Sports Biomechanical Analysis On Forward Single And Double Unders

Research Objective: By exploring the four different movements of forward singlerocking and double unders,this paper finds out the characteristics and rules,briefly describes the rationalization of movements,scientifically describes the details of movements and how to improve the quality of movements,the number of completions and the methods of training,so as to provide reference for coaches and athletes.Research Methods: In this study,A total of 52 male rope skipping subjects were recruited and divided into a professional rope skipper group(experimental group)and an amateur group(control group).All subjects performed single single swing,single double swing,continuous single swing and continuous double swing.Three-dimensional motion capture(Qualisys 3D,A12)and force plate(Kistler-3D,9287C)data were collected simultaneously from all subjects(sampling frequency of 100 Hz and 1000Hz),with surface electromyography(DELSYS)data collected from the professional group subjects(sampling frequency of 1.259259e+003Hz).The three-dimensional coordinates were reconstructed through the VISUAL 3D image analysis system for subsequent data processing.The relevant kinematic parameters of the upper limb shoulder,elbow,and wrist joints,lower limb hip,knee,and ankle joints,and electromyographic signals were exported.The mean and standard deviation of the original kinematic and dynamic data were calculated.Corresponding code was written to eliminate DC bias,filter,and rectify the original electromyographic signals,and calculate the integrated electromyographic value and root mean square amplitude.Research Finding:(1)Temporal characteristics: The total duration of the complete double shake motion was longest in the professional group,and the aerial and buffering durations of the double shake motion were longer than those of the single shake motion.The total duration of each motion in the professional group was greater than that in the control group.(2)Upper limb kinematics: During the pre-swing phase,the elbow joint angle of the continuous double shake was the largest,the wrist joint angle was the smallest,and the right wrist joint angle of the single double shake jump was the smallest.The shoulder joint angle of the professional group was smaller than that of the control group,and the elbow joint angle was greater than that of the control group.The angular velocity of the wrist and elbow joints during the double shake was greater than that during the single shake.During the aerial phase,the shoulder-wrist joint angle during the single shake was greater than that during the double shake,and the elbow joint angle was smaller than that during the double shake.The wrist and elbow joint angles of the professional group were greater and smaller than those of the control group,respectively,and the shoulder joint angle of the double shake was smaller than that of the control group.The angular velocity of the shoulder,elbow,and wrist joints during the double shake was greater than that during the single shake,and the angular velocity of the professional group changed less than that of the control group.During the landing and buffering phase,the shoulder joint angle of the single double shake was the largest,the elbow joint angle of the continuous double shake was the largest,and the wrist joint angle of the single shake was the largest.The shoulder joint angle of the single shake in the professional group was greater than that in the control group,and the wrist and elbow joint angles were smaller than those in the control group,while the shoulder,elbow,and wrist joint angles(3)Lower limb kinematics: During the pre-swing phase,the hip,knee,and ankle angles were greater in single-leg swings than in double-leg swings;in the professional group,the hip,knee,and ankle angles and angular velocities in single-leg swings were greater than those in the control group.During the mid-swing phase,the hip,knee,and ankle joint angles were greater in single-leg swings than in double-leg swings;in the professional group,the hip joint angle in single-leg swings and the hip and knee joint angles in double-leg swings were greater than those in the control group.The angular velocity of the hip,knee,and ankle joints was greater in double-leg swings than in single-leg swings;in the control group,the angular velocity of the lower limb joints was greater than that in the professional group.During the landing phase,the maximum hip and knee joint angles were observed in single-leg swings,while the maximum ankle joint angle was observed in consecutive double-leg swings;in the professional group,the hip,knee,and ankle joint angles in single-leg swings were smaller than those in the control group,while those in double-leg swings were greater than those in the control group.The angular velocity of the lower limb joints was lower in single-leg swings than in double-leg swings,and the angular velocity of the hip and ankle joints in the professional group during double-leg swings was greater than that in the control group.(4)Lower limb kinetics: The peak vertical ground reaction force(VGRF)was greater in consecutive double-leg swings than in single double-leg swings(P<0.05).The explosive force(W/kg)was greatest in consecutive double-leg swings(P<0.01).The peak VGRF and explosive force of single and consecutive single-leg swings in the professional group were lower than those in the control group(P<0.01 and P<0.05,respectively).(5)Surface electromyography characteristics: The middle bundle of the deltoid muscle was the main muscle activated during the pre-swing and landing phases in single-leg swings,while the brachioradialis muscle was the main muscle activated during the pre-swing phase in double-leg swings and during the mid-swing phase in single and double-leg swings.Research Conclusions:(1)There are significant differences in the duration,joint angles,joint angular velocity,etc.between forward single and double unders,as well as significant differences between the professional and control groups.(2)During the preparatory swing phase,the swing amplitude and velocity of the wrist and elbow joints,and the angle changes of the knee and ankle joints all contribute to the completion of the jump rope movement.During the flight phase,the speed of the wrist joint and the degree of extension of the lower limb movements help to increase the number of swings.During the landing and cushioning phase,the movement of the shoulder and elbow joints can effectively reduce the swing speed of the rope,while the angle and velocity changes of the lower limb joints help to reduce the risk of lower limb joint injuries.(3)Double unders require more impact force and explosive power on the ground.Therefore,in the training process,it is necessary to consciously increase the preparatory and cushioning time,and also to increase the training of lower limb explosive power while increasing the driving force of the rope,in order to avoid unnecessary lower limb joint injuries.(4)Single unders use more upper arm muscles,while double unders use more forearm muscles.Therefore,in daily jump rope training,strength training of the upper limbs,especially for the brachioradialis,deltoid middle fibers,and biceps brachii,should be included in the training plan.In the early stage of rope skipping practice,amateurs can take the limb shape of upper limb movement as the main practice goal,try to single / double swing rope skipping by fixing the upper arm.In the middle and late stage of rope skipping practice,lower limb explosive force training and upper limb forearm training are added to the training plan.