排球跳躍發球之時宜探討

Timing the volleyball jump serve

嚴雅婷(Ya-Ting Yen)

指導教授 ： 劉有德

國立臺灣師範大學/運動與休閒學院/體育學系/博士(2009年)

摘要

跳躍發球是一項需要精準動作時宜才能成功將球擊過網的高技能動作，有鑒於國內女子選手因跳躍發球成功率低而減少使用率，而相關文獻多著重在提升該技術的發球品質，因此希望針對跳躍發球的成敗因素進行探究。本研究以量化動作時宜為主軸，希望暸解動作與球的相互關係，透過比較站立與跳躍發球中的相關參數，探討成功與失敗發球之間的差異。以兩台每秒200幅的高速攝影機拍攝動作，並透過Kwon 3D動作分析軟體來獲取各關節點之三維資料。每種發球皆須蒐集不觸網且發進對方場地(4m X 3m)之有效區內的成功試作10次，未發過網的失敗試作次數則因人而異，但最多亦不超過10次。
實驗一以不同肩上發球方式比較不同層級兩組各六位選手間的差異，並探討一般選手肩上發球的策略與成敗因素。結果發現，肩上發球雖對一般選手較為困難，但在有效區的限制下，成功發球時宜在不同層級與發球種類間並無差異，其失敗的主因是擊球時相對高度太低且手腕在擊球瞬時的向上垂直速度太小；肩上發球時宜主要透過收臂來調整，拋球高度較高時擊球動作窗口較小容易失敗，而參與者會有個別的調整方式與失敗因素。實驗二以優秀選手進行跳躍發球並與實驗一的站立發球數據比較。結果發現，跳躍發球的成功率較站立式為低但發球速度快；受拋球高度及跳躍動作的影響，跳躍發球的動作時間窗口較小，難度較高，發球不過網的主因與站立式肩上發球類似；分析選手各自的時宜策略與失敗因素，顯示助跑期與跳躍高度是跳躍發球調整時宜的關鍵，在過程中影響的參數眾多，而且會持續進行調整，所以失敗的原因不完全相同，非單一參數造成而是相互配合下的結果。本研究結論為：1. 由於有效區的限制，成功的發球在不同技能層級與不同發球動作上皆具有動作時宜的穩定性。2. 拋球高度與跳躍反應了動作時間窗口與工作難度的關係，顯示跳躍發球對優秀選手來說是相對較困難的技術。肩上發球與跳躍發球的共同動作要素為揮臂，因此成功試作必須準確地調整揮臂以前的動作以保持揮臂的穩定性。肩上發球是利用收臂啟動的早晚與擊球預備時間來調整，而跳躍發球則是以助跑期與跳躍高度來進行調整。3. 擊球的相對高度太低與球飛出角度太小是造成發球不過網的最終原因，但形成這個原因之因素很多，建議以觀察個別選手動作特性的方式分析探討，以提供教練了解個人失敗的因素，設計訓練的方式，改進選手的發球成功率。

關鍵字

跳躍發球 ； 動作時宜 ； Tau ； 調整策略 ； 失敗因素

並列摘要

Volleyball jump serve is a skilled technique which needs precise timing to make a successful serve. Although the skill generates higher velocity, but the low success rate often prevent the national level of female players from using this powerful skill in the game. Most of the literatures on volleyball jump serves emphasized on improving the quality of the serve, therefore the focus of this study was to explore the key elements in the success/ failure jump serves from a movement timing perspective. The movement was captured by two high speed cameras (200 fps), and was digitized using the Kwon 3D movement analysis software. A successful trial was defined to be served clear the net and landed into a effective zone (4m × 3m) whereas failing to pass the net was defined as the failure . Ten successful serves for each participant were collected and analyzed for each type of serves, and 10 or less failure trials for each service type were collected for each participant.
Exp 1 examined the differences between different types of over-the-shoulder standing serves and 2 different skill levels each with 6 players to investigate the timing strategy of the serves used by the non-elite players and the timing characteristics of success/failure standing serves. The results showed that although standing serves were more difficult for the non-elite players, the timing characteristics and movement stability showed no differences between skill levels and the type of serves for the successful serves under the constraint of effective zone. The low relative height and the small vertical velocity of the wrist at ball strike were the main causes of failure. A successful standing serve was mostly achieved by timing the backswing of the forearm. When the ball was tossed higher, the window of ball strike would be smaller therefore increased the possibility of failure. Individual players often had their specific timing patterns and cause of failure serves. Exp 2 examined the jump serves of the elite players and compared the corresponding data from Exp1. The results showed that jump serves had higher ball velocity but lower successful rate than the standing serves. The higher tossing height and the jump movement of the jump serves made a smaller window for the ball strike therefore a more difficult service skill than the standing serve. The causes of failure for the jump serves were similar to those of the standing serves. Individual analyses on the timing strategies revealed that the approach phase and the jump phase were the 2 key periods of timing adjustment. There were many variables that affect jump serve, and the players continuously made the adjustments in the process, so it is impossible to identify a simple, single factor that caused the failure but rather a combination of several factors may have contributed to one failure jump serve. The conclusions were as follow: 1. Under the constraint of effective zone, there were no significant difference between skill level and serve type on the movement timing and its stability. 2. The ball tossing height and the jump movement reflected the relationship between ball strike window and the task difficulty, showing the jump serve was a more difficult skill than the standing serve. Arm swing was the common element of different serve types. To ensure a successful serve, the timing before the arm swing must be well adjusted in order to maintain the stability of arm swing. The main timing adjustment in standing serves was the backswing of the forearm, and for the jump serves, the approach phase and the height of jump were the 2 main timing adjustment methods. 3. The lower relative height at ball strike and the small angle of ball flight were the ultimate causes for failure serves. Many factors prior to the ball strike could contribute to these final causes. We suggest to analyze individual movement characteristics to better understand the main reasons for failure serves and design individual training program to improve the jump serve performances.

並列關鍵字

jump serve ； movement timing ； tau ； timing strategy ； cause of failure

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