Kinematic Analysis of Free Vertical Split with 720° Turn in Elite Chinese Rhythmic Gymnastics

This study investigates the kinematic characteristics of the free vertical split with 720° turn (C 807). C 807 is the international designation in rhythmic gymnastics for a free vertical split with a 720° turn. This research holds significant importance in enhancing the technical proficiency of gymnasts and reducing their risk of injury. Eight national-level female gymnasts (age = 20 ± 3 years) performed the C 807. Kinematic data were collected using a 3D motion capture system. The movement was divided into four phases, and Visual 3D (V6.0, CMotion, Germantown, MD, USA) software was used for data processing and analysis. The joint angles of the upper and lower limbs, as well as the torsion angles of the lower limb joints, were analyzed. Key findings included tibial torsion, knee hyperextension in the support leg, and changes in elbow flexion during each phase. The center of mass (COM) trajectory showed that, during the backward preparatory swing phase, COM height gradually decreased and slightly increased before the initiation phase. In the initiation phase, COM height initially decreased and then increased, while the rotation phase showed fluctuating but stable COM height. The results highlight the importance of joint angle control and COM fluctuations during movement. Training should focus on leg swing speed, lower limb strength, knee stability, and upper limb coordination to enhance balance, improve rotation speed, and prevent injuries.