Abstract
BACKGROUND:
Being in peak physical condition and having specific motor abilities are necessity for every top-level soccer player in order to achieve success in competition. In order to correctly assess soccer players’ performance, this research uses laboratory and field measurements, as well as results of competitive performance obtained by direct software measurements of players’ movement during the actual soccer game.
OBJECTIVE:
The main goal of this research is to give insight into the key abilities that soccer players need to have in order to perform in competitive tournaments. Besides training adjustments, this research also gives insight into what variables need to be tracked in order to accurately assess the efficiency and functionality of the players.
METHODS:
The collected data need to be analyzed using descriptive statistics. Collected data is also used as input for multiple regression models that can predict certain key measurements: total distance covered, percent of effective movements and high index of effective performance movements.
RESULTS:
Most of the calculated regression models have high predictability level with statistically significant variables.
CONCLUSION:
Based on the results of regression analysis it can be deduced that motor abilities are important factor in measuring soccer player’s competitive performance and team’s success in the match.
Keywords
Introduction
Using software systems for tracking players during the soccer game gives exact information about players’ movements and field awareness which enables sport experts and coaches to make observations and predictions, as well as training adjustments that would further develop players accordingly to their needs and abilities.
Modern soccer is characterized with a large number of complex movements that require players to constantly acquire information and make decisions in order to anticipate opponents’ attacks and respond to them in adequate manner [1]. Soccer is often regarded as an acyclic sport where rhythm and intensity of the game is regularly changing and where players’ movements have a lot of sudden direction and speed changes [2]. It is estimated that soccer game is structured out of periods of maximum intensity (lasting on average 2–8 seconds) followed by submaximal resting periods that usually last 30–90 seconds [3, 4]. Also, the top players in modern soccer perform an increasing number of prolonged sprinting movements (RSA), pushing the limits of speed and distance covered at maximum speeds (35–38 km/h). By analysis of the matches at the World Cup in Qatar, it is confirmed that players endure increasingly more duels and aerial duels with higher intensity and power. Because of all of the aforementioned, success in soccer competitions is dependent on players being in a peak physical condition with high fatigue tolerance and quick recovery rates [5, 6, 7].
Having specific motor abilities is a necessity for every top-level soccer player in order to achieve success in competition. Goal of these specific motor abilities is to provide answers to different challenges unique to soccer game. During a single soccer game, top-level players on average do 50 sudden accelerations and decelerations that require very intensive concentric and eccentric contractions of thigh muscles, hamstring muscles and their synergists.
Numerous research on the topic of soccer players’ performance assessment, that differ in both methodology and data used, have been conducted in recent years. Lago-Penas et al. have analyzed male soccer competition trying to identify statistics in the matches played that shows difference between winning, drawing and losing teams [8]. Using discriminant analysis, they discovered that key variables that separate winning, drawing and losing teams are: total shots, shots on goal, effectiveness, passes, successful passes, ball possession, yellow and red cards. Bloomfield et al. evaluated the physical demands of English Football Association (FA) Premier League soccer of three different positional classifications (defender, midfielder and striker) [9]. It was discovered that player’s position had great influence on percent of purposeful movement time spent of sprinting, running and jumping. This study showed that players at different positions have different physical demands. Reilly, Rienzi et al., Bangsbo have all concluded that elite defenders and attackers have similar average distance covered (10–10.5 km), while midfielders cover significantly more distance (11.5 km) [10, 11, 12]. Also, it was discovered that defenders and midfielders are most often engaged in activities of low to medium intensity, while attackers perform sprints that are both longer and more common [13]. On the other hand, defenders perform more backward and lateral movements than attackers, which use 20–40% more energy than running forward [14]. Bloomfield et al. recently identified major differences in age, height, body weight and body mass index between top level soccer players at different positions [15]. Buttifant et al. stated that agility is one of the most important factors of the game that need to be monitored in order to completely represent demands of the soccer game [16]. Besier et al. discovered that players need to be put through certain training and prehabilitation processes in order to perform at the top level [17]. Debien et al. conducted research about using joint monitoring information about recovery, performance of professional volleyball players and internal training loads in order to provide essential information about the planning of training [18].
