| Objective: To study the effect of angular momentum generated at the starting stage of Attiu’s rotation on the rotational mass of rhythmic gymnasts of different grades.Methods: Six first-level and six major subjects were selected.VICON 3D capture and acquisition system and Kistler force table were used to collect the kinematic and dynamic data of Atitiu’s rotation motion synchronically,and the ground push moment and angular momentum were calculated.Results:（1）the reverse pre-swing stage（AB stage）is long,which is used to store elastic potential energy by body reverse stretching.The first stage is larger than the torsion amplitude of shoulder axis of athletes in the special class.（2）In the starting stage（BC）,rotational angular momentum is generated by fast swinging of arms and pushing off the ground with the left leg.The moment of pushing off the ground of the athletes in the special class and the angular momentum at moment C are greater than the first level.（3）The single-leg extension forming stage（CD segment）is the resistance turning forming stage.The friction between the sole of the supporting leg and the ground consumes angular momentum.The angular momentum of the athletes of the first and specialized classes at moment C is greater than that at moment D.First order is greater than the angular momentum of the special class at time D.（4）In the rotation stage（DE stage）,the rotation Angle is higher than that of the athletes of the special class;Rotation stability: The distance from the center of gravity to the rotation axis of the first level athletes is smaller than that of the professional class,indicating that the first level athletes have higher rotation stability.In the rotation stage,the rotational angular velocity of all subjects decreased,indicating resistance rotation.Conclusion:（1）the body torsion amplitude of rhythmic gymnasts of different grades in reverse pre-swing stage proves that increasing the body torsion amplitude of pre-swing can effectively increase the angular momentum of priming;（2）The analysis of kinematic and dynamic indexes of rhythmic gymnasts of different levels in the starting stage confirmed that the kicking moment had a decisive effect on the starting angular momentum,and the swinging speed of upper limbs also had a certain effect on the kicking moment;（3）The analysis of body rotation Angle and rotation stability of rhythmic gymnasts of different grades in the rotation stage proves that the angular momentum obtained in the starting stage has a great influence on the rotation mass,that is,the greater the starting angular momentum,the higher the rotation mass. |
