Latest research in football - week 18 - 2023

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 Physical Performance Profiles in Norwegian Premier League Female Football: A Descriptive Study

Reference: Int J Sports Physiol Perform. 2023 May 18;1-9.  doi: 10.1123/ijspp.2022-0360. Online ahead of print.

Authors: Markus Vagle, Torstein Dalen-Lorentsen, Håvard Moksnes, Joar Harøy, John Bjørneboe, Thor Einar Andersen

Summary: The purpose was to map anthropometric and physical performance profiles in Norwegian premier league female football players. During preseason, the physical qualities of 107 players were tested on Keiser leg press, countermovement jump, 40-meter sprint, and agility. Descriptive statistics were presented as mean (SD) and median [interquartile range]. Pearson correlations analyses were made for all performance tests, and results presented as R value with 95% CIs. The female players were 22 (4) years of age, stature 169.0 (6.2) cm, body weight 65.3 (6.7) kg; force 2122 (312) N, power 1090 (140) W, sprint 40 m 5.75 (0.21) seconds, agility dominant 10.18 (0.32) seconds, nondominant 10.27 (0.31) seconds, and countermovement jump 32.6 (4.1) cm. Outfield players were faster and more agile than goalkeepers, a difference of 40 m, agility of dominant, and nondominant leg, respectively: 0.20 [0.09-0.32], 0.37 [0.21-0.54], and 0.28 [0.12-45]; P < .001. Goalkeepers and central defenders were taller and heavier compared with fullbacks, central midfielders, and wide midfielders (P ranging from <.02). A difference was found between dominant and nondominant legs for the agility test, showing that players are faster when changing direction with the dominant leg. Our study presents anthropometric and physical performance profiles of Norwegian premier league female football players. We found no difference for the physical qualities strength, power, sprint, agility, and countermovement jump between any outfield playing positions in female premier league players. There was a difference between outfield players and goalkeepers for sprint and agility.



#2 Mental toughness in the Football Association Women's Super League: Relationships with playing experience, perceptions of club infrastructure, support mechanisms and self-esteem

Reference: PLoS One. 2023 May 17;18(5):e0285594. doi: 10.1371/journal.pone.0285594. eCollection 2023.

Authors: Clare Wheatley, Mark Batey, Andrew Denovan, Neil Dagnall

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Summary: Previous research reports a positive association between possession of mental toughness (MT) and high performance in sportspersons. However, the extent to which MT is related to playing experiences and appreciation of club environment in elite women's football has received only limited research attention. Accordingly, the present study investigated MT in the context of the English Football Association Women's Super League (WSL). Specifically, this paper examined relationships between level of MT and external (playing experience, perceptions of club infrastructure, and appreciation of support mechanisms) and internal (self-esteem) factors. A sample of 63 elite female professional football players from the WSL, aged between 18 and 35 years (mean = 25.87, SD = 4.03), completed self-report measures. To objectively validate self-ratings, congruence between self and peer-rated was assessed. This revealed a strong degree of consistency. Subsequent analysis found positive correlations between MT, playing experience (number of years playing football, NoY; and highest level of football achieved, HLA), and External Support. Additionally, Self-Esteem correlated positively with MT, NoY, HLA, and External Support. Moderation analysis found MT interacted with NoY and predicted greater levels of Self-Esteem. Players with lower and mean MT, and more years as a professional were more likely to possess higher Self-Esteem (vs. less years). These outcomes indicated important relationships between MT, External Support, and Self-Esteem. Accordingly, WSL clubs can potentially apply the results of this study to enhance positive player mindset.



#3 Subjective experience, self-efficacy, and motivation of professional football referees during the COVID-19 pandemic

Reference: Humanit Soc Sci Commun. 2023;10(1):215. doi: 10.1057/s41599-023-01720-z. Epub 2023 May 8.

