Background: to know the existing documentation related to exogenous melatonin in the performance of professional soccer players. Methods: critical and systematic review. Data were obtained by looking up the following bibliographic data bases: Web of Science, MEDLINE (via PubMed), Embase, Cochrane Library and Scopus. The used terms were "Soccer Athlete", "Melatonin" and "Soccer Performance", using as a filter: "Humans". The search update was in May 2023. Results: having applied the inclusion and exclusion criteria, 8 articles were selected out of 59 retrieved references. The dose of melatonin administered in the studies ranged between 5 and 8 mg. The outcomes showed a decrease in oxidative stress, muscle damage and inflammatory markers in the melatonin-treated group. Conclusions: Exogenously administered melatonin seems to attenuate some of the effects derived from physical exercise such as oxidative stress, inflammation and muscle damage in professional soccer players, and since it has no potential adverse effects, it could be interesting to apply it in this population. However, the direct effects of melatonin supplementation on physical performance have not been demonstrated, so more research is needed on the intervention period, effective dose and larger participant populations.

It has often been said that Gaelic football (GF) and Australian Rules Football (ARF) are similar sports, and amateur Gaelic footballers have been recruited to play in the professional Australian Football League. Using Wilcoxons’s test, the significant (p < 0.05) factors differentiating winning and losing performance in ARF were indirectly compared to the differentiating factors between winning and losing in GF. Of the 15 key performance indicators (KPIs) that were seen to be significant between ARF teams, six (40 %) were also seen to be significant in discriminating between winning and losing GF teams. A Mann-Whitney U test was then completed to directly compare ARF and GF, twenty-six of the 30 KPIs were seen to be significantly different to each other (p < 0.05). The findings suggest that recruiting a Gaelic footballer based on the belief that their Gaelic background will aid their transition to ARF is not an appropriate decision. Instead, staying with more traditional methods of talent identification – for example anthropometric measurements – is advocated until further research is undertaken in this area.

The purpose of this study was to compare players anthropometric (AP) and body composition (BC) characteristics between different maturity bands (pre-PHV, circa-PHV, post-PHV)) in youth elite football. This study considered 320 male football players (mean age 13.8 y.) from U14 (n=157) and U15 (n=163) age-groups. The Khamis-Roche method was used for calculating the percentage of predicted adult height (PAH) at the time of observation based on which the players were further divided into maturity bands (pre-PHV ≤ 87%, circa-PHV = 88-95%, post-PHV > 95%). Height and weight were measured, body mass index (BMI), fat free mass (FFM), total body water (TBW), body fat mass (BFM), percentage of body fat (%BF), skeletal muscle mass (SMM), FFM of both upper limbs and lower limbs and FFM of trunk were estimated according to In-body 270. All observed AP and BC characteristics differed between maturity bands (F= 139.344 – 7.925; p< 0.001; large effect sizes) except the BFM (F= 2.998; p=0.051; small effect size). Current somatic maturity stage of athletes should be considered while evaluating BC results, otherwise there is a risk of misinterpretation.

Each sport has its specific rules, which determine what is allowed (or not) impacting directly on the sport demands. Studies involving physiological and time-motion measurements have shown that soccer is a highly demanding sport. The new coronavirus disease 2019 (COVID-19) has been a world health crisis. Soccer seasons were interrupted worldwide to avoid spreading the virus. Leagues resumed the season (no fans at the arenas) after several weeks of interruption, causing overlay of schedule. This overlay (e.g., games every Sunday and Wednesday) will cause accumulated fatigue on players, raising the risk of injuries. Considering this condensed calendar, the Fédération Internationale de Football Association (FIFA) has changed (temporarily) up to five substitutions during elite games (instead of three as the regular rule allows). Considering the already published scientific evidence, clearly, the change in the soccer substitution rule due to COVID-19 is insufficient. Implementing unlimited substitutions may benefit soccer players' health, coaches’ jobs, more entertainment for fans and sponsors (e.g., keeping intensity during all game, including on the second half) and eventually prolonging the useful life of the players. A real game-changer!

