03. February 2023

Latest research in football - week 1 - 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 Monitoring training load in youth soccer players: effects of a six-week preparatory training program and the association between external and internal loads

Reference: Biol Sport. 2023 Jan;40(1):63-75. doi: 10.5114/biolsport.2023.112094. Epub 2022 Jan 3.

Authors: Sandra Lechner, Achraf Ammar, Omar Boukhris, Khaled Trabelsi, Jordan M Glenn, Jesper Schwarz, Omar Hammouda, Piotr Zmijewski, Hamdi Chtourou, Tarak Driss, Anita Hoekelmann

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806748/pdf/JBS-40-112094.pdf

Summary: This study examined the effects of a six-week preparatory training program on physical performance and physiological adaptations in junior soccer players. Additionally, we investigated whether a relationship existed between external and internal loads. Youth soccer players (aged 16 years old) from a youth football academy participated in six weeks of pre-conditioning training. Wireless Polar Team Pro and Polar heart rate sensors (H10) were used to monitor physical performance indicators (sprint and acceleration scores, covered distance, maximum and average speed and duration), physiological responses (maximum and average heart rate [HR] and R-R interval, time in HR zones 4+5, and heart rate variability [HRV]), and training load score. Additionally, muscle status and rating of perceived exertion (RPE) scores were measured using digital questionnaires. Significant increases were observed in the majority of physical performance indicators [i.e., sprints (p = 0.015, ES = 1.02), acceleration (p = 0.014, ES = 1), total distance (p = 0.02, ES = 0.87), as well as maximum speed (p = 0.02, ES = 0.87)]. A trend towards improvement was observed in the remaining performance indicators (i.e., distance/min and avg speed; ES = 0.6), training load (ES = 0.2), muscle status (ES = 0.3)), and all physiological responses parameters (ES = 0.1 to 0.6). Significant correlations were found between the majority of external load parameters (i.e., performance indicators) and objective (i.e., physiological responses) and subjective (i.e., RPE, muscle status) internal load parameters (p < 0.001). The highest number of moderate-large correlations were registered between performance indicators and time in HR zone 4+5 (0.58 < r < 0.82), training load (0.53 < r < 0.83), average HR (0.50 < r < 0.87), maximal HR (0.51 < r < 0.54) and average R-R interval (0.58 < r < 0.76). HR zone 4+5, average and maximal HR, average R-R interval, and training load score may help control training parameters and reduce the risk of under- or over-training in youth soccer players. However, these conclusions should be confirmed and replicated in future studies with more diverse subject populations.

#2 Body size, maturation and motor performance in young soccer players: relationship of technical actions in small-sided games

Reference: Biol Sport. 2023 Jan;40(1):51-61. doi: 10.5114/biolsport.2023.110749. Epub 2022 Jan 3.

Authors: Julio Cesar da Costa, Paulo Henrique Borges, Luiz Fernando Ramos-Silva, Vinicius Muller Reis Weber, Alexandre Moreira, Enio Ricardo Vaz Ronque

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806756/pdf/JBS-40-110749.pdf

Summary: The objective of this study was to investigate the relative contributions of body size, skeletal age, and motor performance variables with technical actions through an ecological model during small-sided soccer games, and the interaction of biological maturation with technical and motor performance in young players. In this cross-sectional study, eighty-two young players (14.4 ± 1.1 years), belonging to state-level soccer teams and divided by category (U-13 and U-15), were included. Players having an injury in the evaluation period were not included in the study. Measurements of body size, skeletal age (SA), motor tests, and technical actions in small-sided games (SSG) were performed (3 × 3 plus goalkeeper) in two periods (halves) of four minutes. Differences between age groups were found for SA (ES = -2.36), chronological age (ES = -3.89), body mass (ES = -2.09), height (ES = -1.90), and fat-free mass (ES = -2.09). Positive associations were found between body size (R = 0.43 to R = 0.48) and manipulation (R = 0.50 to R = 0.52) indicators and numbers of technical actions (CB and SS), except for stature with LB (R = -0.42) in the U-13 age group. In the U-15 category, skeletal age (R = -0.29 to R = -0.30) and body mass (R = -0.28 to R = -0.29) were negatively associated with the number of technical actions (RB, NB, LB, and OB) (P > 0.05) and positively with the balance with LB (R = 0.26). In conclusion, body size, SA, and motor performance influenced technical actions in SSG differentially in each category. U-13 heavier players and those with a better motor performance presented higher involvement due to the higher.

#3 Substitute running outputs in elite youth male soccer players: less peak but greater relative running outputs

Reference: Biol Sport. 2023 Jan;40(1):241-248. doi: 10.5114/biolsport.2023.112969. Epub 2022 Mar 16.

