Analysis Of Key Kinematic Factors Affecting The Speed Of Underwater Dolphin Kick

Objective:The purpose of this study is to find out the key kinematic factors that affect the underwater dolphin kick speed by analyzing the video of underwater dolphin kick with full force.Underwater dolphin kick is an indispensable key technical action in modern competitive swimming.Analyzing and finding out the key kinematics factors that affect underwater dolphin kick is helpful for coaches and athletes to improve and optimize their technology.Methods :Based on the full-strength 15 m underwater dolphin leg velocity test of 25 subjects who mastered underwater dolphin kick,the underwater dolphin kick velocity video was taken,and the variables such as velocity,frequency,period,strouhal coefficient,amplitude and joint angle were calculated by analyzing each marked joint point.Results:According to the correlation analysis,the results showed that the underwater dolphin kick was related to the maximum vertical velocity of the shoulder joint and leg,and the maximum angular velocity of the knee joint.the period is positively correlated with the amplitude of each joint,negatively correlated with velocity and negatively correlated with angular velocity.Up-kick and down-kick time is related to up.strouhal coefficient was negatively correlated with mean velocity,positive correlation with amplitude difference between shoulder and hip,and propulsive force.In the underwater dolphin kick,the extension of the joint angle of the leg is inevitable,the extension time of the hip joint is negatively correlated with the velocity,the extension of the knee joint is affected by the hip joint,and the second extension of the ankle joint is associated with the extension of the hip joint resistance.In most subjects,the horizontal velocity of ankle and toe was negative,which was a sign of inefficiency,laborious energy consumption and influence speed.By regression analysis,three sets of equations about average velocity and one set of equations about individual action velocity are obtained.Conclusions:The speed of underwater dolphin kick is variable.strouhal coefficient is the most important kinematic factor for underwater dolphin kick,and the maximum contribution of ankle velocity is the maximum contribution in the contribution of propulsion force.The acceleration of the frequency is achieved by reducing the amplitude and shortening the period.Excessive body ups and downs prolong the cycle.Proper joint angle overstretch helps smooth movement.