THREE-DIMENSIONAL DYNAMIC ANALYSIS OF POLE VAULTING
AbstractINTRODUCTION'-The pole vault is one of the most exciting track and field event. Thus, many mechanical studies have been carried out in order to provide useful information to pole vault coaches and athletes. But, only Barlow (1979) then Gros (1982) realised a dynamic experimental study in two dimensions : they used force transducers to measure the reaction force of the vaulting box. The main contribution of our study is the 3-D approach of the dynamic analysis and the direct measurement of the impulse at the last step before taking off. Two force plates created in our laboratory were used 10 record reaction forces of pole vault trials. The acquisition frequency was 500 Hz. A first force plate put under the pole vault box provided the reaction force acting on the lip of the pole in the three dimensions of the space. Then, a second force plate of the same conception but bigger was fixed under the runway for the measurement of the reaction force at the last touchdown of the foot before the take-off. The both force plates were synchronised using an external electric signal. Such an experimental system allows to compute the total impulse of the system pole-athlete throughout the vault. RESULTS • Before analysing the experimental results, we have filtered the three components of the reaction forces (Fx, Fy, Fz) so as to eliminate the own frequency of the force plates. The knowledge of the dynamics of pole vaulting is necessary for a better understanding of that athletic movement!. Indeed, the simultaneous analysis of the force spelling at the last touchdown of the foot with the runway and of the force applied in the box allows to characterise precisely different events of the v8ult: du ration of the last contact of the foot with the track, impulse al taking-off, time spend between the impact of the tip of the pole in the box and the last touchdown of the foot ... Furthermore, after taking-off, the vaulter contacts the ground through the pole, so a detailed analysis of the reaction force of the vaulting box shows the main phases of a pole vault trials : impact, take-off and rockback, pull-up and turnover and pole release. CONCLUSION • This experimental dynamic system is indispensable in understanding the main phases of pole vaulting and could be a powerful way to improve performances. Nevertheless, that research must be undertaken in collaboration with pole vaulters and coaches because the results will be applied by athletes. Moreover, a program of experimental analysis of pole vaulting has been lead in our laboratory for few years. The dynamic study is also completed with a 3-D cinematographic analysis. Indeed, such a system could allow the measurement or computation of all the mechanical parameters in\l.0lved in pole vaulting and the experimental results could provide to numerical simulations the variation of all the mechanical parameters in order to make them much closer to reality. REFERENCES J. Morlier and M. eid. "Analyse mecanique 3-D du saut ä la perehe". XII French meeting of Mechanics at Strasbourg from the 4th to the 8th of September 1995. J. Morlier and M. Cid. "Three-dimensional analysis of the angular momentum of a pole vaulter". To be published in Journal Of Biomechanics.
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