Latest research in football - week 26 - 2022

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases. 


Following studies were retrieved for this week:

#1 Reduced performance after return to competition in ACL injuries: an analysis on return to competition in the 'ACL registry in German Football'

Reference: Knee Surg Sports Traumatol Arthrosc. 2022 Jul 10. doi: 10.1007/s00167-022-07062-8.

Authors: Dominik Szymski, Leonard Achenbach, Johannes Weber, Lorenz Huber, Clemens Memmel, Maximilian Kerschbaum, Volker Alt, Werner Krutsch

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Summary: ACL injuries are one of the most severe injuries in football, but medical consequences and performance outcomes after return to competition are only rarely investigated. Aim of this study was to analyse the time of return to competition (RTC) in German professional, semi-professional and amateur football. Also, this investigation highlights the rate of career ending and performance outcome after RTC in different playing levels by the measurement of playing level, performed matches and played minutes. Database of this investigation is the 'ACL registry in German Football' with prospectively collected injury data. Between 2014 and 2018, four seasons in professional (1st-3rd league), semi-professional (4th-6th league) and amateur leagues (7th league) were analysed regarding the return to competition period and performance parameters. Data were collected for three subsequent seasons after injury and compared with the pre-injury and injury season. Data collection was performed using standardized methods. A total of 607 ACL injuries were registered during the 4-year period with a mean RTC time of 337.1 day (SD: 183). After primary ACL ruptures, the fastest RTC was found in professional football (247.3 days), while in semi-professional (333.5 d; p < 0.0001) and amateur football (376.2 d; p < 0.0001) a prolonged absence was detected. Re-ruptures occurred in 17.8% (n = 108) and showed similar trend with fastest RTC in professionals (289.9 days; p = 0.002). Within the first three seasons after injury, 92 players (36.7%) in semi-professional and 24 (20%) in professionals had to end their career. Keeping the level of play was only possible for 48 (47.5%) of professionals, while only 47 (29.6%) of semi-professionals and 43 (28.1%) of amateurs were able to. Only in professional football, no significant difference could be seen in the played minutes and games after 2 years compared to the pre-injury season. Lower playing levels and re-ruptures are the main factors for a prolonged return to competition after ACL rupture in German football. Significant reduction in playing level and a high rate of career endings were found for all levels of play. However, only professional players were able to regain their playing minutes and games 2 years after injury, while lower classed athletes did not reach the same amount within 3 years.



#2 Incidence and characteristics of COVID-19 in French professional football players during the 2020-2021 season

Reference: Infect Dis Now. 2022 Jul 8;S2666-9919(22)00146-4. doi: 10.1016/j.idnow.2022.07.001. 

Authors: D Luque-Paz, E Orhant, F Michel, P Kuentz, J-F Chapellier, E Rolland, C Rabaud, P Tattevin

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#3 Whole-body sensorimotor skill learning in football players: No evidence for motor transfer effects

Reference: PLoS One. 2022 Jul 11;17(7):e0271412. doi: 10.1371/journal.pone.0271412. eCollection 2022.

Authors: Tom Maudrich, Hannah Kandt, Patrick Ragert, Rouven Kenville

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Summary: Besides simple movement sequences, precise whole-body motor sequences are fundamental for top athletic performance. It has long been questioned whether athletes have an advantage when learning new whole-body motor sequences. In a previous study, we did not find any superior learning or transfer effects of strength and endurance athletes in a complex whole-body serial reaction time task (CWB-SRTT). In the present study, we aimed to extend this research by increasing the overlap of task requirements between CWB-SRTT and a specific sports discipline. For this purpose, we assessed differences between football players and non-athletes during motor sequence learning using CWB-SRTT. 15 non-athletes (CG) and 16 football players (FG) performed the CWB-SRTT over 2 days separated by one week. Median reaction times and movement times were analyzed as well as differences in sequence-specific CWB-SRTT learning rates and retention. Our findings did not reveal any differences in sequence-specific or non-sequence-specific improvement, nor retention rates between CG and FG. We speculate that this might relate to a predominately cognitive-induced learning effect during CWB-SRTT which negates the assumed motor advantage of the football players.



#4 The effect of pre-match sexual intercourse on football players' performance: a prospective cross over study

Reference: J Sports Med Phys Fitness. 2022 Jul 11. doi: 10.23736/S0022-4707.22.14022-3. Online ahead of print.

