Inter-joint coordination to minimize angular momentum reduction in backward somersault dismounts at parallel bars

Abstract

Backward somersault dismounts at parallel bars in artistic gymnastics are considered fundamental movements for other advanced skills, such as double backward tucked and piked somersaults. It has been previously discussed that angular momentum reduction around the center of mass occurs right before takeoff. However, such angular momentum reduction would decrease the number of rotations during somersaults, making it difficult for a gymnast to perform higher-valued dismounts. We hypothesized that avoiding this angular momentum reduction may be essential for enabling a large number of rotations and tested this hypothesis based on computer-based optimizations. We first determined the best stunt and observed hip flexion in the middle of the stunt, which is an unlikely movement for gymnasts. To avoid conclusions with applications only limited to unusual stunts with such hip flexion, we performed yet another optimization under additional constraints suppressing hip flexion in the middle of a stunt. In both these optimized stunts, angular momentum reduction was observed, thereby rejecting our hypothesis. However, an induced acceleration analysis of these stunts revealed that wrist and shoulder coordination weakened this angular momentum reduction, suggesting the importance of inter-joint coordination for better performance in backward somersault dismounts.