Abstract
This study sought to examine which technical, physiological, tactical and psychological characteristics at age 15 years contribute to successful soccer performance at age 19 years. Participants were male soccer players (n = 114; mean age 15.4 ± 0.3 years), divided into elite and sub-elite groups based on their performance level at age 19 years. Technical, physiological, tactical and psychological characteristics were recorded when players were 15-year olds. Binary logistic regression analysis showed that performance level at age 19 was clearly associated with technical skills of passing and centering as well as agility and motivation levels recorded at age 15 years. These results extend our understanding of career progression in youth soccer and highlight the multidimensional nature of talent development processes in soccer. Moreover, it seems crucial that coaching support should be devoted to the development of passing and centering skills, agility and motivation in the development of youth players.
Introduction
Identification and selection of youth athletes at an early age is an extraordinary challenge due to complexity and non-linear nature of talent development. 1 However, many national federations and club teams invest considerable resources every year to identify talented players at an early age to ensure that the most talented athletes receive high-quality coaching and training conditions.2–3 Identification and selection of potential athletes have often been based on coaches’ or talent scouts’ subjective views. 3 In recent years, there has been increasing attempts to use scientific approaches to talent identification, including measures of physiological, technical, tactical, and psychological skills. 3–4 Cross-sectional research on youth and adult soccer players has attempted to understand which physiological, 4–6 technical, 4,6 tactical 4,7 and psychological characteristics, 4 contribute to current playing status in soccer.
It should be noted, however, cross-sectional studies in which identification and selection of the youth athletes is based on current performance are associated with low predictive value, and their validity and usefulness have been widely questioned. 2 Due to differences in maturation and development, learning abilities, experience, and rapid changes in physiological and anthropometric characteristics during adolescence, selection of athletes based on current performance levels may prematurely exclude late-developing athletes, who could have the potential to attain excellence in the future. 2,3,8
Since the ultimate aim of talent development is to develop athletes who can later progress to top level, it is crucial to find characteristics which could be used in evaluation of long-term potential for development of youth athletes. 2 However, very few studies have attempted to track the development of young talented athletes into adulthood. 9–12 These studies have found that several physiological characteristics, 9 technical skills, such as dribbling, 10 tactical skills, such as positioning and deciding, 11 and psychological skills such as goal commitment, 12 may predict the long-term career progression of young athletes.
Sport development systems vary in different countries, which may influence the career progression of young soccer players. Countries with elite sport development academies recruit individuals at a young age in order to accelerate the development process of the most talented athletes in a specialised pathway. Competition among recruited athletes is high, and athletes may not be issued a playing contract, if performance levels are deemed insufficient or it is anticipated that he/she is unable to reach the top performance level in soccer. 13 In countries with different recruitment and development systems, development processes may be slower due to less investment in high-quality coaching and training environments of talented athletes. The Finnish sport system exemplifies less formal developmental systems, in which athletic development is based around sport clubs, rather than elite academies or schools. In the sports club environment, the most talented athletes practice and play in the same environment as other athletes, and there are usually fewer resources for specific development of these athletes as individuals because they are part of a heterogeneous group.
Developing players who have potential for success later in their soccer career is of interest to every development system in different countries, especially in those with fewer resources available. Due to challenges in evaluating players’ long-term potential based on current performance level, it is crucial to find characteristics which could distinguish between an athlete’s adolescent performance level and future performance potential. 2 However, there have been few studies using a multidimensional approach to identify factors that might contribute to future career progression in soccer club environments. The aim of this study was to examine which technical, physiological, tactical and psychological characteristics at the age of 15 years contribute to successful performance level at the age of 19 years in a soccer club environment.
Method
Participants
General characteristics (means, SDs) of elite and sub-elite youth soccer players (independent sample t-test statistics and effect sizes).
