背景與研究目的：棒球投手重覆進行投擲動作，肩部受傷的機率相當高。目前常用的投手保護策略是限制投球數量。由於目前文獻中投手投球數量與肩部關節活動度、肩部本體感覺的相關探討不足，故本研究以此為方向，探討棒球投手投球數量與肩部關節活動度與肩部本體感覺之關聯。研究方法：以一職業棒球隊為實驗對象，計算其投球數量換算投手濫用指數(PAP)，測量肩部屈曲、伸展、內旋、外旋之關節活動度與主動定位主動復位角度之變化，進而探討投球數量與肩部關節活動度及本體感覺之關聯性。受測者在春訓前進行前測，之後每次投球後進行肩關節活動度及本體感覺測試。結果：10位受測者在投球負荷介入前後，肩關節的角度變化度沒有達顯著差異。肩關節的屈曲伸展及內外旋的本體感覺誤差關節角度變化量有顯著的差異。結論與討論：投手在一定數量的投球過後會造成肩部本體感覺的變化，增加受傷機率。除了投球數量的控制之外，本體感覺的測量也許是一種評估投手疲勞的方式。

Background and Purpose: The baseball pitchers act pitching repetitively. The percentage of injury is quite high. The most common strategy to protect pitcher is the pitching count limited. However, little evidence is available to further confirm the relationship between pitching count, shoulder range of motion and proprioception. This study attempts to investigate the relationship between pitching count, shoulder range of motion and proprioception. Methods: Ten professional baseball pitchers, count their pitching number and translate to pitcher abuse point (PAP) and measure the angle difference of shoulder flexion, extension, external rotation, internal rotation, and active position and reposition. And discussion the relationship between pitching count, shoulder range of motion and proprioception. Results: No significant difference exists in shoulder range of motion after pitching. Significant difference exists in shoulder proprioception after pitching. Discussion and Conclusion: After quite number of pitching will make the difference of shoulder proprioception, and increase the percentage of injury. And the proprioception examination should be another way to evaluation pitcher's fatigue.