Latest research in football - week 51 - 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 Comparison among U-17, U-20, and Professional Female Soccer in the GPS Profiles during Brazilian Championships

Reference: Int J Environ Res Public Health. 2022 Dec 11;19(24):16642. doi: 10.3390/ijerph192416642.

Authors: Ronaldo Kobal, Leonardo Carvalho, Raíssa Jacob, Marcelo Rossetti, Lucas de Paula Oliveira, Everton Crivoi Do Carmo, Renato Barroso

Summary: The purpose of this study was to compare and characterize the physical demand of official matches among under-17 (U-17), under-20 (U-20), and professional (Pro) female soccer players. All matches were from the U-17, U-20, and Pro National Brazilian Championships. Fourteen Pro matches, nine U-20 matches, and four U-17 matches were analyzed. The external load was measured by the global positioning system (GPS) and the internal workload was assessed by the ratings of perceived exertion (RPE) multiplied by the duration of the match. The activity profiles measured were total distance covered (km), total sprint distance (m) (speed > 18 km·h-1), number of accelerations and decelerations (between 1 and 2 m·s-2 and >3 m·s-2), and top speed (km·h-1). For the analysis, we standardized all the metrics (except the top speed) by the time (in minutes) played. The Pro group presented higher sprint distances, number of accelerations and decelerations, and top speeds, compared to U-20 and U-17. There was no difference in the total distance among groups, and there was no difference in any GPS metrics between U-20 and U-17. The RPE was higher in Pro and U-17, compared to U-20; however, the workload-RPE was higher in Pro, compared to both U-17 and U-20 groups. These findings provide important information for the evolution of physical performance according to age categories in elite female soccer players.



#2 Psychosocial Predictors of Drop-Out from Organised Sport: A Prospective Study in Adolescent Soccer

Reference: Int J Environ Res Public Health. 2022 Dec 9;19(24):16585. doi: 10.3390/ijerph192416585.

Authors: Jenny Back, Andreas Stenling, Bård Erlend Solstad, Petra Svedberg, Urban Johnson, Nikos Ntoumanis, Henrik Gustafsson, Andreas Ivarsson

Summary: In recent years an increased drop-out rate in adolescents' soccer participation has been observed. Given the potentially adverse consequences of drop-out from soccer, more information about risk factors for drop-out is warranted. In the current study, Classification and Regression Tree (CRT) analysis was used to investigate demographic and motivational factors associated with an increased risk of drop-out from adolescent soccer. The results of this study indicate that older age, experiencing less autonomy support from the coach, less intrinsic motivation, being female, and lower socioeconomic status are factors associated with an increased risk of drop-out. An interpretation of the results of this study is that coaches play a central part in creating a sports context that facilitates motivation and continued soccer participation. Based on the findings of the current study we propose that soccer clubs implement theoretically informed coach education programs to help coaches adopt autonomy-supportive coaching strategies.



#3 The Three-Level Model of Factors Contributing to High-Intensity Intermittent Performance in Male Soccer Players

Reference: Int J Environ Res Public Health. 2022 Dec 7;19(24):16402. doi: 10.3390/ijerph192416402.

Authors: Juraj Pecho, Zuzana Kováčiková, Ľuboslav Šiška, Martin Mikulič, Marcel Čurgali, Lovro Štefan, Erika Zemková

