目的：軀幹肌力與背部本體感覺在維持身體核心的動作穩定度上扮演著重要的角色，本研究欲探討這兩項因子對於神經肌肉骨骼系統仍處於發展階段的少棒選手來說，與投球的動作表現有何關聯性。方法：27位已有正式比賽經驗的少棒選手接受邀請參與測驗，腹肌與背肌的肌力採用一坐姿軀幹肌力測量裝置量測最大等長肌力。背部本體感覺以量測軀幹前彎復位誤差角度來評估，此項測驗之軀幹動作角度與投球動作皆以電磁場動作分析系統來測量。球速則以運動用之雷達測速槍測量。以皮爾森相關係數分析腹肌及背肌肌力、軀幹彎曲動作之復位誤差與投球動作及球速的關係。結果：背肌肌力(r=0.629, p<0.001)和背肌與腹肌肌力的比值(r=0.567, p=0.002)與球速有顯著相關；背肌肌力與軀幹前彎最大速度亦有顯著相關(r=0.434, p=0.024)。軀幹彎曲復位誤差與球速和各投球動作參數均沒有顯著相關。結論：較強的背肌及維持適當的背肌與腹肌肌力的比值有助於少棒選手的投球表現；肌電圖資料或許比背部本體感覺測驗更適合當作評估投球動作表現的指標。

Purpose: Trunk strength and back proprioception play important roles in maintaining core stability. This study investigated the relationships between these two factors and throwing performance in youth baseball players .Methods: 27 youth baseball players participated in this study. Isometric trunk flexion and extension strength were measure with a strength dynamometer in sitting position. Back proprioception was assessed by measuring trunk flexion repositioning error. This test and throwing movement were measured using an electromagnetic motion analysis system. Ball speed was recorded with a sports radar gun. Pearson correlation coefficients were used to evaluate the relationships between trunk strength, trunk flexion repositioning error and throwing performance (throwing movement and ball speed). Results: Trunk extension strength (r=0.629, p<0.001) and the strength ratio of trunk extension and flexion (r=0.567, p=0.002) had positive relationships with ball speed. Trunk extension strength also had a positive relationship with maximal trunk flexion velocity during throwing (r=0.434, p=0.024). No relationships were observed between trunk flexion repositioning error and throwing performance. Conclusion: Stronger back muscles and maintaining an appropriate strength ratio between back and abdominal muscles may contribute to better throwing performance in youth baseball players. Electromyographic (EMG) data may be more appropriate than back proprioception assessment to be used as an indicator for evaluating throwing performance in these players.