Research On The Relationship Between Kinematics And Myoelectricity Of Female Weightlifters' Snatch Technique

Purpose:The purpose of study is to provide the athletes and coaches with reference to improve snatch techniques by analyzing female weightlifters-Tan Shifang and Tian Donghui's snatches' kinematics,EMG and the relations between these two.Methods:In this study,two German HSVISION SpeedCam MacroVis EoSens high speed cameras and DELSYS EMG Works(?)4.0 EMG test system were used to test the snatch technology of two athletes.Then,SIMI°motion7.0 three-dimensional motion analysis system and DELSYS EMG analysis were used.The system is analyzed and the statistical analysis is carried out on the acquired kinematics(barbell height,barbell speed,barbell acceleration)and EMG data(RMS,EMG time before peak amplitude).Results:By analyzing weightlifters,kinematics and EMG,we can see that:1)At the end of Tan's stretching the knee and bringing the barbell up,barbell acceleration,barbell speed and barbell height are respectively 0.35(m/s2),0.65(m)and 0.40(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 174.87?V and 136.84?V.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they are 0.32(s),0.42(s)and 0.42(s).Tian's barbell acceleration,barbell speed and barbell height are respectively-0.40(m/s2),0.68(m)and 0.45(m)when she almost finishes stretching the knee and bringing the barbell up.Her largest amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are 209.58?V and 171.37?V.And her time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial are 0.33(s),0.35(s)and 0.36(s).2)At the end of Tan's stretching the knee and bringing the barbell up,barbell acceleration,barbell speed and barbell height are respectively 1.78(m/s2),0.81(m)and 0.60(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 387.87?V and 253.72?V.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they are 0.02(s),0.03(s)and 0.08(s).Tian's barbell acceleration,barbell speed and barbell height are respectively 1.11(m/s2),0.58(m)and 0.60(m)when she almost finishes stretching the knee and bringing the barbell up.Her largest amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are 287.04?V and 216.4?V.And her time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial are 0.03(s),0.04(s)and 0.05(s).3)Tan has the secondary force-generation phenomenon at the force starting phase,at the end of force-generation,her barbell acceleration,barbell speed and barbell height are respectively 0(m/s2),1.28(m)and 0.93(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 443.19?V and 383.13?V.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they are 0.02(s),0.13(s)and 0.14(s).The same secondary force-generation happens to Tian,when she almost finishes the force-generation,her barbell acceleration,barbell speed and barbell height are respectively 0(m/s2),1.40(m)and 0.93(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 401.63?V and 266.81?V.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they are 0.15(s)and 0.15(s).4)At the end of inertia rising phase,Tian's barbell acceleration,barbell speed and barbell height are respectively-2.62(m/s2),1.40(m)and 0.93(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 553.01?V and 387.75?.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they are 0(s)and 0.05(s).At the same time,Tian's barbell acceleration,barbell speed and barbell height are respectively-3.42(m/s2),0(m)and 1.29(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 713.27?V and 369.62?V.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they all are 0(s).5)When Tan goes to the phase of squats and muscle support,her barbell acceleration,barbell speed and barbell height are respectively 0.67(m/s2),0(m)and 1.15(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 634.51?V and 302.53?V.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they are 0.04(s)and 0.20(s).At the same time,Tian's barbell acceleration,barbell speed and barbell height are respectively 1.43(m/s2),-0.12(m)and 1.13(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 724.83?V and 322.68?V.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they are 0(s),0.08(s)and 0.08(s).6)At the end of stand-up,Tan's barbell acceleration,barbell speed and barbell height are respectively-0.76(m/s2),0.05(m)and 1.79(m).The amplitudes of the EMG root of medial vastus muscle and trapezius muscle bundle are the largest,which are respectively 281.78?V and 148.42?V.The time of amplitude peak of thoracolumbar fascia musculoaponeurotic layer,deltoid muscle bundle and gastrocnemius medial comes at the earliest,they are 0.08(s)and 0.09(s).Conclusion:The snatch technique of two athletes has shown the structural characteristics of the movement,but both of them have the same unreasonable problems of upper-limbs-and-waist-muscle-groups force's overexertion and disorder.And their force rhythm of snatch technique are not good,so the level of technique movement needs to be improved.