The soccer injury rate is distinctly higher during matches than the training sessions. Rules determine how to play, generating specific kinds of fatigue which is associated with the injury incidence. No research has evaluated the impact of potential rule-induced physical demands in soccer or comparing sports. Understanding the differences might be useful for enhancing rules (e.g., safer sport). Therefore, the aims of this study were: a) to described the differences in the rule-induced physical demands of soccer, futsal, basketball, and handball; and b) to evaluate whether soccer rule-induced physical demands are different than the other invasion intermittent team sports, focusing the impact of the substitutions rules. Data were collected from different sports rules (i.e., soccer, futsal, basketball, and handball), and performed hypothetical corrections to equate the other team sports to the soccer (i.e., court dimensions/number of players). The data showed that soccer has higher rule-induced physical demands: lower substitutions, higher dimensions in absolute (eight to 15 times), and relative (four to eight times) values. Hypothetical corrections showed that soccer has remarkably large differences. Therefore, we conclude that soccer has remarkably higher rule-induced physical demands than other team sports, and allowing unlimited substitutions in soccer is a must.

Studies show that although female soccer players often have shorter change of direction (COD) deficits than males, indicating different biomechanical profiles, there is lack of research on the impact of physical metrics on COD performance in females. The aim of this study was to analyze whether performance metrics based on speed, and jumping could explain the variation in %CODD in young female soccer players. Thirty-three highly trained adolescent female soccer players (age: 16. ± 0.95 years; height: 160.4 ± 5.22 cm; body mass: 55.7 ± 7.22 kg) performed COD180 tests, 10-m and 30-m sprint test and single leg countermovement and horizontal jumps. Acceleration in the first 10 meters of a sprint was identified as a significant predictor of COD180 performance (R2 = 28%), (R2 = 50%), (p

Medical surveillance and risk mitigation protocols to reduce viral transmission have underpinned the return of elite football during the COVID-19 pandemic. This article describes the evidence-informed approach and surveillance findings from the English Football League across a 9-week period at the end of the 2019-20 season. Protocols were devised by the lead EFL Medical Advisor with specialist occupational medicine input. Isolation requirements for cases and contacts were in-line with UK Government regulations, with external contact tracing conducted by local public health authorities. Quantitative PCR testing was conducted twice weekly and within 72 hours of fixtures. 43 individuals, including 18 players returned positive tests. No positive results were returned after week 5 (round 10). Our findings support those from other leagues that with appropriate compliance, elite football can continue safely during this pandemic. We recommend that protocols and compliance should be revised as necessary according to community prevalence and changes in viral transmission dynamics.

Genetics plays an integral role in athletic performance and is increasingly becoming recognised as an important risk factor for injury. Ankle and knee injuries are the most common injuries sustained by soccer players. Often these injuries result in players missing training and matches, which can incur significant costs to clubs. This study aimed to identify genotypes associated with ankle and knee injuries in soccer players and how these impacted the number of matches played. 289 soccer players including 46 professional, 98 semi-professional and 145 amateur players were genetically tested. Ankle and knee injuries and the number of matches played were recorded during the 2014/15 season. Four genes were assessed in relation to injury. Genotypes found to be associated with injury included the TT genotype of the GDF5 gene, TT and CT genotypes of AMPD1 gene, TT genotype of COL5A1 and GG genotype of IGF2 gene. These genes were also associated with a decrease in the number of matches played.

Knowledge of body composition is essential for athletes for their sport performance. It has yet to be determined whether differences in body composition are present between international and non-international players playing in the same elite professional club competition. Similarly, it is not yet clear whether differences in body composition according to ethnic origin exist in the elite professional game, where relative homogeneity is to be expected among soccer players. There is no single anthropometric profile that guarantees sporting success, as the somatotype of football players differs according to their individual characteristics. The aim of this study was to assess the description and comparison of the body composition profile of latin american professional football players playing in european leagues. The sample was composed of 238 subjects football players from European professional football leagues. Differences were found in all variables measured. The present study shows that in Latin American professional football players playing in Europe, there are significant differences in different body composition variables such as weight, height, WC, skinfold and fat values. This means that the treatment of these data and the possible classifications of sporting performance carried out in football clubs should be different to other European or African-American football players.

