前言：本研究目的為比較游泳抓台式出發與起跑式出發在水面下動作之差異。方法：12名國內優秀男子游泳選手，其中6名專長為抓台式出發（平均年齡23±1.9歲，平均身高174±3.5公分，平均體重75±4公斤，50公尺最佳成績25.1±0.6秒）；6名專長為起跑式出發（平均年齡21±1.3歲，平均身高177±4.9公分，平均體重73±3公斤，50公尺最佳成績24.6±0.4秒）。水面上使用一台JVC9800數位攝影機及水面下SONY數位攝影機各乙部，擷取頻率60Hz，以KWON3D 3.1版動作分析軟體，來進行受試者水面下運動學參數分析。統計方法為使用獨立樣本t考驗來檢驗兩組間各項運動學參數在不同出發動作技術之間的差異，顯著水準設為α =.05。結果：本研究結果為抓台式出發與起跑式出發在水面下參數（入水範圍、水面下身體重心最低位置、身體重心最低位置水平與垂直速度、入水後振腰時機）與到達12公尺時間及速度之間皆沒有達到顯著差異。此外，結果發現兩組選手在重心還未到達最低點時，就開始使用海豚式踢腳振腰動作以增加水平速度。結論與建議：在水面下抓台式與起跑式兩種出發方式之間沒有差異性存在。建議游泳運動員在進入水中時可透過入水後角度的改變，在身體完全進入水中後改變身體姿勢來避免潛入水中過深。可透過水中攝影找出每位選手海豚式踢腳的時機點及是否潛入水中過深，並對照於水中滑行平均速度，藉此來建議選手是否適合在水中有較長的潛水時間與潛水距離。

Purpose: The aim of this study was to compare the grab and track competitive swimming starts under water. Methods: Twelve male elite competitive swimmers were participated in this study. The six grab start subjects data were: age23 ± 1.9yrs, heights 174 ± 3.5cm, weights 75 ± 4kg and 50m freestyle 25.1 ± 0.6sec; the six track start subjects data were: age21 ± 1.3yrs, heights 177 ± 4.9cm, weights 73 ± 3kg and 50m freestyle 24.6 ± 0.4sec. Data were collected from two video cameras (60Hz) above and under water. The video data were digitized and calculated with Kwon3D Motion Analysis system. An independent t-test were used to test any differences between the grab and track start, and whether a significant was recorded (p<.05). Results: No significant differences between the two groups on entry area, the body center of mass at lowest position under water, horizontal and vertical velocity under water, dolphin kick opportunity under water, time and velocity to 12m. Sublects of two groups were using dolphin kick before the body center of mass at the lowest position under water. Conclusions: There were no significant between the grab and track starts under water. It was suggested that swimmers should consider including chang entry angle under water, dolphin kick opportunity under water and decided the glide time and distance underwater from video cameras and motion analysis.