Publication:

大專甲乙組棒球投手投球時下肢動力學的分析

在棒球比賽中，投手對比賽勝負占有60-75%的影響性，顯示投手是影響比賽勝負的關鍵。棒球投手在投擲過程中，由於肢體動作會急速的加速及減速，使得下肢肌群容易發生拉傷等神經肌肉系統的運動傷害。許多文獻著重探討投擲過程投擲臂主要使用的肌群，或是著重於探討投擲臂的運動學、時間及動力學參數。然而，在下肢生物力學相關的文獻中，大部份著重於前導腳的運動學探討，或是下肢於投擲過程之地面反作用力的探討，對於投擲過程下肢承受的關節負荷卻沒有文獻直接而明確地加以探討。目的：本研究在於探討甲乙組投手投球時，下肢關節力量、力矩及功率等動力學參數，以觀察甲乙組投擲機制的異同及可能造成下肢傷害的機制。方法：以三維動作分析系統收集反光標誌的軌跡，並以測力板系統同步收集投擲過程中的地面反作用力量及力矩資料進行分析。以獨立樣本t考驗，比較大專甲乙組投手之間各項參數的差異。結果：在投擲機制的部分，在前導腳著地後，甲組支撐腳關節的壓力皆明顯小於乙組，而甲組前導腳關節的壓力皆明顯大於乙組，顯示乙組支撐腳的推進作用較甲組小，使乙組身體重心偏移較少。在乙組關節力矩最大值有顯著差異的參數皆大於甲組，顯示在投擲時，乙組肌肉對投擲動作的作用較甲組大。在運動傷害的部分，乙組投手前導腳膝關節前向剪力的最大值大於甲組投手，且發生於前導腳膝關節屈曲時，這顯示在相等的投擲次數下，乙組投手罹患膝關節疼痛的風險相對較甲組投手高。乙組在投擲時向心與離心收縮變換的頻率多，且向心及離心收縮持續收縮的時間比例短，使得乙組罹患肌肉拉傷的風險較甲組大。對於棒球投手的訓練，建議加強乙組投手下肢肌群的離心收縮訓練，以避免投擲過程肌肉無法承受急速的離心收縮而引發運動傷害。

In a baseball game, the pitcher is a key point of the game because the pitcher has 60-75% of influence in a successful game. Many studies had focused on estimating the loadings a pitcher sustains at the throwing shoulder or elbow during baseball pitching, but less study investigated the loadings in the lower limbs during pitching. Purpose: The purposes of this study were to estimate the kinetics of the lower extremities during baseball pitching by comparing the different competition level, and the findings could lead to understand the injury mechanics at baseball pitching. Methods: Fifteen collegiate baseball pitchers were investigated in this study. VICON 612 motion analysis system was used to record the trajectories of markers with a sampling rate of 250 Hz. Ground reaction forces and moments of the leading leg and supporting legs were recorded by AMTI force plate with a sampling rate of 1000 Hz. The joint forces of the lower limbs were computed with inverse dynamic method. The difference between the joint forces of the first and the second divisions was tested using an independent t test. Results: The compression forces of leading leg of the first division were lower than the second division after supporting leg contacted floor. It indicated the push off effect of the leading leg of the second division was less to shift the center of body mass than the first division. At statistics, maximum of joint moments of the second division were significant larger than the first division. It showed the effect of the muscles activation of the lower limbs was more substantial than the first division on the pitching. For the sport injury, the second division pitchers had larger anterior force acting on the knee joint of supporting leg than the first division when they flexed knee during pitching. It implied the second division pitchers getting higher risk on the knee joint pain than the first division when both division pitchers with the same pitching numbers. Muscle concentric and eccentric contraction time of the first division was longer than the second division during throwing, and transferring frequency of the concentric and eccentric contraction of the first division was less than the second division. It indicated that the second division pitcher would have higher risk of the muscle strain than the first division. It suggested that strengthening the muscle groups of the lower extremity with eccentric contraction is important for baseball pitchers.