Authors: Tal Peleg-Sagy, Lior Zeller, Yonatan Perelman, Lukasz Bortnik, Tomer Maman, Iftach Sagy

Summary: Current research suggests that pre-competition sexual intercourse does not influence athletes' performance. Yet, high quality studies in this field are scarce. We aimed to investigate whether sexual activity negatively influences physiological performance. We conducted a prospective cross over study, which enrolled active players from the first team of a football club in the Israeli Football Premier League during the 2018-19 season. We gathered participants' physiological performance using GPS driven data per match. In addition, we assessed sexual activity the night before using telephone interviews at the end of every match. We used a linear mixed models methodology, accounting for each player as a cluster. We enrolled 14 participants who participated in 88 football matches. The mean age was 29.7 (±3.8) years and the majority were in permanent relationships for longer than six months (78.6%). We identified sexual intercourses the night before the match in nine (10.2%) cases. The average speed during the match was slower when participants had pre-match intercourse (6.5 vs. 6.0 Km/h, p=0.02). The results remained consistent when using linear mixed models analysis adjusted for age, for previous belief that a pre-match sexual intercourse may affect match performance and for player as a cluster (p=0.02, 95% C.I -0.85 - -0.07). Other parameters were not associated with pre-match intercourse. To the best of our knowledge, this study is the first to show that sexual intercourse the night before a football match may have a negative influence on players' performance.



#5 Analysis of the Running Ability Mining Model of Football Trainers Based on Dynamic Incremental Clustering Algorithm

Reference: Comput Intell Neurosci. 2022 Jun 29;2022:3255886. doi: 10.1155/2022/3255886. eCollection 2022.

Authors: Peng Zhao, Fei Xue, Xipeng Zhang

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Summary: Fast-running ability is a very important basic quality of football players. However, players are dynamic. It is difficult for coaches to grasp the running speed, instantaneous acceleration, and other indicators of small athletes in real time with the naked eye. Therefore, to accurately test the performance of athletes in fast-running ability, this paper studies the running ability mining model of football coaches based on the dynamic incremental clustering algorithm. According to scientific procedures and methods, the evaluation model and standard of running ability of Chinese elite female football players are established. The effectiveness of the model is 0.83, as verified by the standard recognition method, which shows that the evaluation model is efficient. The research considers the denoising of the original data. The model has rich data and standard test methods and procedures. It can be used as a measure of the running ability of China's elite female football players in a certain period and range. The research solves the problem of the insufficient running ability of domestic football players. It provides an important reference for training the next generation of excellent national football players.



#6 A complete season with attendance restrictions confirms the relevant contribution of spectators to home advantage and referee bias in association football

Reference: PeerJ. 2022 Jul 4;10:e13681. doi: 10.7717/peerj.13681. eCollection 2022.

Authors: Fabrizio Sors, Michele Grassi, Tiziano Agostini, Mauro Murgia

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Summary: Due to the unfortunate pandemic situation, the phenomena of home advantage and referee bias in sports have recently received a particular research attention, especially in association football. In this regard, several studies were conducted on the last portion of the 2019-20 season: the majority of them suggests a reduction-but not the elimination-of the two phenomena, with some exceptions in which no reduction was found or, at the other extreme, the phenomena were not observed at all. The continuation of the pandemic made it possible to replicate the previous studies considering the complete 2020-21 season, thus with the important added value of having a fully balanced home/away schedule-and a higher number of matches-in the various leagues. In particular, the sample of the present study consisted of 3,898 matches from the first and second divisions of the UEFA top five ranked countries, that is, England, Spain, Italy, Germany, and France. For the home advantage, the following variables were examined: distribution of matches outcomes and home advantage for points (also for previous seasons from the 2014-15 one); ball possession; total shots; shots on goal; and corner kicks. Instead, for he referee bias, the following variables were examined: fouls; yellow cards; red cards; penalty kicks; and extra time. Chi-square tests were used to compare the distribution of matches outcomes, and t-tests to compare home vs. away data for the other variables in the 2020-21 season; Bayesian and equivalence analyses were also conducted. The main results are as follows: (a) the distribution of matches outcomes in the 2020-21 season was significantly different from that of the last five complete seasons with spectators (Chi-square = 37.42, df = 2, p < 0.001), with fewer home victories and more away victories; the resulting values of the home advantage for points were 54.95% for the 2020-21 season, and 59.36% for the previous seasons; (b) for the other home advantage variables, a statistically significant overall advantage for the home team emerged; nevertheless, the strength of the differences between home and away teams was generally small (0.09 < Cohen's d < 0.17), and the corresponding means can be considered statistically equivalent for all variables but the total shots; (c) no statistically significant differences emerged between home and away teams for any of the referee bias variables. These findings demonstrate that the absence of spectators significantly reduced the home advantage compared to previous seasons with spectators. A slight home advantage persisted in the 2020-21 season, probably due to other factors, namely, learning and travel, according to the model by Courneya & Carron (1992). Conversely, the referee bias was not observed, suggesting that it mainly derives from the pressure normally exerted by spectators.