Authors: Fabio Richlan, J Lukas Thürmer, Jeremias Braid, Patrick Kastner, Michael Christian Leitner

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Summary: The present multi-study article investigates the subjective experience of professional football (a.k.a. soccer) referees and players during the COVID-19 pandemic and the so-called ghost games (i.e., games without supporters). Referees from the Austrian Football Association completed questionnaires inquiring about self-efficacy, motivation, and general personal observations and perceptions (e.g., arousal or confidence). In addition, two players and one referee in the Austrian Football Bundesliga were interviewed retrospectively regarding their subjective experience during ghost games and the effects of emotions on behavior and performance using semi-structured, video-taped interviews. Results of the referee survey indicate that the most profound differences between regular games and ghost games lie in the domain of intrinsic motivation and multiple aspects of subjective experience. Specifically, the experience in ghost games compared with regular games was reported by referees as being significantly less motivating, less excited/tense, less emotional, less focused, and overall, more negative, despite being easier to referee and the players behaving more positively. Qualitative analyses of the video-taped interview footage indicated (i) substantial inter-individual variability regarding the extent of the effect of the empty stadiums on the subjective experience of emotions, (ii) consequently, different strategies to regulate emotions and arousal from suboptimal to optimal levels, both before and during competition, and (iii) interactions between reported emotions, arousal, motivation, self-confidence, behavior and performance on the pitch. In addition, non-verbal expressions of emotion were captured using fully automated AI-software that coded facial movements during interviews. The results of this exploratory facial expression analysis revealed varying degrees of arousal and valence in relation to the content of the statements during the interviews, demonstrating the convergent validity of our findings. Our findings contribute to the growing literature on the effects of football games without fans during the COVID-19 pandemic and provide insights into the subjective experience of professional football referees. Concerning referees and players alike, emotions are investigated as potential processes related to home-field advantage and performance in professional football by means of a multi-methods approach. Further, the combination of qualitative and quantitative measures-as well as verbal and non-verbal communication channels-can deepen our understanding of the emotional influence of (missing) spectators on the subjective experience and the behavior of sports professionals is discussed.



#4 Exploring football coaches' views on coach education, role, and practice design: An Australian perspective

Reference: PLoS One. 2023 May 16;18(5):e0285871. doi: 10.1371/journal.pone.0285871. eCollection 2023.

Authors: Erch Selimi, Alexandra Lascu, Fabio Serpiello, Carl T Woods

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Summary: Despite the importance placed on the design and delivery of formal coach education programs by Football Australia, there remains a lack of research relating to how formal coach education strategies support Australian football (i.e., soccer) coaches and their coaching practices. Through a series of semi-structured interviews, 20 highly qualified and experienced Australian senior football coaches shared their perspectives on: (i) coach education, (ii) their role as coach, and (iii) practice design. Findings revealed that formal coach education in Australia was largely ineffective in preparing senior coaches for the realities of senior football. Coaches attributed this to a number of factors, including the content's quality, structure and delivery, which they viewed as rudimentary, outdated, repetitive and lacking in relevance and depth. Coaches also revealed there was an expectation of conformity to the content and practices endorsed by the National Football Curriculum, limiting the value and impact of formal coach education in supporting the development of coaches' theoretical and practical dispositions. These findings point towards a number of broad and systemic issues relating to the conceptual, theoretical and practical foundations of the National Football Curriculum and subsequent courses. If Football Australia are to reach their goal in designing and delivering effective and meaningful coach education programs that support the highly complex and multifaceted role of senior coaching, formal coach education may need to adapt and evolve in a manner that better supports the multi-dimensional and context-specific needs of Australian senior football coaches.



#5 Risk factors associated with football injury among male players from a specific academy in Ghana: a pilot study

Reference: Sci Rep. 2023 May 18;13(1):8070. doi: 10.1038/s41598-023-34826-0.

Authors: Samuel Koranteng Kwakye, Karien Mostert, Daniel Garnett, Andries Masenge