Inequalities between men and women in the workplace are reflected in professional sports, specifically in football refereeing. This phenomenon sometimes becomes sexual harassment, since it is a stereotypically considered male profession, in which women are a minority. In order to measure that behaviour, it is necessary to count on valid and reliable tools. Therefore, the goal of this study was to determine the factorial structure and the discriminant and convergent validity of the ‘sexual experiences questionnaire’, version of the Department of Defence (SEQ-DoD). Eighty-nine male football referees and ninety-four female football referees, with a mean age of 23.30 ± 4.85 years, participated in this studio conducted in Andalusia, Spain. A confirmatory factor analysis was performed using the robust maximum-likelihood estimation method. Goodness of fit was assessed and the factorial invariance was calculated to determine the stability of the model. Subsequently, the validity was confirmed. The results corroborated the validity and reliability of the questionnaire adapted to the population studied. Therefore it can be used as a research instrument.

Considering the importance of assessing the impacts resulting from a sport career, this study aimed at developing and validating a semi-structure interview guide suitable for quantifying the socio-demographic and epidemiological profile of former professional football players. Based on the theoretical frameworks and several methodological procedures, an interview guide was de-veloped, consisting of 3 areas of conceptual organization (A1. Biographical data; A2. Career data; and A3. Post-Career Transition data) and 8 data collection categories (C1. Personal data; C2. Pro-fessional data; C3. Socio-demographic pathway in the post-career; epidemiological pathway; C4. Epidemiological pathway; C5. Moment of leaving the career; C6. Socio-demographic pathway in post-career; C7. Epidemiological pathway in the post-career; and C8. Perceptions on post-career planning). The construction and validation of the interview guide following 4 steps: Ad hoc con-struction of the interview guide (step 1); Review of the interview guide by a panel of experts (step 2); Definition of procedures and protocol for the application of the interview (step 3); Application of the pilot study for face validation of the interview guide (step 4). Thus, in procedural terms, four stages were considered for the construction and validation of the interview guide, namely the Ad hoc construction of the interview guide (i), the review of the in-terview guide by a panel of experts (ii), definition of procedures and protocol for the application of the interview (iii), and the application of the pilot study for the face validation of the interview guide (iv). The results showed that the interview guide for the study of the impacts of the sports careers on the quality of life of Portuguese former football players shows reliability for the collec-tion of qualitative and quantitative information from the respective content analysis. The use of the interview guide characterizes the path of former player, providing information and knowledge on the socio-demographic and epidemiological impact factors resulting from their post-career (sports retirement).

This study represents the first to examine the nutritional status of Moroccan football players. The aim of this research is to assess the energy and macronutrient intake of professional players from a club competing in the Moroccan professional league "Botola-Pro." Moreover, the study tries to find the potential correlation between nutritional intake and physical performance. A total of 27 professional players participated in a seven consecutive-day study, during a microcycle of the preseason period. The dietary intake was evaluated using the self-reported, complemented by a 24-hour recall. The InBody 120 bioelectrical impedance was employed for assessing body composition measurements, while the Yo-Yo test was utilized to evaluate physical performance; which estimates the maximal oxygen consumption level (VO2max). Among these players, their protein intake levels aligned with recommendations (1.6 to 2.2 g/kg of Body Mass). On the other hand, fat intake slightly surpassed the recommended values. However, carbohydrate intake was relatively subdued compared to recommendations of the Union of European Football Associations (UEFA) in the pre-season training phase. A positive correlation was observed (P-value of &lt; 0.001 and R=0.831) between carbohydrate intake and the measure of VO2max. This suggests that an increase in carbohydrate consumption is associated with enhanced performance, especially within the range of 6 to 8 g/kg BM per day. Conversely, a negative correlation was identified (P-value of &lt; 0.01 and R= − 0.847) between the percentage of dietary fat and the VO2max. The findings of this study highlight areas of nutrition that could be enhanced among professional football players to optimize their performance. In effect, nutritional education is necessary for this category of athletes. Thus, an individual care approach is strongly recommended.