Summary: High-intensity intermittent performance in soccer is widely assessed using the yo-yo intermittent recovery level 2 test (YYIR2). This test is usually associated with aerobic-anaerobic performance. However, less is known about the direct or indirect contributions of abilities, including the anaerobic component. This study aims to propose a three-level model of factors contributing to YYIR2 performance, based on the investigation of relationships with aerobic endurance, repeated-sprint ability (RSA), and the linear and change-of-direction speed and power variables. Eighteen soccer players performed the YYIR2, with a 20-m shuttle run test (20mSR), an RSA test with change-of-direction, 5-m and 20-m sprints, and a 505 test, countermovement jump, squat jump, and drop jump. The results showed a significant relationship between the YYIR2 distance and the 20mSR distance (r = 0.721, p = 0.001), as well as with the RSA test mean time (r = -0.594, p = 0.009). In the second level, the 20mSR distance performance was not associated with any of the speed and power variables. However, the RSA test mean time correlated with the 5-m sprint (r = 0.587, p = 0.010), 20-m sprint (r = 0.702, p = 0.001), and 505 test (r = 0.585 p = 0.011) performance. In the third level, the 20-m sprint time was related to the squat jump (r = -0.577 p = 0.012) and countermovement jump (r = -0.768 p < 0.001) heights. In addition to aerobic endurance, this study highlights the importance of the anaerobic component in YYIR2 performance. More specifically, aerobic endurance (52%) and RSA (36%) are the main determinants of YYIR2 performance. Subsequently, the RSA performance is determined by the linear (34-49%) and change-of-direction speed (35%), while the explosive power of lower limbs contributes to sprinting performance (33-59%). Coaches should focus on the development of these abilities to improve the high-intensity intermittent performance of soccer players.



#4 The Association between Occupational Stress and Mental Health among Chinese Soccer Referees in the Early Stage of Reopening Soccer Matches during the COVID-19 Pandemic Outbreak: A Moderated Mediation Model

Reference: Int J Environ Res Public Health. 2022 Dec 13;19(24):16750. doi: 10.3390/ijerph192416750.

Authors: Zongyu Liu, Liangyu Zhao, Shuzhen Wang, Yubo Gao, Liguo Zhang

Summary: The sudden and unpredictable changes caused by the COVID-19 pandemic are a serious threat to the occupational stress and mental health of referees worldwide, which has not attracted widespread attention. The mental health of football referees has a certain influence on their job satisfaction or the accuracy of judgments. This study constructed a moderated mediation model to explore the buffer factors between occupational stress and mental health in Chinese soccer referees in the early stage of reopening soccer matches during the COVID-19 pandemic outbreak. Data from 317 Chinese soccer referees (aged 19-45) were collected through an online questionnaire in September-October 2022. Occupational stress, mental health, job burnout and perceived social support were measured, and moderated mediation model was analyzed. The results of this study showed that occupational stress was negatively correlated with mental health through the mediating effect of job burnout and the moderated effect of perceived social support after controlling for demographic variables. Specifically, the association between occupational stress and mental health was weaker when perceived social support was higher and stronger. The results demonstrate that job burnout and perceived social support played important roles in buffering the negative effects of occupational stress on the mental health of Chinese soccer referees in the early stage of reopening soccer matches during the COVID-19 pandemic outbreak. The findings provide implications for mental health interventions in soccer referees during the public health crises.



#5 Lactate Threshold and Psychomotor Fatigue Threshold in Hot Conditions: Suggestions for Soccer Players Participating in the Qatar World Cup 2022

Reference: Int J Environ Res Public Health. 2022 Dec 18;19(24):17028. doi: 10.3390/ijerph192417028.

Authors: Marek Konefał, Jan Chmura, Małgorzata Charmas, Jadwiga Kotowska, Krzysztof Błażejczyk, Paweł Chmura

Summary: The study aimed at finding relationships between lactate threshold and psychomotor fatigue threshold during incremental exercise in thermo-neutral climate conditions and conditions for the 2022 FIFA World Cup in Qatar simulated in an environmental test chamber. The study included 24 soccer players aged 21.02 ± 3.22 years old. The following procedures were performed: The incremental exercise test to mark lactate concentration-LA (mmol·l-1); Psychomotor test to determine choice reaction time; Designation of the lactate threshold (TLA) and psychomotor fatigue threshold (TPF). Climate conditions: The procedure was performed twice in the climatic chamber: (1) in thermo-neutral conditions-TNC (ambient temperature 20.5 °C and relative air humidity 58.7%), (2) after 7 days-in Qatar conditions-QC (28.5 ± 1.92 °C) and (58.7 ± 8.64%). It was confirmed that the TPF, which reflects the highest efficiency of CNS functioning, occurs at a higher running speed than the TLA. The temperature of 28.5 °C with 58.7% humidity, which is the lower limit of heat stress, causes the psychomotor fatigue threshold to appear at a lower running speed than in thermoneutral conditions. The data recorded in this work may help to understand the specificity of physiological and psychomotor reactions to various climatic conditions.