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Summary: There seems to be no information on the incidence of injury and associated risk factors for academy football players in Ghana. We determine the risk factors associated with match and training injuries among male football players at an academy in Ghana. Preseason measurements of players' height, weight, and ankle dorsiflexion (DF) range of motion (ROM) were measured with a stadiometer (Seca 213), a digital weighing scale (Omron HN-289), and tape measure, respectively. The functional ankle instability (FAI) of players was measured using the Cumberland Ankle Instability Tool (CAIT), and dynamic postural control was measured with the Star Excursion Balance Test. Injury surveillance data for all injuries were collected by resident physiotherapists throughout one season. Selected factors associated with injury incidence were tested using Spearman's rank correlation at a 5% significance level. Age was negatively associated with overall injury incidence (r = - 0.589, p = 0.000), match (r = - 0.294, p = 0.008), and training incidence (r = - 0.314, p = 0.005). Previous injury of U18s was associated with training injuries (r = 0.436, p = 0.023). Body mass index (BMI) was negatively associated with overall injury incidence (r = - 0.513, p = 0.000), and training incidence (r = - 0.395, p = 0.000). CAIT scores were associated with overall injury incidence (n = 0.263, p = 0.019) and match incidence (r = 0.263, p = 0.029). The goalkeeper position was associated with match incidence (r = 0.241, p = 0.031) while the U16 attacker position was associated with training incidence. Exposure hours was negatively associated with overall injury incidence (r = - 0.599, p = 0.000). Age, BMI, previous injury, goalkeeper and attacker positions, ankle DF ROM, and self-reported FAI were associated with injury incidence among academy football players in Ghana.



#6 When and How Do Soccer Players From a Semi-Professional Club Sprint in Match Play?

Reference: J Hum Kinet. 2023 Jan 20;86:195-204. doi: 10.5114/jhk/159964. eCollection 2023 Mar.

Authors: José M Oliva-Lozano, Juan Cuenca-López, Javier Suárez, Paulino Granero-Gil, José M Muyor

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Summary: The aims of this study were to investigate the periods in which sprints occurred during official matches and analyze these sprints considering the effect of the playing position and different contextual variables. Electronic performance and tracking systems were used for the analysis of all sprints performed by players. Matches were recorded by video and synchronized with performance tracking data. A total of 252 sprints were analyzed. The greatest frequency of sprints was observed in the period 1 (0'-15'), followed by period 2 (15'-30') and period 6 (75'-90'), regardless of the playing position (χ2 = 31.35; p = 0.051). Most sprints were non-linear (non-linear sprints: 97.6%; linear sprints: 2.4%) and without ball possession (without ball possession: 95.2%; with ball possession: 4.8%) for all playing positions, but the role of the sprint and the field area in which the sprint occurred were dependent on the position (p < 0.001). Specifically, players covered ~17.55 m per sprint, starting at ~10.34 km/h, reaching ~26.74 km/h, maximally accelerating at ~2.73 m/s2, and decelerating at ~3.61 m/s2. Overall, the playing position and contextual variables had no significant effect on physical performance variables analyzed during these sprints. Therefore, this study allows performance practitioners to have a better understanding of when and how soccer players sprint in match-play. In this regard, this study presents some training and testing strategies that may be considered to improve performance and decrease injury risk.



#7 Rationale and Practical Recommendations for Testing Protocols in Female Soccer: A Narrative Review

Reference: J Strength Cond Res. 2023 May 15. doi: 10.1519/JSC.0000000000004509. Online ahead of print.

Authors: Marco Beato, Naomi Datson, Liam Anderson, Thomas Brownlee, Alex Coates, Andrew Hulton

Summary: The aim of this narrative review is to evaluate the presented literature on tests (aerobic, speed, changes of direction [COD], strength, power, jump, and anthropometry) of the varied components of female soccer and to draw attention to the most suitable protocols to allow practitioners to accurately track players' fitness status. The 2 most common field tests used to assess aerobic fitness are the Yo-Yo intermittent test (level 1 and level 2) and the 30-15 intermittent fitness test because of an ability to measure multiple players at once with a soccer-specific intermittent profile. The sprinting performance can be assessed on distances of <30 m; however, longer distances (e.g., 40 m) allow for achieving peak speed (flying sprint test), which can be assessed using global navigation satellite system. Changes-of-direction capacity has been found to be an important component of players testing and training programs, although there is no "gold standard" to assess COD or repeated sprint ability performance in female players. Lower-limb power can be assessed using jump tests that can use force platforms, jump mats, and optoelectronic devices, while maintaining a good reliability. Several in-direct tests are currently available for assessing anthropometry parameters, such as skinfold thickness, hydrodensitometry, and ultrasound. However, dual-energy x-ray absorptiometry is the most valid and reliable method for assessing body composition in team sport athletes, with the addition of bone health that is a key measure in female athletes. In conclusion, the evidence reported in this review will be able to aid practitioners, coaches, and researchers to decide which tests meet the requirements of their environment.