Procedure
Participants and parents/guardians were first informed of procedures to be used in the study, following which they provided their informed consent prior to participation. Data collection occurred in the athletes’ own practice environments in autumn 2010, after the competitive season in Finland. Measurements for each participant were undertaken according to four categories: technical, physiological, tactical, and psychological characteristics. First, all participants completed self-assessments of tactical and psychological skills in a lecture hall according to standardized instructions provided by the researchers. Second, height and weight of the players were recorded. Finally, technical and physiological tests were carried out in an indoor soccer hall on an artificial grass soccer field. Before these tests, players executed their normal warm-up programs according to the instructions provided by their club coach. After that technical tests were executed following by speed, agility, and countermovement jump tests. This practical session was completed with an endurance test.
Technical characteristics
Two soccer-specific technical skill tests recommended by the Football Association of Finland were used to examine the players’ technical skills. The first test measured dribbling and passing skills (Figure 1). The test started when a player took a first touch, and ended when the finishing line was crossed. The task was to dribble as quickly as possible. The second test measured passing and centering skills (Figure 2). The test started with the player's first touch, and ended with the final pass/cross or if maximum time (90 s) had passed. The task was to score as many points as possible (max. 16 points). Players were allowed to have two practice trials, and the best out of two competitive trials was selected to present players’ technical skills. The rest between two competitive trials in both tests was at least 5 min. The reliability of technical tests was tested with a one week interval test–retest which showed a correlation coefficient of r = .76 (p < 0.001) for dribbling and passing, and r = .70 (p < 0.001) for passing and centering, among a group of 37 soccer players aged 14 to 15 years old.
Dribbling and passing test track. Passing and centering test track.
Physiological characteristics
Speed, agility, explosive leg strength (countermovement jump), and endurance (Yo-Yo test level 1) were measured to examine players’ physical fitness characteristics. A 30 m all-out run from stationary start and agility test were measured with photocells (Newtest Oy, Finland). In both tests, players started 0.70 m behind the photocells which triggered the timer. An eight-figure test track, recommended by the Football Association of Finland, was used as an agility test (Figure 3). The coefficient of variation in sprinting time tests has shown to be approximately 2%.
14
Mirkov et al.
15
have reported 0.84 intraclass correlation coefficient and 2.5% error of measurement for similar type of agility test. Explosive leg strength was measured by countermovement jumping on a jump mat (Newtest Oy, Finland). The coefficient of variation on countermovement jump test is shown to be 2.4%.
14
Endurance performance was measured using the Yo-Yo Endurance Test Level 1.
16
An intraclass coefficient of 0.93 has been reported in the test-retest reliability measure for 20 -m shuttle test among 12 - to 15-year-old children.
17
The best of two trials was selected for further analysis in all physical fitness tests except in the 1-trial endurance test. The rest between two competitive trials in all three tests was at least 5 min.
Agility test track.
Tactical characteristics
A Tactical Skills Inventory for Sports [TACSIS; 18], with subscales of Positioning and deciding, Knowing about ball actions, Knowing about others and Acting in changing situations, was used to assess players’ tactical skills. The inventory consists of 22 items that required the players compare their performance with that of top Finnish players in their age category. Players responded to each item with a six-point Likert scale from 1 (very poor or almost never) to 6 (excellent or always). In previous research, the TACSIS was shown to have good psychometric characteristics. 18 In the current study, the internal consistencies of the four TACSIS sub-scales indicated satisfactory levels, with Cronbach’s alpha coefficients ranging from .73 to .92.
Psychological characteristics
The Psychological Skills Inventory for Sports [PSIS-R-5; 19], with subscales of Motivation, Confidence, Concentration and Mental Preparation, was used to assess the players’ psychological skills. The inventory consists of 29 items that required players to respond with a five-point Likert scale, from 1 (almost never) to 5 (almost always). Items worded negatively were recoded by reversing the 1–5 formats. A high score on each item corresponds to a proposed high value for a psychological skill. In previous research, the PSIS-R-5 was shown to have sufficient psychometric characteristics. 20 In the current study, the four PSIS-R-5 scales indicated good internal consistency, with Cronbach’s alpha coefficients ranging from .71 to .87.