#6 Urinary Metabolomics in Young Soccer Players after Winter Training Season

Reference: Metabolites. 2022 Dec 17;12(12):1283. doi: 10.3390/metabo12121283.

Authors: Hyang-Yeon Kim, Jung-Dae Lee, Yun-Hwan Lee, Sang-Won Seo, Ho-Seong Lee, Suhkmann Kim, Kyu-Bong Kim

Summary: During the off-season, soccer players in Korea attend the winter training season (WTS) to build running stamina for the next season. For young soccer players, proper recovery time is needed to prevent injury or muscle damage. In this study, urinary metabolites in young players after 1, 5, and 10 days of the WTS were analyzed using nuclear magnetic resonance spectroscopy (NMR) combined with multivariate analysis to suggest appropriate recovery times for improving their soccer skills. After NMR analysis of the urine samples obtained from young players, 79 metabolites were identified, and each group (1, 5, or 10 days after WTS) was separated from the before the WTS group in the target profiling analysis using partial least squares-discriminant analysis (PLS-DA). Of these, 15 metabolites, including 1-methylnicotinamide, 3-indoxylsulfate, galactarate, glutamate, glycerol, histamine, methylmalonate, maltose, N-phenylacetylglycine, trimethylamine, urea, 2-hydroxybutyrate, adenine, alanine, and lactate, were significantly different than those from before the WTS and were mainly involved in the urea, purine nucleotide, and glucose-alanine cycles. In this study, most selected metabolites increased 1 day after the WTS and then returned to normal levels. However, 4 metabolites, adenine, 2-hydroxybutyrate, alanine, and lactate, increased during the 5 days of recovery time following the WTS. Based on excess ammonia, adenine, and lactate levels in the urine, at least 5 days of recovery time can be considered appropriate.



#7 Extended Energy-Expenditure Model in Soccer: Evaluating Player Performance in the Context of the Game

Reference: Sensors (Basel). 2022 Dec 14;22(24):9842. doi: 10.3390/s22249842.

Authors: Arian Skoki, Alessio Rossi, Paolo Cintia, Luca Pappalardo, Ivan Štajduhar

Summary: Every soccer game influences each player's performance differently. Many studies have tried to explain the influence of different parameters on the game; however, none went deeper into the core and examined it minute-by-minute. The goal of this study is to use data derived from GPS wearable devices to present a new framework for performance analysis. A player's energy expenditure is analyzed using data analytics and K-means clustering of low-, middle-, and high-intensity periods distributed in 1 min segments. Our framework exhibits a higher explanatory power compared to usual game metrics (e.g., high-speed running and sprinting), explaining 45.91% of the coefficient of variation vs. 21.32% for high-, 30.66% vs. 16.82% for middle-, and 24.41% vs. 19.12% for low-intensity periods. The proposed methods enable deeper game analysis, which can help strength and conditioning coaches and managers in gaining better insights into the players' responses to various game situations.



#8 Effect of Intensified Training Camp on Psychometric Status, Mood State, and Hematological Markers in Youth Soccer Players

Reference: Children (Basel). 2022 Dec 19;9(12):1996. doi: 10.3390/children9121996.

