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Research Article

Analysis of elite soccer players’ performance before and after signing a new contract

Contributed equally to this work with: Miguel-Ángel Gómez, Carlos Lago, María-Teresa Gómez, Philip Furley

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

* E-mail: [email protected]

Affiliation Faculty of Physical Activity and Sports Sciences, Technical University of Madrid, Madrid, Spain

Roles Conceptualization, Data curation, Funding acquisition, Investigation, Methodology, Visualization, Writing – original draft, Writing – review & editing

Affiliation Faculty of Education and Sport Sciences, University of Vigo, Pontevedra, Spain

Roles Conceptualization, Data curation, Formal analysis, Methodology, Resources, Validation, Writing – review & editing

Roles Conceptualization, Formal analysis, Investigation, Methodology, Resources, Validation, Writing – original draft, Writing – review & editing

Affiliation Institute of Cognitive and Team/Racket Sport Research, German Sport University Cologne, Cologne, Germany

• Miguel-Ángel Gómez, 
• Carlos Lago, 
• María-Teresa Gómez, 
• Philip Furley

• Published: January 25, 2019
• https://doi.org/10.1371/journal.pone.0211058
• Reader Comments

The aim of the current study was to analyse performance differences of football players 2-years prior and the year after signing a new contract (the following year) while taking playing position, nationality, player’s role, team ability, and age into account. The sample was comprised of 249 players (n = 109 defenders, n = 113 midfielders; and n = 27 forwards) from four of the major European Leagues (Bundesliga, English FA Premier League, Ligue 1, and La Liga) during the seasons 2008 to 2015. The dependent variables studied were: shooting accuracy, defense (the sum of defensive actions, tackles, blocks, and interceptions), yellow cards, red cards, passing accuracy, tackle success, and minutes played per match. Two-step cluster analysis allowed classifying the sample into three groups of defenders (national important, foreign important, and less important players) and four groups of midfielders and forwards (national important, foreign important, national less important, and foreign less important players). Magnitude Based Inference (MBI) was used to test the differences between player’s performances during the years of analyses. The main results (very likely and most likely effects) showed better performance in the year prior to signing a new contract than the previous year for foreign important defenders (decreased number of red cards), national important midfielders (increased number of minutes played), foreign important forwards (increased minutes played and defense), and national important forwards (increased minutes played). In addition, performance was lower the year after signing the contract compared to the previous one for less important defenders (decreasing defense), national less important midfielders (decreased minutes played), and foreign less important forwards (decreased defense). On the other hand, the players showed better performance in defense and more minutes played the year after signing the contract for less important defenders, national less important midfielders, and foreign less important forwards. These results may assist coaches to decide on when a new contract should be signed or the duration of the contract.

Citation: Gómez M-Á, Lago C, Gómez M-T, Furley P (2019) Analysis of elite soccer players’ performance before and after signing a new contract. PLoS ONE 14(1): e0211058. https://doi.org/10.1371/journal.pone.0211058

Editor: Jaime Sampaio, Universidade de Tras-os-Montes e Alto Douro, PORTUGAL

Received: July 15, 2018; Accepted: January 7, 2019; Published: January 25, 2019

Copyright: © 2019 Gómez et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: Due to the personal data protection law, data will be shared publicly without the name of the players.

Funding: The present study was supported by the Ministry of Economy and competitiveness of Spain with the project “Diseño y desarrollo de un software para el análisis del rendimiento en fútbol” (DEP2016-75785-R). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Incentives are known to play a substantial role in a person’s performance. An important incentive in professional football is signing a lucrative contract. While performance analysis in football has focused on numerous variables in explaining performance, there is limited knowledge on the impact of the time of signing a contract in football. Previous research on performance analysis in football has investigated the players’ performance from an individual point of view attending to physical demands [ 1 ] and technical and tactical indicators [ 2 ] according to different performance levels [ 3 ], playing positions [ 4 – 5 ], players’ role as starters or non-starters [ 6 ], the evolution of physical and technical parameters [ 7 – 8 ] or performance variability [ 9 ]. However, a limitation of this previous research has been to neglect a long-term analysis of a player’s individual performance [ 10 ]. Of further relevance to the present research, Mackenzie and Cushion [ 11 ] have argued that research on performance analysis should identify long term constraints on an individual’s performance which can be used to improve a player’s recruitment policies and to control for social-cultural (e.g., foreign/ national, top elite leagues) influences that impact players’ performance during their careers.

Pertinent to the present research, football players have different fixed contracts that have been argued to affect their efforts with cycles of performance variation at different moments of their career [ 12 ]. Research within sport management has shown that this is particularly evident just before a player signed a new contract (i.e., better performance) and after a lucrative contract was secured (i.e., maintenance or reduction of performance) [ 12 – 13 ]. Frick [ 12 ] studied 1,993 players from the German Bundesliga during the seasons 1995–1996 to 2007–2008 (13 seasons). The results showed that career matches played, matches played during the last season of contract, goals scored, yellow cards, playing position, and region of birth varied depending on signing a new contract as this seemed to have affected the player’s effort and motivation. Della Torre et al. [ 13 ] analysed 275 football players who played at least two consecutive seasons (year before and after signing a contract) in the Italian Serie A during the seasons 2012–2013 and 2013–2014. Their results showed that players perform better during the last year of their contract which is argued to be caused by top elite teams rewarding current/past performances (i.e., subsequent contracts are specially affected by the immediate past performance). Their results showed a pay-performance (current salary) relationship that reinforces good performances. However, this factor has disparities when controlling for player’s origin (national or foreign player) and their level of performance based on performance indicators (important or less important players). In fact, their results showed that domestic players performed better than foreign players due to the better knowledge of the culture of the country, the league, and the club. Accordingly, as football players sign new contracts of about three years of duration or renegotiate their contract with one or two years remaining, the performance analysis of players using key performance indicators is of great relevance to understand the cycle of efforts and motivation based on current contracts, renegotiation, and salary [ 13 ].

Of further relevance to the present research, player-related factors obviously impact on players’ performance. For example, the nationality of players has been argued to be a moderator on the performance effects of signing a new contract in elite football and has been studied from social and management perspectives [ 14 ]. More recently, Della Torre et al. [ 13 ] found that the individual performance during consecutive seasons was stronger for domestic players than foreign players when the end of the contract is near. In addition, a player’s age, his role in the team (categorized based on minutes played as important or less important), the strength of the team in which they play (UEFA ranking) or the evolution of their technical-tactical performances (such as passing, shooting, tackling, or defending behaviours) during the previous and posterior performances after signing or renegotiating a contract may affect the player’s performance from a long-term approach [ 2 – 3 , 6 , 8 – 9 , 12 – 14 ].

In summary, research has indicated that a player is willing to invest more effort when approaching the renegotiation of the same or a new contract. Data shows that this shows in a consecutive increase of his performances mainly during the previous year(s) of his contract [ 12 ]. Presumably this gradual process to deliver better performance allows reaching a better bargaining position for the new contract during the last season before his contract expires or to renegotiate the current contract with one or two years remaining.

In the present paper, we investigate player’s performance variations using technical and tactical performance indicators that arguably reflect the evolution of his efforts in different areas of playing (defense, attack or minutes played). Further, due to the limit of 2-year analyses of previous studies, we will analyse players’ efforts during three consecutive seasons as a novel approach to gaining a better understanding of the signing/ renegotiating of a contract from a longer-term perspective. This analysis will allow illuminating players’ tendencies of adjusting their efforts depending on the remaining years of their contract [ 12 ]. These analyses are likely to be of interest for stakeholders (i.e., coaches, players, managers, and media) in elite football [ 13 ]. Therefore, the current study tries to address the limitations of previous studies (i.e. only using 2-years period of analyses, not using minutes played by the players and key performance indicators, or the omission of some player-related factors that have the potential to affect long-term performance). Thus, the aim of the current study was to analyze differences in performances of individual football players according to the previous (2-years) and the later year after signing/ renegotiating a new contract while taking player-related characteristics into account (age, role in the team as important or less important, nationality, and team’s ability). We hypothesized that performance during the previous season is better (as indicated by the following performance indicators: shooting accuracy, defense, yellow cards, red cards, passing accuracy, tackle success, and minutes played per match) than performance immediately after signing/ renegotiating the new contract. Additionally, we assumed that this should be more pronounced in domestic than foreign players.

Materials and methods

The sample was comprised of 249 players (n = 109 defenders, n = 113 midfielders; and n = 27 forwards) from the French, German, Italian and Spanish professional leagues during the seasons 2008 to 2015. The distribution of players and total match observations for each league and playing position are presented in Table 1 . The use of the sample from 4 of the major leagues of Europe allows increasing the number of observations of Elite athletes that compete at the same level of performance (European professional leagues). This approach follows from previous research, while further reducing the omitted variables bias (less statistical risks) when increasing sample sizes of the same performance characteristics [ 15 – 17 ].

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https://doi.org/10.1371/journal.pone.0211058.t001

The players were selected if they played at least 20 matches (with more than 20 minutes per match) per season and completed a consecutive 3-years period that includes the year two seasons before the end of their contract (year -1), the last year of the contract (year 0) and the year immediately after signing a new contract (year 1). The year when players signed the new contract (considering either when it was renegotiated or when moving to another club) was considered as the reference year (year 0) in order to establish 2 years prior to sign (year -1), and the year after signing the contract (year 1). This allows to compare potential performance improvement due to the new contract with previous years.

The data included the mean performance of 249 players during three seasons (n = 747 mean individual observations). The following player-related characteristics that may affect performance depending on playing position (established by the official webpage of Opta Sports Company considering: defender, midfielder and forward) were: (i) age (year old of player during the year 0), (ii) team ability (UEFA ranking of the team where the player play during the year 0), (iii) player nationality (classified as national or domestic players of their respective leagues), and (iv) player’s role (classified by a k -means cluster using minutes played per match during the year 0 as important: 80.32±6.2 minutes; and less important players: 52.55±12.0 minutes).

The data observations were provided by OPTA Sportsdata Spain Company ( S1 Dataset ). The tracking system of this private company was previously tested by Liu, Hopkins, Gómez and Molinuevo [ 18 ] with acceptable inter-operator reliability. The study does not present the name of the players in order to keep the anonymity following the Company Ethics guidelines, the European Data Protection Law and the approval of the Institutional Review Board (Technical University of Madrid).

The variables (7 variables) were selected because they are arguably the most used performance indicators in the previous literature [ 2 , 18 ]. They have an established impact on individual performance and they can be used numerically to compare footballers over consecutive seasons [ 2 , 18 ]. The seven variables were defined as follows ( https://www.optasports.com/news/optas-event-definitions/ ) [ 18 ]:

• Shooting accuracy (%): shots on target divided by all shots (including blocked attempts).
• Defense : the sum of defensive actions including tackles (“where a player connects with the ball in a ground challenge where he successfully takes the ball away from the player in possession”), blocks (This variable includes blocked passes : “when a player tries to cut out an opposition pass by any means. Similar to an interception except there is much less reading of the pass”; and blocks : “where a player blocks a shot on target from an opposing player”), and interceptions (“where a player reads an opponent’s pass and intercepts the ball by moving into the line of the intended pass”).
• Yellow cards : The yellow cards booked by the referee due to rule violations.
• Red cards : the red cards booked by the referee due to rule violations.
• Passing accuracy (%): successful passes divided by total attempted passes (considering all the types and zones of passes, excluding crosses).
• Tackles success (%): successful tackles divided by total attempted tackles.
• Minutes per match : the number of minutes played during a season divided by the number of matches played during the season.

Statistical analysis

First, the k -means cluster for quantitative variables was used in order to establish cut-off point values for the variable minutes played per match. Then, two cluster were identified for this variable establishing important (n = 188) and less important (n = 61) players. Specifically, this model allows to divide n players’ observations into k clusters (groups) where each observation gets allocated to the cluster with the closest mean value.

