One of the most widely used strategies for performance analysis in different sports is notational analysis through direct observation of technical-tactical actions, which allows to understand the main indicators of sporting performance of the players, both individually and collectively. Football goalkeepers (GKs) are involved in the game differently when compared to the rest of the players in the team and, therefore, they develop different high-level and high-intensity tactical-technical actions. Therefore, the present work aimed to analyse the different performance indicators of football GKs through a search in the following databases: Web of Science (WOS), Scopus (Elsevier), PubMed (NIH) and, SPORTDiscus (EBSCO), until February 2023. The following keywords were used: "Football" or "Soccer", "Goalkeeper" and "Performance analysis". The results show that the main performance indicators are the percentage of avoided goals, the distribution of the ball at the goal kick as well as the number of offensive and defensive actions. Therefore, training sessions should be planned and implemented aimming to improve these skills.
One of the most widely used strategies for performance analysis in different sports is notational analysis through direct observation of the technical-tactical actions of athletes during training sessions or competitions.1–3 In addition, the use of inertial devices has recently been implemented, as they allow the quantification and control of training and competition loads, as well as identifying the physical demands of the players.4 This whole process will allow the coaching staff to obtain data regarding the sporting performance of the team and, specifically, of the players, as well as to provide feedback to the athletes through notational analysis,5,6 to improve technical-tactical situations.7,8
Performance indicators are a combination of actions that describe the performance aspects of a sport, presenting a direct link to success in matches, final ranking, and medal winning.3 Therefore, knowledge related to performance indicators will provide the coaching staff with information regarding the strengths and weaknesses of the players and the team,9 through a qualitative and quantitative approach, as well as allowing to identify and extract relevant data on technical-tactical behaviours.10 On the other hand, the knowledge of performance indicators will allow the creation of an ideal performance profile, which must be developed to present a high performance level.7 Furthermore, a good analysis of performance indicators can make a difference at the sporting level.
This analysis has been carried out in different sports modalities. Football is the most studied sport worldwide,for this reason, goal-scoring opportunities,11 ball possession,12,13 and shots on goal14 have been analysed as the main performance indicators in professional football teams. Therefore, the variables that differentiate winning and losing teams are shots on goal, the number of successful passes, as well as the quality of defensive and attacking actions in the game, with winning teams presenting the best values.15 In addition, match results can be influenced by the location (home or away), and by the ranking of the team.16 On the other hand, due to the Covid-19 pandemic, these indicators have been influenced, with an increase in free kicks, and a decrease in yellow cards, tackles, and attacks.17 However, studies related to sporting performance indicators in football goalkeepers (GKs) are scarce.
However, football GKs have a different involvement in the game compared to other players in the team and perform different high-level and high-intensity tactical-technical actions,18 which can directly and decisively influence the rhythm and direction of the team,19 and result of the football game. Consequently, research has focused on the analysis of the offensive and defensive tactical-technical actions of GKs,20,21 to find out the main performance indicators of GKs, depending on the level of the team22 and the final result of the competitive match.23 In addition, the pedagogical variables that influence the design of training tasks for GKs24 have been . From a defensive point of view, the action of the football GKs focuses on defending the goal, to prevent goalscoring by the opposition team.25 On the contrary, in the offensive process, the GK is fundamental in the construction of the attack26 and is influenced by different conditioning factors of the visiting team, such as high pressure.27
Therefore, given the scarcity of specific research related to the study of individual performance indicators in different sports,16 the main objective of this study was to analyse the main specific performance indicators of football GKs through a compilation of documents from different databases.
Material and methodDesignThis study is framed within the Theoretical Studies.28 A "Process of compilation and selection of studies" was carried out, aiming an update, comparison, and critical analysis of theories or models in a specific field,29 to identify and analyse the documents related to the performance indicators of football GKs, to update the knowledge related with this topic.
Criteria for study selectionTo select as many manuscripts as possible related to the subject of the study, a series of inclusion and exclusion criteria were established (Table 1).
Inclusion and exclusion criteria for selecting documents related to the topic.
For the search of documents, Web of Science (WOS), Scopus (Elsevier), PubMed (NIH), and SPORTDiscus (EBSCO), databases were used. The search was conducted in the four databases, using the keywords, "Football" or "Soccer", "Goalkeeper" and "Performance analysis", in which 256 manuscripts were collected, up to February 2023. To reduce the bias of the identified papers, the search process was carried out by two different researchers (VH-B and JMG). Both results were merged, and the previous inclusion and exclusion criteria were applied. In case of disagreement, a third expert was consulted to obtain agreement (MCE). A total of 12 documents related to the subject of the study were included. A systematic review methodology was used, which is in full swing in the field of Sports Sciences due to being an agile and easy-to-use method, as well as allowing researchers to classify the documents according to specific variables30Fig. 1 shows the flow diagram related to the search procedure used.
