抄録
Round-off is essential the performance of backward somersaults on the gymnastics floor. However, very few studies have focused on the generation of angular momentum during a round–off. This study investigated the mechanism responsible for generation of rotational movement during round–off. Eight male gymnasts performed a round–off to a stretched backward somersault from a one–leg standing position. Each trial was videotaped using 4 cameras to obtain the three–dimensional coordinate data. A 14–segment link model was used to examine the total’body potential energy, kinetic energy, and angular momentum of the somersault and twist axes. The joint forces and torques were calculated using inverse dynamics. The main results were as follows:
1) In the stepping–in phase, a greater decrease in the potential energy of the head and torso correlated with an increased angular momentum around the somersault axis for the entire body.
2) During the leg swing phase, the angular momentum of the lead leg, head, and torso increased around the somersault axis, with energy primarily transferred from the torso to the thigh of the lead leg owing to the power generated by the joint forces.
3) In the handstand phase, the angular momentum of the lead and trail legs decreased and increased, respectively, around the somersault axis. Energy from the joint power generated by joint forces flowed from the thigh of the lead leg to the torso and the torso to the thigh of the trail leg.
4) In the snap–down phase, the angular momentum of the lead and trail legs decreased around the somersault axis, whereas those of the head and torso increased. The energy generated by the joint forces flowed from the thighs of the lead and trail legs to the torso.
5) In the take–off phase, the body’s position was elevated at the expense of a decrease in angular momentum.
6) The angular momentum around the center of mass for the twisting axis indicated that although the overall angular momentum was zero, the lead and trail legs exhibited positive angular momentum, whereas the head and torso showed negative angular momentum.
