以穿戴式裝置比較不同層級棒球打者軀幹及手部之揮棒技術

Comparison of the swing techniques of the torso and hands between baseball batters of different skill levels using wearable devices

緒論：慣性感測器(IMU)已可準確檢測出棒球打擊的運動學參數。本研究目的是要應用IMU比較甲組與乙組棒球打者在跨步期與揮擊期髖部、胸部與手部之運動學差異。方法：十二位受試者參與研究。六位大專甲組球員，六位大專乙組球員，皆為右打者。三顆IMU分別黏貼於髖部、胸部與右手手背，分析跨步期與揮擊期時間、跨步期抬腳與著地時之髖部側向加速度、髖部旋轉角速度、胸部旋轉角速度以及揮擊期髖部旋轉角速度峰值、胸部旋轉角速度峰值、手部旋轉角速度峰值數據與各部位峰值距離擊球瞬間之時間。使用Mann-Whitney U test檢定，比較棒球甲組、乙組打者之間的運動學差異。結果：甲組打者跨步期時間顯著低於乙組打者(p < .01)，但揮擊期時間甲組顯著長於乙組打者(p < .01)。甲組打者跨步期著地時的髖部側向加速度、髖部角速度、胸部角速度皆顯著低於乙組打者(p < .01)。不過，在隨後的揮擊期中，甲組打者髖部、胸部與手部角速度峰值皆顯著高於乙組打者(p < .01)，並且其髖部、胸部與手部角速度峰值發生的時間點皆比乙組打者更接近擊球瞬間(p < .01)。結論：甲、乙組打者在跨步期著地瞬間的髖與胸部動作、揮棒動作的時間分配與揮擊期動力表現皆有所不同。具體來說，相較於乙組打者，甲組打者會縮短跨步期的時間，並在著地時維持較少的髖部與胸部轉動；著地後，甲組打者會延長揮擊期時間，並在更接近擊球瞬間前發展出較高的髖部、胸部與手部角速度峰值。本研究結果以及以慣性感測器偵測的方法可提供球隊選材、教練與選手增進打擊能力之用。

Introduction: Inertial measurement units (IMUs) have accurately detected kinematic parameters during baseball batting. This study aimed to investigate differences in hip, upper torso, and hand kinematics between elite and sub-elite college baseball batters during the stride and swing batting phases. Methods: Six elite and six sub-elite college players participated in this study. Three IMUs were attached to the hip, upper torso, and back of the batting hand to detect the timing of stride and swing phases, peak hip horizontal acceleration, peak rotational angular velocity, and peak upper torso rotational angular velocity at the foot-off and foot-on of the front foot. During the swing phase, peak hip velocity, peak upper torso velocity, peak hand velocity, and the duration from the three different body position’s peak rotational angular velocity to contact between the bat and the ball were collected. Kinematic differences between elite and sub-elite batters were assessed using Mann- Whitney U tests. Result: The stride phase was shorter in elite college batters than in sub-elite players (p < .01), while the swing phase was longer in elite players than in sub-elite batters (p < .01). The hip horizontal acceleration, hip angular velocity, and chest angular velocity at foot-on were lower in elite batters than in sub-elite batters (p < .01). However, hip, chest, and hand angular velocities during the swing phase were higher in elite batters than in sub-elite batters (p < .01). Moreover, a shorter duration between each body segment’s peak velocity and contact between the bat and the ball was observed in elite batters than in sub-elite batters (p < .01). Conclusion: Elite and sub-elite college batters showed differences in timings, front foot-on, and kinematics of the hip, upper torso and hand during the swing phase. Specifically, a shorter stride phase and reduced hip and chest rotation at foot planting were found for elite batters compared to sub-elite batters. In contrast, elite batters prolonged the swing phase and developed higher hip, chest, and hand velocities closer to impact. This study’s findings and applied method of IMU usage may contribute to performance assessment practices and improving batting skills.