Variable codification
The manuscripts selected for the study sample were classified based on different variables. Different guidelines established by previous researchs were followed.31 Also, to increase the analysis of the documents and extract more relevant results about the object of study, a series of subject-specific variables and variables for the analysis of the methodological quality of the manuscripts have been specified. This will allow researchers to carry out an exhaustive analysis of the different documents.
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General Variables: Author/s, Year, Title y Main purpose.
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Specific variables of the documents: Keywords, Type of document, Database, Type of study, Sample 1, Sample 2, and Sport Science discipline.
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Specifics variables related to the topic: Instruments used, Actions studied, Variables analysed, and performance indicators.
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Methodological quality variables of the studies: Quality of the documents.
A procedure for registering and classifying studies previously used in the field of Sports Sciences has been carried out, as it is an easy, flexible, and agile methodology for its development.30 It allows the classification of the documents according to the different variables selected by the authors.31,32 In the same way, this process is characterized by the development of a series of phases, as this is one of the most important premises when carrying out a systematic review of the literature.33Fig. 2 shows the phases that have been followed.
Phase 5, corresponding to the analysis of the methodological quality of the documents, was performed based in the Law et al.34 questionnaire. For the evaluation of each of the documents, a process of selection of external experts was carried out, who had to meet a series of inclusion criteria associated with knowledge of the review topic:
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To have doctoral degree in Sports Sciences.
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To have knowledge and experience in training for football GKs (minimum 5 years).
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To be a football coach (level 1, 2, and/or 3).
Firstly, a total of ten experts were selected to perform the evaluation process. After implementing the inclusion criteria, the number of experts was reduced to six. The level of voluntariness of each of the experts for participation was considered. A process of training and familiarization with the questionnaire was carried out, to increase the reliability of the scores to be made. This training and reliability procedure had four stages35: 1) Preparatory stage, 2) Selection stage of the coders, 3) Training stage of the observers and, 4) Reliability stage. Finally, an analysis of intra-observer reliability (p = 1.0), and inter-observer reliability (p = 0.93) was performed. This reduced the risk of bias in the scores, as well as brought greater reliability and validity to the process of evaluation. After scoring the manuscripts, a score was given to each paper based considering the average of the scores given by the experts, thus obtaining its methodological quality36:
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Excellent methodological quality (A), scores upper than 75.
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Good methodological quality (B), scores between 51 and 75.
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Low methodological quality (C), scores lower than 50.
To determine the reliability between the different observers and the scores a reliability analysis was performed. Multirater Kappa free37 index was used, to find out if the experts assessed equally. The value of 1.0 was the most reliable reference.38 The software used for the analysis was the Statistical Package for the Social Science (v27, 2021,IBM SPSS, Armonk, NY, USA).
ResultsThe documents selected are shown in Table 2 according to the general and specific variables of the documents and to the specific variables related to the topic and the methodological quality variable (Table 3).
General and specifics variables of the documents.
Id: Item of the documents; TD: Type of documents; DB: Database; S1: Sample 1; S2: Sample 2; SSD: Sport Science Discipline; JA: Journal Article; Quant.: Empirical study with quantitative methodologic; NS: No specified, TS: Theorical study.
Specifics variable related to the topic and quality variable.
A: Excellent methodological quality; B: Good methodological quality.
This study aimed to compile a collection of documents related to the study of individual performance indicators in football GKs, to understand the main actions and variables of the study, as well as the instruments used to analyse the different game situations.The results of the systematic review highlight that there are few documents related to the study of the technical-tactical actions of football GKs. The main indicators of individual performance in GKs are offensive actions (short ball movements, long ball movements, etc.), defensive actions (blocks, deflections, clearances, etc.), actions related to physical preparation (sprint, the intensity of movement, distance covered, impacts, etc.), and actions related to psychological requirements (attention and concentration routines, patterns for penalties, etc.). In football, the GK is the key player in initiating attacking and defensive plays.24,25
Regarding the databases, most of the studies are indexed in WOS (n = 11), as it is one of the platforms with the largest number of scientific documents. All of them have been published in scientific journals, using theoretical studies (n = 1), or empirical studies with quantitative methodology (n = 11), in which 66% of the manuscripts have been published after 2018. In the scientific literature, we did not find previous documents with the same results as ours, however, it can be affirmed that the GK actions are determinant in the offensive and defensive process of a football team.21,27 Therefore, research related to GKs in football is a topic of recent interest by researchers, mainly focused on the analysis of training and competitive information, to comprehensively analyse the main performance indicators of GKs.
Considering the instruments used for data collection and coding, a great diversity of devices was observed to evaluate sports performance in football GKs. Sainz de Baranda et al.,39 and Liu et al.22 use the OPTA SportData Spain Company Software (Madrid), to extract the data from the game statistics, and performed the analysis. In the same way, publicly accessible websites are used for data extraction, such as the website of the Spanish Football Federation,40 or using television recordings.41 This great diversity of tools for the identification and extraction of data shows the great possibility that exists to carry out the analysis of game actions without the need to carry out the development and validation of valid and reliable instruments using the Delphi method, as this will require an indispensable amount of time.42 To analyse and present the most up-to-date possible data, it is recommended to use the gambling statistics that are publicly available on official platforms.