Background: Blood flow restriction training (BFRT) uses occlusion during low-intensity resistance training (&lt;50% of repetition maximum, 1RM) to reduce arterial blood flow and venous return, imposing greater metabolic stress but similar muscular hypertrophy and strength gains as high-intensity resistance training (HIRT). However, no study, to date, has incorporated BFRT in a collegiate strength and conditioning setting to assess ecological validity. We aimed to investigate the effects of adding 6-weeks of accessory BFRT or HIRT to NCAA Division III soccer players prescribed resistance training regimen on muscle strength and hypertrophy. Methods: Male and female (n=17) athletes were randomly assigned to complete biceps curls 2x/week under BFRT or control (HIRT), following the regularly scheduled strength training. Bicep strength (1RM) and circumference (BC) were assessed at weeks 0, 3, and 6. Results: In men, no significant interaction between time and condition was observed for BC (p=0.861), though condition (BFRT vs Control, p=0.025) and time (p=0.024) were significant. For 1RM, there was no significant interaction between time and condition (BFRT vs HIRT, p=0.067) or of condition (p=0.598), but there was a significant effect of time (p=0.004). In women, there was no significant interaction between time and condition (p=0.765) or of condition (p=0.971) on BC, but time was significant (p=0.045). For 1RM, there was no significant interaction between time and condition (p=0.227) or of condition (p=0.741), but time was (p=0.018). Conclusion: BFRT induced similar increases in muscle strength and hypertrophy as HIRT in soccer players, suggesting that BFRT could be incorporated into collegiate athlete training.

This paper analyzes if the Financial Fair Play (FFP) regulations set by UEFA have influenced the auditing fees charged to the football clubs. In addition, it explores the determinants of audit fees. We use a two-sample t test with equal variances to determine whether differences are present. After this, we carry out a panel data regression with clubs fix effect to estimate the determinants of audit fees in football clubs. Our findings reveal an increase of audit fees after the implementation of FFP regulations. On top of that, audit fees are explained by the presence of foreign investors if the audit firm is one of the Big4 and if the auditor is a woman. The regulation change has an impact on the audit fees charged by auditors for their services. However, this increase can be compensated across future years given the improving financial situation of clubs; therefore, the auditors’ risk diminishes and subsequent audit fees may be reduced. UEFA should monitor audit fees as well as the quality of the audit reports, which have become crucial to obtaining the license to participate in UEFA competitions.

Weight and age interact to modify cognitive effects of head acceleration events after two seasons of youth football Abstract This is a follow-up study of youth American football players in a second season of play. Season-one findings identified a relationship between a head acceleration measure (HITsp) and cognitive score changes with weight modifying the effect in 9 to 10 year-olds. Sixty-eight youth completed a second season of play wearing helmet-mounted sensors and were assessed with neuropsychological tests pre- and post-season. Regression analysis of the full sample demonstrated a small but significant negative effect of HAE on cognition as indexed by test score changes: R2 = .06, F = 4.06, p = .024. Outcome differences between those who started playing at ages nine to 10, compared to those who started between 11 and 13 were identified: t(66) = -3.39, p<.01, d = -.84, 95th CI -2.77 to -.72. Regression models including players’ weights found that the relationship of weight to outcome was different by group: greater negative cognitive effects were found in younger-heavier players (R2 = 0.21, F =3.21, p = 0.03) and older-lighter players (R2 = 0.18, F =4.26, p <.001). These findings confirmed a negative relationship of HAE and cognitive change and point to player weight as an important developmental factor to consider in understanding concussion biomechanics.

While Europe was beginning to deal with the resurgence of COVID-19 due to the Delta variant, the European football championship took place, June 11 - July 11, 2021. We studied the inversion in the decrease/increase rate of new SARS-COV-2 infections in the countries of the tournament, investigating the hypothesis of an association. Using a Bayesian piecewise regression with a Poisson Generalized Linear Model, we looked for a changepoint in the timeseries of the new SARS-COV-2 cases of each country, expecting it to appear not later than two to three weeks after the date of their first match. The two slopes, before and after the changepoint, were used to discuss the reversal from a decreasing to an increasing rate of the infections. For 17 out of 22 countries (77%) the changepoint came on average 14.97 days after their first match [95% CI 12.29 to 17.47]. For all those 17 countries, the changepoint coincides with an inversion from a decreasing to an increasing rate of the infections. Before the changepoint, the new cases were decreasing, halving on average every 18.07 days [95% CI 11.81 to 29.42]. After the changepoint, the cases begin to increase, doubling every 29.10 days [95% CI 14.12 to 49.78]. This inversion in the SARS-COV-2 case rate, happened during the tournament, provides evidence in favor of a relationship