Data analysis
Independent samples t-tests were conducted to investigate group differences in technical, physiological, tactical, and psychological characteristics. Standardized differences in means (effect sizes) were computed for independent samples t-tests, classified according to arguments of Batterham and Hopkins, 21 suggesting nomination of effect size values as trivial ( < 0.2), small (0.2–0.6), moderate (0.6–1.2), large (1.2–2.0) and very large (>2.0).
Binary logistic regression analysis was performed to identify technical, physiological, tactical and psychological characteristics that may contribute to performance level in soccer at the age of 19. Before the regression analysis, all variables were divided into tertiles (low, moderate, high) based on results of the players in this study. Thereafter, binary logistic regression analysis was performed using the enter procedure, with the lowest group as a reference point. Model accuracy was assessed using the Hosmer and Lemenshow test. 22
Results
Technical, physiological, tactical, and psychological characteristics (means ± SD) of elite and sub-elite soccer players at the age of 15 (independent sample t-test statistics and effect sizes).
Binary logistic regression with the lowest group as a reference point.
Discussion
The present study adopted a multidimensional approach in examining technical, physiological, tactical and psychological characteristics of youth soccer players at the age of 15 years, comparing players who reached an elite performance level in the Finnish sport system at the age of 19 years, and those who did not. Due to cultural and social differences in the Finnish sport development system, the career progression of youth Finnish soccer players may be different to soccer players in other countries. A key finding of this study was that, in the Finnish sport development system, elite performance level at the age of 19 years was associated with key performance aspects of passing and centering, agility, and motivation measured at the age of 15 years. The correct classification of elite and sub-elite level players based on these three measures was 86%. This finding suggests that these technical, physiological and psychological characteristics may be valuable in predicting long-term development in youth soccer players in the Finnish sport development system, although it does not deny that a small proportion of players can develop into elite footballers despite not displaying high scores in these measures at age 15 years.
Previous work by Gonaus and Müller 9 suggested that physiological characteristics may be used in prediction of future career progression in youth soccer across different age groups. In the current study, youth soccer players who reached the elite performance level at the age of 19 outscored other players in speed 30 m, agility, and endurance at the age of 15. There was also a small observable difference between groups in performance of the countermovement jump. In addition, players scoring high in agility were about 10 times more likely to reach the elite performance level at the age of 19 years, than low-scoring players. These findings are in line with data from earlier studies, showing the importance of physiological characteristics in soccer, 4,5,13 and also support the findings of Gonaus and Müller 9 about the predictive value of agility in future career progression in soccer. Previous research has shown that the fastest development in physiological capacities usually occurs at the same time as the maximal height spurt at the age of around 14 years. 23 Findings of our study highlight the importance of using this time period effectively in developing physiological characteristics, and especially agility, of young soccer players. The players with better physiological capacities may have a greater possibility of achieving success later in their soccer career, although there is a limitation here. This is because use of physiological data in predicting future performance has been questioned due to advantaging early-maturing athletes compared to late-maturing peers in these characteristics. 2,8,24 In our study, there was significant difference between groups in weight, and also some small observable differences between groups in age and height, which may explain some of the differences between groups in physiological characteristics.
Our study showed that assessing technical skills instead of physiological characteristics may decrease advantages of early-maturing athletes compared to late-maturing peers. Previous studies have shown that dribbling the ball is a discriminatory technical skill in youth soccer players of different performance levels and may even be predictive of future success. 10 In the current study, both technical skills tests (dribbling and passing, passing and centering), discriminated youth players who reached the elite level at the age of 19 years from those who did not. In addition, youth soccer players who scored in the moderate or highest category in passing and centering were about eight to ten times more likely to reach the elite level at the age of 19 than low-scoring players. Technical skills, such as dribbling the ball and passing, are critical to performance in soccer, 4,10,13 and the fastest development in technical skills occurs in the prepubertal years. 25 Based on these key findings from our study, it could be suggested that the focus should be made in developing a wide range of technical skills, such as controlling, dribbling, passing, centering and shooting a ball, in young talented soccer players especially during childhood and early adolescence. The players with more developed technical skills may have a greater possibility of achieving a successful performance level later in their soccer career. It is important to note that technical proficiency in skills such as dribbling may be complemented by enhanced agility of developing players, another discriminating variable. Clearly, youth coaches need to take the opportunity to enhance the skill performance repertoire of learners rather than focus on a limited range of capacities (like focusing on defensive skills only as is more common in the Finnish developmental system [see below]).
