棒球投手平地與投手丘投球動作的運動學分析

The kinematic difference of baseball flat pitching and mound pitching

目的：平地投球是初學者、傷後復出投手必經的重要訓練，但過去並沒有研究比較平地與投手丘上投球動作的差異。因此本研究的目的希望藉由比較運動學參數找出兩者的動作差異，作為發展訓練方法的依據。方法：本研究對9名男性國中投手（1名左投手，8名右投手，身高171.3±9.6cm，體重62.8±10.9kg）進行檢測，受試者完成熱身後，對前方3m處附有一高於地面80cm，長寬分別為60Ｘ40cm的目標的棒球擋網投擲5個直球，取球速最快的3球進行分析。以10臺紅外線攝影機（Vicon MX13）（200Hz）搭配NEXUS軟體拍攝投手丘上及平地的投球動作，再以Visual3D軟體計算受試者全身的運動學參數，最後以成對t檢定比較兩種情況下運動學參數的差異。結果：有無投手丘主要影響投球時的下肢和軀幹動作，上肢動作則不受影響。在前導腳著地瞬間，投手丘上投手重心垂直方向速度較大，軸心腳膝關節彎曲角度較大，前導腳膝關節彎曲角度較小。在手臂加速過程中，軀幹較前傾。結論：本研究找出投手由平地轉換到投手丘上時，軸心腳在推進時膝關節要更彎曲，前導腳在著地時膝關節要更伸展，手臂加遺時軀幹會有更前傾的角度。投手必需針對這些不同點去做特別調整。至於投手的重心速度如何轉變成球速則需進行更深入的研究。Purpose: Flat pitching is an important training method for the beginners, and rehabilitated pitchers. But no previous study has been investigated the biomechanical difference between flat and mount pitching. The purpose of this study was to compare kinematic differences between these two conditions of the junior high school pitchers. Methods: Nine junior high male pitchers were participated (1 left-handed, 8 right-handed, height 171.3±9.6 cm, weight 62.8±10.9 kg) in this study. After the pitchers warmed up, each one pitched 5 balls toward a 40x60 cm square target which is 80 cm high and 3 m in front of the pitchers. The three fastest pitches hitting on the target were analyzed. Ten Vicon CCD cameras (200Hz) and Nexus software were used to collected kinematics data. Visual 3D software was used to compute the kinematics data. Paired t-test was used to compare kinematic variables between these two conditions. Results: The major significant differences appeared on lower limb and trunk variables, but no significant difference on upper limb. At the leading foot touchdown, the mount pitching had more vertical center of mass (CM) velocity, more pivot leg knee flexion and smaller leading leg knee flexion than the flat pitching. At the arm acceleration phase, the trunk tilts much forward. Conclusion: The results showed the kinematic differences which should be taken notice by coaches and pitchers when pitcher switch from flat ground to the mount. In the future, we can try to find how the CM velocity transforms to ball speed.