| Summary: | 碩士 === 高雄醫學大學 === 運動醫學系碩士班 === 98 === Background: Previous studies have discussed the effect of approaching muscular fatigue on pitching biomechanics, they found that after pitching, there were not only significant changes in kinematics but also in kinetics. As the pitchers’ muscles begin fatiguing, their pitching mechanics may be altered, and this changes may increase the risk of injury. Another study found that the pitchers’ joint range of motion were affected immediately after pitching, and they didn’t recover after 24 hours. There was few studies follows the pitchers’ recovery stage after pitching.
Purpose: The purpose of this study is to investigate the effect of fatigue on baseball pitching. Furthermore, the relationship between recovery time and fatigue after pitching will also be investigated.
Methods: Twenty high school male pitchers were recruited in this study. The Biodex was used to measure pitchers’ muscle strength after warm-up and pitching. Goniometer was also used to measure the joint range of motion of each pitcher. All pitchers were observed for the following three days. A repeated-measure analysis of variance was used to compare muscle strength and range of motion data between pre-pitching and the following three days. Pair t-test was used to compare the differences between dominant hand and non-dominant hand in muscle strength and range and motion.
Results: Regarding to muscle strength data, there were significant decrease in empty can test (p = 0.033) and shoulder abduction (p = 0.001) after pitching. There were significant decrease in shoulder internal rotation (p = 0.038) and external rotation (p = 0.026) in day1 after pitching. The joint range of motion (ROM) in shoulder external rotation increased after pitching. But the dominant hand compared with non-dominant hand in ROM, there were significant decrease in shoulder internal rotation, and significant increase in shoulder external rotation. The kinematics analysis by motion system found that most of the subjects’ shoulder external rotation angle increased at maximum shoulder external rotation, and knee flexion angle decreased at the instant of ball release in the last ten pitching performances. All the pitchers’ ball velocity decreased significantly.
Conclusion: In pitching practice, it may reduce muscle strength in shoulder abductors and rotators. Decrease in shoulder internal rotation angle was also observed. This could be the risk of factors for throwing injuries among baseball pitchers. The effect of muscle fatigue on pitching motion was apparent at maximum shoulder external rotation and ball release. The shoulder external rotation angle increased at maximum shoulder rotation and elbow extended earlier at ball release after muscle fatigue. The immediate effect of muscle strength and range of motion recovered from fatigue after at least two days rest. Therefore, the fatigue resulted from this pitching simulation were recoverable. Furthermore, this pitching practice maybe acceptable for high school pitchers.
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