in success returns in higher speed and small target size. Conclusion: 1. Tennis players had the same success rate in forehand and backhand stroke. The performance was not influenced by target size and ball-speed. 2. Responding to different ball-speed, players would maintain movement initiation time. But they would initiate acceleration earlier and shorten MT, PT, and AT. 3. Verbal ball-speed judgments were not influenced by target size and forehand-backhand, but player could identify difference among ball speeds. 4. Verbal ball-speed judgment in success returns was not different compared to faults. But action-based measures revealed that, in higher ballspeed and small target size conditions, players perceived slower ball speed in success returns. Our finding in action-based measures support action-specific effect.