目的：探討排球前、後排扣球2種不同躍起方向之助跑急停跳，起跳期下肢動作的運動生物力學特性之差異，以提供該專項技術起跳動作之診斷、指導及肌力訓練一參考訊息。方法：10名大學優秀男子排球選手為受試者。6臺Qualisys光學攝影機(180 Hz)與2塊AMTI三軸測力板(1800 Hz)同步擷取資料。以The MotionMonitor軟體進行資料處理，並以動力學逆過程算得下肢內在動力學參數。利用SPSS統計軟體進行相依樣本t-test，統計顯著水準定為α= .05。結果：在運動學方面，相較於前排扣球，後排扣球具有較短的起跳動作時間及較大的併步距離。在動力學方面，相較於前排扣球，後排扣球之先行腳具有較大的最大淨踝關節伸肌力矩與離心功率、最大淨髖關節伸肌離心及向心功率；後排扣球之跟隨腳具有較大的最大淨踝關節伸肌力矩、最大淨踝關節伸肌離心功率、最大淨膝關節與髖關節伸肌向心功率。結論：排球前、後排扣球兩跳躍技術，起跳階段有不同的技術需求，若後排扣球要獲得較大的前衝利益，排球運動員除了採較大的併步距離外，還需加強其兩腳踝關節伸肌群與先行腳髖關節伸肌群之爆發力，以達成快速的制動，且還需有較大的兩腳髖關節伸肌群與跟隨腳膝關節伸肌群的爆發力，以達成快速的蹬伸，以此才能縮短觸地時間，減少水平速度的損失，以此期可提供排球運動員肌力訓練時一參考依據。

Purpose: To compare lower extremity biomechanics during the take-off phase of front-row spike and back-row spike tasks in order to further provide the information for the teaching and training in these skills. Methods: Kinematics and ground reaction force data were synchronized to obtain from ten subjects, using six Qualisys cameras (180 Hz) and two AMTI force palates (1800 Hz). Data were analyzed by using the MotionMonitor analysis software. An inverse dynamic process was used to calculate the kinetically parameters for the lower extremity. Statistical analysis was used the t-test to evaluate the differences in dependent variables between two spike skills. The significance level was set at α = .05. Results: The back-row spike skill had a significantly shorter movement time of take-off phase and a longer step distance than the front-row spike skill. The back-row spike skill produced a significantly greater peak ankle extension moment, peak ankle extensors’ eccentric power, peak hip extensors’ eccentric power, and peak hip extensors’ concentric power in comparison to the front-row spike skill in lead leg. The back-row spike skill produced a significantly greater peak ankle extension moment, peak ankle extensors’ eccentric power, and peak knee and hip extensors’ concentric power in comparison to the front-row spike skill in trail leg. Conclusions: Spike skill at back-row in volleyball players required greater leg strength and power to form a faster take-off as well with greater step distance. This can enhance the rush forward benefits for jumping toward the upper front.