| Shuttlecock is an emerging modern sports project,inherited from the Chinese folk game shuttlecock-kicking,and combined with the rules of modern ball games.It is characterized by simple equipment,easy development,strong skill,high ornamental value,and wide popularity.It has become one of the most popular sports mong men and women,old and young in recent years.In order to make shuttlecock more extensive at home and abroad,boosting the all-in fitness,and it is indispensable to carry out the competition of shuttlecock,for which the basic research,such as the optimization and improvement of action technology,professional physical training,etc.,is indispensable.Biomechanical research is a common means of improving motion technology.The existing methods of sports biomechanics are used to study the commonly used movements,and analyze its action principle,which helps to improve the athletes' exercise technology so as to improve their performance.Based on this,through collecting and analyzing the body kinematics data and the EMG data of major surface muscle groups of shuttlecock players when they perform four different serve technique actions,this study explores the biomechanical laws of different serve techniques,and compare the differences between them so as to provide theoretical reference for shuttlecock players and coaches in technical and physical training,.Based on the above objectives,the main methods used in this study are: through the use of 3D motion capture system and surface electromyography test and analysis system,the body kinematics data and the EMG data of 22 major surface muscles on both sides of their body when the players perform four different serve technique actions were collected,and the experimental results were obtained by post-processing and statistics.The main results of this study are as followed:(1)According to the swing cycle time-length ratio,the three stages of the positive instep serve are similar to those of the medial part of the foot.The initial and middle swinging stages of the arc ball on the outside of the foot were obviously less than those of the other three serve movements,and the end of the swing was significantly longer than the other three serve movements.The swinging of the instep volley serve is obviously longer than the other three serve movements at the beginning and the end of the swing is obviously less than the other three serve movements.The reason for this result is that the motion space distance of the swing of the instep volley serve is larger than that of the other three types of serve in the initial stage,and the relative proportion of the end of the swing is less because the speed of the swing is faster than the other three kinds of serve movements at the end of the swing.2)In terms of the speed and acceleration of the four serve actions,the maximum speed of the toes of the instep volley(13.90±0.93)and the maximum acceleration(363.74±47.64)were significantly greater than the other three service movements(P<0.01).From the range of joint movements of the whole action cycle,the difference between the two hip joints of the four types of tee movements was very significant(P<0.01);the knee joint results showed that the knees between the four tee movements The differences in the range of motion of joints were very significant(P<0.05).The results of ankle joints showed that the differences in the range of motion of most ankle joints of the four types of tee movements were very significant(P<0.01).The overall results show that the range of motion of the lower limbs of the lower limbs is greater than that of the other three types of tee movements.(2)In terms of the velocity and acceleration of the four serve actions,the maximum velocity(13.90 ±0.93)and the maximum acceleration(363.74 ±47.64)of the toe tip of instep volley serve were significantly higher than those of the other three serve movements(P < 0.01),and the maximum velocity and acceleration of the tip of the four serve movements were significantly higher than those of the other three serve movements(13.90 ±0.93)and(363.74 ±47.64)respectively.According to the range of joint activity in the whole motor cycle,there were significant differences in most of the hip joints between the four serve movements(P < 0.01).The results of knee joint showed that there were significant differences in the range of knee motion among the four serve movements(P < 0.05).The results of ankle joint showed that there were significant differences in most of the ankle motion ranges among the four serve movements(P < 0.01).The overall results show that the range of movement of the three joints of the lower limbs is larger than the other three serve movements.(3)The amplitudes of the biceps humerus muscle and gastrocnemius muscle and biceps femoris were larger in the four types of serve motion in the early stage of swinging,and the amplitude of the root mean square root in most muscles was higher in the middle period of swing than that in the middle part of the swing.The amplitudes of muscle root mean square in the late swinging stage of the four kinds of serve movements are at a low level,the reason is that the muscles mainly play the role of buffering and stabilizing the body at the later stage of swinging.During the whole serve stage,some muscle integral EMG values appeared higher at the early stage of swinging,and most of the muscle integral EMG values at the middle swing stage showed higher values,and some muscle integral EMG values at the end of wobble were higher than those at the end of wobble stage.Most of the muscle integral EMG values were at a low level.The results of muscle contribution rate showed that the contribution rate of the three stages of four serve movements was mainly concentrated in the lower extremities and the biceps brachii muscle was also included in the early stage of swinging.The main conclusions of this study are as followed:(1)The kinematic data show that in the four common shuttlecock serve movements,the proportion of swinging in the initial stage,the middle swing stage and the end swing stage is different,and the three stages of the foot arch serve are similar to those in the medial part of the foot,and the three stages are similar to those in the inner part of the foot.The initial and middle swinging stage of the outer hair arc ball was less than that at the end of the swinging stage,but the last stage of the swing was much more.The initial swing of the instep volley serve is more,and the end of the swing is less.The results of speed and acceleration show that the inside of foot serve is small in speed,good in stability and small in threat to the opponent,and the instep volley serve is fast,poor in stability and high in threat.(2)The angle of the three joints of the lower extremities showed the trend of decreasing first and then increasing,and the range of the joints of the instep volley serve movement was obviously larger than that of the other three serve movements.The serve that needs the biggest torso twist is the instep volley serve,the second is the arc serve by the lateral foot,the standing instep serve,and the the serve by the inside of the foot.(3)The data of surface electromyography(EMG)show that in the middle stage of swinging human body uses the most muscle groups,and the degree of muscle activation is relatively large,and the number of recruited muscle fibers is also larger.At the end of wobble,some muscle groups were activated because of the adjustment of body posture,and the lower limbs were the main ones.The integral electromyography(EMG)of the left and right sides of the three swinging stages of the four kinds of serve movements was larger than that of the quadriceps femoris muscle and gastrocnemius muscle of the lower limb.The results showed that the degree of co-activation of most of the left side was lower than that of the right,the degree of ankle co-activation was generally lower than that of hip joint and knee joint,and the degree of co-activation was higher at the beginning and middle of the swinging of the instep volley serve. |
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