Can the tumble turn performance be improved by aligning the push-off force vector to the centre of mass trajectory?

The freestyle tumble turn is a critical element of competitive swimming, because an effective push-off from the wall combined with proper body alignment may contribute significantly to overall performance. Previous analyses have focused on variables like peak push-off Force (F_peak) and the Tuck Index (TI), ignoring force direction and body alignment. This study explored the hypothesis that exit velocity (v_out) and turn performance depend on the alignment between the push-off force vector and the centre of mass (COM) trajectory, resulting in better turn performance. High-speed synchronized video and force data (F_peak) were collected from seven trained swimmers performing 21 tumble turns at maximal effort. From these data the COM-force vector alignment was calculated and correlated with v_out and various force components. No significant correlation was observed between v_out and the average angle difference between the force vector and COM trajectory, suggesting that precise alignment is less critical than anticipated. However, a strong correlation was found between v_out and the projection of the force vector onto the COM vector (r = 0.76, p < 0.001), indicating that effective force transfer to the COM is a major determinant of turn performance. Moderate correlations were also found between v_out and peak horizontal and vertical forces. These findings suggest that tumble turn performance may benefit more from efficient force transfer than precise vector alignment. To better understand the efficiency of swimming thrust, the role of vertical forces and phase-specific wall contact mechanics will have to be elucidated.