Second, a two-step cluster analysis was used to classify the players into different categories based on player-related characteristics (age, team ability, player’s nationality and player’s role). The model allows the inclusion of categorical and continuous variables in order to find the best clustering solution. Then, this statistical analysis automatically determines the "optimal" number of clusters (player’s groups) using the Schwartz’s Bayesian Information criterion (Silhouette measure of clusters cohesion and separation and the variables importance). In addition, the log-likelihood distance measure was used to compute the similarity between clusters. Due to the non-significant effect when classifying the groups depending on team’s ability (variable importance = 0.0), the model was run without this variable (Silhouette measure indicated good results of 0.75, 0.70 and 0.68 for defenders, midfielders and forwards, respectively). Then, the sample was split into three groups of defenders (national important, foreign important, and less important players) and four groups for midfielders and forwards (national important, foreign important, national less important and foreign less important players). Table 2 shows the results (distribution of players) of this two-step cluster analysis for all the playing positions.

https://doi.org/10.1371/journal.pone.0211058.t002

Third, these groups were considered as the independent variable when comparing the performance indicators (dependent variable). Then, the player’s performance during the years (-1, 0 and 1) was analyzed using repeated measures ANOVA for normally distributed variables and the Friedman test for non-normally distributed variables. In addition, the pairwise comparisons (years -1, 0 and 1) were tested using the magnitude-based inference (MBI) method with the Hopkins’ spreadsheet [ 19 – 20 ]. This method uses the log-transformation of data in order to reduce bias due to non-uniformity error. The effect size (Cohen's d units at 90% CI) was estimated using pooled standard deviation for comparisons with the following magnitude ranges: 0–0.2 trivial; >0.2–0.6 small; >0.6–1.2 moderate; >1.2–2 large; >2 very large. The MBI analyses were assessed using the smallest worthwhile difference (0.2 times the standardization), estimated from the between-subjects standard deviation. The differences are defined as unclear if the confidence intervals (CI) for the difference in the means included substantial positive and negative values (±0.2*standardization) simultaneously. In order to control for differences between pairs of comparisons (years), the magnitude of a clear difference was assessed as follows: >0.25 trivial; 0.25%–75% possibly, 75%–95% likely, 95%- 99% very likely, and >99% most likely. The magnitude is considered unclear if the CI overlaps the positive and negative thresholds [ 19 – 20 ].

The descriptive results, repeated measures ANOVA, Friedman test and Two-step cluster analyses were performed using the statistical software IBM SPSS for Windows, version 22.0 (Armonk, NY: IBM Corp.).

The descriptive results (means and standard deviations), the repeated measures ANOVA, and Friedman tests results of the variables studied for defenders according to the player’s characteristics during the years prior to the end of their contract and immediately after signing a new contract are presented in Table 3 . The repeated measures tests showed significant differences (p<0.05) of red cards for important national defenders, yellow cards and minutes played for less important defenders, and defense for foreign important defenders.

https://doi.org/10.1371/journal.pone.0211058.t003

The results of MBI (see Fig 1 ) showed that foreign important players decreased the number of red cards (very likely effect) from year -1 to year 0. The results for less important players showed a decreased performance in defense (very likely effect) from year -1 to year 0 and they increased their performance in the number of minutes played (most likely effect) and in defense (very likely effect) from year 0 to year 1.

Asterisks indicate the likelihood of MBI effects as follows: *possibly, **likely, ***very likely, **** most likely.

https://doi.org/10.1371/journal.pone.0211058.g001

The descriptive results (means and standard deviations), the repeated measures ANOVA, and Friedman tests results for midfielder according to the group of players during the years studied are presented in Table 4 . The results showed statistically significant differences (p<0.05) of defense and minutes played for national less important players and minutes played for national important midfielders.

https://doi.org/10.1371/journal.pone.0211058.t004

The MBI results for midfielders (see Fig 2 ) showed that national less important players decreased the minutes played (very likely effect) from year -1 to year 0. Additionally, the players increased the minutes played (very likely effect) and defense from year 0 to year 1 (very likely effect). The results for national important players showed an increase in the number of minutes played from year -1 to year 0 (very likely effect). The foreign important players increased the minutes played and defense performance (very likely effect) from year -1 to year 0.

https://doi.org/10.1371/journal.pone.0211058.g002

The descriptive results (means and standard deviations) and the Friedman tests results for forwards according to the group of players during the years studied are presented in Table 5 . Statistical significant results (p<0.05) were identified in minutes played for foreign and national important players, for passing accuracy in national less important forwards, and in defense performance for foreign less important forwards.

https://doi.org/10.1371/journal.pone.0211058.t005

The MBI results for forward playing position (see Fig 3 ) showed that foreign less important players decrease defense performance (very likely effect) from year -1 to 0. Moreover, these players increased minutes played (very likely effect) and defense performance (most likely effect) from year 0 to year 1. Lastly, national important players increased the minutes played from year -1 to 0 (very likely effect).

Asterisks indicate the likelihood of MBI effects as follows: *possibly, **likely, ***very likely.

https://doi.org/10.1371/journal.pone.0211058.g003

The aim of the present study was to analyse differences in performance of individual football players depending on the previous (2-years) and the later year after signing or renegotiating a new contract, while taking player-related characteristics into account (age, role in the team as important or less important, nationality, and team’s ability). This approach enabled to gain a better understanding of the effects of signing a new contract over consecutive seasons. In contrast to the common perception among sports fans that players become lazy and expend less effort once they have signed a long-term contract [ 18 ], or conversely start to deliver better performances in order to reach a promising bargaining position in the last season before the contract expires, the present results do not provide clear support for this hypothesis. In this respect the present findings are not supportive of previous studies reporting evidence for a relationship between performance and contract duration in sports in general [ 21 – 23 ] and specifically in soccer [ 13 , 14 , 24 – 27 ].

Overall, our results do not demonstrate a clear association between performance and contract duration. While the minutes played and defense showed significant differences for years -1 and 1 in national less important defenders and midfielders and foreign less important forwards, with better values during the year after the new signing of a contract, no differences were found for the rest of the variables or other groups of players. Hence, the results do not support our hypothesis that performance during the previous season is better than the performances immediately after signing the new contract. On the contrary, the current results showed, for example, that performance was worse for the less important defenders (defense variable), national important midfielders (minutes played per match variable), and foreign less important forwards (defense and minutes played variables) during the previous season of signing a new contract (see Fig 4 ).

https://doi.org/10.1371/journal.pone.0211058.g004

Previous studies suggest that the nationality of footballers may affect the relationship between performance and signing a new contract. Hence, the nationality of players can be considered as a moderator on the performance effects of signing a new contract. For example, Della Torre et al. [ 13 ] found that the individual performance during consecutive seasons is stronger for domestic players than for foreign players when the end of the contract is near. The findings of the current study do not support this evidence. There are no substantial differences between foreign and national players (see Fig 4 ). For example, national and foreign important midfielders increased the minutes played from year -1 to year 0. When the year after signing a contract is considered, no differences were found between national and foreign important players in any playing position. More studies are needed in order to clarify this conflicting pattern of results in the literature [ 13 ].

To the best of our knowledge, this is the first study analyzing the association between performance and contract duration depending on playing position. The current findings do not support previous studies [ 12 – 13 ]. According to our results, players did not perform better during the last year of their contract suggesting that maybe signing a new contract has no clear impact on the player’s motivation as it has been proposed previously. This may be due to the limit of 2-years analysis adopted in previous studies or the different performance indicators used in the current study. Future studies should scrutinize these findings.

However, managers, supporters and players should be careful when interpreting these results. Given the complexities of soccer, the match-performance trends of the players in the current study could also reflect the actions of the opposing team and teammates. Thus, individual performances could be influenced by collective strategies and tactics potentially disguising small effects that signing a new contract might have on observable individual performance indicators. Future research should possibly examine not only individual performances in isolation but also consider collective performance indicators [ 8 – 9 , 28 ].

The present study is not without limitations. The relationships between previous and actual performances could be affected by the current salary of the players and the opportunities of signing a new contract [ 13 ]. Accordingly, the analysis of football players’ performance should be mediated by the seasonal performances of their career and their market value. These variables should be included in future works. More variables (e.g. technical, tactical and physical indicators) and countries (i.e. specific leagues with the same or different foreign recruitment policies as European competitions) should be considered to provide conclusive evidence on the relationship between performance and contract duration. Further, we did not control for: (i) the duration of the contract signed and years remaining which might result in differential effects depending on the length of the newly signed contract; (ii) if the player moves to another club or stays with the same club; or (iii) the specific playing position during each year for the players analysed. Therefore, a fruitful avenue for further research would be to conduct multifactorial analysis of signing a contract in football [ 12 – 14 ].

In conclusion, this paper investigated the association between performance, contract duration, and nationality of the players in elite soccer. The research does not demonstrate a clear association between performance and contract duration using datasets from the French, German, Italian, and Spanish professional leagues during the seasons 2008 to 2015. Players’ performances did not show a clear decline or improvement during the two years before signing or renegotiating a new contract. Hence, the common assumption of football spectators that players perform better when playing for a new contract and “take a break” once they signed a new contract was not identified in the present data.

Practical applications

From a player’s recruitment or renovation perspective, the performance displayed during the past or the following seasons before or after a new contract can help managers and coaches to decide when a new contract should be signed, the duration of the contract or the salary of the player. While previous work [ 12 – 13 ] might be indicative of having short term contracts for players and waiting until the last year before a contract runs out to resign a player, the present results do not support this reasoning. On the contrary, players sometimes increased performance after signing a new contract.

Supporting information

S1 dataset. ibm spss dataset of players’ performances obtained by optasports company..

https://doi.org/10.1371/journal.pone.0211058.s001

Acknowledgments

The present study was supported by the Ministry of Economy and competitiveness of Spain with the project “Diseño y desarrollo de un software para el análisis del rendimiento en fútbol” (DEP2016-75785-R).

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Forecasting Goal Performance for Top League Football Players: A Comparative Study

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• Nikolaos Giannakoulas   ORCID: orcid.org/0009-0000-2314-2202 19 ,
• George Papageorgiou   ORCID: orcid.org/0000-0002-9361-8621 19 &
• Christos Tjortjis   ORCID: orcid.org/0000-0001-8263-9024 19  

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In this paper, we review the literature on Sports Analytics (SA) and predict football players’ scoring performance. Based on previous years’ performance, we predict the number of goals that players scored during the 2021–22 season. To achieve this, we collected advanced statistics for players from five major European Leagues: the English Premier League, the Spanish La Liga, the German Bundesliga, the French Ligue1 and the Italian Serie A, for seasons from 2017–18 up to 2021–22. Additionally, we used one-season lag features, and three supervised Machine Learning (ML) algorithms for experimental benchmarking: Linear Regression (LR), Random Forest (RF) and Multilayer Perceptron (MLP). Furthermore, we compared these models based on their performance. All models’ results are auspicious and comparable to each other. LR was the best performing model with Mean Absolute Error (MAE) 1.60, Mean Squared Error (MSE) 7.06 and Root Mean Square Error (RMSE) 2.66. Based on feature importance analysis, we established that every player’s upcoming scoring performance is strongly associated with previous season’s goals (Gls) and expected goals (xG).

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This research is co-financed by Greece and the European Union (European Social Fund-SF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning 2014–2020» in the context of the project “Support for International Actions of the International Hellenic University”, (MIS 5154651).

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Giannakoulas, N., Papageorgiou, G., Tjortjis, C. (2023). Forecasting Goal Performance for Top League Football Players: A Comparative Study. In: Maglogiannis, I., Iliadis, L., MacIntyre, J., Dominguez, M. (eds) Artificial Intelligence Applications and Innovations. AIAI 2023. IFIP Advances in Information and Communication Technology, vol 676. Springer, Cham. https://doi.org/10.1007/978-3-031-34107-6_24

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Reducing Injuries in Soccer (Football): an Umbrella Review of Best Evidence Across the Epidemiological Framework for Prevention

• Oluwatoyosi B. A. Owoeye   ORCID: orcid.org/0000-0002-5984-9821 1 , 2 ,
• Mitchell J. VanderWey 1 &
• Ian Pike 3 , 4  

Sports Medicine - Open volume  6 , Article number:  46 ( 2020 ) Cite this article

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Soccer is the most popular sport in the world. Expectedly, the incidence of soccer-related injuries is high and these injuries exert a significant burden on individuals and families, including health and financial burdens, and on the socioeconomic and healthcare systems. Using established injury prevention frameworks, we present a concise synthesis of the most recent scientific evidence regarding injury rates, characteristics, mechanisms, risk and protective factors, interventions for prevention, and implementation of interventions in soccer. In this umbrella review, we elucidate the most recent available evidence gleaned primarily from systematic reviews and meta-analyses. Further, we express the exigent need to move current soccer injury prevention research evidence into action for improved player outcomes and widespread impact through increased attention to dissemination and implementation research. Additionally, we highlight the importance of an enabling context and effective implementation strategies for the successful integration of evidence-based injury prevention programs into real-world soccer settings. This narrative umbrella review provides guidance to inform future research, practice, and policy towards reducing injuries among soccer players.

This review provides a one-stop evidence reference regarding the prevention of soccer injuries, including evidence and perspectives on the implementation of proven interventions.