The role of psychological characteristics in elite athlete development has been highlighted in many studies.26–28 For example, high motivation has been shown to facilitate skill acquisition, enabling athletes to invest requisite time for practice and commitment to development.26–28 In our study, motivation discriminated between elite and sub-elite players. There were also small differences in concentration between groups. In addition, youth soccer players who scored in the moderate or highest category in motivation, at 15 years, were about seven to 10 times more likely to reach the elite performance level at the age of 19, than low-scoring players. Findings suggested that in coaching process of young talented soccer players, the focus should be made in promoting the development of players’ motivation towards soccer. The motivation of young players may be enhanced by, for example, using tenets of self-determination theory to support their perceived competence, autonomy and social relatedness throughout the talent development process. 29 The emphasis should also be made in developing concentration of young soccer players. A player with a high motivation level may have a greater possibility of achieving success later on a soccer career.
In contrast to findings from an earlier study by Kannekens et al., 11 tactical characteristics appeared not to contribute much to the future performance level of participants in this study. However, statistically significant differences between groups were found for ‘Acting in changing situations', and small differences were also found for ‘Positioning and deciding' as well as ‘Knowing about others'. These findings were partly in line with data reported in earlier studies which have suggested that ‘Positioning and deciding' is a key tactical skill that discriminates between players at different performance levels.11,13 Our findings about the discriminatory power of ‘Acting in changing situations' and ‘Knowing about others' may be, in part, due to the Finnish development system which has traditionally focused more on developing defensive skills of the players compared to attacking skills. Together these findings suggest, that the development of tactical skills, especially procedural knowledge, is important in coaching young soccer players. In the Finnish development system, our findings suggest that a greater emphasis should also be made in developing a range of attacking skills of talented players, such as dribbling in tight spaces, as we argued above.
Although the correct classification of elite performance level at 19 years based on technical, physiological and psychological characteristics in this study was high, the variables together explained only 43% of the variance in the performance level at this age, suggesting that also other things affect future career progression of young players. In this study, players were followed up only until they were 19 years, and their technical, physiological, tactical and psychological chacteristics were assessed only once at 15 years. Concerning these issues, it is possible that some players characterised as sub-elite might develop quickly during late adolescence and reach the elite level in adulthood, even if they were sub-elite at 19 years.
A key methodological contribution of this study was the use of a retrospective longitudinal tracking in identifying multidimensional factors that support career progression in soccer. However, in investigating developing players, the interpretation of these results has been challenging due to large observed variations in the recorded variables at different ages. A key limitation of this study was that, the data did not include information on multidimensional development of these players between the ages 15 and 19 years. Further research is needed to apply longitudinal designs, analyzing the development of players year by year as they progress. In this study, players were also followed up only to 19 years of age, so there is also a need to follow these players further in order to observe which of them would eventually reach elite status (e.g. international level) and professional status (e.g. national level) in their careers.
Conclusion
Our results provided some important insights on understanding of career progression in youth soccer highlighting the importance of the multidimensional nature of talent development processes. In the Finnish soccer developmental system, based on local sports clubs, results clearly highlighted the significance of passing and centering skills, agility and motivation in the development of youth players. By supporting the development of these skills during childhood and early adolescence, youth soccer players may have better opportunities for reaching elite performance level later in their sport careers.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by Sports Institute foundation; and Ellen and Artturi Nyyssönen foundation.