The use of principal components analysis provided information about the main characteristics of teams, based on a set of indicators, instead of displaying individualized information for each of these indicators. In this work we have considered reducing an extensive data matrix to improve interpretation, using the principal components analysis. Subsequently, with new components and with a multiple linear regression, we have carried out a comparative analysis between the best and bottom teams of LaLiga. The sample consisted of the matches corresponding to the 2015/16, 2016/17 and 2017/18 seasons. The results showed that the best teams were characterized and differentiated from bottom teams in the realization of a greater number of successful passes and in the execution of a greater number of dynamic offensive transitions. The bottom teams were characterized by executing more defensive than offensive actions and showing a fewer number of goals, a greater ball possession time in the final third of the field. Goals, ball possession time in the final third of the field, number of effective shots and crosses are the main performance factors that influence the offensive success of football. This information allows us to increase knowledge about the key performance indicators in football.

A Mild traumatic brain injury (mTBI) or concussion has become a public health problem in the United State. Sports and recreational activities are major sources of concussions; with the most incidents connected to American football. Recently, many companies and research institutions have started studying concussions and introduced some means of protection and some alarming systems of strong jolts. The major detection and protection system currently available on the market is the electronic helmet (e-helmet) composed of measurement devices to record head impact acceleration. The most commonly used devices in e-helmets are accelerometers to measure linear acceleration and gyroscopes for rotational/angular acceleration. Using smart textiles for concussion detection is currently uncommon and limited due to the lack of literature studying their voltage related errors. Actually, there are few works that characterize some voltage-force related errors for such type of sensors but for small impact forces and under bench testing while the behavior of those sensors was not described for higher ranges of applied forces and in field situations. This paper previews some common techniques used in e-helmets for concussion detection and highlights electronic textiles and smart fabric sensors that could be very useful for these applications. It discusses and validates the general behavior of such type of sensors under high impact forces and on field testing instead of bench testing, and also it characterizes the effect of increasing the thickness of the sensing element layer on the sensor. A custom-made pressure sensor was created of some available fabrics to be embedded within the padding of a football helmet to quantify the impacting force to the head. The sensor is mainly composed a Semi Conductive Polymer Composite SCPC layer with modifiable thickness that was modified three times with 0.2, 0.4, and 1.6mm to characterize the general behavior of the sensor due to a high amount of impacts and correlated with the thickness. A pendulum system was built to test the pressure sensors, while a special camera and an open-source video analysis software, Tracker was used to track the pendulum bob. The speed and the acceleration of the pendulum bob were measured, then the impact force was calculated and a voltage-force response was obtained. The results showed that no meaningful improvement occurs by small increase in the thickness but better sensor behavior could be obtained by significant increment to observe any difference. Despite that at a very high impacts, the suggested sensor with Velostat layers is not giving the real voltage readings that reflect the actual applied forces but it gives a helpful information that illustrate the distribution of the force through identification the place of the highest and lowest voltage readings regardless of the exact values of those readings. However, the proposed smart textile pressure sensor could be applicable in future e-helmet designs with additional research-based improvements especially on the structure of the sensing element layer to be able to withstand such high impacts which in turns improves the overall sensor performance and accurately measures pressure in concussion-inducing ranges.

The aim of this study was to identify gender differences in technical-tactical behaviour in football. To this end 68 matches of the first division of the Spanish men’s and women´s league, corresponding to 2016/17 season were analyzed. A comparison of medians was carried out using the Mann-Whitney U-test were conducted as post hoc test and a grouping of the variables through the clustering bootstrapping technique in both groups. We have detected statistically significant differences regarding all accurate passes, in favour of men, as well as a greater number of yellow cards. In female football, a greater number of picking up free balls, interceptions, lost balls, recoveries, challenges and attacks, both positional and counterattacks, are produced. The clustering analysis also allowed that in male football, the circumstance of receiving a red card is closely related to the number of goals conceded and most of the shots on goal are achieved by positional attacks. In women's football, ball possession on own half is closely related to the number of losses. These results could be useful for gender-specific training information for optimal preparation. However, more research is warranted to establish the main gender differences and characterize women's football.