This paper gives insight into the key abilities that soccer players need to have in order to perform in competitive tournaments. This provides useful information, to both coaches and players, that could be used to optimize and control training plan and methodology. Beside training adjustments, this research also gives insight into what variables need to be tracked in order to accurately assess the efficiency and functionality of the players during the monitored games.
Materials and methods
Dataset
The qualitative level of professional football teams and their autonomy introduce certain limitations to the dataset in a quantitative sense. Technical conditions often do not allow access to the players’ data. Namely, it is very difficult to access club databases, due to their protection at the institutional level, as well as the protection of players’ privacy. This limits the synchronization and homogenization of subjects, especially variables for such multidimensional testing. Fortunately, this study was conducted on a relatively large dataset of seventy top-level soccer players, all of whom were playing either for teams competing in the Serbian Super Liga (country’s top soccer league competition): FK Red Star Belgrade, OFK Beograd and FK Radnički 1923, or Serbia national team (ranked 25 on FIFA rankings). Data was gathered during thirty soccer games played across Serbian Super Liga and UEFA club competitions, as well as games played by Serbia national team in 2018 FIFA World Cup qualification.
Data consists of 34 features split into three different groups.
Morphological characteristics:
Body weight (kg) – BW Body height (cm) – BH Body mass index (kg/m2) – BMI Body fat mass (%) – BFM Body muscle mass (%) – BMM
Characteristics used to analyze motor abilities of a participant are given in the list below. All of the loads and mechanics of the movements are carefully selected based on the analysis of the forces and momentums that are being applied on the knee joint and feet [19, 20].
Starting acceleration for 10 meters without the ball (m/s2) – ACC10mWOB Starting acceleration for 20 meters without the ball (m/s2) – ACC20mWOB Starting acceleration for 30 meters without the ball (m/s2) – ACC30mWOB Time needed to cover 10 meters without the ball (s) – V10mWOB Time needed to cover 20 meters without the ball (s) – V20mWOB Time needed to cover 30 meters without the ball (s) – V30mWOB Starting acceleration for 10 meters with the ball (m/s2) – ACC10mWB Starting acceleration for 20 meters with the ball (m/s2) – ACC20mWB Starting acceleration for 30 meters with the ball (m/s2) – ACC30mWB Time needed to cover 10 meters with the ball (s) – V10mWB Time needed to cover 20 meters with the ball (s) – V20mWB Time needed to cover 30 meters with the ball (s) – V30mWB Acceleration index 10/20 meters – AI10/20m (represent quotient of dividing ACC10mWB with ACC20mWB) Acceleration index 10/30 meters – AI10/30m (represent quotient of dividing ACC10mWB with ACC30mWB) Agility without ball on zig-zag test (s) – ZZWOB Agility with ball on zig-zag test (s) – ZZWB Index of ball control skills – IBCS (represent quotient of dividing ZZWB with ZZWOB) Jump without arm swing (cm) – JWOS Jump with arm swing (cm) – JWS 10 repeated jumps (cm) – RJ Aerobic power on Shuttle Run test (m/ml/kg/min) – SHR
Characteristics used to determine soccer player’s competition performance:
Total distance covered (m) – TD Total distance covered with speeds in the range 0–8 km/h (m) – TDW Total distance covered with speeds in the range 8–15 km/h (m) – TDLI Total distance covered with speeds on anaerobic threshold in the range 15.1–19 km/h (m) – TDAT Total distance cover with speeds on VO2max in the range 19.1–23 km/h (m) – TDVO2max Total distance cover with submaximal and maximal speed over 23 km/h (m) – TDMI Percent of effective movements (%) – %EM (represents percent of distance covered with speeds over anaerobic threshold relative to the total distance covered) High index of effective performance movements – HIEPM (represents index of high intensity movements relative to the technical/tactical tasks)
Third group of features was collected during games by using BioIRC Tracking Motion software system, that employs two identical highspeed cameras in full HD resolution and one control camera with “high speed” capabilities. Interface of the tracking software is showed in the Fig. 1a. Software part of the system for digital processing of video recordings (tracking of players movements) is based on determining the level of similarity of the object’s color statistical distribution [21]. This software allows linear, individual and whole team tracking of current position and history of movement of their own and opposing players in any moment or period of time of the analyzed soccer match [22]. Figure 1b shows total trajectory of a single player during a halftime with different classifications based on movement intensity. This tracking gives coaches and experts insight into player’s movement tendencies and play development in the field, which are valuable inputs in analysis and correction of game and training plan [23]. Figure 2a shows quantitative measurements of player’s movement intensity during a halftime and Fig. 2b shows only the player’s movements with the high intensity.