Authors: Okba Selmi, Danielle E Levitt, Ibrahim Ouergui, Bilel Aydi, Anissa Bouassida, Katja Weiss, Beat Knechtle

Summary: During training camps, training load is purposefully intensified. Intensified training loads (TL) are associated with psychological variations, increased fatigue, insufficient recovery, decreased muscular performance, and biological changes in adult athletes, but whether these changes occur during training camps in youth athletes has not been established. The aim of this study was to assess changes in psychometric status, vertical jump performance (i.e., height), and hematological markers before and after an intensive training camp in youth soccer players. In this case, 15male youth soccer players (mean ± SD: age: 14.8 ± 0.4 years; height: 172.0 ± 6.9 cm, body mass: 60.8 ± 7.9 kg; training experience: 5.2 ± 0.7 years) completed a 2-week training program consisting of 1 week of moderate TL (MT) and 1 week of intensive training camp (TC). Rate of perceived exertion (RPE), TL, monotony, strain, and psychometric status (total quality of recovery (TQR) and well-being indices (sleep, stress, fatigue, and muscle soreness) were monitored before each first daily training session across two weeks. The profile of mood states (POMS), countermovement jump (CMJ) height, and blood markers (complete blood count, urea, and creatinine) were assessed before and after TC. TL (d = 5.39, large), monotony (d = 3.03, large), strain (d = 4.38, large), and well-being index (d = 7.5, large) scores increased and TQR (d = 4.6, large) decreased during TC. The TC increased tension, fatigue, and total mood disturbance and decreased vigor (all p <0.01). CMJ performance p < 0.01, d = 0.52, moderate), creatinine (p < 0.01, d = 1.29, large), and leukocyte concentration (p < 0.01, d = 1.4, large) and granulocyte concentration (p < 0.01, d = 1.93, large) increased after TC. Percentage of lymphocytes (p < 0.05, d = 1.17, large) and monocytes (p < 0.01, d = 1.05, large) decreased while the percentage of granulocytes (p < 0.05, d = 0.86, large) increased significantly. Well-being, quality of recovery, mood, granulocyte concentration, and creatinine were all altered during the week-long intensified training camp. These results may provide coaches with valuable information about psychometric status and physiological fatigue and recovery of youth soccer players to better prescribe and adjust training loads during intensive training periods.



#9 The Effects of Soccer Specific Exercise on Countermovement Jump Performance in Elite Youth Soccer Players

Reference: Children (Basel). 2022 Nov 30;9(12):1861. doi: 10.3390/children9121861.

Authors: Max Lyons Donegan, Steven Eustace, Rhys Morris, Ryan Penny, Jason Tallis

Summary: The aims of the study were to examine the test-retest reliability of force-time (F-T) characteristics and F-T curve waveform of bilateral and unilateral countermovement jumps (CMJ) in elite youth soccer players and to evaluate the effects of competitive match-play on CMJ performance. 16 male youth soccer players completed CMJs on two separate occasions to determine reliability, and immediately pre, post and 48 h following a competitive match. Coefficient of variation (CV%), Intra-class correlation coefficient (ICC) and limits of agreement were used to assess reliability of discreate CMJ variables. Single factor repeated measures ANOVA were used to determine the effects of match play. Statistical parametric mapping was used to evaluate the repeatability of the CMJ force-time waveform and the effects of match play. Jump height had limited reliability in all three jumps and only a select few jump specific F-T variables were found to be reliable (CV < 10%, ICC > 0.5). Select variables were reduced immediately post game but recovered 48 h post game. The F-T curve waveform was found to be repeatable but did not differ following match-play. This study suggest that select F-T variables change following match-play and may be suitable tools to allow practitioners to detect decrements in performance. These data may help inform practitioners to use the most appropriate F-T variables to assess fatigue and recovery, with implications for performance and injury risk.



#10 Extracellular and Intracellular Concentrations of Molybdenum and Zinc in Soccer Players: Sex Differences

Reference: Biology (Basel). 2022 Nov 25;11(12):1710. doi: 10.3390/biology11121710.