#7 Emergent Coordination of Heading in Soccer: Of Two Players and a Single Ball

Reference: Res Q Exerc Sport. 2022 Jul 15;1-7. doi: 10.1080/02701367.2022.2088674. Online ahead of print.

Authors: David Smith, Frank T J M Zaal, Daniel Memmert

Summary: In many sports situations, two or more players need to coordinate their actions to make sure that one of them intercepts a ball or opponent. We considered how two soccer players head back a thrown ball. Two accounts for the joint decision making by both players were considered. These two accounts not only differ in their theoretical basis but also have vastly different implications for training practice. In a first account, players know their areas of responsibility for interception, and combine this with their prediction of the ball's landing location. In a second account, the coordination emerges from the unfolding dynamics of the system of informationally connected players and ball. According to this second account, especially for balls aimed in between the two players, both of the players may start moving and one player sees that the ball will be interceptable for the other player, and subsequently yields the interception. We instrumented soccer players and the ball with Kinexon sensors and had pairs of players head back the thrown ball. In line with the second account, the results showed a fair number of instances where the player who intercepted the ball had to move the longest distance. Furthermore, considerable movement by both players was not an exception. The results can be taken as a first step towards an understanding of joint coordination as an emergent phenomenon.



#8 The association between the Healthy Eating Index (HEI-2015) score and body composition among Iranian soccer players and referees: a cross-sectional study

Reference: J Nutr Sci. 2022 Jul 11;11:e57. doi: 10.1017/jns.2022.49. eCollection 2022.

Authors: Mohammad Beba, Tohid Seif-Barghi, Sakineh Shab-Bidar, Habib Yarizadeh, Aliyu Jibril Tijani, Cain C T Clark, Kurosh Djafarian

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Summary: For an optimal performance, soccer players and referees need to consume a high-quality diet. The Healthy Eating Index (HEI) is a tool that can estimate diet quality and has been shown to be associated with body composition. The aims of the present study were first to determine the HEI-2015 score of the diets consumed by athletes and second its association with different body composition parameters of athletes. We conducted a cross-sectional study on 198 soccer players and referees. Dietary intakes were recorded using a validated food frequency questionnaire (FFQ), and HEI scores were calculated. Body composition parameters were measured using the bioelectrical impedance analysis. The mean score for the HEI-2015 was 65⋅04. A multiple linear regression model showed significant associations of the HEI-2015 score with percent body fat (PBF), percent muscle mass (PMM), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) in male soccer players aged <18 years, body mass index (BMI) in male soccer players aged ≥18 years and BMI and waist-to-height ratio (WHtR) in male soccer referees after adjustment for covariates (P < 0⋅05). The mean overall score for the HEI-2015 shows that Iranian soccer players and referees have an acceptable quality of diet. We also found significant associations between the HEI-2015 score and different body composition parameters in male soccer players and referees but we did not find any significant association in female athletes (P > 0⋅05).



#9 Does External Load Reflect Acute Neuromuscular Fatigue and Rating of Perceived Exertion in Elite Young Soccer Players?

Reference: J Strength Cond Res. 2022 Jul 8. doi: 10.1519/JSC.0000000000004296. Online ahead of print.

Authors: Antonio Martínez-Serrano, Tomás T Freitas, Xavi Franquesa, Edgar Enrich, Milos Mallol, Pedro E Alcaraz