Turnovers in the National Football League (NFL) occur whenever a team loses possession of the ball due to a fumble, or an interception. Turnovers disrupt momentum of the offensive team, and represent lost opportunities to advance downfield and score. Teams with a positive differential turnover margin in a given game win $70\%$ of the time. Turnovers are statistically rare events, occurring apparently randomly. These characteristics make them difficult to predict. This investigation advances the hypothesis that turnovers are predictable in NFL football. Machine learning models are developed to learn the concept: At any point within a football game, what is the likelihood that a turnover will be observed on the next play from scrimmage? Results presented suggest evidence to support the working hypothesis. Under certain conditions, both fumbles and interceptions can be anticipated at low false discovery rates (less than $15\%$). This approach may be useful to inform in-game strategies to mitigate the negative consequences of turnovers by an offensive team, or to maximize their probability by a defensive squad.

One of the most significant developments in the sports world over the last two decades has been the use of mathematical methods in conjunction with the massive amounts of data now available to analyze performances, identify trends and patterns, and forecast results. Football analytics has advanced significantly in recent years and continues to evolve as it becomes a more recognized and integral part of the game. Football analytics is also used to forecast game outcomes, allowing bettors to make educated guesses. This article describes mathematical concepts related to football analytics that enable a better betting strategies. We explain how the pitch is partitioned into different zones and we define possession sequences. Furthermore, we explain what an expected goals model is and which expected goals model we use in this research. Furthermore, we define two general characteristics of a player evaluation method, each corresponding to one of the equations of the Dawson model. Based on these characteristics, we describe the developments of several general approaches for evaluating players in the context of the Dawson model.

Safely resuming sporting events while the coronavirus is spreading is challenging – yet possible – if the science is taken into account. Two main ways the coronavirus can spread among football players is through air-suspended microdroplets (and possibly aerosols), and via contact with contaminated surfaces. Here we estimated virus survival in dried saliva droplets on a football pitch (i.e., on the grass) and on the ball itself, and compared these measures between mid-day and nighttime matches. We find, based on experiments with the enveloped phage Phi6 – a surrogate for SARS-Cov-2 – that while the virus survives reasonably well on both pitch and ball during a nighttime match (~10% survival), virtually no viruses survived the 90-minute duration of a mid-day match on a hot, sunny day. These results, taken together with studies reporting rapid deactivation of coronavirus in aerosols by sunlight, suggest that playing football in mid-day reduces the likelihood of transmission between players, and thus increases players’ safety.

Sports are framed within the context of the Olympic spirit and are, therefore, within the vision and mission of the Olympic Committee, aimed at “building a better world”. This is identified as a fundamental value and sustainability is therefore explicitly considered to be a “working principle” of this. In this research an analysis of the performance of professional European football teams publicly listed on stock markets, restating the income statements according to the Value-Added perspective is carried out. This takes into account the effective sustainable contribution in the distribution of added value with reference to the human, structural, debt, infrastructural, and risk capitals of these organisations. The Value-Added Statement is considered as a part of the broader CSR Reporting and can be traced back to the late 1970s. However, it is in widespread contemporary use and is regarded as being both a credible and a tested measure. In this paper, the authors apply a slightly modified and simplified version of this tool to these publicly listed European football clubs as a proxy for wider professional sport. This research demonstrates that, although professional sports clubs are profit-oriented, the distribution of wealth generated by the added value is unbalanced. In most cases, at least in financial terms, shareholders are the most disadvantaged and athletes are the most rewarded.

This paper draws an earlier book (with Evans and Higgins) entitled Bad Call: Technology’s Attack on Referees and Umpires and How to Fix It (hereafter Bad Call) and its various precursor papers. These show why it is that current match officiating aids are unable to provide the kind of accuracy that is often claimed for them and that sports aficianados have been led to expect from them. Accuracy is improving all the time but the notion of perfect accuracy is a myth because, for example, lines drawn on sports fields and the edges of balls are not perfectly defined. The devices meant to report the exact position of a ball – for instance ‘in’ or ‘out’ at tennis – work with the mathematically perfect world of virtual reality, not the actuality of an imperfect physical world. Even if ball-trackers could overcome the sort of inaccuracies related to fast ball speeds and slow camera frame-rates the goal of complete accuracy will always be beyond reach. Here it is suggested that the purpose of technological aids to umpires and referees be looked at in a new way that takes the viewers into account.