Interface for BioIRC Tracking Motion software system (a); Total trajectory of a single player during a halftime with different classifications based on movement intensity (b).
In order to determine player’s performance, collected data need to be analyzed. In order to summarize given dataset, descriptive statistics were used in order to calculate measures of central tendency and measures of dispersion: mean (X), standard deviation (SD), standard absolute error (Std. Error Aps.), standard relative error (Std. Error Rel.), coefficient of variation (cV%), minimum (Min) and maximum (Max) values.
In order to check equality of probability distribution, Kolmogorov-Smirnov nonparametric test was used. To determine shape of the distribution skewness (SKW) and kurtosis (KRT) were calculated.
Descriptive statistics for the whole dataset consisting of 70 top-level soccer players are given in the Table 1. Looking at the results, it can reliably be stated that dataset is homogenous. Coefficient of variation (cV%) is in the range of 6.21% (for variable BMM) and 45.9% (for variable BMI).
Descriptive statistics of the whole dataset for morphological variables
Descriptive statistics of the whole dataset for morphological variables
Quantitative measurements of player’s movement intensity during a halftime (a); The player’s movements performed with the high intensity (b).
Coefficient of variation results (cV%) are in the range of 4.09% (for variable V30mWOB) and 53.81% (for variable V10mWOB), so it is clear that results of all tested top-level soccer players’ motor abilities are part of the homogenous set. Also, it can be deduced that measured variables are highly reliable given that cV% does not go over 12.52%, except in the case of V10mWOB (cV%
Descriptive statistics of the whole dataset for motor abilities variables
Descriptive statistics of the whole dataset for motor abilities variables
Coefficient of variation results (cV%) are in the range of 9.02% (for variable TDW) and 41.61% (for variable HIEPM), so it can be deduced that results of all tested top-level soccer players’ competition performance variables are part of the homogenous set. Also, it can be deduced that measured variables are highly reliable given that cV% does not go over 41.61%. Results of skewness are in the range of
Descriptive statistics of the whole dataset for competition performance variables
Descriptive statistics of the whole dataset for competition performance variables
Determination of the degree of relationship between dependent and independent variables was accomplished by using one-dimensional and multi-dimensional correlations – Multiple regression analysis. General degree of correlation between top-level players’ competition performance, motor abilities and morphological variables is calculated by using multiple Z-scores – centroid method. Statistical significance of a correlation coefficient is calculated with 95% confidence interval and
Results
Using top-level soccer players’ motor abilities characteristics as independent variables, we are able to determine relationship with key competition performance characteristics: total distance covered (TD), percent of effective movements (%EM) and high index of effective performance movements (HIEPM). Best regression prediction models were chosen based on two criteria:
By the percent of correct model predictions about player movements during the game By the least error of the estimate, or the most precise prediction model
Results of regression analysis using motor abilities variables for predicting total distance covered during a game based on the whole dataset (all players on the pitch) show that general regression model achieved Adjusted R Square of 49.5% with the Standard Error of the Estimate of
ANOVA test results for the best multiple regression model predicting total distance covered
ANOVA test results for the best multiple regression model predicting total distance covered
Optimal regression model used following independent variables: ACC10mWOB, ACC20mWOB, ACC30mWOB, ZZWB, ZZWOB, AI10/20m and IBCS. Table 5 shows coefficients for aforementioned regression model.
Coefficients of the best multiple regression model predicting total distance covered
Optimal regression model is statistically significant given
ANOVA test results for the best multiple regression model predicting HIEPM
ANOVA test results for the best multiple regression model predicting HIEPM
Following motor abilities characteristics were chosen as regression model’s independent variables: ACC10mWOB, ACC20mWOB, ZZWB, ZZWOB, AI10/20m, JWOS, JWS and RJ. Table 7 shows coefficients for aforementioned regression model.
