前言：棒球是一種需要反覆進行過肩投擲的運動，長時間累積下來會讓肩關節周邊的軟組織產生慢性的適應而造成活動度的改變，有些選手會發生盂肱關節內旋活動度缺損glenohumeral internal rotation deficit (GIRD)，它可能會引起後續肩部傷害。方法：本研究以一間高中甲組棒球隊為對象，收案22位男生。記錄球員基本資料包括年齡，球齡，身高，體重，投擲手，守備位置，運動傷害史及手術史；使用手機應用程式GetMyROM測量肩關節活動度，若非投擲側肩關節內旋角度較投擲側≧13度者，定義為GIRD組，<13度者，定義為非GIRD組；使用Lafayette手持式測力儀測量肩部等長肌力；使用Philips Lumify攜帶型超音波檢查棘上肌肌腱及後關節囊厚度；使用統計軟體SPSS處理資料。結果：受試者平均年齡為17.43±0.60歲，GIRD盛行率為18.2%，全體選手投擲側的內旋及肩胛棘於肩關節外展0度和90度之角度有顯著減少，且投擲側的棘上肌肌腱及後關節囊厚度有顯著增加；GIRD組可能有左打，投手及外野手比率較高的傾向，非GIRD組投擲側的外旋及肩胛棘於肩關節外展0度之角度及非投擲側的被動內旋角度較小。結論：攜帶型測量儀器利於發掘出GIRD，而棘上肌肌腱厚度，後關節囊厚度和肩胛運動障礙是應特別注意的因子，運動醫學專科醫師及運動防護員應及早在青少年棒球選手介入，以預防嚴重運動傷害的發生。

Introduction：Baseball is a sport which needs repetitive overhead throwing. Long-term exposure might lead to chronic adaptions to soft tissues of shoulder and result in changes in range of motion (ROM). Some players might have glenohumeral internal rotation deficit (GIRD) which triggered further shoulder injury. Methods：Twenty-two male players in one high school baseball team were recruited. The basic data including age, years of play, body height, body weight, dominant side, fielding position, injured and surgical history were recorded. The range of motion was measured by the APP tool (GetMyROM). The GIRD group is defined as the ROM of the internal rotation of nondominant shoulder minus that of dominant side is greater or equal to 13 degrees. Others is belonged to non-GIRD group. The isometric strength of shoulder was measured by handheld dynamometer (Lafayette). The thickness of supraspinatus tendon and posterior joint capsule were examined by handheld ultrasound (Lumify, Philips). The data was analyzed by using statistical software (SPSS). Results：The average age of participants was 17.43±0.60 years old. The prevalence of GIRD was 18.2%. The internal rotation of shoulder and scapula tilting angle at abduction on 0 and 90 degrees of dominant side of all players significantly decreased. The thickness of supraspinatus tendon and posterior joint capsule of dominant side significantly increased. Left-handed hitter, outfielder and pitcher might be more in GIRD group. The external rotation and scapula tilting angle at abduction on 0 and 90 degrees of dominant side and internal rotation of shoulder of nondominant side were less in non-GIRD group. Conclusion：Portable tools were convenient to discover GIRD. The thickness of supraspinatus tendon, thickness of posterior joint capsule and scapular dyskinesis were special factors of GIRD. Sports medicine physicians and athletic trainers should intervene earlier to prevent severe sports injury in adolescent baseball players.

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