| Summary: | 碩士 === 國立成功大學 === 工程科學系 === 106 === SUMMARY
Many studies showed that the hyperabduction is a possible risk factor to overhand athletes. Defined foot contact timing was the start of pitching cycle, and ball release was defined the end of pitching cycle. Twenty four pitchers with shoulder vertical abduction angle under 80 degree and twenty pitchers with shoulder vertical abduction angle over 90 degree, they were recruited in this study. All subjects pitched at an outdoor mound. Three dimensional motion analysis system with 8 CCD cameras were used to measure whole body kinematics at 300 Hz. Pitchers were defined as Group1 (under 80° group) if their throwing shoulders displayed less than 80° vertical abduction angle at the foot contact, and pitchers were defined as Group2 (over 90° group) if their throwing shoulders displayed more than 90° vertical abduction at the foot contact. This study showed that shoulder horizontal abduction angle,shoulder vertical abduction angle, forearm pronation angle, trunk backforwardd angle,trunk rotation angle and pelvis rotation angle were significantly different at the instant of foot contact (FC) between Group1 and Group2. These results indicated that shoulder vertical abduction angle, pelvis rotation and trunk rotation at FC timing changed the pitching mechanism, affecting the upper torso kinetics and kinematics at the whole pitching cycle. It would further affect their accuracy and performance. Further, we found Group2 pitchers didn’t effectively utilize the body rotation during the pitching motion, and it would lead to restraint of the pitching performance. From the result of kinetics, Group2 displayed a greater shoulder force/moment in their throwing arm as compared with Group1. The greater force/moment in the Group2 will increase the loading on biceps, rotator cuff and para-scapular muscle which may further increase the risk of shoulder injuries. Such as shoulder impingement syndrome or thoraic outlet syndrome. Group1 pitchers and Group2 pithcers have similarity in pitching speed. However, Group2 pitchers presented a little faster ball speed than Group1,but Group1 is more accurate than Group2. Group2 with a great shoulder and elbow total work in the arm acceleration phase which can also increase the risk of elbow injuries. These findings are useful for pitchers and coaches to have a better understanding of pitching biomechanics in pitchers shoulder vertical abduction at foot contact. Further training program or improvement ways may be necessary to improve pitching motion and decrease the risk of injury.
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