Overall evidence supports the use of the 11+ neuromuscular training warm-up and focused strength training, and there is emerging evidence for load management programs to mitigate injury risk among soccer players.

Theory-driven dissemination and implementation studies are needed to improve the adoption, adherence, appropriate adaptation, scale-up, and sustainment of evidence-based injury prevention interventions in soccer.

The findings from this review provide guidance to inform future research, practice, and policy towards reducing injuries among soccer players.

Soccer (football) is the most popular sport in the world [ 1 ], with some 270 million involved in the sport worldwide in 2006 [ 2 ]. For approximately 110,000, it is a profession and thus a source of income; for some 38 million registered players, it is a team game organized within leagues and competitions; and for about 226 million others, it is an enjoyable exercise surrogate for fitness and health [ 2 ]. The health benefits of soccer as “medicinal exercise” are well documented, for example, improved cardiovascular health, mental health, and bone health [ 3 ]. However, there is a paradoxical negative effect of soccer on health when players get injured (e.g., obesity or post-traumatic osteoarthritis after an anterior cruciate ligament injury) [ 4 , 5 ]. Furthermore, soccer injuries exert a significant burden on socioeconomic and healthcare systems [ 6 ]. Founded on established epidemiological frameworks describing the sequence of research steps to effective injury prevention practice [ 7 , 8 ]—from identifying injury rates to the implementation of effective interventions—we present a narrative umbrella review that articulates best available evidence to inform guidelines, practice, and policy towards mitigating the risk of injuries in soccer, and in turn maximizing the benefits of participation among individuals.

To achieve the above-mentioned purpose, we conducted methodical searches across five databases (MEDLINE, SPORTDiscus, PsycINFO, CINAHL, and Cochrane Database of Systematic Reviews) from January 2010 to January 2020 to identify all systematic reviews, meta-analyses, reviews, and original research (where limited or no reviews were available) across soccer injury studies that investigated injury incidence, characteristics, mechanisms, risk and protective factors, interventions for prevention, and implementation and evaluation of interventions. A summary of the search records for our primary source of data (systematic and narrative reviews) is presented in Table 1 , and details of the search terms used—key concepts and search words—are presented in an additional file ( Supplementary File ). Our search strategy involved the use of relevant search descriptors of “OR” and “AND” to combine search/key words and key concepts, respectively, after each search word was exploded (exp) to capture all literature possible. Search records were limited to articles with full text, written in the English language, and relating to humans. The same methodology was used to obtain primary research articles where no reviews were available.

Injury Rates

Injury incidence among soccer players differs across levels of participation, age, type of exposure, and sex. The incidence of injuries in soccer is mostly significant during games/matches, ranging from 9.5 to 48.7 injuries/1000 h among competitive male youth players, 2.5 to 8.7 injuries/1000 h among male professional players, and 12.5 to 30.3 injuries/1000 h among female players [ 9 , 10 , 11 , 12 ] (Table 2 ). The incidence of injuries appears higher among males vs. females, and injury incidence is higher during games/matches vs. practice/training for all participation categories, among both male and female players [ 10 , 11 , 12 ]. Soccer players younger than 12 years of age have a lower injury rate (1.0–1.6 injuries per 1000 h) compared to older players [ 9 ].

Injury Location and Type

Most soccer injuries occur in the lower limbs (60–90%), especially the ankle, knee, and thigh [ 10 , 11 , 12 , 13 , 14 ]. Among male players, the most common injuries affect the hamstring muscles followed by the ankle, knee, and groin [ 11 , 13 ]. Comparably, among female players, knee and ankle injuries are the most common, followed by thigh/hamstring injuries [ 10 , 13 ].

Thigh, Knee, and Ankle Injuries

Most thigh injuries result from strains with a high proportion of hamstring injuries, despite quadriceps injuries leading to longer absence from play [ 15 ]. The prevalence and history of hamstring injury is greater among adult professional players (40%) compared to under-20 players (18%) [ 16 ]. Up to 18% of severe soccer injuries presenting at hospital emergency departments involve the knee [ 17 ]. One such injury involves the anterior cruciate ligament (ACL). The ACL injury rate among females (2.0/10,000 athlete exposures) is 2.2 times higher than that of males (0.9/10,000 athlete exposures), independent of participation level [ 18 ]. Ankle injuries account for up to 20% of all soccer injuries with ankle sprains constituting 77% of all ankle injuries [ 14 , 19 ].

The prevalence of concussion in youth soccer appears to be relatively low with an incidence of 0.19 (95% CI 0.16–0.21) concussions per 1000 athletic exposures and 0.27 (95% CI 0.24–0.30) concussions per 1000 athletic exposures among male and female players, respectively [ 20 ]. A higher concussion incidence has been consistently reported among females [ 10 , 20 ].

Injury Mechanisms

Overall, about two-thirds of soccer injuries are traumatic and the other one-third (27–33%) are caused by overuse [ 11 , 12 , 21 ]. These findings are based on a medical attention/time-loss injury definition, and emerging evidence from studies using an all-complaint injury definition suggests that overuse onset injuries may be as prevalent as acute onset injuries [ 22 ]. About two-thirds of traumatic injuries are contact injuries, of which 12–28% are caused by foul play. Notably, non-contact injuries account for 26–58% of all injuries [ 13 , 21 ]. Injuries occur primarily during the initial or final 15 min of the match, indicating the significance of an appropriate warm-up and the effects of fatigue on players [ 23 ].

Risk and Protective Factors

Non-modifiable risk factors, player position.

Goalkeepers are at a lower overall risk of injury compared to outfield players in the male game [ 24 ]. Independent of goalkeepers, current evidence is inconsistent regarding the association between player position and injury risk; however, it appears that strikers may be at a greater risk as compared with other outfield players during matches [ 24 ].

Previous Injury

A history of previous injury continues to be the most consistent and strongest risk factor for future injury, and this also holds true for specific injuries [ 9 , 25 , 26 , 27 , 28 , 29 ]. For example, a history of previous hamstring injury is associated with future hamstring injury among male players [ 25 , 28 ], previous ACL injury is associated with risk of future ACL injury [ 29 ], and previous ankle sprain injury is related to the emergence of new ankle sprain injuries [ 27 ].

Current evidence regarding age as a risk factor for soccer injury is limited. One systematic review suggested that increasing age was a risk factor for future hamstring injury among male players [ 25 ]. Another systematic review concluded that existing literature was insufficient to infer any relationship between age and the risk of ACL injury among soccer players [ 29 ]. In a single prospective study, age > 14 years was a significant risk factor for future acute knee injury among female players [ 30 ].

Familial predisposition for ACL injury is associated with increased risk of ACL injury and acute knee injury [ 29 , 30 ].

Overall, the incidence of injuries is higher among males vs. females [ 10 , 11 ]; however, female sex is associated with increased ACL injury risk [ 29 ].

Competitive Setting

Game exposure demonstrated increased injury risk compared to practice for both male and female soccer players [ 29 , 31 ]. Furthermore, within the practice setting, the risk of injury is higher for scrimmage compared to normal practice and walk-through [ 29 ].

Shoe-Surface Interaction

Current research suggests there is an association between higher shoe-surface interaction and increased ACL injury risk [ 29 ].

Pre-season Knee Complaints

Females presenting with pre-season knee complaints appear to be at increased risk for acute knee injury during the season [ 30 ].

Early Sport Specialization

Though there is a lack of substantive evidence for soccer specifically, early sport specialization has been found to be associated with a greater risk for overuse injuries across multiple youth sports [ 9 ]. One study showed that female soccer players 12–15 years of age playing on more than one team had increased risk for lower extremity overuse injuries [ 32 ].

Growth and Leg Length

Elite male youth soccer players are at greater risk for traumatic injury in the year of peak height velocity [ 33 ]. A recent prospective study of male soccer players aged 10–12 years shows an association between an increase in leg length throughout the season and risk for overuse injury [ 34 ]. The same study suggests an association between longer leg length and risk of overuse injury among male soccer players aged 13–15 years. Additionally, they found a higher weight and a decreased growth rate to be associated with an increased risk of acute injury.

Modifiable Risk Factors

Evidence regarding load-injury relationships among soccer players is still emerging as reviews remain sparse in this area of inquiry. Current evidence across team sports indicates that load, in terms of player exposure and/or exertion, could either be an independent protective or risk factor for injury, depending on whether load administration is optimal and progressive or suboptimal (e.g., load spike), respectively, and that this relationship is likely moderated by other risk factors for injury [ 35 , 36 , 37 , 38 , 39 , 40 ]. Prospective studies showed that a high amount of absolute (accumulated or cumulative) load, based on different calculations of load measures (e.g., 1-weekly, 2-weekly), was associated with greater risk of injury among elite youth and professional soccer players [ 39 , 40 , 41 ]. These findings suggest that it may be expedient to have an absolute load threshold, for example, weekly load threshold, to further mitigate injury risk in soccer, especially youth soccer [ 39 , 40 ]. Altogether, available evidence suggests that avoiding a spike in load (e.g., the acute to chronic workload ratio) is associated with less soccer injuries [ 39 , 40 , 41 ].

Neuromuscular Factors

Hamstring/quadriceps strength ratio imbalance is a key risk factor for hamstring muscle injury; specifically, decreased hamstring strength relative to quadriceps strength is a risk factor for knee ligamentous injuries in both male and female youth soccer players [ 29 , 42 ]. Decreased single leg hop distance is also associated with increased hamstring injury risk [ 43 ]. While current evidence is inconclusive for muscle strength asymmetry (i.e., right vs. left) as a risk factor, eccentric hamstring strength asymmetry is specifically indicated as a key predictor of injury among male youth soccer players [ 26 ]. Furthermore, eccentric hamstring strength (< 256 N) and single leg hamstring bridge scores of less than 20 reps on the right leg are associated with increased risk of hamstring strain [ 43 ]. Poor landing mechanics, specifically, increased dynamic knee valgus, is associated with increased risk for lower limb injury, including ACL injury [ 9 , 42 , 43 ]. Leg dominance and leg asymmetry also relates to increased risk of injury; a difference of 15% or greater, between an individual’s dominant and non-dominant limb, has been shown to predict future injury [ 42 ]. An asymmetry of greater than 4 cm on the anterior reach portion of the Y-balance test places athletes at 2.5 times greater risk for injury among male youth soccer players [ 42 , 43 ]. Hip external rotation strength scores using handheld dynamometry of less than 18% of the individual’s body weight is associated with lower extremity and back injuries [ 43 ]. Additionally, the literature suggests that the risk of injury may increase with altered neuromuscular firing during dynamic movements like cutting or landing, and dynamic stability deficits may increase lower extremity injury risk for male youth soccer players [ 42 ].

Protective Factors

Although mention of protective factors in review level evidence did not exist at the time of this evidence review, findings from original research previously described (under modifiable risk factors) signify load management as a viable target for mitigating injury risk in soccer. For example, an in-season relative load measure of acute to chronic workload ratio of 1 to 1.25 significantly reduced injuries among youth players [ 40 ], and a reduced absolute load significantly reduced injuries among youth and adult professional players [ 39 , 40 ]. Additionally, current evidence suggests that improved neuromuscular capacity and control, including increased quadriceps, hamstring, hip flexor strength, and movement control are protective against injuries among soccer players [ 9 , 26 , 29 , 42 , 43 ].

Opportunities for Prevention

Effective interventions.

Drawing from available evidence regarding modifiable risk factors and protective factors for soccer injuries, injury prevention experts have developed and tested interventions for reducing musculoskeletal injuries in soccer. There is extensive high-quality evidence (including two reviews of systematic reviews) showing the clinical effectiveness of exercise-based interventions in the form of neuromuscular training (NMT) warm-up programs in reducing all soccer-related injuries across sex, ages, and skill levels. Specifically, the 11+ (formerly called the FIFA 11+) warm-up program reduces overall injury rate (i.e., all injuries) by 30 to 47% [ 23 , 44 , 45 , 46 ], lower limb injury rate by 39 to 44% [ 44 , 45 ], overuse injury rate by 55%, and knee injury rate by 52% [ 47 ]. Emerging evidence also suggests that the 11+ Kids (a version for children under 12 years old) is efficacious (48% reduction for all injuries) for reducing injuries in younger players [ 48 ]. Additionally, the “Knee Injury Prevention Program” (KIPP) has the potential to significantly reduce non-contact lower limb injury and overuse injury among young female soccer players by 50% and 56%, respectively [ 47 ].