Authors: Víctor Toro-Román, María Concepción Robles-Gil, Diego Muñoz, Ignacio Bartolomé, Jesús Siquier-Coll, Marcos Maynar-Mariño

Summary: Molybdenum (Mo) and zinc (Zn) play important roles in the process of adaptation to physical training. The aims of the present study were: (i) to analyze the differences in extracellular (plasma and urine) and intracellular (erythrocytes and platelets) Mo and Zn concentrations between sexes and (ii) to relate extracellular Zn concentrations with biomarkers of muscle damage and muscle mass. The present study involved 138 semi-professional soccer players divided according to sex: male (n = 68) and female (n = 70). Mo and Zn concentrations were determined by inductively coupled plasma mass spectrometry. Erythrocytes, platelets, creatine kinase (CK), and lactate dehydrogenase (LDH) values were also determined by automatic cell counter and spectrophotometric techniques. There were no sex differences in Mo and Zn intake. Male soccer players obtained higher values of erythrocytes, CK, and LDH (p < 0.05), and showed higher plasma and urinary concentrations of Mo and Zn (p < 0.05). Female soccer players showed relatively higher Zn concentrations in erythrocytes (p < 0.05). Finally, positive correlations were observed between extracellular Zn concentrations with CK, LDH and muscle mass. Extracellular concentrations of Mo and Zn were higher in male soccer players. However, the relative concentrations of Zn in relation to the number of erythrocytes were higher in female soccer players.



#11 Primary Headaches and Physical Performance: A Professional Youth Female Soccer Team Study

Reference: Brain Sci. 2022 Dec 12;12(12):1702. doi: 10.3390/brainsci12121702.

Authors: Magdalena Kobus, Elżbieta Żądzińska, Marcos Michaelides, Koulla Parpa

Summary: The vast majority of the research on acute post-traumatic incidents in athletes focuses on migraines. Physical exercise might reduce the frequency of migraines as well as trigger a migraine attack. The objectives of the study were to evaluate primary headache prevalence in professional young female soccer players and to assess whether headaches are related to physical performance. To the best of our knowledge, this is the first study that has considered the relationship between primary headaches and physical performance assessment. The research was conducted in 19 females aged 12-17 from a professional youth soccer academy. Players completed a questionnaire about health status and then performed laboratory physical tests (e.g., cardiopulmonary tests, countermovement and squat jumps, handgrip, sit-and-reach tests). Subsequently, players were separated into a headache group and a headache-free control group. In the analysed group, eight female players (42%) suffered from primary headaches. Among the performance parameters, a significant result was found in terms of flexibility. Females from the headache group had higher results in the sit-and-reach test than females from the control group (p = 0.029). Flexibility as well as mobility in migraine patients is an area with significant potential for further investigation, as little research has been conducted to date.



#12 The Influence of a Specific Cognitive-Motor Training Protocol on Planning Abilities and Visual Search in Young Soccer Players

Reference: Brain Sci. 2022 Nov 26;12(12):1624. doi: 10.3390/brainsci12121624.

Authors: Andrea Casella, Emanuele Ventura, Francesco Di Russo

Summary: The benefits of sport activity on cognition and especially on executive function development are well-known, and in recent years, several kinds of cognitive-motor training (CMT) have been proven effective in adults and older people. Less is known about possible CMT benefits in children. This study aims to confirm the positive influence played by CMTs on specific executive functions (planning abilities and visual search) in young soccer players. Twenty-four 10-year-old athletes were recruited and randomly assigned to the experimental (Exp) and control (Con) groups of 12 players. Both groups were trained for 10 weeks, twice a week (90 min per training), following standard soccer training (technical-tactical exercises). The Exp group, during the first training session of the week, in the last 22 min, performed the experimental treatment, which consisted of a psychokinetic CMT. Both groups were examined before and after the ten-week training using the Tower of London and WISC-IV cancellation tests. Results revealed that the Exp group, following treatment, reported significantly better scores than the Con group in all the cognitive measures. We concluded that the proposed CMT is more effective than motor training alone at improving planning abilities and visual search abilities, even in children.



#13 Relationship between anatomical injury site of rectus femoris muscle strain and time taken to return to play in Japanese professional soccer players

Reference: J Orthop Surg (Hong Kong). 2022 Sep-Dec;30(3):10225536221141786. doi: 10.1177/10225536221141786.

