目的：賽季前是棒球選手調整體能的關鍵時刻，投手在投球動作分期中的跟隨期可能會造成肩關節轉肌群離心損傷，離心肌力訓練對肩關節外轉肌群有其重要性。本研究欲探討離心訓練對於賽季前職業棒球投手肩關節外轉肌群肌力表現之影響。
方法：本研究以中華職棒之本國籍投手8名為受試者，分為兩組：1.訓練組（N＝4，年齡：28±3歲；身高：180.1±1.4公分；體重：86.6±4.5公斤）。2. 控制組（N＝4，年齡：28±2.2歲；身高：181.5±6.3公分；體重：92±12.3公斤）。控制組維持球團既定的訓練，訓練組除正常的訓練外，並以等速肌力儀(Biodex System 3) 進行慣用手肩關節外轉肌群角速度60°/s、120°/s、180°/s的向心-離心訓練，連續四週，每週兩次，每個角速度各反覆十次。在離心訓練前後以角速度180°/s、300°/s進行向心肌力測試，觀察肩關節內外轉肌力的變化。
結果：經4週訓練後訓練組與控制組慣用手、非慣用手之內轉肌群在角速度180°在最大力矩、最大力矩之相對力矩皆有明顯退步（p <.05）。兩組慣用手、非慣用手在角速度300°的肌肉力量比值皆有顯著進步（p <.05）。訓練組在角速度300°的平均動力與總作功量較控制組有進步的趨勢，所有肌力變項兩組間無顯著差異。
結論：賽季前對職棒投手肩關節額外實施四週外轉肌群向心-離心訓練；並不能有效提升外轉肌群肌力，但向心-離心訓練有延緩肌力下降趨勢。賽季前投手肌肉有疲勞現象產生導致肌力下滑，是否因訓練期間其他體能訓練所造成的影響，則有待進一步的研究。

Purpose: to investigate the influences of concentric- eccentric training on the shoulder external rotation strength in professional baseball pitcher during preseason.
Methods: subjects were eight Taiwanese male professional baseball pitchers, and they were randomly assigned to the training group (N=4, mean age was 28±3 years, weight was 86.6±4.5 kg, high was 180.1±1.4 cm), and the control group(N=4, mean age was 28±2.2 years , weight was 92±12.3 kg, high was 181.5±6.3 cm). The control group was asked to stay with the same work out routine and the training group performed shoulder external concentric and eccentric training (Biodex System 3) at 60, 120, and 180 degree per second with the regular throwing arm other than the regular work out routine twice a week for four weeks. Each angle performed for 10 repetitions. The concentric strength was assessed at 180 and 300 deg/sec of shoulder external rotation before and after eccentric training to observe strength changes in the rotator cuff.
Result: After 4 weeks of training, the peak torque and the peak torque/body weight of the internal rotation muscle at 180 degree angle between the dominant throwing arm and the non-dominant throwing arm showed significant decreases (p <.05). The muscle strength of the dominant throwing arm and the non-dominant throwing arm for two groups at the 300 degree angle showed significant increases (p <.05). The dominant throwing arm of the training group showed more improvement at the 300 degree angle then the control group, but no significant differences in the variables of strength were shown for both groups.
Conclusion: the implementing of 4 weeks of concentric and eccentric external rotation muscles in the preseason did not effectively enhance the external rotation muscle strength, however, the concentric and eccentric training might slow down the muscle strength decrease. Is it because of other fitness training that caused of overtraining which lead to decrease of muscle strength in professional baseball pitchers during preseason would have to be researched more.

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