In a recent systematic review, the application of a variety of exercise-based injury prevention programs for youth players was found to reduce injury rates by up to 46% [ 49 ]. Furthermore, the risk of hamstring injuries can be reduced by up to 51% when the Nordic Hamstring exercise is implemented in isolation [ 50 ]. A recent meta-analysis showed that ankle injuries can be reduced by as much as 40% [ 51 ] and a meta-analysis of meta-analyses [ 52 ] demonstrated that a 50% reduction can be achieved for all ACL injuries in a heterogeneous sample of athletes, including soccer players, when NMT warm-up is implemented.

Specific instructions on how to perform aforementioned NMT warm-up programs can be found in the International Olympic Committee’s “Get Set” app, an innovative and accessible mobile app that provides continued access to illustrative and video information regarding effective sport- and body-specific NMT warm-up programs, including the 11+ program. The 11+ program can also be accessed from the following website: https://www.youtube.com/watch?v=RSJIp7e7fyY

Although concussions are not frequent in soccer, sustaining a concussion may present severe and lasting negative health consequences [ 53 ]. It is important for coaches, parents, and administrators to be aware of concussion signs and symptoms and know what to do if concussion is suspected. For concussion prevention, there is evidence that education about concussion among key stakeholders, e.g., coaches, referees, and parents, can reduce the incidence of concussion and facilitate improved outcomes [ 54 ]. Interventions for primary (e.g., rule change and avoiding a slippery playing surface) and secondary (e.g., concussion recognition and decision on return to playtime) prevention are mainly informational for coaches and parents/guardians. A popular evidence-based educational tool is the Concussion Awareness Training Tool, available at https://cattonline.com .

Cost-Effectiveness of Interventions

Literature regarding the cost-effectiveness of injury prevention interventions in soccer is limited. A reduction of 43% was reported in healthcare costs in the training group that underwent an NMT warm-up similar to the 11+ program with additional use of a wobble-board, when compared to a standard practice control group [ 55 ]. Similarly, the “11+ Kids” program showed a 51% reduction in healthcare costs when compared with a regular warm-up [ 56 ].

Implementation and Evaluation

Literature regarding the evaluation of the implementation of efficacious/effective interventions such as the 11+ and other NMT warm-up programs is advancing despite the lack of reviews [ 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ]. However, of all the studies currently available, only two reported using an implementation framework to evaluate a preventative program. The Reach Effectiveness Adoption Implementation Maintenance Framework was used in both studies: one to evaluate an NMT warm-up program for knee/ACL prevention, and the other to evaluate the Adductor Strengthening Program for groin injury prevention [ 57 , 59 ]. Overall, the execution of NMT warm-up programs when implemented ranged between low and moderate [ 60 , 68 ].

To improve the spread and implementation of evidence-based injury prevention intervention in soccer, an understanding of implementation contexts is imperative. Although more rigorous theory-driven studies are needed to further understand potential contextual moderators of successful/unsuccessful implementation, a small number of studies have investigated perceived facilitators and barriers to NMT programs across levels of soccer participation (Table 3 ).

Current Best Practices for Implementation

Literature regarding best practices for onward translation of evidence-based injury prevention programs into routine practice in community and professional soccer remains sparse, and the urgent need for research in this field of inquiry has been identified [ 70 ]. The following conclusions have been reached in existing literature:

Preseason structured coaching workshops have the potential to effectively increase coach attitudes, perceived behavioral control, self-efficacy, and intention and subsequent implementation of NMT programs [ 64 , 71 , 72 ]. However, it remains unclear whether high levels of behavioral determinants, i.e., cognitive and psychosocial factors, would ultimately result in high levels of program adherence and maintenance over time [ 57 ].

Coach-led delivery of the 11+ appears to be relatively sufficient in implementing the program; evidence on the advantage of having additional support or supervision from research or team staff, e.g., strength and conditioning coach, an athletic trainer, or physiotherapist, is mixed [ 57 , 60 , 71 ].

For maximum effectiveness, coaches need to ensure quality delivery to their teams by performing NMT warm-up exercises with proper technique and adhering to the program guidelines, while adapting it to fit their local setting. A minimum of 2× weekly appears to be optimal and thereby recommended [ 58 , 61 ].

Quality implementation requires soccer associations and organizations at the federal, provincial, and community levels to enact policies that enforce injury prevention programs and education and policies that require coaches to use proven NMT warm-up programs such as the 11+ [ 60 , 73 , 74 ].

Conclusions and Call to Action

This review provides guidance to inform future research, policy, and practice towards reducing injuries among soccer players. It presents a one-stop evidence reference regarding the burden, etiology, and prevention of soccer injuries, including current opportunities for evidence-based interventions and their implementation. To achieve desired outcomes and population-level impact from injury prevention research evidence, evidence-based interventions need enabling contexts and effective implementation strategies for a successful integration into real-world settings. Consequently, innovators (e.g., researchers) and implementation actors at the organizational (e.g., football associations, government/public health agencies, non-profit organizations, football clubs) and individual (e.g., coaches, strength and conditioning personnel, medical staff) levels have critical roles to play and are urged to rise to the occasion.

Researchers need to acquire an appreciable level of proficiency in dissemination and implementation research designs to build upon current literature to advance dissemination and implementation science in soccer injury prevention. Specifically, theory-driven dissemination and implementation studies are needed to improve the adoption, adherence, appropriate adaptation, delivery, scale-up, and sustainment of evidence-based injury prevention interventions such as the 11+ in soccer. Researchers should move beyond randomized controlled trials evaluating efficacy in NMT programs (considering that there is extensive evidence supporting NMT efficacy ) to evaluating strategies for implementation in randomized controlled and pragmatic (e.g., quasi-experimental) trials. Further, researchers should use current information on implementation barriers to and facilitators of evidence-based interventions and knowledge from implementation science to conceptualize and test potential implementation strategies. In addition, soccer organizations and their staff, especially coaches, have the obligation of ensuring safety among their players. Collectively, researchers, knowledge brokers, policymakers, leaders, and administrators in soccer and other related organizations need to work collaboratively to move current injury prevention evidence into action in order to protect players’ current and future health.

Availability of data and materials

Data sharing is not applicable to this article as no datasets were generated during the current study.

Abbreviations

Anterior cruciate ligament

Neuromuscular training

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Acknowledgements

The funding for this review was managed by Pike, I. and Babul, S. of the British Columbia (BC) Injury Research and Prevention Unit and BC Children’s Hospital Research Institute and coordinated by Richmond, S. of the Canadian Injury Prevention Trainee Network.

Provided by the British Columbia Alliance for Healthy Living Society, Canada, and supported by the Saint Louis University, MO, USA.

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OO conceived the study and did the initial systematic literature search. MV did the updated literature search. OO and MV drafted the manuscript, and OO and IP substantially revised it. The authors read and approved the final manuscript.

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Owoeye, O.B.A., VanderWey, M.J. & Pike, I. Reducing Injuries in Soccer (Football): an Umbrella Review of Best Evidence Across the Epidemiological Framework for Prevention. Sports Med - Open 6 , 46 (2020). https://doi.org/10.1186/s40798-020-00274-7

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The lifeflight legacy: 40 years in 40 photos, august 28, 2024, for former nfl players, football before age 12 not linked to worse health later in life: study.

Data from 4,189 former NFL athletes who spanned the ages of 24-89 show no evidence playing organized football younger than age 12 led to more cognitive, mood, sleep, cardiovascular or other health issues later in life. These results, which are published in Sports Medicine, contrast with previous small studies from a decade ago.

A recent study looking at more than 4,000 former professional football players showed no connection between starting the sport before age 12 and higher rates of depression, anxiety, dementia or memory problems later in life, researchers at Vanderbilt University Medical Center and Harvard University found.  

The Football Players Health Study at Harvard University collected data from 4,189 former NFL athletes who spanned the ages of 24-89. While former professional players who started playing before age 12 had more cumulative football exposure (as in, total duration of their football career and more signs/symptoms of sports-related concussions during their career), there was no evidence that the group who started playing organized football younger had more cognitive, mood, sleep, cardiovascular or other health issues later in life, the researchers wrote.  

These results, published in  Sports Medicine , contrast with previous small studies from a decade ago. A series of prior studies evaluated a few dozen symptomatic former professional football players and found that those who started in the sport before age 12 had health problems — such as worse depression, greater apathy and structural brain differences —in their post-career years compared to those who started playing football at age 12 and after, said  Douglas Terry , PhD, assistant professor and clinical neuropsychologist in the Department of Neurological Surgery and co-director of the  Vanderbilt Sports Concussion Center . 

“I believe this is the largest study on this topic, and we didn’t see a signal that starting to play before 12 led to adverse health outcomes. The huge number of survey respondents underscores how committed former players are to understanding the long-term health outcomes of the sport,” said Terry.

According to senior author  Aaron Baggish , MD, a cardiologist at the Massachusetts General Hospital Heart Center, “There may be other aspects of youth football participation that are linked to later life health. The key to protecting amateur and professional players is using large and varied cohorts to identify which risks are or are not worthy of attention.” 

Playing sports in childhood boosts children’s cardiovascular conditioning, ability to work as a team, and self-esteem, so Terry wants to see future studies further clarify the risks of youth football in those who do not end up in the NFL since most boys do not go on to play at the professional or even collegiate level.  

Terry, co-first author along with  Rachel Grashow , PhD, MS, director of epidemiological research initiatives for the Football Players Health Study at Harvard University, statistically accounted for a variety of factors that were not considered in previous studies, including primary football position (lineman or not), number of professional seasons, index of prior concussions signs or symptoms, as well as age, race and BMI. 

Research Driven by Input from Former NFL Players

The Football Players Health Study at Harvard University, launched in 2014, is a comprehensive research program dedicated to examining the multifactorial causes that impact the health of former NFL players. The research has been informed by the players themselves, who have provided input on the health concerns and conditions they face after a career in football. An interdisciplinary team of researchers from Harvard University and Harvard Medical School and its affiliated teaching hospitals, including those in the Mass General Brigham system, conduct research from neurology, cardiology, sports medicine, rehabilitation medicine, chronic pain and public health. While concussion and head injury are of paramount concern, the study examines all aspects of player health across the life span. Former players can find important resources to support their health in  this section  of the study’s website. 

This work was supported by the Football Players Health Study at Harvard University, which is funded by the National Football League Players Association (NFLPA). The content is solely the responsibility of the authors and does not necessarily represent the official views of Harvard Medical School, Harvard University and its affiliated academic healthcare centers. The NFLPA had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; preparation, review or approval of the manuscript; and the decision to submit the manuscript for publication. 

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Characterizing Neurobehavioral Dysregulation Among Former American Football Players: Findings From the DIAGNOSE CTE Research Project

The Journal of Neuropsychiatry and Clinical Neurosciences | Pulukuri SV, Fagle TR, Trujillo-Rodriguez D, van Amerongen S, Bernick C, Geda YE, Wethe JV, Peskind ER, Katz DI, Alosco ML, Palmisano JN, Tripodis Y, Adler CH, Balcer LJ, Reiman EM, Shenton ME, Cummings JL, Stern RA; DIAGNOSE CTE Research Project. Characterizing Neurobehavioral Dysregulation Among Former American Football Players: Findings From the DIAGNOSE CTE Research Project. J Neuropsychiatry Clin Neurosci. 2024 Jul 22:appineuropsych20230133. doi: 10.1176/appi.neuropsych.20230133. Epub ahead of print. PMID: 39034669. https://pubmed.ncbi.nlm.nih.gov/39034669/

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The Football Players’ Health Study at Harvard University: Design and objectives

Ross zafonte.

1 Football Players Health Study at Harvard University, Harvard Medical School, Boston, Massachusetts

2 Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Massachusetts General Hospital, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts

Alvaro Pascual‐Leone

3 Berenson‐Allen Center and Division for Cognitive Neurology, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts

Aaron Baggish

4 Cardiovascular Performance Program, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts

Marc G. Weisskopf

5 Department of Environmental Health, Harvard TH Chan School of Public Health, Boston, Massachusetts

Herman A. Taylor

6 Department of Medicine, Cardiovascular Research Institute, Morehouse Medical School, Atlanta, Georgia

Jillian Baker

Sarah cohan, chelsea valdivia, theodore k. courtney, i. glenn cohen.