Authors: Kengo Shimozaki, Junsuke Nakase, Kazuki Asai, Rikuto Yoshimizu, Mitsuhiro Kimura, Tomoyuki Kanayama, Yusuke Yanatori, Hiroyuki Tsuchiya

Summary: The rectus femoris has three myotendinous or myoaponeurosis junctions and causes three types of muscle strain anatomically. We aimed to investigate the anatomical injury site of the rectus femoris muscle strain in professional soccer players as well as the characteristic findings on magnetic resonance imaging (MRI) and to evaluate its relationship with the time taken to return to play at competition levels. Thirteen Japanese professional soccer players who sustained injuries to the rectus femoris were included in this study. The mechanism of injury, anatomical injury site, severity, absence of hematomas, and time taken to return to competition were evaluated. Ten patients were injured while kicking and three while sprinting. The anatomical injury site was the origin aponeurosis in two cases, intramuscular tendon in eight cases, and distal aponeurosis in three cases. The severity was one-degree in three cases and two-degree in 10 cases. Hematomas were observed in five cases. Cases with injuries caused by sprinting, two-degree injuries, or clear hematomas were associated with significantly longer periods of return to play than the other cases. Additionally, patients with distal aponeurosis-type injuries tended to take a long time to return to the competition. In rectus femoris muscle strain, it is important to evaluate the anatomical injury site, severity, and absence of hematomas on MRI. Not only the injury mechanism, a clear hematoma, and high severity but also distal aponeurosis injuries may be associated with long periods of return to play at competition levels.



#14 Knee Isokinetic Profiles and Reference Values of Professional Female Soccer Players

Reference: Sports (Basel). 2022 Dec 12;10(12):204. doi: 10.3390/sports10120204.

Authors: Isabel Brígido-Fernández, Francisco García-Muro San José, Guillermo Charneco-Salguero, José Miguel Cárdenas-Rebollo, Yolanda Ortega-Latorre, Ofelia Carrión-Otero, Luis Fernández-Rosa

Summary: Few studies have previously evaluated isokinetic parameters in female soccer players in comparison to those in males. The aim of this study was to describe normative quadriceps (Q) and hamstring (H) muscle strength values in professional female soccer players and to examine differences between dominant leg (DL) and nondominant leg (NDL). A standardized test protocol of concentric knee extension and flexion test protocol was conducted using the dynamometer isokinetic system (IsoMEd 2000). All the participants were healthy female professional soccer players from Spanish first and second division teams. Players were assessed for peak torque (PT) and maximum work (MW) values at 60°/s, 180°/s, and 240°/s. The mean difference was 7.17 (p-value = 0.0036), 4.4 (p-value = 0.0386), and 4.25 Nm (p-value = 0.0241) at speed 60°, 180°, and 240°/s, respectively. No statistically significant differences were detected for H-Q values between DL and NDL. This difference was 6.44 (p-value = 0.0449), and 5.87 J (p-value = 0.0266) at speed 60°, and 180°/s. The present study can be a tool that health professionals working with female professional soccer players in their care can use to assess and monitor a particular player.



#15 Congested Period in Professional Youth Soccer Players Showed a Different High Decelerations Profile in the Group Performance and a Specific Positional Behaviour

Reference: J Funct Morphol Kinesiol. 2022 Nov 29;7(4):108. doi: 10.3390/jfmk7040108.

