目的：本研究目的在於探討改變棒球縫線之高度、寬度對於棒球飛行過程中水平、垂直之偏移量以及球速之影響。方法：以正常棒球、特製高低縫線棒球與特製寬窄縫線棒球為受試球體樣本，天母棒球場室內牛棚為實驗場地；使用Jugs發球機投擲37.5m/s二縫線直球，搭配使用兩台60Hz之Sony數位攝影機拍攝球體飛行軌跡影像，並且使用SIMI動作分析軟體系統透過3D座標空間轉換，計算球體飛行本壘板前後空間中的水平偏移量、垂直偏移量、球速等運動學參數。結果：顯示在水平偏移方面為特製高低縫線球（總偏移量為0.036m）＞特製寬窄縫線球（總偏移量為0.031m）＞正常球（總偏移量為0.020m）；垂直方面為正常球（總偏移量為0.137m）＞特製高低縫線球（總偏移量為0.128m）＞特製寬窄縫線球（總偏移量為0.123m）；球速方面則無明顯的差異。結論：與正常棒球相比較，改變棒球縫線之高度與寬度會影響棒球飛行過程中水平和垂直之偏移量，特別是高低縫線球會有較大的水平偏移量。由於特製高低與寬窄縫線球在飛行過程中的速度與正常球並無明顯差異，且其飛行軌跡會自動且有規律的變化，因此，選手可以相對於投擲變化球有較低運動傷害風險的直球投擲方法，混合應用正常棒球及不同縫線特性的棒球，以便能模擬出有如實際比賽投手配球的情境，此對於棒球訓練有一定程度的貢獻。

This study investigated the effects of the baseball seams on flying trajectories and velocities. Standard baseballs, high-low seam baseballs and wide-narrow seam baseballs were pitched with two-seam fastball by using the Jugs pitching machine at 37.5m/s in the indoor bullpen. Two Sony digital cameras (60HZ) were used to collect date and a SIMI motion analysis system was used to analyze parameters such as the horizontal displacement, the vertical displacement and the velocity. The result indicated that first, the high-low seam baseball has the most amount of horizontal displacement (about 0.036 m), and the wide-narrow seam baseball (about 0.031 m) also has a bigger horizontal displacement than the standard baseball (about 0.020 m). Second, the standard baseball has the most amount of vertical displacement (about 0.137 m) than the other two kinds of baseballs. The high-low seam baseball (about 0.128 m) has a bigger vertical displacement than the wide-narrow seam baseball (about 0.123 m). Third, three kinds of baseballs have almost the same velocity curve. The findings suggested that changing the baseball seams would affect both the horizontal and vertical displacements of flying trajectories. In particular, the high-low seam baseball has the most amount of displacement at the horizontal axis compared with the standard baseball. Therefore, the baseball with the changing seam could be used and simulated in a real pitching situation during batting practice, because of automatically changing flying trajectory.