7 Harvard Law School, Cambridge, Massachusetts

Frank E. Speizer

8 Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts

Lee M. Nadler

9 Dana Farber Cancer Center, Harvard Medical School, Boston, Massachusetts

The Football Players Health Study at Harvard University (FPHS) is a unique transdisciplinary, strategic initiative addressing the challenges of former players’ health after having participated in American style football (ASF). The whole player focused FPHS is designed to deepen understanding of the benefits and risks of participation in ASF, identify risks that are potentially reversible or preventable, and develop interventions or approaches to improve the health and wellbeing of former players. We are recruiting and following a cohort of former professional ASF players who played since 1960 (current n  = 3785). At baseline, participants complete a self‐administered standardized questionnaire, including initial reporting of exposure history and physician‐diagnosed health conditions. Additional arms of the initiative are addressing targeted studies, including promising primary, secondary, and tertiary interventions; extensive in‐person clinical phenotyping, and legal and ethical concerns of the play. This paper describes the components of the FPHS studies undertaken and completed thus far, as well as those studies currently underway or planned for the near future. We present our initiatives herein as a potential paradigm of one way to proceed (acknowledging that it is not the only way). We share what we have learned so that it may be useful to others, particularly in regard to trying to make professional sports meet the needs of multiple stakeholders ranging from players to owners, to fans, and possibly even to parents making decisions for their children.

1. INTRODUCTION

Over the last 20 years, there has been increasing concern both about the acute injury effects as well as the long‐term consequences to athletes participating in high‐impact contact sports. 1 These are not new concerns. Incidental case reports of acute traumatic injuries resulting in significant incapacitation and even deaths had been reported for over 50 years. More recently, chronic or late‐onset significant morbidity associated with participation in high‐impact sports has become of increasing concern, as reports of significant neurodegenerative diseases occurring in former prominent athletes, particularly related to those who played professional American style football (ASF), have made news in both the scientific as well as the lay press. 2 Other chronic conditions, including musculoskeletal, cardiovascular, sleep disorders and behavioral mental health conditions have also been reported. 3 , 4 However, for the most part, the published literature falls short in providing sufficient data to make informed judgments to quantify the magnitude of the risks associated with ASF for any of these conditions. This has the unfortunate effect of placing a burden on former players, potential players, and their families, as well as other stakeholders to make potentially lifestyle and health‐related decisions without adequate facts. It should be noted that this manuscript is designed to describe a strategic programmatic response to a research need and a series of studies under a large umbrella rather than a single study.

In an effort to better document the potential long‐term consequences of participation in ASF, the National Football League Players Association (NFLPA) in 2014 put forward a nationally advertised major Request for Proposals to study the health and welfare status of retired professional ASF players. The proposal asked for studies to assess and develop potential new preventive, diagnostic, and therapeutic interventions that would mitigate potential long‐term consequences of participation in the sport. In response, Harvard University developed the Football Players Health Study (FPHS), which was designed as a multidisciplinary investigative team approach to address these issues. This effort was formally funded in 2014 . The goal of the Football Players Health Study at Harvard University (FPHS) is to further understand the benefits and risks of participation in ASF, identify those risks that are potentially reversible or preventable, and develop interventions or approaches to improve the broad array of issues impacting the health and wellbeing of former ASF players.

From the onset, it was clear that the success of this program would be dependent on understanding and being committed to the concept of ongoing engagement with the population of interest in a participatory approach throughout the research process. 5 We initially conducted a number of focused meetings with representatives of the NFLPA as well as former ASF players from a variety of other player associations. These sessions provided input into prioritizing clinically meaningful targets for assessment, intervention, and potential functional improvements. Follow‐up meetings led to working groups of Harvard University faculty who came together to design a comprehensive set of studies, as indicated below, around the theme of “the whole player, the whole life.” Issues considered included, but were not limited to, identifying factors that could mitigate risk of having an injury; understanding consequences of injury as well as other factors associated with participating in the sport at the professional level on short and long‐term health impacts; and, to the degree possible, understanding the long‐term consequences for both physical and social impacts of having participated in the sport. In addition, we proposed to explore potential new approaches to therapeutics to lessen long‐term consequences of the unique exposures and putative injuries to which players are exposed. Not the least of our objectives was to determine the magnitude of the risk rates of a wide variety of outcomes. Such data would give all stakeholders better estimates for making potentially life‐changing decisions regarding participating in ASF. Because of the complex nature of player‐team relationships, a group of bioethics and legal scholars formed an additional unique component of our studies to explore and address the ethical and legal implications of the way professional ASF is organized. Finally, a significant component of our efforts is to keep the former players informed of our progress. This has been done through both a series of former player advisor group meetings and social media efforts to both inform former players on the progress of the studies and encourage participation in the ongoing efforts.

This paper describes the components of the FPHS studies undertaken and completed thus far, as well as those studies currently underway or planned for the near future. We present our initiatives herein as a potential paradigm of one way to proceed. We fully acknowledge that our approach is not the only way, but believe that what we have learned may be useful to others, particularly in regard to trying to make professional sports meet the needs of multiple stakeholders ranging from players to owners, to fans, and possibly even to parents making decisions for their children.

2. SCOPE OF THE STUDIES

We initially established two important Advisory groups. The first was made up of former NFL players who represented a spectrum of regional areas of the US, positions played, and different age groups. These former players provided essential insight into the concerns and questions that were most germane to the former player groups. The second was a group of local physician/scientists representing the range of research domains believed to be important to consider. Both groups have continued to evaluate and provide input into the research designs undertaken.

The range of studies can be divided into three broad categories (Figure ​ (Figure1). 1 ). Within each of these categories, there are a number of substudies, some of which have been completed, some which are ongoing, and some which are still in the planning or early implementation stages. In addition, an important component is communication and return of results to the participating former players and other stakeholders.

Range of studies undertaken, ongoing, and planned [Color figure can be viewed at wileyonlinelibrary.com]

2.1. Former player studies

A major effort of the FPHS focuses on studies of former NFL players with the goal of assessing risk factors associated with participating in professional ASF and the putative long‐term consequences to their health and wellbeing. This plan requires a coordinated set of studies. Initially, we needed to assess components related to the exposures that are or have been a necessary part of the game. Further, we are attempting to quantitate the current physical, social, and neurocognitive state of former players, and testing within nested case‐control subgroups newer diagnostic techniques and remote assessment tools. Eventually, we would hope to introduce potential new therapeutic modalities that may enhance the lives of former players after they leave the game.

2.1.1. Cohort questionnaire studies

Beginning in 2014, we sought to enlist the participation of an as large as possible cohort of former ASF players who had participated in the NFL (or former American Football League). Our criterion for enrollment was “formerly played professional football at any point from 1960 to present.” “Formerly played” was defined as having received compensation as a player from an NFL team. The year 1960 was chosen because by that time the transition from the soft, leather helmet to the hard, plastic helmet had been established throughout the league. The eligibility to join the cohort is a dynamic one in which younger players are invited and encouraged to enroll as they declare themselves retired. In addition, as subsequent substudies identify former players who had not enrolled in the initial round of cohort data collection, they are invited to provide baseline data.

To determine the topics to include in the initial standardized questionnaire, we held focus group meetings with both former players and research advisors. We first identified the parameters that would permit us to measure some of the characteristics of “exposure” in professional football (eg, position played, years of play, nature of some of the injuries during active playing years, essential demographics, etc). We also identified a number of health‐related domains of concern, for which we believed, by using well‐validated questions, we could establish baseline health status for the proposed cohort. Because a significant portion of the eligible cohort had either a home address or an email address, but not both, we needed to assess the potential difference in response patterns that might occur using one rather than both methods for contact. We selected approximately 500 former players at random who had both home addresses and emails to assess the response rate and degree of completion of the various components of the questionnaire. We determined that the response patterns and degree of completeness were no different between administering the questionnaire by email (REDCap C ) vs Scantron c paper questionnaires, and thus both methods were used for those for whom we had appropriate contact information.

The original main sources for defining former players were lists provided by the NFL Players Association, supplemented by NFL Profootball Reference. 1 Additional sources, many overlapping, included a number of philanthropic associations formed by former player groups, wives of current and former players, and other regional and local groups. These groups were asked to communicate with their members and to inform them of the study. 2 Figure ​ Figure2 2 describes the sources and number of former players for whom we initially believed we had obtained a contact address. Initially, we estimated that approximately 20 000 individuals played for one or more of the approximately 30 teams over the years starting in 1960. Of these, we estimated that approximately 4000 had died before the beginning of the follow‐up period. In February 2015, at the time of our first effort to contact the former players, and over the initial 3 years of follow‐up, we were able to confirm 14 538 individuals who met the criteria as former active players. Other members of the initially constructed lists had included coaches, management staff, and others who were not active players. We were able to confirm anticipated valid home addresses for approximately 12 713 players. In addition, we had available potential email addresses for 8542. Using combined mailings for both paper questionnaires and web‐based methods, we estimated that 13 403 former players with appropriate years played eligibility received our questionnaire in one or both forms (only the first method used to respond was counted). At present, the cohort is made up of 3785 former players who have completed our initial questionnaire. Newly retired players are continuing to enroll and plans exist to follow them over time.

Flow chart of former player contacts [Color figure can be viewed at wileyonlinelibrary.com ]

2.1.2. Content and purpose

Our standardized questionnaire captures demographic and football exposure information that allows us to characterize the former players by age, race, football experience, and other usual characteristics of behavior related to lifestyle and general risk factors for injury and illness associated with participating during their playing years as well as postplaying years. In addition, we use well‐established questions to assess outcomes in a number of health domains. 3 Other illnesses, surgeries, and medical conditions since retirement, which are self‐reported as confirmed by health practitioners, also are collected.

The data obtained from the cohort by questionnaire serves two essential purposes. The initially obtained data provides cross‐sectional estimates of the frequency of occurrence of health outcomes in a variety of domains. Along with these questions on outcomes, we are obtaining detailed information on exposure in organized football as well as general lifetime risk and behaviors that may affect these outcomes.

2.1.3. Limitations

The overall response rate for the entire eligible cohort to date is approximately 30%. This is not dissimilar to other pro athlete cohorts. 6 In selected exposure groups, we have found response rates by important demographic characteristics such as age, position played, and the number of seasons to be relatively comparable to the overall eligible population. In addition, although we can identify the prevalence of different health outcomes in our baseline data, the possibility of bias in estimating rates of these conditions among all former ASF players must be considered if players with certain conditions were more or less likely to join our cohort than those without the conditions. Importantly, though, this is not as problematic for studies of exposure‐health outcome associations with the cohort data, as such outcome‐dependent (or exposure‐dependent) participation or nonresponse does not create spurious associations between an exposure and outcome if no true association exists. 7

The prospective component of the population cohort study began in January of 2019, with follow‐up questionnaires sent to all former players who previously responded, and with newly reported medical conditions documented by follow‐up to the players’ health care providers. The relation between exposures identified at baseline and the occurrence of new outcomes after baseline identified by such cohort follow‐up is much less susceptible to any biases related to participation in the baseline questionnaire. In addition, those former players who did not respond to the initial questionnaire will be given another opportunity to join the study. A few remote‐based substudies among the cohort members have been undertaken, either based upon the initial questionnaire responses or de novo ancillary hypotheses that are currently underway and are described in detail under the Targeted Studies section below.

2.2. In‐person assessment studies

An additional purpose of the cohort baseline questionnaire was to use the collected data on health status to identify former players who self‐reported to be either “afflicted” or “nonafflicted” in four important health‐related domains. A limited number of these participants, in matched groups by age and race, have been selected to be invited to come to Boston to undergo detailed specialized testing using both best‐available technology and some novel or exploratory technology to assess how self‐reported status in the domains of neurocognitive, cardiac, musculoskeletal pain, and sleep relate to objective measures in each of these domains. The first objective will use a multimodality protocol designed to provide a comprehensive phenotypic assessment of former players, with an emphasis on clarifying the link between subjective complaints or prior diagnoses (or lack thereof) identified on the questionnaire and gold‐standard objective assessments of disease status. Depending on the observed correlations, these objective measures, although in relatively in small numbers of subjects, can be used to test several hypotheses related to exposure in football by using nested case‐control designs.

For those participants who come to Boston for the in‐person assessments (IPA), we have developed a medical navigation system. At the end of the session, each subject who participates in the IPA will meet with an appropriate study team member to have the opportunity to discuss all clinical findings. Follow‐up for any incidental, clinically relevant findings will be recommended. When appropriate and desired, the subject will be helped with referral to clinical care facilities in his local community. This medical navigation also serves as an educational and guidance program geared toward the specific needs of participants across the study.

