| ObjectiveEstablish a core stability evaluation method that meets the special characteristics of freestyle skiing aerials(aerials).To explore the core stability training movements and basic characteristics of aerials.To analyze the effect of Core Stability Training(CST)on the core stability(CS)and landing kinetics of young aerials athletes,and the relationship between CS and landing kinetics.Method(1)To establish the core stability evaluation method for youth freestyle skiing aerials athletes using testing method,factor analysis and delphi method.(2)Using EMG to test the involvement of core muscle when athletes complete CST movements,the results were quickly clustered and analyzed,and explore the basic characteristics of aerials CST.(3)Eighteen aerials athletes were randomly divided into training group(TG)and control group(CG),which were subjected to an 8-week CST intervention to test the athletes CS indexes.Using a Kistler dynamometer and Vicon Motion System motion capture system,the athletes vertical jump and 360° jump landing kinetics were collected to compare the changes of athletes CS and landing kinetics before and after the training,and to analyze the correlation between CS and landing kinetics.Result(1)Twenty-one CS indexes including 2 dimensions of body shape and conditional ablity were screened.The weight analysis resulted that the fullness(body weight,ketorai index,waist circumference/height*100)in body shape(0.33)and the maximal strength(squat,trunk flexion,lateral tilt,rotation and extension isometric strength)in conditional ability(0.67)were important factors influencing the CS of aerials.(2)The EMG data were analyzed by cluster analysis,and the 37 CST movements were classified into 3 categories: anterior lateral chain,which was dominated by the rectus abdominis and external abdominal oblique;spiral chain,which was dominated by the erector spinae and external abdominal oblique;and posterior lateral chain,which was dominated by the erector spinae and gluteus maximus.(3)Combining the characteristics of aerials techniques and the results of EMG clustering analysis,the basic features of core stability training were summarized: emphasizing exercises in nonstable and non-symmetrical states,close connection between CST and aerials techniques,and reasonable arrangement of CST load.(4)There was no significant effect of 8-week CST on the body shape.The TG had significantly better trunk flexion,lateral tilt,rotation isometric strength,over-top squat,L-sit control,single-leg triple jump,and single-leg closed-eye balance test than the pre-training and CG.The squat,side bridge,and back hyperextension were significantly better in the TG and CG than pre-training.The vertical jump first trough/phase,end/phase,360° jump sagittal axis and frontal axis center of pressure,peak power hip changing range,peak power knee changing range of CG were significantly better than pre-training and CG.In the TG,vertical jump peak power hip changing range,peak power knee range and 360° jump peak power knee range were significantly better than pre-training.In the CG,the vertical jump and 360° jump peak power knee range was significantly better than pretraining.(5)In vertical jump,the second peak/weight was positively correlated with weight and kurtosis index;The peak power hip changing range was negatively correlated with waist circumference.In 360° jump,the first trough/phase was positively correlated with height,chest circumference,waist circumference,weight and kurtosis index;The first trough/phase was positively correlated with chest circumference;The waist circumference/height*100 was negatively correlated with second peak/phase and second trough/phase;The peak power hip range was positively correlated with height and trunk length.(6)In vertical jump,side bridge was positively correlated with first peak time,first trough time,second peak time,and first peak/weight,and negatively correlated with first trough/phase;Trunk rotation isometric strength was positively correlated with first peak time,first peak/weight,and first trough/weight;The first peak/weight was positively correlated with trunk lateral tilt isometric strength,singleleg triple jump,and negatively correlated with single-leg balance;The first trough/weight was positively correlated with the squat,trunk flexion,extension,lateral tilt isometric strength;The 10V-up were positively correlated with the second peak/phase and negatively correlated with the second peak time;The sagittal axes centers of pressure were positively correlated with the back hyperextension;The frontal axis of pressure were negatively correlated with the single-leg balance and the singleleg closed-eye balance;The peak power ankle changing range was positively correlated with the back hyperextension.In 360° jump,trunk rotation isometric strength was positively correlated with first trough time and negatively correlated with end/phase;The trunk extension isometric strength was positively correlated with first peak/weight and first trough/weight;The end/phase was positively correlated with single-leg balance and single-leg closed-eye balance,and negatively correlated with trunk lateral tilt isometric strength,side bridge and single-leg triple jump;The peak power hip range was positively correlated with squat and single-leg triple jump;The first peak/phase was positively correlated with pull-up;The peak power knee changing range was negatively correlated with single-leg triple jump.Conclusions(1)This study established the CS evaluation method for Chinese young aerials athletes and quantitatively analyzed the index test results.The results of the backgeneration test and its application in Study 3 proved the feasibility and validity of the evaluation method,which provided theoretical and practical references for the future scientific exercise training monitoring.(2)Statistical rapid cluster analysis was used to classify the 37 CST movements into 3 categories: anterior lateral chain,spiral chain and posterior lateral chain,and the total stimulation intensity of various CST movements on core muscle groups was calculated by the graphic area algorithm of the plane rectangular coordinate system,and coaches and athletes could select the corresponding exercise movements according to the graphic value or plane rectangular coordinate diagram to improve the targeting of CST for aerial skill athletes.Coaches should follow the following basic features when making CST program for aerials athletes: emphasize CST in non-stable and non-symmetrical state,connection between CST and aerials,and reasonable arrangement of CST load.(3)The 8-week CST has no significant effect on the body form of young aerials athletes,has significant effects on core strength,endurance,balance and lower limb explosive power.CST can reduce the gradient of force change in vertical direction,reduce the displacement of the center of pressure in each direction,improve the stability of human center of gravity and the rate of change of impact load per unit time.Reduce the range of hip and knee joint changes at peak power,improve the lower limb and trunk stiffness,make the trunk in a more upright position to complete the landing cushion,thus reducing the inertia of postlanding rollover,which is conducive to the improvement of landing stability of aerials athletes. |
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