Authors: Borja Muñoz-Castellanos, Alberto Rabano-Muñoz, Bernardo Requena, Luis Suarez-Arrones, Jose A Asian-Clemente

Summary: Present soccer demands are increasing in terms of running requirements and the number of matches until youth soccer players experience several periods of fixture congestion during the season. Currently, congested periods have not been extensively studied in this population. For this reason, this study aimed to compare the running demands of professional youth soccer players in congested periods according to their specific playing positions. Twenty youth players were grouped according to their position: Central Defenders (CD), Fullbacks (FB), Midfielders (MF), Wide Midfielders (WM) and Strikers (ST). A GPS system was used to monitor the players during the first (M1), second (M2) and third (M3) matches played during a congested period, measuring their total distance covered (TDC), DC 18.0-20.9 km·h-1, DC 21.0-23.9 km·h-1, DC > 24.0 km·h-1, number of high accelerations (>2.5 m·s-2), number of high decelerations (<2.5 m·s-2) and peak speed (km·h-1). M1, M2 and M3 showed the same TDC, DC 18.0-20.9 km·h-1, DC 21.0-23.9 km·h-1, DC > 24.0 km·h-1, number of high accelerations, and peak speed (p > 0.05). The statistical analysis showed significant differences between M1, M2 and M3 in the decelerations recorded between M1 and M3 (p < 0.05). Likewise, each position showed specific behaviours during the congested period, with all showing at least one difference in DC 18.0-20.9 km·h-1, 21.0-23.9 km·h-1 or >24.0 km·h-1 between M1, M2 and M3 (p < 0.05). In conclusion, coaches should pay attention to the fatigue produced by the number of high decelerations. Secondly, an individualized training protocol should be considered according to the running requirements of each position when youth professional soccer players are involved in a congested period.



#16 Exploring psychosocial risk factors for dropout in adolescent female soccer

Reference: Sci Med Footb. 2022 Dec 1;6(5):668-674. doi: 10.1080/24733938.2022.2088843.

Authors: N Viktor Gredin, Jenny Back, Urban Johnson, Petra Svedberg, Andreas Stenling, Bård Erlend Solstad, Andreas Ivarsson

Summary: We examined the manner in which age, participation in other sports, socioeconomic status, perceived sport competence, achievement goal orientations, and perceived motivational climate may interact to predict the risk of dropout among adolescent female soccer players. Self-reported data from 519 female soccer players between 10 and 19 years of age (M = 13.41, SD = 1.77) were analysed using a person-centred approach to uncover the interactions among risk factors and their relative predictability of dropout. Perceived motivational climate was identified as the main predictor, where relatively lower levels of mastery climate were associated with a higher dropout tendency (absolute risk reduction [ARR] = 12.2% ±6.1% [95% CL]). If combined with relatively lower levels of mastery climate, then relatively lower levels of perceived sport competence were related to higher dropout risks (ARR = 16.5% ±9.5%), whereas, in combination with relatively higher levels of mastery climate, then relatively lower levels of ego-orientated achievement goals were associated with higher dropout rates (ARR = 10.8% ±12.6%). Our findings afford novel insights into the interactions between, and the relative importance of, various risk factors for dropout in adolescent female soccer. This knowledge may be useful for soccer associations, clubs, and coaches when developing guidelines and strategies that aim to foster young females' sustained participation in organised soccer.



#17 Determining age-specific velocity thresholds for elite youth female soccer players

Reference: Sci Med Footb. 2022 Dec 1;6(5):581-588. doi: 10.1080/24733938.2021.1991585. Epub 2021 Oct 18.

Authors: Alice Harkness-Armstrong, Kevin Till, Naomi Datson, Stacey Emmonds

Summary: This study aimed to establish age-specific velocity thresholds for Under (U)14 and U16 elite youth female soccer players. Data was collected using 10 Hz GPS units during 50 matches from 187 players (U14 n = 89; U16 n = 98). Spectral clustering identified velocity thresholds for high-speed running (HSR), very high-speed running (VHSR), and sprinting (SPR), for 699 half-match observations (U14 n = 369; U16 n = 330). Linear mixed modelling determined youth (U14 and U16) and age-group (U14 or U16) velocity thresholds, and compared distances covered between these and existing senior thresholds. The effect of playing position and playing half on velocity thresholds was also quantified. Youth velocity thresholds of HSR (≥3.00 m·s-1), VHSR (≥4.83 m·s-1), and SPR (≥5.76 m·s-1) were estimated from the model. Age-group and playing position influenced velocity thresholds but playing half did not. Adoption of youth and age-group velocity thresholds resulted in greater distance covered at HSR, VHSR, and SPR (p < 0.001; moderate-large effect size [ES] = 0.86-1.97) compared to senior thresholds. Both age-groups covered similar distances (trivial-small ESs = 0.002-0.23) when adopting youth and age-group velocity thresholds. These youth thresholds provide an alternative to arbitrary velocity thresholds within the literature, and thresholds derived from senior players or other populations, to inform appropriate quantification and interpretation of physical data within this population.