In terms of the analysed actions, there is a predominance of analysis of technical-tactical actions in a defensive situation.19,20,23 Specifically, saves,40,43 the movements of GKs during penalty kicks,44,45 and the distribution and effectiveness of passes at the goal kick46 have been previously analysed. For the analysis of the previous actions, different variables have been evaluated depending on the approach to the problem and the objectives defined in each of the studies. The main variables are those actions in which the GKs intervene with the ball in play, for example, when having to pass or kick.46,43 Also, actions without the ball have been previously analysed, such as movements before contacting the ball or at the moment of contacting .45,23 There is a relationship between the actions and the analysed variables, as there are similarities between them. It is recommended that more research related to the subject under study can be carried out in the future because it is essential to understand in detail the technical-tactical interventions of the GKs during training sessions and matches, as well as when the team plays as a home or away team. With these information, it will be possible to envision which aspects are more important to work and develop in the GKs training process. Consequently, it is necessary to perform more researchassociated to the understanding of all the actions that influence the sporting performance of the football GK.
In relation to the performance indicators, relationships are established between the percentages of saves and goals conceded with the effectiveness of the GKs actions.23 In addition, indicators connected with physical demand also emerge, such as the number of sprints,20 the distance covered,19 or the speed of movement.45 On the other hand, the number of saves, whether they are blocks, clearances, or rejections,22 the efficiency in passing,46 or the possession of the ball by the GK47 are available as indicators. Knowledge of GK indicators in football facilitates the analysis and the design of training sessions by the coaching staff. It is essential to analyse all the technical-tactical actions involved in the sporting performance of the GK in football, and even to study the variables related to anticipation and reduction of movement time.48 For this reason, it is recommended that the number of publications related to the performance indicators of football GKs can be increased to broaden knowledge and improve the preparation of GKs.
Finally, in terms of the methodological quality of the documents, it should be noted that 83% of the documents have a good methodological quality since they obtained an average score of between 50 and 75. The studies by Gavião et al.40 and Mikikis et al.23 were of excellent methodological quality. This process enables to identify and reduce the risk of bias in the results obtained in the studies. It is also recommended that different tools can be used to analyse this factor, such as the PEDro scale,49 the MINORS scale,50 or the CERT scale.51 The type of design carried out in each of the documents, randomized controlled, comparative studies, and related to the study of the proposed intervention, respectively, can also be considered.
ConclusionsPerformance indicators allow us to comprehensively understand those aspects or skills that describe the aspects related to the performance of a sport, and which are directly linked to success. GKs in football are considered the last man to defend a shot on goal, influencing goalscoring, or not, and, consequently, the final result of the match of football. Therefore, identifying the main performance indicators of GKs is of vital importance for the coaching staff of football teams to project which skills or GK actions are needed to be improved during training, the enhance performance in the match of football.
The main performance indicators of football GKs are characterized by the fact that they contribute to the positive development of different tactical-technical offensive and defensive actions. In addition, aspects such as the distribution and effectiveness of short and long passes, the ability to hold the ball at the feet, as well as the number of effective shots and saves made are considered. Training sessions should improve these skills, because they will have a negative influence on individual and team performance..
Regarding the limitations of the study, it is worth highlighting the scarcity of literature regarding performance indicators in football GKs, who are responsible for the last possibility to avoid goalscoring by the opposition team in a game of football . In the future, it is recommended to carry out new studies to analyse the sporting performance indicators of GKs, and, consequently, to be able to design specific training tasks for the improvement and development of these aspects, aiming an improvement in the performance of GKs, which will directly influence the overall performance of the team.
Informed consent of study participantsThe review study was conducted in accordance with the ethical provisions of the Declaration of Helsinki (2013), and in compliance with the guidelines of Regulation (EU) 2016/679 of the European Parliament and of the Council of 27 April 2016.
Agradecimientos y financiaciónEl trabajo se ha desarrollado dentro del Grupo de Optimización del Entrenamiento y Rendimiento Deportivo (GOERD), de la Facultad de Ciencias del Deporte, de la Universidad de Extremadura. Todos los autores han contribuido en la realización del manuscrito y certifican que no ha sido publicado ni está en vías de consideración para su publicación en otra revista. Además, Este trabajo ha sido parcialmente subvencionado por la Ayuda a los Grupos de Investigación (GR21149) de la Junta de Extremadura (Consejería de Empleo e Infraestructuras); con la aportación de la Unión Europea a través de los Fondos Europeos de Desarrollo Regional (FEDER). Los autores Fernando J. Santos y Mário C. Espada son apoyados por Instituto Politécnico de Setúbal y Foundation for Science and Technology I.P., Grant /Award Number UIDP/04748/2020. Además, el autor José M. Gamonales es beneficiario de una Ayuda del Programa de Recualificación del Sistema Universitario Español, Campo de Conocimiento: Biomédico (Ref. de la Ayuda: MS-18).