#8 Quantifying the efficacy of protective eyewear in pediatric soccer-induced retinal injury

Reference: J AAPOS. 2023 May 13;S1091-8531(23)00093-9. doi: 10.1016/j.jaapos.2023.02.009.

Authors: Andrew Suh, Matthew Lam, Yasin Shokrollahi, Pengfei Dong, Linxia Gu, Donny Suh

Summary: Ocular injury is common in children playing sports. Sports-related eye injuries, if severe enough, can lead to permanent vision impairment. Soccer, the most popular sport in the world, is a sport in which players rarely use protective eyewear. The purpose of this study was to determine how eye injuries are induced by a soccer ball impact and to evaluate whether eye protection influences the effects of impact. A finite element (FE) computer simulation was used to simulate soccer ball trauma on a model of the eye with and without eye protection. Protective eyewear of different materials (polycarbonate and acrylic) was modeled to investigate the optimal medium for eye protection. Stress and strain experienced by the eyeball was quantified by the FE computer simulation in each model. Protective eyewear was found to be effective in lowering ocular stress and strain by absorbing and redirecting energy from the ball. Compared to the unprotected eye model, polycarbonate eyewear reduced the average stress the retina experienced by 61%, whereas the acrylic model reduced the average stress by 40%. Polycarbonate and acrylic eyewear also reduced the maximum strain experienced by the retina by 69% and 47%, respectively, reducing the severity of deformations of the eye on impact. These findings suggest that wearing protective eyewear, especially when made of polycarbonate, can be an effective means of reducing injury-inducing retinal stress. The use of eye protection is thus recommended for pediatric patients participating in soccer.



#9 Maturity-Related Variations in Morphology, Body Composition, and Somatotype Features among Young Male Football Players

Reference: Children (Basel). 2023 Apr 13;10(4):721. doi: 10.3390/children10040721.

Authors: Denis Čaušević, Babina Rani, Qais Gasibat, Nedim Čović, Cristina Ioana Alexe, Silviu Ioan Pavel, Lucian Ovidiu Burchel, Dan Iulian Alexe

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Summary: The study aimed to investigate differences in anthropometry, body composition (BC), and somatotype in young football players of the same chronological age according to the maturity stage. Overall, 64 elite players (age: 14.28 ± 0.46 years) were evaluated for standing and sitting body height, girth measures, and BC using the bioelectric impedance scale and skinfold thickness. In total, two-thirds (73.44%, n = 47) of football players were classified as on-time maturers, 12.50% (n = 8) were early maturing, and 14.06% (n = 9) were late maturing. Standing and sitting height, leg length, fat-free mass, and muscle mass were significantly different (p < 0.001) across maturity groups. A significant decrease (p < 0.05) with maturity progression was seen for subscapular and suprailiac skinfolds along with a girth increase at all sites (p < 0.05). Early maturers were balanced ectomorphs, while on-time and late maturers featured mesomorph-ectomorph characteristics. The obtained results suggested that mature players have better BC presented as a lower fat percentage along with higher muscle mass, advantages in circumferences, and longitudinal dimensions of the body with highlighted mesomorph features. Maturity can have a substantial influence on body measures, thereby affecting sport-specific performance. Early maturers can use their anthropometric advantages and compensate for a lack of talent, consequently preventing even participation of physically undeveloped players in training. A better understanding of maturity, BC, and somatotypes can help in the selection of young talented players.



#10 An 11-week school-based "health education through football" programme improves musculoskeletal variables in 10-12-yr-old Danish school children

Reference: Bone Rep. 2023 Apr 29;18:101681. doi: 10.1016/j.bonr.2023.101681. eCollection 2023 Jun.

