Influence of kinematics and muscular activations on pole vault performance Frère J. 1*, Göpfert B.2, Slawinski J. 3, Tourny-Chollet C.4 1
2
* CETAPS EA3832, University of Rouen, France,
[email protected] Laboratory of Biomechanics & Biocalorimetry, University Basel, Switzerland,
[email protected] 3 Research Center for Expertise, Team Lagardère Paris, France,
[email protected] 4 CETAPS EA3832, University of Rouen, France,
[email protected]
Introduction In pole vault, when the pole is fully straightened (PS), the vaulter is reversal and in contact with his pole until the pole release (PR). The maximum height of vaulter’s CG (HP) appears ideally at bar clearance. Since he is suspended from the pole, the vaulter is theoretically able to alter the trajectory of its CG to improve the performance. However, the vertical velocity of the vaulter reached its maximum around PS 1 and decreased until HP. This study focuses on the phase between PS and HP and aims to determine if the upper-limbs muscles activity or the kinematics of the vaulter’s CG are relevant for performance.
Materials and methods Seven experienced pole vaulters performed between 5 to 10 vaults at 90% of their respective best performance. The vaults were recorded at 50 Hz by one video camera between the maximum pole bending and bar clearance. To reconstruct the 2D vaulter’s CG 2 positions, the anthropometric table of de Leva and © the body marks digitization (SIMI Motion , SIMI Reality Motion Systems GmbH, Unterschleissheim, Germany) were used. HP was compared with an estimated maximum vertical height of vaulter’s CG (HPest) at PS time, in considering the vaulter in a free flight from this time. Thus, if HP is higher than HPest, a positive index of performance was obtained, and inversely for a negative index of performance (Fig. 1).
Fig. 1: Calculation of HPest (m) and index of performance (%) from vaulter's CG kinematics at PS time. HCG (m) and v (m/s) are respectively the vertical height and resultant velocity of the vaulter's CG at PS and g is gravity.
The activity of both upper limbs muscles was recorded (Biovision, 2500 Hz, SENIAM-Standard): the deltoideus pars clavicularis, infraspinatus, the biceps brachii, the triceps brachii, and the latissimus dorsi
muscles. The dominant side is the arm connected to the upper handgrip on the pole. The EMG data were averaged by wavelets 3 transformation. Pole vaulters with a positive index of performance and those with a negative index were divided into two groups. The muscular activity was compared between both groups from total intensities 4 and spherical separation in time domain.
Results From the kinematics recorded at PS, HPest was on average 4.64 ±0.21 m while HP was 4.68 ±0.23 m. If, on average, HP was higher than HPest, the difference was not significant (P>0.05). Inversely to HCG and performance indexes, HPest, vertical velocity at PS, and at PS were significantly correlated to HP (r=0.68, r=0.93, and r=0.89, respectively). The performance index varied between -3.30 and 7.47% among all vaults measured (n=24). Four athletes composed the positive index group and three athletes composed the negative index group. The comparison of total intensity of each muscle between both groups did not show any significant difference in this phase of the vault. However, the spherical separation in time domain significantly separated (P
