| Performance analysis has become an indispensable main content in football training and match,especially how to correctly use performance analysis to evaluate the performance level of young football players.The accuracy of the analysis of the performance of young athletes in official football games often affects the continuity of their football careers.The sports performance of football players in the game is a relatively complex system,which is not only a comprehensive manifestation of physical fitness,technical and tactical capabilities,and intelligence,but also affected by the external environment during the game.The sports performance of football players in the game is a relatively complex system,which is not only a comprehensive manifestation of physical fitness,technical and tactical capabilities,and intelligence,but also affected by the external environment during the game.Under the influence of various factors such as the team's game strategy,coaches'tactical arrangement,the ability level of the players on the field,the position on the court,the level of the opponent,the venue,the climate,etc.,the athlete's technical and tactical performance is often in dynamic change.But unlike the analysis of sports performance of adult athletes in competitions,the sports performance of young athletes is inevitably influenced by the special factor of relative age effect.At the same time,experts,scholars and football practitioners from all areas generally believe that the reason for the low level of football development in my country is mainly the lack of reserve talents for football,especially the low quality of talent training is also the key to the development of youth football.At present,there are still many problems in the scientific training of young football players,especially the lack of objective analysis and judgment on the sports performance of young football players.Therefore,how to objectively and correctly evaluate the sports performance of young athletes requires young football coaches and practioners to rethink and understand.This article uses the literature method,expert interview method,experimental verification method,statistical analysis method,and inductive analysis method to re-analyze the content of sports performance analysis and relative age effect in the game,and combined with practical argumentation research to obtain the following results:Study 1:Selected 2051 football players who participated into the National Games in 2017,and 6745 young football players of the U14–U20 age group who participated in the bone age test announced by the Chinese Football Association's official website in 2017 as the research objects.The nonparametric chi-square X2test method was used to analyze the skewed distribution of the athletes'different birth quarters(Q1–Q4),and the meta-analysis method was used to compare the effect value of the athletes'quarterly birth distribution.The results of the study showed that the relative age effect of the competitive series young football players in China exists not only in male groups and also in female groups as well as in diffrenent age groups.The number of birthdates in the first quarter was significantly higher than that in the fourth quarter(p<0.05);The relative age effects of elite athletes in different positions of defenders,midfielders and forwards samely showed significant differences(p<0.05);and espeically for positions with higher physical requirements(ie goalkeepers and central defenders),the effective value of relative age effects were more obvious.According to the OR statistics,the relative age effect increased with the ascending age groups in Chinese men's sports.However,after the female athletes entered the pubertal development period(U16–U20),the relative age effect showed a reverse trend as that in the male athletes..Study 2:Selected 187 athletes aged U10-U16 who participated into the 2019Shanghai Campus Eilte Youth Football Player Training Camp as a research object,adopted 10 and 40 meters sprint,countermovement jump,Straight legs kneeling and pushing solid ball at level of the chest,5×25 one-time forward and back running and T-test.The nonparametric chi-square X~2 test method was used to analyze the skewed distribution of the data results and the athletes'different birth quarters,and the one-way analysis of variance(One-way ANOVA)was used to analyze the athletes'individual performance capabilities and birth quarters.The results of the study showed that there was no relative age effect in the birth dates of athletes of other age groups.Most physical performance were not affected by the birth distrubution(p>0.05).Only part of perfomance showed significance(p<0.05)such as the followings:the effect of relative age has no significant difference among different genders and different ages of Shanghai campus football youths(p>0.05).Most physical performance is not affected by the distribution of birth dates(p>0.05),but some physical performance were affected by the distribution of birth dates(p<0.05),such as:In 10 men's 40-meter sprint,U12 men's T-test and U16 men's40-meter sprint,5X25-meter one-time return running and T-test were found the significant differences(p<0.05).The U10 group's athletes born in the first and second quarters performed better than the fourth quarter(7.70±0.23s),the results in the first,second,and third quarters of the U12 group were better than the fourth quarter(15.71±0.88s),and the 40-meter sprint of the athletes born in the first,second,and third quarters was also found in the U16 group better than the fourth quarter(6.05±0.26s),the 5X25m one-time return running was better in the first and second quarters than the fourth quarter(36.22±1.67s)and the T-test results in the first quarter(12.23±0.4 s)was better thatn the fourth quarter(13.19±0.58s).There was a significant difference between the U10 women's 40-meter sprint