壘球擲準動作之運動學分析

Abstract

摘 要 本研究目的為比較不同技能水準之實驗參與者壘球擲準表現與動作型態之差異，藉由運動學分析，探討女壘選手與一般女大學生投擲動作型態普遍上之差異，分別針對選手的正確動作技巧及一般人的錯誤動作型態，進行說明解讀，並對於一般人學習投擲技巧提出具體之建議。八位大專甲組女子壘球選手與八位不具壘球投擲經驗之女大學生為實驗參與者，實驗工作為對著16公尺之目標範圍進行壘球擲準工作，每人投擲15顆，利用高速攝影機（200Hz）與陀螺儀動作分析系統（120Hz）擷取每次投擲動作，以進行各參數的計算分析，並利用Excel、Mathematica軟體製作上肢角度變化圖與肘、肩關節角角圖。發現：比較兩組投擲準確性成績，發現選手組優於一般組達顯著差異t(14)= 6.851, p<.05。比較兩組球速，發現選手組球速大於一般組達顯著差異t(14)=5.684, p <.05。比較兩組出手瞬間跨步前導腳（左腳）膝關節角度之平均值，選手組小於一般組達顯著差異t(13)＝-2.932, p<.05。比較兩組球出手瞬間軀幹與水平面夾角及頭部與水平面夾角，雖未達顯著差異但接近顯著差異，皆為選手組大於一般組t(13)= 1.971, p =.089、t(13)= 2.180, p =.070。比較兩組球出手瞬間上肢部位（腕、肘、肩）角速度之平均值，發現肘關節角速度選手組大於一般組達顯著差異t(13)= 2.339, p<.05。製作上肢角度變化圖，觀察後發現選手具有出手前肘關節角度短時間內變小再變大之情形，本研究解讀為「引肘向前」之動作技巧，反觀一般組未曾出現此現象。製作肘、肩關節角角圖，發現選手組與一般組的最大差異來自於起始動作後，「後擺」與「抬肘」之動作型態。依據本實驗目的，經由結果之統計分析與討論，對於一般人投擲動作提出下列建議：進行投擲動作時，除了加強後擺、抬肘，使投擲手引肘向前的動作技巧，亦須注意應將跨步加大以利投擲時身體維持較低之重心，並在投擲動作中，應保持身體往前加速，而避免頭部與軀幹過度後仰。Abstract The purpose of the study was to examine the differences in the softball target throwing performances. The movement kinematics was analyzed for the throwing movement from 8 elite women softball players and 8 novice female college students. The participants were required to use the over arm throwing pattern to throw a softball at a target 16 meters away for 15 trials. A high speed (200Hz) camera and the Gypsy18 motion capture system (120 Hz) were used to capture the throwing movement and the ball trajectory; The Microsoft Excel and Wolfram Mathematica were used for processing the data. The results showed that the softball players had significantly more accurate throwing performance than the novices, t(14)= 6.851, p<.05, and a higher ball velocity at release, t(14)=5.684, p <.05. For the throwing movement, the softball players had a significantly smaller knee angle for the lead leg at ball release, t(13)＝-2.932, p<.05; the trunk and head angles with respect to the horizontal plane at the ball release were larger, although did not quite reach the significant level, for the softball players, t(13)= 1.971, p =.089, t(13)= 2.180, p =.070. For the kinematics of the throwing arm at ball release, only the elbowangular velocity was found significantly larger for the softball players than the novices, t(13)= 2.339, p<.05. Qualitative analyses on the angular displacement of the elbow joint showed a consistent decrease-increase profile before ball release, characterizing the skill of “lead elbow” which was not found in any novices’ performance. In addition, observation on the angle-angle diagram of the shoulder-elbow joints showed that the differences of the throwing pattern between the 2 groups mainly came from the “back swing” and “elbow lift” segments. Based on the findings of the study, we suggest thefollowing points to be emphasized in teaching target throwing task: for the throwing arm, focusing on the back swing, elbow lift movement and practicing the “lead elbow” technique; for the non-throwing arm movement, the thrower should take a larger forward step and keep the center of gravity low; preventing the head and trunk leaning backward during the throwing movement in order to maintain the forward speed.