目的：評估網球雙手反拍擊球動作上肢肌肉活化狀態。方法：以8位優秀女子網球選手為研究對象，利用表面肌電計來量測選手上肢雙臂肱二頭肌、肱三頭肌、屈腕肌和伸腕肌共8個肌群，並使用高速攝影機來決定反拍擊球過程各期別的分期點，以均方根肌電振幅大小來量化分析各肌群的活化狀況。結果：所有肌群以加速期肌肉活化程度最大，準備期時肌肉活化程度最低。準備期時，慣用手屈腕肌和非慣用手伸腕肌活化程度較大，雙手肱二頭肌活化程度最小且顯著低於其他肌群（p < .05）。加速期時，慣用手肱三頭肌和非慣用手屈腕肌活化程度最大；非慣用手屈腕肌活化程度顯著大於慣用手屈腕肌（p < .05）。跟隨期時，慣用手與非慣用手皆以屈腕肌活化程度較大。結論：優秀選手在雙手反拍揮拍動作過程中，以準備期時肌肉活化程度最低，加速期肌肉活化程度最大，尤其是慣用手肱三頭肌和非慣用手屈腕肌，選手訓練時必須強化以避免受傷。

Purpose: The purpose of this study was to evaluate muscle activation of the upper extremity during the tennis two-handed backstrokes. Methods: Eight skilled female tennis players were asked to perform in this study. Muscle activity was determined using surface electromyographic (EMG) techniques, and the critical instants of backstrokes were determined using high-speed video camera. The EMG activity was recorded from eight upper limb muscles (biceps brachii, triceps brachii, flexor carpi and extensor carpi muscles of both right and left arms). EMG rms values of the burst of different phases were individually calculated. Results: The muscle activation during acceleration phase was larger than other phase. Overall, the least muscle activation observed in the arm muscles during back swing phase. During back swing phase, the flexor carpi of the dominant arm and extensor carpi of the non-dominant arm had high muscle activity. The activity of both arm biceps brachii was significantly lower than the other muscles. The activities of the triceps brachii of the dominant arm and flexor carpi of the non-dominant arm were greatest during the acceleration phase. The activity of flexor carpi of the non-dominant arm was significantly greater than flexor carpi of the dominant arm. The activity of both flexor carpi was greater than the other muscles during follow-through phase. Conclusions: Based on the findings of this study, the muscle activation during back swing phase was smaller than other phase; acceleration phase was larger than other phase. The activities of the triceps brachii of the dominant arm and flexor carpi of the non-dominant arm were greatest during the acceleration phase. Tennis players should strengthen these muscles in order to prevent injury.