2.3. Targeted studies

While the development of the cohort of former players was being established, a number of opportunities to investigate a wide variety of issues related to the nature of the kinds of injuries and potential long‐term outcomes were identified through a local process of request for proposals among all of the Harvard institutions. These targeted studies are funded from the original grant proposal award. These were initially identified as Pilot Studies and more recently characterized as Targeted Studies. These studies take advantage of local ongoing work in the Harvard community by requesting research proposals for modest efforts that would provide data that could lead to substantial outside funding to expand the research and/or have significance to the former ASF player population. The proposals are competitively evaluated and considered for 1‐ to 2‐year funding periods. The criteria for funding are whether the study is considered innovative, feasible, and achievable in a limited funding period, considering the potential roadblocks to success and whether the proposers had the requisite skills and experience to conduct the research. These criteria are rated competitively by external, independent, domain‐specific experts, and funding decisions are made by the study leadership based on evaluation scores and programmatic needs. The studies are divided into basic science or pathophysiologic studies in both nonhuman and human (though not necessarily football player) populations, and studies in both active and retired ASF players. The targeted studies are each summarized by domains and described briefly in Table ​ Table1 1 .

Targeted Studies

Abbreviations: BCH, Boston Children's Hospital; BU, Boston University; BIDMC, Beth Israel Deaconess Medical Center; BWH, Brigham and Women's Hospital; DFCI, Dana‐Farber Cancer Institute; HSL, Hebrew Senior Life Institute for Aging Research; McLean, McLean Psychiatric Hospital ; MGH, Mass General Hospital; MSM, Morehouse School of Medicine; NEU, Northeastern University; Wyss, Wyss Institute at Harvard.

A wide variety of Targeted Studies were developed over the initial 3 years of the study (Table ​ (Table1). 1 ). These include very basic immunologic assessments of impacts resulting from an acute injury, outcomes related to repeated mild traumatic brain injury in animals, cardiac assessment in active and retired players, video analysis of the biomechanics of exposure and the development of mechanical preventive strategies for stress to the knee during active exercise, among others. Similar additional basic and applied studies that are currently underway and being planned are also included in Table ​ Table1 1 .

More recently, we have begun to develop remote assessment and intervention studies.

Because of the practical limitations of bringing large numbers of former players to Boston, it is clear that to the degree we can obtain standardized data remotely from former players living across the country we can increase our power to test a variety of hypotheses. Several such attempts are already underway. For example, using a smart phone‐based application specifically developed for the FPHS, we conducted a remote study of a neurological function using the effects of dual tasking on measures of balance (The Team Study). 17 Participants who downloaded our Team Study app 4 provided repeated measures over several weeks of balance and walking while doing mental arithmetic, with the data being transmitted remotely. Assessments of the results of this effort are currently underway. A second example is the Brain Health Study that uses a standardized series of cognitive assessment tools, remotely administered on an encrypted website, providing detailed assessments in several brain function domains. At the end of the procedures, the results are compared to a large standardized database, and we are able to provide individual participants with a personalized assessment of their cognitive function and styles. To date, 349 former ASF players have completed this assessment.

Other remote cohort substudies are currently just getting underway or are in the planning stages. These include the development of a scalable sleep intervention program to improve pain, quality of life, and health in former players; a goal‐directed resilience training study to mitigate chronic pain in a group of players living in the greater Atlanta area; and a study of personal networks with the potential to inform the development of tools to enhance health‐positive networking.

As a result of the initiation of a detailed follow‐up questionnaire study of all responders to the first round of baseline questionnaires, starting in 2019, we are collecting prospective incidence data over a 4‐year period in the established cohort and have increased opportunities for further remote studies in selected subgroups of the population. Those former players who did not respond to the initial questionnaire will be given another opportunity to join the study.

The basic population we are studying is largely a public and relatively easily identifiable cohort of former players. Therefore, one of the unique challenges of the study is to maintain the confidentiality of all medical information being gathered. Essential to gaining the trust of the former players, every possible effort to protect the security and confidentially of all health‐related data provided is made. To this end, we secured a Certificate of Confidentially from the National Institute of Health for each individual research protocol developed which includes former player participants. The Certificate prohibits disclosure of identifiable, sensitive research information to anyone not connected to the research (with certain exceptions; see https://humansubjects.nih.gov/coc/index ). In addition, all data obtained are held in secure, custom‐built data repositories. All identifiable data are coded and removed from any working files. Access to identifying data is on a need‐to‐know basis, and only by specifically trained and vetted personnel.

2.4. Law and ethics initiative

At the onset of this effort, we recognized that because of the nature of the potential competing stakeholders’ interests in the NFL (owner, players, agents, physicians, families, fans, etc.), the interactions of these stakeholders raised myriad potentially complex legal and ethical considerations. Our Law and Ethics team's first task was to determine not only who these stakeholders were, but also to map the nature of their interactions. This effort encompassed a variety of distinct projects with the primary goal of understanding the legal and ethical issues that may enhance or impede players’ health and welfare. In keeping with the mantra, “the whole player, the whole lifetime,” this component of the study examined issues at various points of a player's lifetime—from competing for a spot in the NFL Combine, to active years of play, to retirement planning, and the way players and family members dealt with health issues after their playing years were over.

A series of studies were undertaken to assess how stakeholders’ perspectives interact (Table ​ (Table2). 2 ). We identified who the stakeholders in player health were, evaluated their legal and ethical obligations, and assessed the current successes as well as gaps and opportunities for each stakeholder in protecting and promoting player health. 20 , 21 In addition, we applied a series of legal and ethical principles to arrive at recommendations for positive change where needed. 22 A second effort compared the NFL's policies and practices to those in place in Major League Baseball, the National Basketball Association, the National Hockey League, the Canadian Football League, and Major League Soccer, to assess best practices and make recommendations for areas deemed in need of improvement. 23 In addition to these major reports, a series of additional studies on the legal and ethical aspects of the game were carried out over the first 3 years of the study. These include an examination of team doctors’ conflicts of interest and the ethical management thereof, an examination of the applicability of the Americans with Disabilities Act and the Genetic Information Nondiscrimination Act to NFL football and the NFL Combine, and an analysis of the applicability of workplace safety laws and guidelines (such as the Occupational Safety and Health Agency) to professional football. We also conducted a qualitative assessment project with one‐on‐one interviews of approximately 50 current and former players and another 50 of their family members. The output of this study is ongoing. The goal was to better understand the perspectives of these key stakeholders on the following topics: overall professional football experience, improving player safety, health, family, and social issues, support as a professional athlete, life after football, risk disclosure, and risk‐taking, health care and club medical staff, medical screenings, and injury and pain management. These data produced a theoretical evaluation of the path that a hypothetical college football player might face, from a legal and ethical perspective, in trying to enter the sport. 24

Law and ethics studies

2.5. Communications and return of results

A significant effort to inform the former ASF player community about the overall study and to, when possible, provide them with updates that relate specifically to their concerns in specific domains, is being carried out. To date, these efforts have focused on a variety of digital media pathways including emails; social media such as Twitter, Facebook, and LinkedIn; informational videos on the Study website; and status reports. Some of the remote player studies that are web‐based provide opportunities for rapid feedback of results to the participants (eg, Brain Health Study, Personal Networks Study). In addition, we have developed a process for providing contextual information from subject matter experts to not only interpret individual results appropriately but also to potentially offer suggestions to improve the participants’ daily lives and health outcomes. Similar approaches apply to results return for other emerging cohort analyses which are positioned within the framework of and providing motivation for, the player taking a proactive approach to their health. In addition, player advisors meet with investigators approximately once per year in person and participate in regular telephone conference calls to both discuss results and to communicate player issues of which they have become aware.

3. DISCUSSION

To date, we have established the largest ongoing study of living ASF former players. Because we continue to recruit both medium‐term and long‐term former players, as well as newly retired players, we anticipate that the cohort will grow in both size and significance as we move forward over the years. The current overall response rate to our questionnaire is approximately 28% across all position player groups. However, with regard to the distribution of responses within this group across age, years played, and positions played, our responders are similar compared to the entire potential cohort of former players who have not yet responded (Table ​ (Table3). 3 ). While there are limited studies for comparison among professional, team sport athlete populations, a recently reported study in a cohort of professional rugby players, with a response rate of 28%, is consistent with our own results. 6

Cohort responders with data in NFL Pro‐Reference (PFR) database compared to non‐responders in the database (preliminary assessment as of September 2018)

Clearly, there are limitations to drawing definitive conclusions from what is essentially a voluntary participatory sample from the fully defined population of former players. These include issues of both sampling bias as well as generalizability. There are also issues of comparability of this cohort of essentially former super athletes to other men of comparable size, age, and race who were not as athletic. Thus, comparing the generalizability of the findings in these studies of former ASF players to the general population can only be done with caution. With regard to outcomes, we were able to show that the actual number of reported Anterior Cruciate Ligament (ACL) tears among our participating former players’ years of play 25 corresponded almost exactly to that which would be predicted from data in the literature in two reports on ACL tears in active players summarizing the last 20 years. 26 , 27 In spite of this initial evidence of representativeness, any estimates of prevalence among our current responders can only be considered preliminary and used with caution. As we move forward with our 4‐year follow‐up assessment, we would anticipate our incidence data would become more generalizable within the total cohort.

One of the major objectives of initiating these studies was to define the nature of the risks these former players experience in their postplaying years, from the time they are no longer actively playing through the remainder of their lives. Too often, both the peer‐reviewed scientific literature and the lay press consists of anecdotal, unique, and often dramatic case reports. Even in the studies that have used collected samples from a series of cases, one cannot make estimates of the actual levels of risk. There would appear to be no question that there are potential long‐term health risks associated with participation in professional ASF, but the magnitude of these risks remains elusive. In addition, most published studies of health risks offer limited potential avenues for mitigation or prevention. The future health and well being of potential players both during the time they are playing as well as in their post play lives will be enhanced by developing a more quantitative understanding of the risks and possible benefits associated with life in football.

No less important in our studies is the possibility of understanding potential pathophysiologic mechanisms associated with or related to some of the variety of injuries and medical conditions associated with ASF. Because of the way the various studies described above have been undertaken, we have the opportunity to explore some of these mechanisms of injury and repair both in human and other animal species. In one case, a pilot/targeted study has led to a formal phase 3 clinical trial. 18 One of our original cardiac pilot studies was instrumental to a multiyear NIH‐funded effort to examine mechanistic underpinnings of pathologic heart remodeling in football athletes. Two targeted studies designed to assess the potential for intervention for reducing chronic pain or hypertension are also underway. If newly designed brain contrast assessments in our IPA studies correlate with standardized neurocognitive testing, these efforts may provide a further understanding of the chronic repetitive head injury.

4. TURNING SCIENCE INTO ACTIONABLE INSIGHTS

Future studies linked to biological targets will hopefully yield quality of life improvements for players and former players, but predicting who might become affected, what specific exposures increase that risk, whether there are postplaying activities that will mitigate that risk, and whether, once affected, the condition can be treated or its impact minimized, remains to be determined. Even while waiting for definitive studies, there may be opportunities to demonstrate potentially important interventions. Several analyses on the initial data have resulted in publications or manuscripts related to domains of interest. For example, our data strongly suggest that voluntary or forced weight gain during active playing years increases downstream risk in a variety of domains, providing valuable information for player education and clinical practice. 28 Similarly, a recent analysis of long‐term outcomes from having torn an ACL during active play suggests that, besides increased risks of significant arthritis and subsequent knee replacement, there is a need for assessing former players for potential cardiac risks, as there appears to be a modest excess of myocardial infarction among these former players. 25 These findings suggest that former players should undergo cardiovascular risk assessment, and that certainly for those with post ACL injuries and resulting chronic knee pathology, or chronic significant weight gain during playing years, consideration of custom designed exercise programs is warranted. Evaluating the impact of providing specific information in a focused form to former players is an obvious and important component that is being developed as part of our long‐term follow‐up plans.

5. CONCLUSIONS

The Football Players Health Study at Harvard University is a broad and ambitious research and translation program that attempts to securely capture data from all aspects of former ASF players’ lives. We anticipate that such data will help to quantify the potential long‐term risks associated with ASF. As more pathophysiologic data and risk quantification are obtained, we anticipate the information will be useful to drive more informed player decision‐making. We would also anticipate that results will lead to appropriate interventions as these men age, and thus enhanced health and wellbeing outcomes.

CONFLICT OF INTERESTS

Dr. Zafonte was partially supported by the National Institute on Disability, Independent Living, and Rehabilitation Research (90DP0039‐03‐00, 90SI5007‐02‐04, and 90DP0060), the National Institutes of Health (4U01NS086090‐04, 5R24HD082302‐02, and 5U01NS091951‐03), and US Army Medical Research and Materiel Command (W81XWH‐112‐0210). He also serves as Co‐PI on a T‐32 and receives funding from the Football Players Health Study at Harvard University, which is funded by the NFL Players Association. Dr. Zafonte received royalties from (a) Oakstone for an educational CD—Physical Medicine and Rehabilitation: a Comprehensive Review; (b) Demos publishing for serving as coeditor of the text Brain Injury Medicine. Dr Zafonte serves on the Scientific Advisory Board of Myomo, Oxeia Biopharma, BioDirection, and ElMINDA. He also evaluates patients in the MGH Brain and Body—TRUST Program, which is funded by the NFL Players Association.