Summary: This study aimed to analyze the acute and residual effects of increased high-speed running (HSR) demands during an in-season training microcycle in young elite soccer players on localized neuromuscular fatigue (NMF) of the knee extensors (KE), posterior chain muscles, and rating of perceived exertion (RPE). Thirty-four elite young soccer players (age = 17.1 ± 0.8 years) were assessed in 2 consecutive days at different time points (baseline, POST-activation gym-based session, POST-small-sided game [SSG], POST-training 1 [TR1], POST-6H, POST-24H, POST-preventive gym-based session, and POST-training 2 [TR2]). Neuromuscular fatigue of the KE and posterior chain muscles was measured with a maximum voluntary isometric contraction (MVIC). External (total distance, number of accelerations or decelerations, and HSR distance) and internal (RPE) load was assessed during the SSG, TR1, and TR2 sessions. Players were divided through a median split, into "HIGH" or "LOW" group according to the training demands. The alpha level was set at p ≤ 0.05. A 2-way mixed effects model ANOVA showed a significant decreased in 90:20 MVIC after TR1 in the "HIGH" HSR group (p = 0.037; effect size [ES] = 0.45). No significant differences in RPE were found after TR1 (p = 0.637; ES = 0.58) and TR2 (p = 0.109; ES = 0.62) when comparing the "HIGH" HSR group with the "LOW" HSR group. Assessing player's force production capabilities can be an effective strategy to detect NMF when HSR demands are acutely increased. Special caution should be taken when prescribing the training load of the training session based solely on RPE, as NMF might be present.



#10 Impact of technical and physical performance on match outcome over five elite European soccer seasons

Reference: J Sports Med Phys Fitness. 2022 Jul 11. doi: 10.23736/S0022-4707.22.14018-1. Online ahead of print.

Authors: Ryland Morgans, Patrick Orme, Rocco DI Michele

Summary: The technical and physical performance, a key part of overall soccer performance, tend to evolve due to changes in game rules, playing styles, and training methodology. Nevertheless, little has been reported in the literature on how match performance has changed over time in elite championships and leagues. Thus, this study aimed to assess the impact of selected technical and physical team performance indicators on match outcome over five seasons in the Russian Premier League. Twenty-two technical and physical team performance variables, recorded with an optical tracking system, were examined in 1186 matches played in the Russian Premier League during the 2016-2017 to 2020-2021 seasons. For pooled data in all examined seasons, shots on target were higher in won vs. drawn and lost matches. Percentage of challenges won was higher in won vs. drawn and lost matches. Sprint distance, counterattacks, shots, interceptions, recoveries, crosses, and the percentage of successful tackles all showed small though significant differences between match outcomes. Slightly greater odds of a more favourable match outcome were involved by increases in all selected variables, except crosses, showing an opposite effect. In the 2020-2021 season, ball possession time reported a slightly higher impact on match outcome than in previous seasons. The present results show that some technical performance variables have a great effect on match outcome, while other technical indicators and physical metrics have a smaller though still potentially relevant impact. These effects do not substantially differ acrss the five examined seasons.



#11 Substitutions in football - what coaches think and what coaches do

Reference: J Sports Sci. 2022 Jul 13;1-10. doi: 10.1080/02640414.2022.2099177. Online ahead of print.

Authors: Joris Wittkugel, Daniel Memmert, Fabian Wunderlich

Summary: Substitutions are probably the most important opportunity for football coaches to actively influence a match in progress. The present article presents two studies investigating substitutions in football from two different methodological perspectives: Study I, a survey reporting the opinions of 73 licensed coaches, and Study II, data-based analysis of a total of 41,301 substitutions from 7,230 matches in seasons 2014/15 to 2018/19 of the top four European football leagues. The coaches stated to prefer offensive substitutions over defensive substitutions and additionally indicated that changing the current score was more likely to be a reason for substitution than keeping the score. The analysis of the data revealed that not offensive, but neutral substitutions, where the player is replaced by a player of the same playing position, were most frequent. However, offensive players participated significantly more frequently in substitutions. In addition, a high level of score dependence was found, as more than half of the defensive substitutions were made while winning and more than half of the offensive substitutions were made while losing. The present study sheds light on the substitution behaviour of coaches in football and intends to stimulate discussion on the optimal timing and the type of substitutions.



#12 Cultural similarity and impartiality on voting bias: The case of FIFA's World's Best Male Football Player Award

Reference: PLoS One. 2022 Jul 13;17(7):e0270546. doi: 10.1371/journal.pone.0270546. eCollection 2022.

Authors: Michael R Johnson, Ian P McCarthy

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Summary: Previous studies on voting bias in competitive awards have not fully considered the role of cultural similarity. Using data for the Best FIFA Men's Player Award, we evaluate the extent of voting bias in this Award using three cultural similarity factors (cultural distance, cultural clusters, and collectivism), six established in-group factors (nationality, club, league, geography, ethnicity, religion, and language) and the impartiality of the voter's country. Using statistical and econometric methods, we find that voter-player cultural similarity is positively associated with voting bias and find no evidence of impartiality when it comes to cultural or national ties. We also find that media voters are less biased than captain voters and coach voters, and that coaches are less biased than captains.



