本研究之主要目的是：一、透過3D運動學的分析，來瞭解沙灘女子排球選手與室內排球選手沙地起跳動作技術的差異。二、透過下肢肌群的肌電訊號分析受試者沙地起跳時，下肢肌群在不同分期的施力方式與差異。以8位女子沙灘選手與8位女子室內選手為研究對象，二部Casio EX-FH20數位攝影機（210 Hz）與一套Noraxon肌電測系統（1,000 Hz）進行同步，擷取二組受試者在沙灘排球場地跨步起跳動作的運動學參數與肌電訊號，以獨立樣本t考驗來分析所得之資料，統計顯著水準定為 .05。本研究之主要結果為：一、「沙灘選手」有較佳的起跳合速度與起跳垂直速度，所以有最大的跳躍高度，和接近垂直的起跳角度。沙灘選手右腳支撐期時間較短，且沙灘選手有較大的下蹲緩衝角度，所以下蹲期的時間在起跳過程中所占的比例最長；而下肢關節活動角度較大，也導致有較長的上升作用期，能有效提升跳躍高度。二、在整個起跳過程中，二組受試者主要肌群的施力順序呈現相似的趨勢，其主要作用肌群施力順序為：右腳支撐期為股直肌與股內側肌；下蹲期為股內側肌與股直肌，但腓腸肌與股二頭肌有逐漸增加的趨勢；上升期為腓腸肌、脛前肌與股二頭肌。本研究結論：沙灘選手的下肢肌群在沙地起跳時可以產生較大的收縮，亦顯示下肢肌群間施力的順序更具協調性。透過本研究的結果，將有助於選手在沙地起跳的技術有所提升，讓沙灘排球選手的起跳能力能夠發揮更大的效益。

The purpose of this study was to investigate the variability of takeoff movement skills on sand surface between beach volleyball and indoor volleyball players through the 3D kinematics analysis. This study further investigated the variability of lower limb muscle contraction at different takeoff movement phases between beach volleyball and indoor volleyball players through the electromyography analysis. Eight female beach volleyball players and eight female elite indoor volleyball players were participated in this study. Two Casino EX-FX20 digital cameras (210 Hz) were synchronized with Noraxon™ electromyography system (1,000 Hz) to collect the biomechanical parameters, while players performing the straddle jump movement on sand surface. Independence t-test was used to evaluate the straddle jump performance differences between two groups. Statistical significance level was set at .05. Results showed that beach volleyball players performed larger vertical and resultant velocity in takeoff, and jump higher with a nearly vertical takeoff angle. Moreover, beach volleyball players had shortest right foot supporting phase and had larger flexion angles in the lower extremity joints, hence players could have longer acting period during upward and resulting larger jumping height. Players from both groups showed similar muscles firing sequences during takeoff movement. The rectus femoris and vastus medialis were active in the right foot support phase. Then, vastus medialis and rectus femoris were the main acting muscles in downward phase but gastrocnemius and biceps femoris activate increased at the same time. The tibialis anterior and biceps femoris were more activated in the upward phase. However, during the whole takeoff movement, beach volleyball players showed larger muscle contraction and better coordination than indoor volleyball players. The results of the study could provide the insight of segment-muscle coordination. This information could help players to improve jumping skill in the sand court, and beach volleyball players showed their jumping ability as possible.