Dr. A. Pascual‐Leone was partly supported by the Sidney R. Baer Jr. Foundation, the National Institutes of Health (R01MH100186, R21AG051846, R01MH111875, R01MH115949, R01MH117063, R24AG06142, and P01 AG031720), the National Science Foundation, DARPA, the Football Players Health Study at Harvard University, and Harvard Catalyst| The Harvard Clinical and Translational Science Center (NCRR and the NCATS NIH, UL1 RR025758). Dr. A. Pascual‐Leone serves on the scientific advisory boards for Neosync, Neuronix, Starlab Neuroscience, Neuroelectrics, Magstim Inc, Constant Therapy, and Cognito; and is listed as an inventor on several issued and pending patents on the real‐time integration of transcranial magnetic stimulation with electroencephalography and magnetic resonance imaging.

Dr. Baggish has received funding from the National Institutes of Health/National Heart, Lung, and Blood Institute, the National Football League Players Association, the American Heart Association, the American Society of Echocardiography and receives compensation for his role as team cardiologist from US Soccer, US Rowing, the New England Patriots, the Boston Bruins, the New England Revolution, and Harvard University.

All authors in this study are or were either partially or fully supported by the Football Players Health Study at Harvard University which is in turn sponsored by the NFLPA.

AUTHOR CONTRIBUTIONS

All authors participated in the conception and design of the study, acquisition, analysis, and interpretation of the data, participated in drafting and revising the manuscript and approved the final version submitted to AJIM. All authors agreed to be accountable for all aspects of the study to ensure that questions related to its accuracy and integrity are appropriately investigated and resolved.

ETHICS APPROVAL AND INFORMED CONSENT

The work was performed at Harvard Medical School. The institutional review board of the Beth Israel Deaconess Medical Center, Boston, USA approved this study and all participants provided written consent before participating in the research. We secured a Certificate of Confidentially from the National Institute of Health for each individual research protocol developed which includes former player participants. The Certificate prohibits disclosure of identifiable, sensitive research information to anyone not connected to the research (with certain exceptions; see https://humansubjects.nih.gov/coc/index ).

ACKNOWLEDGMENTS

The authors wish to acknowledge and thank the former ASF player community, our participants and advisors, and the past and present staff of the Football Players Health Study at Harvard University for their outstanding commitment to improving former ASF player health. The authors would like to specifically thank Kelsey Palmer and Chloe Young who provided extensive administrative and editorial support on the manuscript. All authors this study are or were supported by the Football Players Health Study at Harvard University which is in turn sponsored by the National Football League Players Association.

DISCLAIMER BY AJIM EDITOR OF RECORD

John Meyer declares that he has no conflict of interest in the review and publication decision regarding this article.

Zafonte R, Pascual‐Leone A, Baggish A, et al. The Football Players’ Health Study at Harvard University: Design and objectives . Am J Ind Med . 2019; 62 :643‐654. 10.1002/ajim.22991 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]

1 NFL Profootball Reference, an on‐line website that follows NFL player statistics both currently and historically.

2 Most of these sources overlapped with the main sources of identified contact information obtained from the NFL Players Association, and the NFL Alumni Association.

3 2008‐2012 PROMIS Health Organization and PROMIS Cooperative Group.

4 The applications was designed specifically for Apple iPhones and participants were invited to access many functions that measured a number of physiologic parameters while, standing, walking, and dual tasking.

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DCU research project examining online hate in football launches podcast series

The first episode, which looks at the challenges in defining and investigating the issue, features an interview with Dr Theo Lynn on the data analysis involved in the project. Multiple papers from the project have been based on analysis of millions of social media posts using deep learning techniques.

Dr Gary Sinclair also features in the opening episode where he speaks about the role of social media platforms in the regulation of hate speech on their platforms. He points to the difference in the online landscape following the acquisition of X (formerly known as Twitter) by billionaire Elon Musk.

The series is presented by Dr  Colm Kearns , who is also a principal investigator on the project.

The next episode in the series will focus on the effect abuse has on players. To be released on 3rd September, it will feature an interview with emotional welfare specialist Sue Parris. Later in the month, the third episode will feature an interview with freelance Guardian journalist Julia Belas Trindade.

Over the last three years,  the Tackling Online Hate in Football project has sought to address the issue of online hate with a combination of quantitative data analysis, nuanced qualitative critical analysis and grassroots activism against hate speech. The project has brought together a range of diverse expertise (data analysis, network building, interview skills, discourse analysis, etc.) and engaged with all of the relevant stakeholders (player representatives, governing bodies, policy makers, social media platforms, fan organisations, etc.) in seeking to create a comprehensive solution. All of these aspects of the project will be covered in different episodes throughout the series.

Previously, the team published a data analysis of a huge sample of posts in a Manchester City fan form in an effort to track discourse around sportswashing amongst the clubs fan base. The study received widespread media attention leading to appearances on the BBC World Service among other media platforms.

For media enquiries related to this research, contact Conor O'Donovan and Rob Hanrahan at [email protected]

August 31 – September 6, 2024  |  No. 515

Concussion studies by Australia’s top football codes have stalled amid scientific controversy over the causes of neurodegenerative diseases in players. By Wendy Carlisle .

The contested science of head injuries in sport.

A core member of the NRL’s concussion research group is also one of the most outspoken critics of the link between repeated head injury in sport and the neurodegenerative disease chronic traumatic encephalopathy (CTE).

Dr Rudy Castellani, a professor of pathology at the United States’ Northwestern University, says CTE is an “invented disease … conjured out of thin air” by scientists at Boston University’s CTE Center.

In an expert statement for insurers fighting a US$1.3 billion settlement involving more than 1700 former American National Football League players and their families last year, Castellani accused the Boston University scientists of using “spurious staining techniques … unprecedented in neuropathology” that may have intentionally “manipulated” their findings.

In a response, the Boston facility said all brain donors had been “comprehensively evaluated by a team of three board-certified neuropathologists, who reach a consensus on the final research diagnoses”. The university said tissue samples “were shared with another 60 academic institutions and more than 130 peer reviewed manuscripts in respected scientific journals had been published”.

Castellani’s views corroborate the Australian NRL’s multimillion-dollar research program into former elite-level rugby league players, which to date has concluded there is no link between concussion and depression or other cognitive problems.

Castellani has provided expert witness statements to multiple football codes asserting CTE is not a neurodegenerative disease but was instead “normal ageing”.

At World Rugby’s concussion conference held in Amsterdam in late 2022, Castellani said it was “pure hypothesis at best” to say CTE was caused by “sport exposure”.

“I don’t think this is healthy to stamp neurodegenerative disease on the foreheads of athletes without proper scientific support,” he said. “We are now equating sports to an environmental exposure like pesticides or something like that.”

In 2022, the National Institutes of Health, part of the United States Department of Health and Human Services, issued a consensus statement by the world’s top neuropathologists stating that CTE was a unique neurodegenerative disease “caused in part” by prolonged exposure to repeated head injury.

At the same conference in Amsterdam, the NRL’s lead researcher, Associate Professor Andrew Gardner, said CTE was a “hypothesis” that needed to be “tested”.

Gardner reported that three quarters of the 200-plus former elite players studied by the NRL were doing “absolutely fine”, while the remaining quarter were having problems, which ranged from “some” to “significant” and “unfortunately diabolical”.

It’s the “diabolical” cases that caused grief to NRL investigators last year. Complaints sparked two separate investigations into the NRL research program, one by Sydney University’s human ethics committee and another by the NRL itself.

In these, families reported they were not told of dementia diagnoses. Other families complained that their opinions were not sought by researchers to see how they were living their lives.

“They should live a day in my life,” said Sheree Miller after being told her husband, Glenn Miller, a former Penrith Panthers and Newcastle Knights player, had a normal memory for a 54-year-old.

By 2021, with her husband in decline, Sheree accompanied Glenn to see the NRL researchers to learn he had been diagnosed with Alzheimer’s disease some years before.

Sheree said she “threw a hissy fit”. She said the family GP had not been informed of the diagnosis.

“Is Glenn another statistic? What are you doing for the participants? How many other men are going through this?”

Other former players diagnosed with dementia included former St George player Trevor Crow, then aged 59.

Diabolical cases, such as Miller’s and Crow’s, were left out of key NRL studies because of the dementia diagnosis. One such study reported depression and cognitive status were not correlated with concussion.

In mid 2024, citing “privacy reasons”, Sydney University and the NRL quietly found there were no issues with the NRL’s research but declined to release details of their review. None of the families were spoken to about their concerns.

Castellani told The Saturday Paper he was unaware of the investigations into the NRL’s research program, describing Dr Gardner and his colleagues as “among the most exceptional neuropsychologists and scientists on earth, with unassailable integrity”. He said Gardner was “a tribute to your continent; I wish there were more people like him in the US”.

The AFL’s $25 million concussion study, announced in 2022, has also stalled. Despite promising a new era of “transparency”, the AFL now refuses to answer questions about whether or not it has even started.

The $25 million project is a reboot of the code’s “landmark” 2013 project, which the AFL later admitted had withered from neglect.

That project was “under-funded and under-resourced”, according to an AFL investigation called in the wake of revelations that its former top concussion adviser, Dr Paul McCrory, had included plagiarised material in several articles, a number of which were retracted. The British Journal of Sports Medicine asked if McCrory had “warped the concussion narrative” in such a way as to make concussion seem like a less serious injury.

The AFL has criticised research showing most players would be still suffering brain injury well beyond when they would have returned to play under current concussion protocols.

The Monash University study, published in June, reported levels of certain blood biomarkers associated with brain injury in 81 concussed players in the Victorian Amateur Football Association (VAFA), compared with 56 controls. It reported elevated levels of the serum GFAP and NfL levels for at least four weeks after an injury and in a smaller number up to 26 weeks.

Researchers concluded these prolonged biomarkers suggested current return to play protocols, which are 12 days in the AFL, should be revised and made more “conservative”.

Lead researcher Dr Stuart McDonald said the best way of explaining the blood biomarkers was they were “just bits of brain in your blood”. He said: “It’s crude to put it that way, and we are talking very small amounts, but that’s what it is.”

The AFL said the Monash paper wasn’t relevant. General manager of corporate affairs Jay Allen said: “A study based on the VAFA, which has a minimum 21-day stand down, and then comparing it to the professional AFL competition minimum 12-day return to play, is not balanced.”

There are also questions over the AFL’s key brain injury project – a brain donation scheme for former players, to aid research.

The league accepts that studying brains of deceased players is critical for its longer-range projects to be meaningful, and for the search for an in-life diagnosis of CTE. At the moment it is only diagnosable post-mortem.

In 2020, a Victorian coroner recommended the AFL “actively promote brain donation to the Australian Sports Brain Bank” in order to make a meaningful contribution to player safety, but to date no brain-donor program has been established.

In late 2023 Victorian coroner John Cain turned his focus on CTE prevention. Cain was investigating another AFL CTE casualty – former Richmond player Shane Tuck, who suicided aged 38 with what his family called a “war zone” in his head.

Cain deferred to the expert evidence of leading US CTE expert Dr Robert Cantu of Boston University, who recommended a reduction of contact training and the introduction of smart mouthguards embedded with accelerometers designed to measure the quantum of hits to which a brain is exposed.

Cantu explained that the risk of developing CTE was directly correlated to cumulative hits to the head, and the quantum of those hits over time, and not concussion.

“Cumulatively they may have a greater impact than concussion alone, which is very less frequent,” Cantu said. “And those are the majority of hits that somebody takes over their career.”

According to CTE expert and adjunct professor at Swinburne University of Technology Alan Pearce, the AFL prefers to talk about concussion rather than the dangers of repeated head injury. The concussion protocols and head injury assessment (HIA) focus on what he calls the “symptomatology paradigm” – that is, hits that cause concussive symptoms.

“CTE is not caused by concussion. It’s due to exposure of small impacts over many years,” Pearce told a recent corporate fundraiser for the Concussion Legacy Foundation Australia in Melbourne. “Those people diagnosed with CTE had long careers and started contact sports from the age of five ... We’ve had players diagnosed with CTE who have never had a concussion.”