Authors: Malte Nejst Larsen, Alessia Terracciano, Trine Kjeldgaard Møller, Charlotte Sandager Aggestrup, Pasqualina Buono, Peter Krustrup, Carlo Castagna

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Summary: The aim was too investigate the effects of the "11 for Health" programme on musculoskeletal fitness. A total of 108 Danish children aged 10-12 years participated in the study, with 61 children in the intervention group (IG, 25 girls and 36 boys) and 47 children in the control group (CG, 21 girls and 26 boys). Measurements were conducted before and after an 11-week intervention consisting of twice-weekly 45-min football training sessions for IG or continuation of normal Physical Education program for CG. Whole-body dual X-ray absorptiometry was conducted for evaluation of leg and total bone mineral density as well as bone, muscle and fat mass. Standing Long Jump and Stork balance tests were employed to assess musculoskeletal fitness and postural balance. During the 11-week study period, leg bone mineral density as well as leg lean body mass increased more (p < 0.05) in the intervention group (IG) compared to the control group (CG) (0.021 ± 0.019 vs 0.014 ± 0.018 g/cm2 and 0.51 ± 0.46 vs 0.32 ± 0.35 kg, respectively). Moreover, body fat percentage decreased more in IG than in CG (-0.6 ± 0.1 vs 0.1 ± 0.1 %-points, p < 0.05). No significant between-group differences were found in bone mineral content. Stork balance test performance increased more in IG than in CG (0.5 ± 2.6 vs -1.5 ± 4.4 s, p < 0.05), whereas no between-group differences were found in jump performance. The school-based football programme, 11 for Health, with twice-weekly 45-min training sessions over 11 weeks improves various, but not all evaluated parameters related to musculoskeletal fitness in 10-12-yr-old Danish school children.



#11 A Comparison of Training and Match Play External Load During a Congested In-Season Period in English League 2 Football

Reference: J Strength Cond Res. 2023 May 15. doi: 10.1519/JSC.0000000000004458. Online ahead of print.

Authors: Adam Fleming, Matthew Walker, Mark Armitage, Mark Connor, Marco Beato

Summary: This study aimed to investigate if external training load metrics differ between training days and match day (MD) during a period of fixture congestion and to verify if external load metrics vary based on playing positions. Training and MD data were collected in a part of the competition phase of the 2020-2021 season (6 weeks) in the English Football League 2 (N = 20 players, mean ± SDs: age = 24.4 ± 4.7 years). Global Navigation Satellite System units (Catapult S7 Vector 10 Hz) were used to monitor external load metrics. The metrics were duration of training, total distance (TD), high-speed running distance (HSR), sprinting distance, relative intensity (m/min), total accelerations (TotAcc) (>3 m·s-2), and total decelerations (TotDec) (<-3 m·s-2). This study found that duration, TD, relative intensity, HSR distance, sprint distance, TotAcc, and TotDec were different (p < 0.001, d = small to moderate) between MD and match day minus two (MD-2) or match day minus one (MD-1); however, during match day minus four (MD-4), only relative intensity was significantly lower (p < 0.001) compared with MD output. Therefore, MD-4 was the most demanding training session of the week (after the MD), and during MD-2 and MD-1, coaches decreased players' load to favor players' readiness. Moreover, this study found that MD and MD-1 resulted in statistically different values across several metrics between different playing positions (defenders < midfielders and strikers), whereas metrics in MD-4 and MD-2 were not statistically different, which highlights that in these sessions, players have similar external loads independently from their playing positions.



#12 A bespoke sleep monitoring and sleep hygiene intervention improves sleep in an U18 professional football player: A case study

Reference: J Sports Sci. 2023 May 14;1-8. doi: 10.1080/02640414.2023.2213032. Online ahead of print.

Authors: Luke Edinborough, Jessica Hill, Mark Jarvis, Stewart Bruce-Low, Charles R Pedlar

Summary: This case study reports on a professional football player (age: 17.6 years) who was referred for sleep monitoring and intervention after reporting excessive night-time awakenings. The player undertook a series of subjective sleep assessments and objective sleep monitoring (activity monitor). Based on the data presented, a sleep hygiene intervention was prescribed. Numerical comparisons were made between pre-intervention (Pre) and post-intervention (Post) values. Objective values were also compared to reference data from a similarly aged professional cohort from the same club (n = 11). Wake episodes per night (Pre: 7.9 ± 3, Post: 4.5 ± 1.9; -43%) and wake after sleep onset (WASO; Pre: 74.3 ± 31.8 mins, Post: 50.0 ± 22.8 mins, -33%) were improved from Pre to Post. Compared to the reference data, mean wake episodes per night (Pre: 7.9 ± 3.0, reference: 4.6 ± 2.6; -42%) and WASO (Pre: 74.3 ± 31.8 mins, reference: 44.3 ± 36.5 mins; -40%) were all lower compared to Pre levels. Whilst causality cannot be proven, we observed multiple sleep metrics improving following an intervention. This provides a potential framework for practitioners looking to provide targeted sleep assessment and intervention.



