| Objective: The pole vault is one of the most complicated track and field events,with the skill of running,jumping,and gymnastics.Run-up and takeoff are considered as the most important stages,which determine success in the pole vault.This study aimed to analyse and compare the biomechanical parameters of different level athletes during pole vault run-up and takeoff,to explore the technical characteristics of the transition between run-up and takeoff,and to build a parameter system and a linear prediction model to effectively and comprehensively evaluate pole vault performance,which provides reference and help for the training and competition of pole vault.Methods: A large-scale three-dimensional(3D)motion capture system(200 Hz)and three force platforms(2000 Hz)were used to collect the kinematics and ground reaction force data of male elite pole vaulters.In the biomechanical characteristics research of pole vault run-up and takeoff and analysis of key biomechanical indicators,5 first class athletes,4 master athletes and 3 international master athletes were analysed.This study calculated the athlete’s center of mass(COM)velocity,COM height,ground reaction force(GRF),lower limb joint moment,mechanical energy of pole vault run-up and takeoff,and the maximum center of mass(COM)height component,pole kinematics,and key biomechanical variables at takeoff.Mann-Whitney U test was utilised for biomechanical parameters between each two groups within international master athletes,master athletes,and first class athletes.Wilcoxon signed ranks test was used between each two corresponding biomechanical parameters of the second-to-last step,the last step,and takeoff.In the factor analysis of biomechanical parameters of pole vault run-up and takeoff,26 biomechanical parameters of 30 successful vaults were analysed by factor analysis,and linear regression analysis was conducted on the extracted factors.Results: 1.Biomechanical characteristics of different level male athletes during pole vault run-up and takeoff,The horizontal velocity of the international master athletes at the last two steps and takeoff was significantly higher than that of the first class athletes(p < 0.05).The horizontal velocity of the international master athletes at the last step and takeoff was significantly higher than that of the master athlete(p < 0.05).In the three support phases,the average peak value of the normalised vertical ground reaction force and horizontal braking force of the international master athletes was lower than that of the master athletes.In the support phases of the second-to-last step and takeoff,the average peak value of the normalised horizontal propulsive force of the international master athletes was higher than the average value of the other two groups.The normalised takeoff mechanical energy of the international master athletes was significantly higher than that of the first class athletes at the last two steps and takeoff(p < 0.05).The normalised mechanical energy of the international master athletes was also significantly higher than that of the master athletes(p < 0.05).2.Biomechanical characteristics of the transition between run-up and takeoff.The takeoff horizontal COM velocity was significantly lower than that of the last two steps(p < 0.05).The takeoff vertical COM velocity was significantly higher than that of the last two steps(p < 0.05).The athletes’ relative COM height at three moments of leaving the ground was significantly different between each other(p < 0.05).The relative COM height of the last step was the lowest,and that of takeoff was the largest.The peak values of normalised vertical ground reaction force of three touchdowns were significantly different between each other(p < 0.05),gradually increasing from the second-to-last step,the last step to takeoff.The peak value of normalised horizontal braking force of the takeoff support phase was significantly higher than that of the last two steps(p < 0.05).The peak value of normalised horizontal propulsive force of the takeoff support phase was significantly lower than that of the last two steps(p < 0.05).The normalised peak hip extension moment of the takeoff support phase was significantly higher than that of the last two steps(p < 0.05).The normalised peak knee extension moment of the last step was significantly greater than that of the second-to-last step and takeoff(p < 0.05),and the normalsied peak knee extension moment of takeoff was significantly higher than that of the second-to-last step(p < 0.05).The normalised peak ankle plantar flexion moment of the last step support phase was significantly lower than that of the second-to-last step and takeoff(p < 0.05),and that of the second-to-last step was significantly lower than that of takeoff(p < 0.05).The normalised takeoff mechanical energy was significantly lower than that of the second-to-last step and the last step(p < 0.05).3.Factor analysis of the biomechanical parameters of pole vault run-up and takeoff.The observations of the Bartlett sphericity test statistic of factor analysis was2213.767(p < 0.01).Three factors were extracted by factor analysis: F1,F2,and F3.The F1 could be explained as the factor related to the athletes’ run-up and takeoff mechanical energy and horizontal propulsion GRF.The F2 could be explained as the factor related to the athletes’ run-up and takeoff velocity and body posture.The F3 could be explained as the vertical velocity of takeoff and the vertical GRF factor.The mean maximum COM height of the 30 vaults was 4.974 m.The score of F2 and F1 increased by 1,and the maximum COM height increased by 0.131 m and 0.112 m,respectively.The F3 did not participate in the prediction of performance.4.Analysis of key biomechanical indicators of male elite pole vaulters.The maximum COM heights of successful vaults between each different level athletes were significant different(p < 0.05).There were also significant differences between H2 of each different level athletes(p < 0.05).The H3 of the international master athletes was significantly greater than that of the first class athletes(p < 0.05).The H2* of the international master athletes was significantly greater than that of the master athletes and the first class athletes(p < 0.05).The pole compression chord length and compression rate of the international master athletes were significantly higher than those of the first class athletes(p < 0.05).The pole compression speed and rebound speed of the international master athletes were significantly higher than those of the first class athletes(p < 0.05),and the pole compression speed of the international master athletes was significantly higher than that of the master athletes(p < 0.05).The takeoff time of the international master athletes was significantly shorter than that of the first class athletes(p < 0.05).Conclusion: 1.As the level of athletes improve,(1)the COM height of athletes raise before releasing the pole accounts for a larger percentage(H2 > 4.0 m,H2* > 0.6 m),indicating a strong ability on the pole;(2)the greater bending of the pole results in higher utilization of elastic energy,faster compression rate(faster than 0.24 m/s)and rebound rate of the pole,and larger kinetic energy;(3)touchdown is shorter at takeoff(less than 0.115 s);(4)the COM velocity,GRF and mechanical energy of the international master athletes indicate their higher sports competence.2.The differences between the biomechanical parameters of the second-to-last step,the last step,and takeoff,including COM velocity,COM height,GRF and mechanical energy,might display the technical characteristics of pole vault movement transition,which indicate the kinematic and kinetic transition characteristics of pole vault from run-up to takeoff.3.According to the factor score and the linear regression model,the technical characteristics of the athletes could be evaluated,and the athlete’s performance could be predicted and explained more comprehensively.4.During the process from the second-to-last step,the last step to takeoff,the normalised vertical ground reaction force and horizontal braking force during the support phase gradually increased,and the horizontal propulsion force gradually decreased.The international master athletes showed different peak characteristics of ground reaction force compared with lower level athletes in three touchdowns,suggesting an optimised run-up and takeoff lower limb movement pattern and force generation strategy.5.Pole vault is a track and field event with personalised techniques.Although athletes from different levels had certain trends in specific biomechanical parameters,the parameters of some athletes were significantly higher or lower than those from the same level and other levels,and some athletes had their own personal transition characteristics during the run-up and takeoff. |
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