Coefficients of the best multiple regression model predicting HIEPM
Results of regression analysis using motor abilities variables for predicting percent of effective movements based on the whole dataset (all players on the pitch) show that general regression model achieved Adjusted R Square of 46.3% with the Standard Error of the Estimate of
ANOVA test results for the best multiple regression model predicting %EM
ANOVA test results for the best multiple regression model predicting %EM
Described model uses following independent variables: ACC10mWOB, ACC20mWOB, ZZWB, ZZWOB, AI10/20m, JWOS. Table 9 shows coefficients for aforementioned regression model.
Coefficients of the best multiple regression model predicting %EM
The results of regression analysis are based on the fact that motor abilities represent basic measurements of potential/quality of player’s competitive performance, even though they are not the only factors in achieving success in a soccer match. In the competitive conditions of the soccer game, it is necessary to have high level of motor abilities and physical fitness, in order to be able to: respond to sudden changes of tempo and unpredictable high-intensity technical movements, anticipate events on the field and react to them in a timely manner, complete technical/tactical tasks, position yourself correctly etc.
Negative values of coefficient
Using Tracking Motion software system to collect information and regression models to analyze relations between soccer player’s motor abilities and his competitive performance, it is possible to use this system for:
Diagnostics – To evaluate current form of the players Correction of training program – To profile training methods and regiments and predict projected level of competitive performances Prognostic capabilities – To predict competitive results by evaluating current competitive performance of the team
Based on the results of regression analysis it can be deduced that motor abilities are important factor in measuring soccer player’s competitive performance and team’s success in the match. In the modern soccer, especially at the top level, it is necessary to have players with high level of motor abilities in order to adequately respond to game’s physical and technical/tactical challenges. It is especially necessary to be able to perform numerous high-intensity movements and skills at the speeds that exceed 18 km/h.
It can be stated that correlation between top-level soccer players’ level of competitive performance and their general and specific physical conditioning and skills has been confirmed. Based on the results of regression analysis, it can be stated that internal reliability of players’ total distance covered during first and second half of the soccer game, both for team as a whole and per position, is very high. Movements of the whole team (Cronbach
The applicative and innovative importance of this work is reflected in the fact, that in an exact and useful way, it connects the results of soccer players’ performance obtained by laboratory and field measurements with the results of competitive performance obtained by direct software measurements of player movements during the game. Of particular importance is the precise determination of correlations between variables for each line and for the team as a whole. This procedure combines the analytical-diagnostic procedure and predictive factors of morpho-functional and motoric potentials for success in soccer.
Results of this research should be looked as indicators that could be used to follow players’ conditioning and competitive performance, as well as to control and optimize training program. The whole focus of this research was on the physical and functional performance and its influence on the competitive performance of soccer players, which in itself represents an extremely complex and large field of study. However, another very important and complex coexisting filed in the general sport preparation is mental preparations. Study of mental preparations exists within its own complex mechanisms and field, and is complicated enough in itself that it requires special studies and research.
Further studies will focus on obtaining larger dataset by analyzing more soccer games of different teams (more players), with variety in terms of technical/tactical tasks and a level of competition. This would provide the possibility to confirm correlation between variables on a larger sample. There is also a hope that future research will also focus on influence of both mental preparations and physical performance on competitive performance of soccer players.
Funding
The research was funded by the Ministry of Science, Technological Development and Innovation of the Republic of Serbia, contract number (Agreement No. 451-03-47/2023-01/200378). This research was also supported by a project that received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 952603 (SGABU project). This article reflects only the authors’ views. The Commission is not responsible for any use that may be made of the information it contains.
Data availability
Dataset used in this research is a private property of the soccer teams that were part of the study. Dataset contains sensitive information that could give insight into the identity and abilities of soccer players, most of which are still active professionals in the highest soccer competitions.
Ethics statement
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants involved in the study. All the measuring and testing in the research have been performed in accordance with the standards of the Internationa Biological Program (IBM) and Union of European Football Associations (UEFA).
Footnotes
Acknowledgments
The authors have no acknowledgments.
Conflict of interest
The authors declare that they have no conflict of interest.