#13 Differences in kinetic characteristics during countermovement jump of football players with cerebral palsy according to impairment profiles

Reference: Front Physiol. 2023 Apr 26;14:1121652. doi: 10.3389/fphys.2023.1121652. eCollection 2023.

Authors: Matías Henríquez, Rafael Sabido, David Barbado, Alba Roldan, Jose L L Elvira, Javier Yanci, Raúl Reina

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Summary: The purpose of this study was 1) to determine and compare kinetic parameters during the realization of a countermovement jump (CMJ) between footballers with cerebral palsy (CP) and non-impaired footballers, and 2) to analyze the differences in this action between different players' impairment profiles and a group of non-impaired footballers. This study involved 154 participants comprising 121 male footballers with CP from 11 national teams and 33 male non-impaired football players recruited as the control group (CG). The footballers with CP were described according to the different impairment profiles (bilateral spasticity = 10; athetosis or ataxia = 16; unilateral spasticity = 77; minimum impairment = 18). All participants performed three CMJs on a force platform to record kinetic parameters during the test. The group of para-footballers presented significantly lower values than the CG in the jump height (p < 0.01, d = -1.28), peak power (p < 0.01, d = -0.84), and the net concentric impulse (p < 0.01, d = -0.86). Concerning the pairwise comparisons between CP profiles and the CG, significant differences were found for the bilateral spasticity, athetosis or ataxia, and unilateral spasticity subgroups compared to the non-impaired players for jump height (p < 0.01; d = -1.31 to -2.61), power output (p < 0.05; d = -0.77 to -1.66), and concentric impulse of the CMJ (p < 0.01; d = -0.86 to -1.97). When comparing the minimum impairment subgroup with the CG, only significant differences were found for jump height (p = 0.036; d = -0.82). Footballers with minimum impairment presented higher jumping height (p = 0.002; d = -1.32) and concentric impulse (p = 0.029; d = -1.08) compared to those with bilateral spasticity. Also, the unilateral spasticity subgroup reports a higher jump height performance than the bilateral group (p = 0.012; d = -1.12). These results suggest that the variables related to power production during the concentric phase of the jump are crucial for the performance differences between groups with and without impairment. This study provides a more comprehensive understanding of kinetic variables that would differentiate CP and non-impaired footballers. However, more studies are necessary to clarify which parameters better differentiate among different profiles of CP. The findings could help to prescribe effective physical training programs and support the classifier's decision-making for class allocation in this para-sport.



#14 The Influence of Subjective Perceptions and the Efficacy of Objective Evaluation in Soccer School Players' Classification: A Cross-Sectional Study

Reference: Children (Basel). 2023 Apr 23;10(5):767. doi: 10.3390/children10050767.

Authors: Federico Abate Daga, Franco Veglio, Gian Maria Cherasco, Samuel Agostino

Summary: The first objective was to investigate the influence of subjective perceptions and the efficacy of objective evaluation regarding the classification of soccer school players by their level of performance. The second objective was to advise on accurate collocation according to objective assessment of players' performance. An objective evaluation of the players' motor performance abilities and coaches' subjective perceptions of the players' levels of performance was conducted with 34 young football players (U11) from Torino FC soccer school. The players were allocated to three groups based on their perceived performance level at the start of the season. The players were evaluated using a field test battery, and team coaches provided subjective ratings of the players' abilities. MANOVA showed significant differences between the playing levels (F = 2.185, p < 0.05; partial η2 = 0.34) in the 10 × 5 shuttle run, 20 m sprint test (objective evaluations), heading, understanding of the game, positioning on the field, speed and agility (subjective perception) (F = 1.951, p < 0.05; partial η2 = 0.43). A discriminant analysis of the field test scores revealed that 76.5% of players were correctly categorised in one of the three performance-level groups. However, the first group (the best players) had the lowest predictive accuracy rate (58.3%). By comparison, the second group (the average players) had a much higher predictive accuracy rate (83.3%), and the third (the weakest players) had the highest (90.0%).


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