1998 年 64 巻 623 号 p. 2429-2436
The purpose of this study is to derive the reasonable lifting movement from analysis of biomechanical characteristics of the snatch, back lift (BL) and leg lift (LL) in a skilled weightlifter. During the snatch lift, the differences between skilled and unskilled lifter appear in EMG and joint torque patterns. The skilled lifter utilizes the double knee bend technique and motor unit recruitment patterns in agonist and antagonist about joint might be reasonable to lift heavy weight. The present data suggest that skilled weightlifter has acquired the higher neuromuscular performance, which is required the control among the recruited muscles with regard to the tension and the timing of the coactivation and the contraction-relaxation. From comparison of BL and LL, it is suggested that BL has higher EMG activity and produces a much higher shear force about L 5/Sl joint which induces a low back injury. In case of LL, the shear force about L 5-Sl joint depends on the lifting posture. Moreover, it is revealed that the skilled weightlifter might have a lower shear force than unskilled person. From the experimental results, it is shown that the detailed instruction about lifting posture is needed to reduce the incidence of low back injury.