Evolution of technical and physical match performances in the chinese soccer super league

Resumen

As the most popular sport in the world, soccer is complex and unpredictable. The performance analysis in soccer has a relatively long history, but it is still very young when compared to other disciplines. Soccer has evolved across time because of changes of rules, match tactics and strategies, increases in professionalism, the use of new technologies, global exposure, and transformations in training and player selection process. Understanding these evolutionary tendencies can provide valuable information to estimate, for example, future match and training demands, to assist in the player selection and talent identification, or to predict the impact of rule changes. In practice, for the coach staff, they are not only required to be familiar with the demands of modern players in technical-tactical and physical aspects and potential impact of situational, environmental variables, even the influence of players’ age on these match parameters, but also expected to understand the key performance indicators and their impact along the seasons when determining the match outcome. Purpose: The general aim of the current PhD. thesis is to analyse the modern trends in Chinese soccer performance, with specific reference to the physical and technical performance of matches played in the Chinese Soccer Super League (CSL) between 2012 and 2017. To achieve the aims of this research, this PhD. thesis can be summarized in five chapters and separated into the following three sections. Firstly, identifying the match-related statistics which discriminate between winning, drawing and losing teams in the CSL (Chapter 2); secondly, modelling the effects of situational factors (match location, strength of team and opponent) and environmental-related factors (relative air humidity, temperature and air quality index) on the technical and physical match performance of the CSL (Chapter 3); then, exploring the evolution of physical and technical performance parameters in the CSL (Chapter 4) and determining whether the role of every performance indicator has varied from a long-term perspective (from 2012 season to 2017 season) (Chapter 5); finally, identifying the evolution and influence of players’ age on the technical and physical match performances according to different playing positions in the CSL (Chapter 6). Methods: Data of this PhD. thesis was collected from 1,429 CSL matches from the 2012 season to the 2017 season (six seasons) using a validated live football statistics system—Amisco Pro (Amisco, Nice, France). In Chapter 2, 1,056 balance matches (identified via clustering analysis) of six seasons were selected. Sixteen technical, eleven physical and two situational variables were analysed using one-way analysis of variance and discriminant analysis. While in the next study, the generalised mixed modelling was employed to determine the effects of situational factors (match location, strength of team and opponent) and environmental-related factors (relative air humidity, temperature and air quality index) on the technical and physical match performance, based on the data of all 240 matches in the season 2015 (Chapter 3). Fourteen technical performance-related indicators and 11 physical performance-related indicators were analysed using a mixed linear model for repeated measures, significant main effects of season on teams’ performance were followed up using the Bonferroni correction (multiple comparisons) (Chapter 4). Seventeen technical performance-related indicators, eleven physical performance-related indicators and two situational variables (match location and quality of opposition) were analysed using the Binary logistic regression models to measure the level of association between these factors and match outcome (Win/Lose-draw) over the six seasons studied (Chapter 5). A total of 28,547 matches participation from 923 players (Five playing positions and four age groups) were collected during six seasons, 14 technical performance-related parameters and six physical performance-related parameters were analysed using one-way analysis of variance to determine the difference between four age groups according to their playing position (Chapter 6). Results: Study 1: The results showed that winning teams performed significantly better than losing-drawing teams in the following match-statistics: shots, shots on target, 50-50 challenge won, off-sides, sprinting distance, sprinting effort, sprinting distance in ball possession, high-speed-running distance in ball possession. Losing teams had significantly higher averages in crosses, passes, forward passes, sprinting distance out of ball possession, high-speed-running distance out of ball possession. Discriminant analysis showed that the variables that best discriminated between winning, drawing and losing teams were shots on target, sprinting distance in ball possession, quality of opposition, passes and forward passes. Study 2: Increase in the rank difference would increase the number of goal-scoring related, passing and organising related actions to a small-to-moderate extent (Effect size (ES): 0.37–0.99). Match location had small positive effects on goal-scoring related, passing and organising related variables (ES: 0.27–0.51), while a small negative effect on yellow card (ES= -0.35). Increments in relative air humidity and air quality index would only bring trivial or small effects on all the technical performance (ES: -0.06–0.23). Increases in humidity would decrease the physical performance at a small magnitude (ES: -0.55–-0.38). Teams achieved the highest number in the physical performance-related parameters at the temperature between 11.6 and 15.1 ℃. Study 3: Although there were some irregularities, performance variables generally showed significant upward trends across the six seasons (p<0.05), resulting in significant increases from 2012 season to 2017 season in the total sprint distance (2,069.7±509.3 m vs. 2,272±493.6 m; p<0.001; effect size [ES]: 0.40), number of sprints (100.1±22.8 vs. 104.8±20.8, p<0.001; ES: 0.22), high-speed distance (2,568.4±503.5 m vs. 2,823.1±479.2 m; (p<0.001; ES: 0.52), and high-speed effort (187.5±36.1 to 204.7±33.7; p<0.001; ES: 0.49). Furthermore, there were ~23% more crosses (p<0.001; ES: 0.45), ~12% more shots on target (p<0.001; ES: 0.22), and ~11% more opponent penalty area entries (p<0.001; ES: 0.20) in the 2017 season than in the 2012 season. Study 4: The results revealed that shots on target, possession, total distance in possession of the ball, total distance out of ball possession, and match location exerted a decreased influence on winning the matches from 2012 to 2014 seasons. However, these indicators play a more important role in winning matches from 2014 to 2017 seasons. Additionally, the quality of opposition has a continuously increaseded negative effect on the match outcome. Study 5: The running performance of players decreased as their ages increased, especially for high-intensity running. However, older wide midfielders and attackers (beyond 30 years) who are still playing in the league presented similar physical efforts. Full-backs and attackers performed more passes and forward passes as older the players are. Midfielders take more passes and crosses when they are near 30 years old. Midfielders and attackers have a higher shot ability (number of shots, shots accuracy) when they are older. Conclusions: In the CSL, shots on target, sprinting distance in possession of the ball, quality of opposition, passes and forward passes had more power in discriminating match outcome in balance games. Situational variables had major effects on the technical performance and environmental-related factors affected mainly the physical performance. Besides, physical performance, especially high-intensity running distance, together with technical performance parameters, such as crosses, shots on target, and opponent penalty area entries, have increased over six seasons in the CSL. There are significant trends of factors influencing the match outcome: shots on target, possession, total distance out of ball possession; and match location exerted a decreased influence on winning from 2012 to 2014 season, while its impact increased after the 2014 season. The quality of opposition had an increasing negative influence on the match outcome over the seasons. Lastly, high-intensity running distance decreased as their ages increased. However, older wide midfielders and attackers (beyond 30 years) who are still playing in the league presented higher physical efforts. Midfielders take more passes and crosses when they are near 30 years old. Midfielders and attackers have a higher shot ability when they are older.