ワインドアップポジションとセットポジションからのストレートによる投球のバイオメカニクス的比較：高校野球投手における投球速度および投球動作中の下肢と体幹に着目して

抄録

  The purpose of the present study was to clarify the profiles of the lower limb and trunk motion during baseball pitching in relation to their differences between the wind-up and the set positions, and to determine how the ball pitching velocity can be increased in the set position. The subjects were 12 high school baseball pitchers (age: 16.4±0.5 yr, height: 173.7±4.8 cm, weight: 64.8±8.1 kg). Pitching was assessed using a three-dimensional motion system and 2 multicomponent force plates. It was found that 1) the maximum and average pitched ball velocities were significantly lower in the set position than in the wind-up position, 2) the maximum ground-reaction force of the pivot and stride legs and the impulse of pivot during the stride phase (from the time of maximal stride knee height to the time of maximal anterior push-off force) were significantly lower in the set position than in the wind-up position, and 3) the maximum upper torso/trunk twist angular velocity and the pelvis/upper torso angular velocity at moment of the stride foot contact were significantly lower in the set position than in the wind-up position. These results indicate that 1) the ball pitching velocity in the set position is lower than in the wind-up position. In addition, the factors associated with this lower ball velocity are suggested to be 2) decreased momentum of the pivot leg and 3) decreased rotation motion of the trunk during the arm acceleration phase.
  Therefore, in order to increase ball pitching velocity in the set position, increasing the moment to the rear of the pivot leg during a short period and improvement of lower limb strength/power with the extension movement of the hip and knee joint may be important factors.