目的：本研究之目的是以個案研究之方式比較一位職業級與一位一般大學甲組的打擊者在打擊內角、外角、及正中球路時核心肌群肌電訊號之差異。方法：本研究收取兩位打者：一位為美國職棒大聯盟1A優秀打者，另一位為大學甲組一般選手。利用無線肌電訊號擷取系統收取豎脊肌、腹橫肌、腹直肌與腹外斜肌在揮棒動作擊球前期以及擊球後期時分別針對正中球路、外角及內角球路打擊時的核心肌群活化的情況進行比較。結果：研究結果發現，優秀選手在擊球前主要以豎脊肌、腹橫肌、及腹直肌的肌肉活化，特別是腹橫肌，而大學甲組選手則在腹直肌與腹外斜肌的收縮為主；在擊球後，優秀選手還是以豎脊肌及腹橫肌的收縮為主，而一般選手還是同樣使用腹直肌及腹外斜肌。在打擊不同球路部分，優秀選手在打擊正中球路時使用腹橫肌、腹直肌、與豎脊肌，而在打擊外角球路及內角球路會使用更多豎脊肌，大學甲組選手則使用腹直肌與腹外斜肌。結論：優秀打者與一般打者具有不同的軀幹肌肉活化策略，可針對選手強化腹橫肌、腹直肌、及豎脊肌的肌力訓練。

PURPOSE: The purpose of this case study was to compare the different of core muscles electromyographic(EMG) activation between a professional and an immature baseball hitter during batted the ball which pitch located in middle, inside, and outside corner. METHODS: Two baseball hitters (a professional and an immature player) were participated in the study. The Zebris EMG Bluetooth Measuring System was used to measure the EMG activation of lumbar erector spinae (LES), transverse abdominal (TrA), rectus abdominis (RA), and external oblique abdominis (EO) during batted the ball which pitch located in middle, inside, and outside corner. RESULTS: The result was showed that the primary EMG activation of the professional player is LES, TrA, and RA, and the immature player used more RA and EO before they hit the ball. When hit the ball which pitch located in middle, inside, and outside corner, the professional player used more LES, TrA, and RA during hit the ball located in middle corner and used more LES during hit the ball located in inside or outside corner. The immature players used more RA and EO to hit the ball in any location. CONCLUSIONS: The different core muscles activation strategy was found between the professional and immature batters. The results revealed that LES, TrA, and RA muscle strengthening are needed to reinforce in order to enhance the batting ability.