RESUMEN
Objective To analyze the dynamics of vault springboard designated to using in formal competitions by the Federation International de Gymnastique (FIG), and find a new method measuring the reaction force of the springboard, so as to provide scientific supports for diagnosis of its take-off technique. Methods The stiffness values of GYMNOVA soft and hard springboards were derived by method of material mechanics, then the springboards were then tested with static, dynamic experiments and computer simulations. In the static experiment, two video cameras with the sample frequency of 600 Hz were placed at a 90° angle to capture the deformation of the springboards under the loads of 160, 180, 210 and 230 kg, respectively. In the dynamic experiment, a volunteer performed drop jump (DJ) from a 1.25 m high platform onto the hard and soft springboards, respectively, while a camera was employed to capture the deformation at the sample frequency of 300 Hz. All the three cameras were calibrated using a 2-dimensional framework, and the changes of the board height, velocity under different loads and acceleration of center of mass (COM) of the human body in DJ experiment were all obtained by digitizing the videos using SIMI MOTION software. Finally, modeling and computer simulation were performed to simulate the DJ in the dynamic experiment. Results The equation F=kx+c describing force-displacement of both the springboard was obtained. The depressing displacements of the board under different loads in the static experiment were close to those calculated by the equation. The vertical reaction force curve in DJ calculated by the equation was highly correlated to that obtained by acceleration of COM. The coefficient of multiple correlation was all greater than 0.86. Conclusions The study developed a new method for measuring the vertical reaction force of the springboard based on board depressing displacement and velocity with the help of high-speed camera. This method, which can be employed with convenience to rapidly monitor the board reaction force during take-off, provides scientific supports for enhancement of vaulting techniques and plays an active role in prevention of vaulting injuries.