Expert-Specific Trunk and Head Coordination During Rumba Cuban Rocks: A Comparative Analysis of a Former Japanese...

Introduction: Understanding segmental coordination of the pelvis, ribcage, and head is essential for interpreting expert technique in rotation-dominant Latin dance movements. This study examined expertise-related differences in three-dimensional trunk coordination during the Rumba Cuban Rocks by comparing a former Japanese national champion with competitive male dancers. Methods: Seventeen inertial measurement units (IMUs; Xsens MVN Link) recorded pelvis, ribcage, and head kinematics during three consecutive Cuban Rocks across five trials. Horizontal-plane displacements and peak angular velocities were calculated, and the Champion Dancer's values were compared with group means using one-sample t-tests or Wilcoxon signed-rank tests, as appropriate. Results: The Champion Dancer showed significantly smaller medio-lateral pelvic displacement (0.237 ± 0.005 m vs 0.279 ± 0.003 m, P < .01) and larger horizontal-plane pelvic rotational peak angular velocity (3.003 ± 0.173 rad/s vs 2.380 ± 0.168 rad/s, P < .001), indicating a rotation-dominant strategy with reduced sway. Smaller antero-posterior ribcage displacement was also observed in the Champion Dancer (0.038 ± 0.005 m vs 0.057 ± 0.001 m, P < .01). A figure-eight-like ribcage trajectory, identified from visual inspection of the horizontal-plane trajectories, was observed in the Champion Dancer, although this feature was not quantitatively evaluated. Ribcage horizontal rotational peak angular velocity (1.622 ± 0.030 vs 2.186 ± 0.168 rad/s, P < .01) and lateral tilt peak angular velocity (0.485 ± 0.049 vs 0.791 ± 0.071 rad/s, P < .001) were significantly smaller, suggesting moderated transmission of pelvic motion to the upper trunk. Head displacement was markedly smaller, indicating superior stabilization. Conclusion: These findings indicate a hierarchical coordination pattern characterized by pelvis-driven motion, constrained ribcage movement, and high head stability. This study provides biomechanical evidence describing trunk and head coordination during a rotation-dominant figure, offering insight into expert technique and instructional practice in competitive Latin dance.