#13 Stakeholder views of current laws surrounding alcohol at UK football matches: Is it a case of using a "sledgehammer to crack a nut"?

Reference: Int J Drug Policy. 2022 Jul 9;107:103789. doi: 10.1016/j.drugpo.2022.103789. Online ahead of print.

Authors: Jack G Martin, Richard Giulianotti, Comille Bandura, Stephen Morrow, Kate Hunt, Angus Bancroft, Richard I Purves

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Summary: In 2021, a fan-led review of football governance in England recommended that legislation surrounding alcohol and football be reviewed to determine whether it is still fit for purpose, the first such review since the mid-1980s. Restricting football fans' alcohol consumption has been debated in the UK for over 40 years. However, more research is needed into the current attitudes of fans and influential stakeholders on this matter. Focus groups with football supporters (n=79) and semi-structured interviews (n=15) with key organisational stakeholders were conducted between November 2019 and February 2021. Focus groups included fans who regularly attended matches and supported various teams from professional leagues in Scotland and England, casual fans who usually watched games at home or in bars, and fans who followed the Scotland and England national teams. Stakeholders were selected to represent organisations likely to be instrumental in any regulatory change, such as the UK and Scottish Governments, Police, football supporters' groups and safety organisations. The current law does not allow for alcohol to be consumed within view of the pitch. Participants from England suggested this could be changed. While in Scotland, where the legislation only allows alcohol to be sold in hospitality, most participants were in favour of allowing the general sale of alcohol at football stadia via a pilot scheme. The reasons for these changes included: reducing unhealthy drinking behaviours; minimising the health and safety risk of fans arriving at the stadium just before kick-off; and a potential increase in much needed revenue for clubs. Our data suggests an evidence-based review of current laws regarding alcohol and football may be appropriate. However, any discussion regarding changes to the law regarding alcohol at football stadia, including potential pilot schemes, should be evaluated and monitored in terms of both financial impact and the impact on public health and safety.



#14 Reliability of spatial-temporal metrics used to assess collective behaviours in football: An in-silico experiment

Reference: Sci Med Footb. 2022 Jul 15. doi: 10.1080/24733938.2022.2100460. Online ahead of print.

Authors: Martin Corsie, Paul Alan Swinton

Summary: The purpose of this study was to investigate the reliability of spatial-temporal measurements applied within collective behaviour research in football. In-silico experiments were conducted introducing positional errors (0.5, 2 and 4 m) representative of commercial tracking systems to match data from the 2020 European Championship qualifiers. Ratios of the natural variance ("signal") of spatial-temporal metrics obtained throughout sections of each game relative to the variance created by positional errors ("noise") were taken to calculate reliability. The effects of error magnitude and time of analysis (1, 5 and 15 mins; length of attack: <10, 10-20, >20 s) were assessed and compared using Cohen's f2 effect size. Error magnitude was found to exert greater influence on reliability (f2 = 0.15 to 0.81) compared with both standard time of analysis (f2 = 0.03 to 0.08) and length of attacks (f2 = 0.15 to 0.32). the results demonstrate that technologies generating positional errors of 0.5 m or less should be expected to produce spatial-temporal metrics with high reliability. However, technologies that generate errors of 2 m or greater may produce unreliable values, particularly when analyses are conducted over discrete events such as attacks, which although critical, are often short in duration.



#15 Visual occlusion effects on youth football players' performance during small-sided games

Reference: PLoS One. 2022 Jul 15;17(7):e0268715. doi: 10.1371/journal.pone.0268715. eCollection 2022.

Authors: Sara Santos, Bruno Gonçalves, Diogo Coutinho, Gabriel Vilas Boas, Jaime Sampaio