#18 The Effects of Fixture Congestion on Injury in Professional Male Soccer: A Systematic Review

Reference: Sports Med. 2022 Dec 17;1-19. doi: 10.1007/s40279-022-01799-5. Online ahead of print.

Authors: Richard Michael Page, Adam Field, Ben Langley, Liam David Harper, Ross Julian

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Summary: Professional soccer teams are often required to compete with ≤ 4 days recovery between matches. Since congested schedules reduce recovery time between matches, players are possibly at an increased injury risk. To date, there are no published systematic reviews on the impact of match congestion on injuries during professional male soccer. The aim of this systematic review was to assess the effects of fixture congestion on injuries during professional soccer. Following pre-registration on the Open Science Framework ( ) and conforming with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, systematic searches of four electronic databases (PubMed, Scopus, SPORTDiscus, and Web of Science) were conducted by independent researchers from inception until February 2022. Articles were included if they were original articles written in English and contained relevant time-loss injury data (injury that results in unavailability for training and/or match-play) for male professional soccer players regarding periods of fixture congestion (a minimum of two matches with ≤ 4 days recovery). A total of eight articles were included in the review. Five studies identified that congested fixture schedules expose players to increased match injury incidence, although layoff duration was typically lower during congested periods. Two studies identified that training and overall injury incidence were higher during congested periods, with another study identifying a lower training injury incidence during congested periods. Injury risk is, overall, increased during fixture-congested periods; however, the layoff duration is typically shorter. The current findings have implications for practitioners regarding the management, periodisation, monitoring, and design of training and competition schedules.



#19 Elite female football players' perception of the impact of their menstrual cycle stages on their football performance. A semi-structured interview-based study

Reference: Sci Med Footb. 2022 Dec 1;6(5):616-625. doi: 10.1080/24733938.2021.2020330. Epub 2021 Dec 29.

Authors: Phoebe Read, Ritan Mehta, Craig Rosenbloom, Elena Jobson, Katrine Okholm Kryger

Summary: This study assesses how female footballers perceive how their menstrual cycle impacts their physical and psychological performance, informing future research and intervention. Semi-structured interviews, developed using piloting and peer review took place with fifteen elite female footballers from two English WSL clubs (age: 25.2 [18-33]). Data was audio recorded, transcribed verbatim, and analysed thematically using NVivo. All players (100%) perceive their menstrual cycle to negatively impact performance. Analysing 27,438 words of data revealed five themes: A) symptoms, B) preparation, C) performance, D) recovery, and E) management. Over half (53%) of players experienced decreased appetite and sleep quality prior to performance during menstruation. Competitive performance was perceived to be most negatively impacted during menses (54 references) following by the pre-menstrual stage (23 references). During menstruation, the most impacted physical performance indicators were power (93%) and fatigue (87%). Psychologically, confidence, focus, and reaction to criticism were commonly affected (66.7%). Players reported missing training (13.3%) and matches (13.3%) due to severity of impact. Recovery was affected during the pre-menstrual (26.7%) and menstrual (66.7) stages. Players self-manage symptoms using over the counter (66.7%) and prescription (26.7%) medication, some prophylactically prior to competition (46.7%). This first attempt to ascertain player perception in football exposes a clear negative impact on performance. The complex interplay of biopsychosocial and logistical factors, lack of awareness and education highlight the need for further research. Intervention is necessary and immediate initiation would be prudent, starting with simple measures such as basic self-management advice, education, and provision of sanitary products.


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