running and the U12 women's straight legs kneeling and and pushing solid ball(p<0.05).From the results,the female athletes in the U10 group performed better in the first,second,and fourth quarters than in the third quarter(7.74±0.38s),and in the U12group,results recorded in the first and second quarters were more far than those in the third quarter(2.40±0.12m).Study 3:Due to the regulations that FIFA does not allow athletes to wear any wearable devices in official matches,and the attention of mainstream match performance analysis softwares are not focus on the youth matches,the young athletes'actue physical performance in matches lack objective evaluation and analysis.This study was to develop one video tracking system in cooperation with the professor of computer science at Shanghai Jiaotong University.For the sake of improving the target tracking accuracy of the video tracking system,the Kernelized Correlation Filter(KCF)was used to tracking the phycial performance of athletes in matches.With the field practice testing,paired analysis of variance(Paired Samples T test)and Pearson correlation analysis,this video tracking system was compared with the mainstream sports performance analysis software(Catapult)to verify the effectiveness and accuracy of the system for football games in order to provide objective actual results of physical performance for follow-up research(Research 4).From the statistical results of the research data,there was no significant difference between the two physical fitness monitoring for the athletes in match(p>0.05),and the two statistical results were highly consistent(Cor>0.89).Study 4:The 25 athletes of the Shanghai U20 men's football team participating in the 13th National Games of China were the research object.The vedio real-time tracking system equipment developed by Study 3 was used to track and analyze the sports performance of the research object.The non-parametric X~2 test method was also used,and one-way analysis of variance(One-way ANCOVA)was used to combine the physical fitness or technology to comparably analyze and football players'different birth quarters or positions on the field.The results showed that the Shanghai U20 men's football team,which finally won the 13th National Athlete's U20 group men's football competition,had a significant relative age effect(p<0.05).The number of athletes born in the first quarter accounted for more than half of the total number(52.83%)was significantly higher than the number of births in the fourth quarter(19.05%).The goalkeeper had more obvious height advantage(185.50±3.54cm)and weight advantage(80.00±0.00kg)than other players in the position,and the results was defender>midfielder>forward.A quarterly birth distribution study of 8 athletes whose playing time reached 70%or more of the total time in the 7 games of the Shanghai U20 men's football finals showed that athletes born in the first quarter accounted for 62.5%of the total number,which was significantly more than The number of people born in the fourth quarter(12.5%).From the results of one-way analysis of variance,the technical,physical and shooting performances of athletes who completed the game in 90 minutes are not significantly different from different birth quarters(p>0.05),so the relative age effect did not exist.However,the average number of shots showed that the athletes born in the first quarter had a better performance in shooting the goal than the those born in the fourth quarter(0.60±0.51),and in terms of the average number of shooting missed comparative to the athletes born in the other two quarters,the value should be low(0.40±0.51).Judging from the technical(including shooting)and physical performance related to the position,the technical research results unshowed a significant difference(p>0.05).However,in the total running distance and middle speed running distance of the midfielders and defenders showed significance(p<0.05),the total distance running and middle speed running distance of the midfielders were the largest(10618.13±968.56m and 861.68±280.37m),which were significantly higher than those distance of the defenders(9786.96±806.0m and 568.45±249.52m).To sum up,there was a significant relative age effect whatever for the different age,gender and competitive level of Chinese competitive youth football players.In particular,Chinese young elite football players were in line with the results of the previous researches on the relative age effect of world youth football players.Among the male athletes,the relative age effect enhanced with the increase of age,while it was steply weaken whille the female athletes entering puberty.In Chinese Shangahai campus football,there was no relative age effect among the youth athletes'age distribution,body shape and most physical performance.There were the significance only in some physical performance with the results of relatively early born athelets better than that of those born relatively late.The study on U20National Games men's competition found that the relative age effect showed a significant impact on the number of appearances and playing time of the young football players,but it showed no effect on skills and physical performance.At the same time,there existed certain difference the physical performance and shooting techniques of players in terms of different positions.Therefore,performance analysis in youth football matches should be a comprehensive analysis.Besides of skills and physical fitness,it should also be comprehensively considered the external environmental factors and relative age effects in the match so as to ensure a comprehensive and objective understanding of the athletes'true performance in case of avoiding erroneously evaluated and incorrectly treated for the athletes who are relatively young but with talents in football... |
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