Of more than 100 donor brains analysed at the Australian Sports Brain Bank, 48 have been diagnosed with CTE. They include NRL and rugby union players, AFL players Danny Frawley, Shane Tuck and Graham “Polly” Farmer, and Heather Anderson, the first AFLW player to be diagnosed.

At the corporate fundraiser for the Concussion Legacy Foundation Australia, sitting at table one, were AFL retirees Nathan Murphy and Paddy McCartin.

Murphy, who played for 15 minutes in Collingwood’s grand final win last year before suffering a career-ending hit, is grateful for the AFL’s decision to retire him. “They ended my footy career,” said Murphy, before reframing it: “I mean, they saved my life.”

Nick Maxwell, a former Collingwood captain and All-Australian, said hearing Pearce talk about CTE was a shock. “I was surprised to hear that,” he said, “and I played footy from the age of five.”

This article was first published in the print edition of The Saturday Paper on August 31, 2024 as "Head games".

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Wendy Carlisle is a freelance journalist specialising in reporting head injury in contact sport.

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August 31 – September 6, 2024 Edition No. 515

‘Very colourful terms’: Is this the end of the Jacqui Lambie Network? Rick Morton

Pezzullo: Labor has ‘picked a side’ in war with China Jason Koutsoukis

Kim Williams on the ABC’s great divide Martin McKenzie-Murray

Labor and merit-based appointments Karen Barlow

Fixing Australia’s plan to end gendered violence Kristine Ziwica

Reef bleaching outpaces Outlook report Mike Seccombe

The contested science of head injuries in sport Wendy Carlisle

Hostility between Hezbollah and Israel appears to abate Jonathan Pearlman

Children don’t belong in prison Lidia Thorpe

The Canberra disconnect Chris Wallace

The real power of independents John Hewson

Jon Kudelka cartoon, August 31, 2024 Jon Kudelka

The statistical closet

The power of folk singer Grace Petrie Jane Cornwell

Apple TV+’s Sunny Sarah Krasnostein

Pinchgut Opera’s Eternal Light Chantal Nguyen

Deaf in dance: feeling the beat Fiona Murphy

Two stories Mark O’Flynn

Brothers and Ghosts Rhoda Kwan

Beam of Light Carmel Bird

Jilya Monique Grbec

Asparagus Andrew McConnell

The unbearable awkwardness of Father’s Day Anita Punton

‘You say I can’t, so I’m going to do it’: blind surfer Matt Formston Martin McKenzie-Murray

No. 515 Liam Runnalls

True or false: a seahorse is a fish. Cindy MacDonald

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cycling   August 31, 2024

‘You say I can’t, so I’m going to do it’: blind surfer Matt Formston

Martin McKenzie-Murray For legally blind Paralympic cyclist turned surfer Matt Formston, every challenge is an opportunity to think bigger, including tackling the ‘Mount Everest of surfing’.

cricket   August 24, 2024

The curse of sporting superstitions

Martin McKenzie-Murray Superstition dictates the lives of many athletes and sports fans, from the order of putting on a kit to talking to inanimate objects – and the author is not immune.

sport   August 17, 2024

Breaking bad: spinning the Raygun narrative

Martin McKenzie-Murray Was the routine of Australian Olympic breaker Raygun – which received a zero-point score in Paris – ironic, spectacularly inept or just insulting?

sport   August 10, 2024

Paris 2024: memes and memories

Martin McKenzie-Murray It’s not only the gold medallists who earn their moment in the Olympic spotlight. Athletes of all kinds have proved themselves to be spectacularly meme-worthy.

sport   August 3, 2024

The 2024 Paris Olympics so far

Martin McKenzie-Murray Drama is part of every Olympic Games and true to the nature of the French capital, the Paris edition has delivered this essential ingredient.

afl   July 27, 2024

A watershed win, a waterless flight for Fremantle

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• Library of Congress
• Research Guides

Sports Industry: A Research Guide

• Introduction
• General Resources
• Sports Marketing & Management
• Venue Management & Naming Rights

Search the Library's Catalog

• Sports Betting
• Subscription & Internet Resources
• Using the Library of Congress

While several professional football leagues have come and gone, the focus of this section will cover the National Football League (NFL), the premier league for professional football (American-styled football) worldwide. The National Football League was established in 1922 with eight teams when the American Professional Football Association changed its name to the National Football League soon after. During the late 1960's, it merged with another professional football league, the American Football League (AFL) expanding the number of teams to 13. While the NFL has been a not-for-profit since the 1940’s, in 1966, the league itself (not the individual teams) became a 501(c)(6) non-profit organization when it merged with the American Football League, but in 2015 the League announced it was planning to drop its tax-exempt status.

Presently, the NFL is made up of 32 teams with a newly realigned conference structure implemented in 2002. The League is governed by a Commissioner and the Executive Committee, which includes one representative—an owner or top officer—from each team. Few professional sports have experienced the growth, stability, and success as the National Football League. Its longevity and expansion is a testament to that success. Its effort to branch out into international markets has been less successful. It created the World League of American Football in 1991 (it changed its name to NFL Europe in 1995) but attendance fluctuated, and it ceased in 2007. The NFL also began playing games in London in 2007. It began with at least one game a season, and later added more. In October of 2018 it was announced that in 2019, there would be a total of four games played in the UK - two at Wembley and two at Tottenham Hotspur’s new stadium. Also, in the 2017 and 2018 seasons, one game was played in Mexico City.

The NFL utilizes a number of different types of revenue sharing methods. Retained revenues and shared revenues are the two main types of revenue sources for NFL franchises. Retained revenues, consisting of revenue generated and kept by individual teams, include 60% of stadium (gate) receipts for home games, naming rights, sponsorship, luxury suite revenue, concessions and local broadcast rights. A few points on revenue:

• Building new stadiums and selling stadium naming rights have contributed enormously to the revenues of NFL franchises. This trend has continued to grow within the league - since 1990 16 new stadiums have been built.
• The primary source for shared revenue in the NFL is through national broadcast rights fees, away game ticket sales, and licensing. In December 2011 the NFL announced a new media deal running though the 2022 season.
• The NFL's marketing enterprise has also generated substantial revenue for the league via NFL Ventures. Organizationally, NFL Ventures includes several subsidiary elements: NFL Enterprises primarily concerned with the advertising, publicizing, promoting, broadcasts of NFL games; NFL Properties which oversees the licensing and sponsorship; NFL Productions which produces NFL-related programming; and NFL International which promotes the NFL internationally.

Salary Caps

Despite the NFL's longevity, the league finds itself challenged by the current player free agency and team salary cap system. The salary cap is the result of league revenue sharing between teams and players, which is based on an agreement of defined gross revenues (DGR). The league then defines the share of DGR that will go to each franchise's player roster. The salary cap actually serves as a ceiling placed on spending which is equally applied to all teams. In comparison to the other professional sports implementing the salary cap system, the NFL has proven to be effective at managing player salaries and the expanding cost involved in operating the league.

Other Leagues

Other leagues have been established. This includes the XFL which is a professional American football league in predominantly mid-sized to major markets founded in 2018 using the same name as a league founded in 2001. In 2023 there are eight teams and the season is ten games and runs from February to May.

There is also the United States Football League (USFL) which is also a professional American football league that first played in 2022. The league operates eight teams in four cities as of 2023.

Books & Periodicals

These are just a few of the more business-themed resources related to football. Note that there may also be relevant information in the General Resources section of this guide.

The following materials link to fuller bibliographic information in the Library of Congress Online Catalog . Links to digital content are provided when available.

Internet Resources

We have included some resources that are not business specific in an effort to provide sources that can help researchers understand the sport itself and its structure.

• Compensating Differentials and the Social Benefits of the NFL External In this paper Gerald Carlino utilizes wage equations to measure differences in compensation in various metropolitan areas which have NFL franchises. The study looks at the effects that NFL franchises and new stadiums have on cities and residents, and the value of the investment. Working Paper No. 02-12/R ( Research Department, Federal Reserve Bank of Philadelphia)
• "An Evaluation of the Economic Impact of National Football League Mega-events" External This piece was written by Victor A. Matheson and Robert A. Baade and published August 2011. This article is mostly focused on big events and not regular season play.
• "Exclusive: Leaked Documents Show Operating Profits For NFL Ventures Rose 29 Percent Last Year" External This piece by Tommy Craggs published in July 15, 2011 was originally published on a Deadspin, this article on leaked NFL Ventures documents with 2009 and 2010 financial information.
• "Getting to the 2011-2020 National Football League Collective Bargaining Agreement." External International Journal of Sport Finance by Kevin G. Quinn. May 2012 (Vol. 7, No. 2 : pp. 141-157) This is an historical look at the relations between the union and the players league particularly the 1993 Collective Bargaining Agreement, this article is examines the economic issues leading up to the 2011 NFL lockout and the resultant CBA with the NFLPA. Also available in the ABI-INFORM database.
• "Padding Required: Assessing the Economic Impact of the Super Bowl," External Matheson, Victor A. and Robert A. Baade. European Sport Management Quarterly. January 2004 (Volume 6, 2006, Issue 4). This ran in a special edition of the on Impact and Evaluation of Major Sporting Events
• "Should Cities Be Ready for Some Football?" External Business Review by Gerald Carlino and Edward Coulson The authors examine the issue of whether the public should finance stadiums for NFL franchises if cities benefit from having NFL franchises and new stadiums. This publication has published articles about sports in the past including "FROM BEN HUR TO YOGI BERRA Discussion of that Fabulous Convalescent, the Spectator Sports Industry" in August 1961. External This also ran in the Second Quarter 2004 (pp. 7-17) of the Business Review.
• "Super Bowl or Super (Hyper)Bowl? Assessing the Economic Impact of America's Premier Sports Event" External This was written by Robert A. Baade and Victor A. Matheson This article looks at the economic impact of a Super Bowl on a host city.

Official Sites

• Canadian Football League (CFL) External
• National Football League (NFL) External
• National Football League - Operations External
• National Football League Players Association External
• XFL External
• Athlon Sports.com - NFL External
• CBS - NFL External
• ESPN.com - NFL External
• FOXSports.com - NFL External
• NFL Network External
• Prof Football Reference External
• Sports Illustrated - Pro Football External
• Spotrac.com - NFL External The site was begun as a tool for fantasy players but not includes team payroll, player valuation, and is more of an overall research tool.

If you are looking to search the catalog for more general titles see the Search the Library's Catalog page. Additional works on the business of football and histories of individual franchises in the Library of Congress may be identified by searching the Online Catalog under appropriate Library of Congress subject headings. Choose the topics you wish to search from the following list of subject headings to link directly to the Catalog and automatically execute a search that will allow you to browse related subject headings. Please be aware that during periods of heavy use you may encounter delays in accessing the catalog. For assistance in locating the many other subject headings which relate to football as a business, please consult a reference librarian .

• Football--United States.
• Football--Economic aspects.
• Football teams.
• Football teams--United States.
• National Football League.
• National Football League--History.
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• Last Updated: Jul 3, 2024 11:51 AM
• URL: https://guides.loc.gov/sports-industry

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SB Nation fantasy football cheatsheet 2024: Printable rankings, sleepers, ADP choices, rookies, & more

If you’re waiting until the last minute to draft your fantasy football team, we’ve got you covered! We’ve got printable rankings, a rundown of sleepers and key rookies, and plenty more for 2024 fantasy football drafts.

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Share All sharing options for: SB Nation fantasy football cheatsheet 2024: Printable rankings, sleepers, ADP choices, rookies, & more

We have reached the best part of the sports calendar year.

No, no, not football season, although the return of the NFL certainly plays a role. No, we have reached fantasy football season. If your leagues are anything like ours, you are on the cusp of draft time.

Which means hours upon hours doing your research to gain that critical advantage over your league mates.

However, if you want to gain just a little more of an advantage, the experts here at SB Nation are ready to help. Here you will find everything you need to crush your draft, win your league, and make the player who finished last do something embarrassing next fall. We hear the “Waffle House Challenge” is a fun thing to do ...

So go ahead and dive through everything we have for you, from rankings, sleepers, rookies and much, much more.

Fantasy football rankings (Aug 30)

QB rankings RB rankings WR rankings TE rankings D/ST rankings

Printable rankings (Google spreadsheet)

Running backs Why Josh Jacobs is particularly a steal Wide receivers Tight ends Kickers

Best running back handcuffs

Deep Sleepers

Running backs Wide receivers

Quarterbacks Wide Receivers

Who to pick in the first two rounds

Who should I pick No. 1? Who to pick in the first two rounds with picks 1-3 Who to pick in the first two rounds with picks 4-6 Who to pick in the first two rounds with picks 7-9 Who to pick in the first two rounds with picks 10-12

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