網球發球是一種高揮拍速度的肩部動作型態，在動作過程中需要肌力與肌爆發力 的參予。網球選手要獲得最佳的運動表現，其肩關節必須在動態與穩定中取得平衡，而肩關 節肌群協調與同步收縮的能力是其中的關鍵。由於肱肩盂關節天生的不穩定，必須依賴肩部 之肌肉組織來提供發球時肩關節動態穩定的力量；而且，肩內、外轉肌肉力量不平衡之程度 直接反應了肩部傷害之發生機率。因此，了解網球選手肩內、外轉肌力之特徵可供給教練評 估運動表現的客觀依據，以及醫學臨床上肩部運動傷害之參考數據。故本研究的主要目的在 探討女性網球選手肩關節內、外轉肌力的特徵；次要目的在比較各組間肩外轉╱內轉之肌力 比。 研究結果顯示， 大專甲組選手肩內轉與外轉之最大肌力顯著大於大專乙組及高中組（ p<0.05 ）；大專甲組選手肩外轉╱內轉之肌力比明顯低於大專乙組及高中組。

　　　　　The overhead tennis serving is an explosive, high-velocity athletic movement that requires muscular strength and power, coordination and synchronicity of muscular contraction. To achieve peak performance in the athlete's shoulder during overhead serving, there must be an optimal balance between mobility and stability. Since static glenohumeral stabilization is inadequate, so overhead serving motion must rely on the neuromuscular components of the shoulder to provide dynamic stability during the overhead serving. The degree of muscular imbalance between the external and internal rotators differed based on the presence of pathology in the subjects in their study. Therfore, the purpose of this study was to evaluate shoulder internal and external strength characteristics for female tennis players. Secondary purpose was to compare the differences among three performance-based tennis players in shoulder rotation strength and external/internal ratio. The results of this study indicated the elite-level tennis players had higher shoulder internal and external rotation strength than collegiate and high school tennis players (p<0.05). The shoulder strength in external/internal ratio was shown that elite-level collegiate tennis player was significantly lower than that of college and high school tennis players (P<0.05).