在訓練或比賽中，排球選手最常使用的動作是垂直跳，而最常使用的跳躍方式是 「立姿蹲下後起跳」。這種肌肉收縮方式也稱為「伸展縮短週期」，意為一個向心收縮緊跟 在離心收縮之後。本研究的假設是在選手垂直跳時，較短的轉換期時間及較大的離心及向心 肌電圖值下，會跳得較高。實驗的儀器包括有：體表肌電圖、電子量角器及測力板。受試者 之比目魚肌活性及桌關節角度分別以體表肌電圖及電子量角器偵測，同時在測力板上進行三 次最大垂直跳。實驗結果顯示當進行最大用力垂直跳時，體表肌電圖值在離心收縮期與跳躍 高度成負相關； 向心收縮期與跳躍高度成正相關， 且二者在統計學上皆達到顯著水準（ P<.05 ）。

　　　　　The most frequent movement that volleyball players act during contest or training is jumping, and the most frequent jumping strategy is " countermovement jump ". This kind of muscle contraction is also called " Stretch-shortening cycle " which means that eccentric (stretch) contraction precedes the concentric contraction. The hypothesis of this study was when players perform vertical jumps, the shorter the coupling time and the larger the integral EMG value in both eccentric and concentric phase, the higher the players jump. The surface EMG, goniometer and force platform were used as study equipment. Subjects were asked to perform 3 maximal effort vertical jump on the force platform with surface EMG monitoring the right Soleus muscle and goniometer monitoring the right ankle angle. The results indicate that when performing maximal countermovement jump. the EMG value in eccentric phase is negative correlated with jumping height and the concentric phase is positive correlated with jumping height, and both of these two correlation has statistically significant differences (P<.05).