Kinematics And EMG Characteristics Of Forehand Volley Technique Of Male Tennis Players At Different Levels

Research purposes: In this study,the forehand volley technique of first-and second-class male tennis players was tested and recorded by motion capture system and surface electromyography acquisition system.The purpose of this paper is to analyze the kinematics and electromyography characteristics of forehand volley technique of first-class and second-class male tennis players,compare their differences,provide theoretical data reference for special technical training of second-class tennis players,and provide theoretical basis for coaches,athletes and tennis lovers to improve forehand volley technique training.Research methods: 1.Subjects: There are three national first-class tennis players(age 21 2.64 yr,height 181.33±4.04 cm,weight 68.66±2.30 kg,training years9.66±3.78yr)and three second-class tennis players(age 21 2.64yr;Height174.66±3.51cm;The weight is 64.66±2.51kg;Training years 7.66±1.52yr).2.Experimental scheme: The subject stands at a position 1.8-2m away from the net,and the sender feeds the ball to the forehand position of the subject at the bottom line.It is required that the height of delivering the ball should be above the hip joint and below the shoulder joint of the subject.Test and record the complete forehand volley hitting process of the first-class and second-class male tennis players from the preparation posture to the end of hitting the ball with swing,select the best five hitting actions of each person,and analyze their preparation stage,lead stage,hitting stage and swing with swing.3.Using green pupil vision infrared 3D high-speed camera(sampling frequency is 120 frames/second),the subjects’ motion information is collected.According to the judgment standard of motion stage,the motion is divided into stages and the time is counted,and the required data such as joint angle,joint speed,center of gravity height and hip rotation are derived.In this paper,NORAXON3.14 wireless surface electromyography acquisition and analysis system is used to filter,rectify and smooth the original surface electromyography data,and calculate the muscle discharge time sequence,integral electromyography value and contribution rate.4.Mathematical statistics: The results are expressed by means of mean standard deviation(M±sd),the data are sorted by Excel 2016 and origin2017 64 bit,and the test data are statistically analyzed by SPSS23.0.Independent sample T test was used to compare the differences between the two groups of athletes.P<0.05(*)indicates significant difference,while P<0.01(**)indicates highly significant difference.Research result: In the starting stage,the right shoulder joint angles of the first-classathletes and the second-class athletes are 55.7 and 44.84 respectively,the right elbow joint angles are 51.46 and 37.97 respectively,and the right shoulder joint velocities are 0.76m/s and 0.44m/s respectively,which have significant differences.There is no significant difference in muscle integral electromyography between the two groups,but there are differences in their active muscles.The active muscle in the first group is the posterior part of the left deltoid muscle with a contribution rate of25.29%,while the active muscle in the second group is the right brachioradialis muscle with a contribution rate of 45.3%.At the stage of shooting,there are significant differences in the angles of left shoulder joint and right elbow joint between the first-class and second-class athletes,which are 36.69 and 64.68respectively;52.96and44.04.At this stage,there is a significant difference in the application of the right pectoralis major between the first-class and second-class athletes.The integral EMG value of the right pectoralis major in the first-class group is 110.7u V*s,while that in the second-class group is 27.4u V*s,and their contribution rates are 19.62% and 6.32%,respectively.At the batting stage,there are significant differences in right shoulder joint angle,left shoulder joint angle and hip rotation between the first-class athletes and the second-class athletes.The first-class and second-class hip rotation are 8.71 and-12.89,respectively,and their P values are0.000<0.01.At the swing stage,there were significant differences in the integral EMG values of the right brachioradialis muscle between the two groups at the angle of right shoulder and elbow joint.The integral EMG values of the right brachioradialis muscle in the first and second class groups were 36.02 u V*s and 72.01 u V*s,respectively.Research conclusion: 1.The first-class athletes are more relaxed than the second-class athletes in the starting and shooting stages,and the left hand has obvious active pushing and shooting to help the shooting.2.The first-class athletes make full use of each muscle,while the second-class athletes’ right brachioradialis always in a tense state from the beginning of preparation to the end of swing.Their forehand volley technique is highly dependent on the right brachioradialis,and their large muscles are not fully mobilized.