Effect of Stored Elastic Energy in the Bending Pole on Performance of Elite Japanese Pole Vaulters: An Estimation Based on Box Reaction Force Vector

Background/Objectives: In pole vaulting, the capacity to store elastic energy within the pole (Epole) significantly influences performance. This study investigated the characteristics of Epole storage by analyzing the box reaction force and vector angle. Methods: Eight male pole vaulters, including World Championships participants, were examined. A motion capture system (VICON) and force plates (Kistler) were used to measure the vector angle (angle between the compression force (CF) and box reaction force vectors) and horizontal velocity of the center of gravity (COG) (Vcogh). Epole was calculated as the integral of the CF (estimated from the box reaction forces), and pole bending displacement. The relationships between each variable and the peak height of COG (HP) were assessed using Pearson’s product–moment correlation coefficients. Results: HP correlated with Vcogh in the pole plant (PP) (r = 0.82) and Epole (r = 0.94). Vaulters with a higher HP maintained a vector angle < 2° between 20% and 80% of the pole bending phase, indicating closer directional alignment between the box reaction force vector and pole chord direction, whereas vaulters with lower HP exhibited larger vector angles (4–8°), associated with a relative reduction in the axial component of force transmitted to the pole. Conclusions: A smaller vector angle effectively enhanced the CF, thereby increasing pole bending and promoting greater accumulation of Epole. Therefore, maintaining a small vector angle may enable more effective force transmission along the pole chord, and vector angle characteristics and PP horizontal velocity may assist appropriate pole selection and training strategies to enhance elastic energy storage and performance.