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Summary: This study aimed to explore how youth players' physical, technical and positional performance may be affected by visual occlusion when playing under different SSG pitch sizes. Under-15 players performed two experimental scenarios: a) normal situation, without visual occlusion; b) visual occlusion, by using an eye patch in the eye corresponding to the dominant foot. These scenarios were tested in a small (40x30m) and a larger pitch (50x35m). Players' positional data was used to compute tactical and time-motion variables. In addition, technical analysis was comprised using video footage. Playing with visual occlusion in the larger pitch size induced higher distance covered while walking but lower running distance (p < .05). Although no statistically significant effects were identified between the normal and visual occlusion conditions for the tactical behaviour and technical performance a lower number of successful passes (small to moderate effect sizes) and higher regularity in the distance to the opponent's team centroid (moderate effect size) were found with visual occlusion. Players covered more distance and achieved higher maximum speed in the larger compared to the small pitch (moderate to large effect size, p < .05), while also increasing their distance to both team's centroid and increasing the regularity to these distances (moderate to large effect size, p < .05). Overall, despite similar effects for tactical and technical variables, some important practical information can be depicted. Accordingly, coaches may use the visual occlusion to promote more stable and regular behaviors while decreasing the physical demands. Larger pitches may be used to increase the distance between players' and teams, as well as to induce higher physical load in both the normal and visual occlusion conditions. From the technical perspective, coaches may design smaller pitches to emphasize the use of the non-dominant foot during the occlusion scenario and promote the pass during the normal scenario.



#16 Soccer coaches vs. sport science and medicine staff: who can more accurately predict the skeletal age of high-level youth soccer players?

Reference: Sci Med Footb. 2022 Jul 13;1-10. doi: 10.1080/24733938.2022.2100461. Online ahead of print.

Authors: Ludwig Ruf, Stefan Altmann, Christian Kloss, Sascha Härtel

Summary: Biological maturity is an important aspect in the context of talent identification and development processes within elite youth soccer players. The aim of this study was to investigate the accuracy of soccer coaches (SC) as well as sports science and medicine staff (SSMS) to predict the skeletal age of high-level youth soccer players. We also aimed to evaluate the inter-rater reliability of the skeletal age predictions among the SC and SSMS. Skeletal ages were collected for 89 male academy soccer players registered for the U12 to U16 age groups at a professional German Bundesliga club. In addition, 12 SC and five SSMS provided their skeletal age predictions for each player of their respective age group. Standardised mean differences and equivalence testing were performed between actual and predicted skeletal ages. Intra-class correlations (ICC) were calculated to assess the inter-rater reliability. For the SC, differences between predicted and actual skeletal ages were trivial and equivalent to zero for the U12, U14, and entire sample, while for the SSMS, standardised mean differences ranged from trivial to small for all age groups and the entire sample. ICC for skeletal age predictions for the entire sample was good among the SC and excellent among the SSMS, but was somewhat lower when age groups were analysed separately. While, on average, predictions were close to the actual skeletal age, SC were slightly more accurate than the SSMS. However, variability among the SSMS was large on an individual level.



#17 Temporal patterns of fatigue in repeated sprint ability testing in soccer players. Acute effects of different initial heart rates: a comparison between genders

Reference: J Sports Med Phys Fitness. 2022 Jul 11. doi: 10.23736/S0022-4707.22.13822-3. Online ahead of print.

Authors: Bruno Ruscello, Laura Pantanella, Pietro Iemme, Cristoforo Filetti, Marco Porta, Stefano D'Ottavio, Lorenzo Marcelli, Gennaro Apollaro, Gabriele Morganti, Alberto Grossi, Mario Esposito, Elvira Padua

Summary: Repeated sprint ability (RSA) in soccer is deemed fundamental to ensure high level of performance. The aim of this study was to investigate the acute effects of two different initial heart rates on fatigue when testing RSA in males and females' soccer players and to compare the respective patterns of fatigue. 19 female soccer players (age: 22.5±3.3 years, height 163.9±7.3 cm, body weight 54.3±6.4 kg, BMI 20.6±1.5 kg·m-2) and 15 male soccer players (Age: 17.9±1.5 years, height 175.9±5.8 cm, body weight 68.5±9.6 kg, BMI 22.3±1.5 kg·m-2) participated in this study. Heart rates reached at the end of two different warm-up protocols (~90 vs ~ 60% HRmax), have been selected and the respective RSA performances were compared, within and between the groups of participants. Two sets of ten shuttle-sprints (15+15 m) with a 1:3 exercise to rest ratio with different initial HR% were administered, in different days, in randomized order. To compare the different sprint performances, we employed the calculated Fatigue Index (FI%). Blood lactate concentration (BLa-) was also measured before and after testing, to compare metabolic energy. Significant differences among trials within each set (P<0.01) were found in both genders. Differences between sets were found in male players, (Factorial ANOVA 2x5; P<0.001), not in female. BLa- after warm-up was higher in 90% vs. 60% HRmax (P<0.05), in both genders but at the completion of RSA tests (after 3 minutes) the differences were not significant (P>0.05). difference between genders were found, suggesting specific approach in testing and training RSA in soccer players.


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