目的：比較捕手低蹲姿(壘上無人)和高蹲姿(壘上有人)膝關節角度、力矩、肌肉活性與牽制表現之差異。方法：六名甲組棒球捕手，隨機分別在壘上無人(低蹲姿)和壘上有人(高蹲姿)的條件下，盡全力進行蹲捕-起身-傳球動作，以三維動作分析系統收集蹲捕膝關節運動學參數以及牽制動作時間，以測力板收集動力學參數，以表面肌電儀擷取股四頭肌與股二頭肌的肌肉活性，並將動作分成蹲姿期、起身期與投擲期。結果：低蹲姿於蹲姿期的膝關節屈曲角度顯著大於高蹲姿，而膝關節力矩與高蹲姿相比後並沒有顯著差異；高蹲姿於蹲姿期的股直肌與股二頭肌活化皆顯著大於低蹲姿，而起身動作時間顯著快於低蹲姿。結論：不同的蹲姿動作型態下，確實有不同的膝關節生物力學特性與可能發生的傷害機轉。捕手採用低蹲姿時，於蹲姿期有較大的膝屈曲，然而，採用高蹲姿時，雖有較快的起身動作表現，但於蹲姿期卻有較高的膝肌群活化程度。因此，捕手長時間蹲捕恐會增加膝關節負荷與過度使用情形，提高捕手膝關節傷害發生的風險。

Purpose：The purpose of the study was to compare kinematics, joint moments and muscle activities of knee, and movement time between low-squat (without base loads) and high-squat (with base loads) conditions. Methods: Six elite catchers were recruited from Division I baseball team, and performed squatting-standing-throwing movement with their maximal efforts. Motion analysis system with ten high-speed cameras, force plates, and surface electromyography were used to measure kinematic and kinetic parameters, muscle activity, and movement time. The squatting-standing-throwing motion was divided into three phases, including squatting, standing, and throwing. Results: The results showed that the low-squat condition had significantly greater angles of knee flexion than the high-squat condition during squatting phase; however, there was no significant difference in the results of knee joint moments between two conditions. The high-squat condition were significantly higher muscle activations of knee than the high-squat condition during squatting phase, but had faster standing movement time. Conclusion: These two squatting patterns caused different knee biomechanics and may have different mechanisms of knee-related injuries. Catchers using low-squat position had greater knee flexion during squatting, whereas they using high-squat position had higher muscle activations of knee, but faster standing movement. Thus, the findings indicate that catchers with squatting positions for long periods of time may overuse and increase loading of knee joint to increase the risk of knee injury.