青少年棒球投手投球量累積對投球動作之影響

Effects of accumulated pitching volumes on pitching mechanism in teenage baseball pitchers

緒論：在青少年棒球選手眾多損傷因子中，最為相關的是過多的投球量，因此對球數累積後所造成的負荷對投球動作、運動表現改變以及肩肘損傷因子的評估是值得去探討的。故本研究目的在探討青少年棒球投手在投球量累積後，投球動作運動學與動力學的變化。方法：招募36名男性國中青少年投手參與實驗，使用六台紅外線高速攝影機(Motion analysis corp, 250 Hz)、一塊測力板(Kistler, 2500 Hz)，並搭配使用雷達測速儀收取實驗數據。實驗以模擬比賽形式進行，開始前先收取5球投球動作作為前測資料，再來研究對象需進行五局、每局20球的投擲，在整個投球試驗共會投擲100球，並以最後的5球作為投球數累積的後測數據。使用成對樣本t檢定進行前、後測投球運動學與動力學參數差異之分析。結果：發現青少年投手投擲100球後，為中到中高程度疲勞，並且球速顯著下降。骨盆軀幹與上肢關節動作的運動學變化，集中出現在手臂加速期。在肩關節最大外旋時，肩水平內收、肘屈曲角度減少，肩外旋、骨盆軀幹旋轉、軀幹屈曲角度增加。球投出手時，骨盆旋轉、軀幹屈曲角度增加。動力學則是在球出手時前導腳的垂直力量減少、伴隨前後方向衝量增加。結論：青少年棒球投手在投球數量累積後，會產生疲勞的現象，除了球速下降外，也會出現代償動作使投球機制改變，從而增加上肢傷害的潛在風險。基於保護選手的立場，青少年棒球投手投球量的限制與監控是必要的。未來可再進一步探討其關節受力變化，可以更完整的了解投球機制變化趨勢與可能損傷風險進行後續討論。

Introduction: The workloads of baseball pitchers are significant risk factors for injury in adolescent players. Increased pitching volumes and repetitive throwing may result in overuse injuries and alter the pitching mechanism, increasing the risk of pitching-related injuries to the elbow and shoulder. This study analyzed the effects of accumulated pitching volumes and changes in the pitching mechanism's biomechanical parameters among adolescent baseball pitchers. Methods: We recruited 36 teenage male right-handed baseball pitches who use an overhand delivery. After warm-up, each subject performed five pitches as the pre-test data collection. Each participant then pitched five simulated innings, consisting of 20 pitches per inning with 8 minutes of rest between innings. Each participant threw 100 total pitches, and the last five pitches were used as the post-test data. A motion analysis system with six cameras (Motion Analysis Corp, 250 Hz) was used to collect 3D reflective marker trajectories, and joint kinematics were calculated. A force plate (Kistler, 2500 Hz) was used to collect ground reaction force (GRF) data from the stride leg. Ball speed was measured by pocket radar. Muscle fatigue levels were assessed by self-reported rating of perceived exertion (RPE) and visual analog scale (VAS). A paired t-test was used to compare differences between pre-test and posttest pitching biomechanics parameters. Results: The results showed that pitching velocity was significantly decreased (p = .001), and both RPE and VAS were significantly increased (p < .001) after pitching 100 balls. Alterations in pitching kinematics were primarily noted at the pelvis, trunk, and upper arms during the acceleration phase of the pitching cycle. The vertical GRF of the stride leg at the point of ball release significantly decreased (p = .012), and anterior-posterior momentum significantly increased (p < .001). Conclusion: Teenaged baseball pitchers became fatigued after repetitive pitching, and pitching velocity decreased as pitching volume accumulated. In addition, compensatory alterations to the pitching mechanism following fatigue might increase the potential risk for upper arm injuries. The pitching volumes of teenage pitchers should be monitored during games and daily training. Future studies should include joint kinetics during pitching to effectively discuss the related risk of injury.