Authors: Michael G Sydney, Martin Wollin, Dale Chapman, Nick Ball, Jocelyn K Mara

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806762/pdf/JBS-40-112969.pdf

Summary: Coaches consider substitute players to be a substantial factor in influencing the outcome of a soccer match. Substitute players are expected to make physical impact on the match by superseding the running output of the player they replaced and are a key tool for managing in-game fatigue and influencing the outcome of a game. This study investigated the physical impact and internal response of substitute players, compared to starting and full-match players. We also sought to determine if differences between substitution statuses were influenced by playing position. Players wore 15-Hz global positioning system tracking devices across 29 competition matches and were categorised according to their substitution status (full-match, starters, substitutes) and playing position (external defender, midfield, external attacker and central attacker). Peak total (TD) and high-speed running (> 5.0 m/s) distance (HSRD) were calculated using 1-, 2- and 5-minute rolling epochs. Relative running demands were reported as TD and HSRD per minute of total playing time. Substitute players performed less peak TD and HSRD in 1-, 2- and 5-minute epochs, and reported lower RPE compared to starting and full-match players. In contrast, substitutes performed greater relative HSRD per minute than starting and full-match players (p < 0.001, |d| range = 0.35-1.34). In conclusion, substitute players may have a relative physical impact but do not replicate or supersede the peak demands of full-match players. Coaches and practitioners should implement targeted warm-up interventions to enhance substitute readiness to meet the peak running demands in order to have a more effective physical impact.

#4 Effects of pitch size on soccer players' physiological, physical, technical, and tactical responses during small-sided games: a meta-analytical comparison

Reference: Biol Sport. 2023 Jan;40(1):111-147. doi: 10.5114/biolsport.2023.110748. Epub 2022 Jan 21.

Authors: Filipe Manuel Clemente, Gibson Moreira Praça, Rodrigo Aquino, Daniel Castillo, Javier Raya-González, Markel Rico-González, José Afonso, Hugo Sarmento, Ana Filipa Silva, Rui Silva, Rodrigo Ramirez-Campillo

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806761/pdf/JBS-40-110748.pdf

Summary: One of the most often-used task constraints in designing small-sided games (SSGs) is the manipulation of pitch size to promote increases or decreases in the relative area per player. Such adjustments cause changes in the acute responses during SSGs. This systematic review with meta-analysis aimed to compare the effects of smaller vs. larger pitch sizes on soccer players' physiological, physical, technical, and tactical responses during SSGs. Comparisons between smaller and larger pitches were not considered based on a specific size, but also between using at least two dimensions in the same comparative study, aiming to understand differences between using smaller and larger (independently of the specific dimensions). The data sources utilized were PubMed, PsycINFO, Scielo, Scopus, SPORTDiscus, and Web of Science. The database search initially yielded 249 titles. From those, 41 articles were eligible for the systematic review and meta-analysis. Results revealed that, compared to smaller pitches, SSGs played on larger pitches induced greater values for heart rate (p < 0.001; ES = 0.50), rate of perceived exertion (p < 0.001; ES = 0.70), total distance (p < 0.001; ES = 1.95), high-speed running (p < 0.001; ES = 1.20), stretch index (p < 0.001; ES = 1.02) and surface area (p < 0.001; ES = 1.54). No significant differences were found between pitch size regarding the numbers of accelerations (p = 0.232; ES = 0.45), decelerations (p = 0.111; ES = 0.85), passes (p = 0.897; ES = 0.02), dribbles (p = 0.823; ES = -0.05), or positional centroid (p = 0.053; ES = 0.56). Larger pitch sizes can be implemented as a meaningful task constraint to increase the internal and external load experienced by soccer players during SSGs, as well as to increase the dispersion of players while acting together. These results were found independent of format and age group.

#5 Injury incidence and risk factors in youth soccer players: a systematic literature review. Part II: Intrinsic and extrinsic risk factors

Reference: Biol Sport. 2023 Jan;40(1):27-49. doi: 10.5114/biolsport.2023.109962. Epub 2022 Jan 3.

Authors: Mauro Mandorino, Antonio J Figueiredo, Masar Gjaka, Antonio Tessitore

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806737/pdf/JBS-40-109962.pdf

Summary: Injury is defined as a complex phenomenon determined by the non-linear interaction of several intrinsic and extrinsic factors. The objective of the present study was to perform a systematic literature review on the injury risk factors in young soccer players. After electronic database searching, articles in line with the inclusion criteria were selected for the systematic review. Injury risk factor data were extracted and grouped in intrinsic and extrinsic risk factors. The main findings of the current review are as follows: (1) alteration in neuromuscular control such as limb asymmetry and dynamic knee valgus are important intrinsic risk factors; (2) maturation status may impair neuromuscular control and increase the risk of injury; (3) fatigue and poor recovery contribute to the onset of overuse injuries; (4) the impact of anthropometric factors is still unclear; (5) previous injuries increase the risk of re-injuries; (6) highly skilled players are more exposed to risk of injuries; (7) high external workloads increase the risk of injuries; (8) playing position, as well as sport specialization, exposes young soccer players to greater injury risk. Many factors (e.g., neuromuscular control, training load, maturity status) can modify the susceptibility to injury in young soccer players. Being aware of the complex interaction between these factors is essential to identify players at higher risk of injury, develop adequate prevention strategies, and from a scientific point of view move from a reductionist to a complex system approach.

#6 Warm-up optimization in amateur male soccer players: A comparison of small-sided games and traditional warm-up routines on physical fitness qualities

Reference: Biol Sport. 2023 Jan;40(1):321-329. doi: 10.5114/biolsport.2023.114286. Epub 2022 May 10.

Authors: Rohit K Thapa, Filipe M Clemente, Jason Moran, Felipe Garcia-Pinillos, Aaron T Scanlan, Rodrigo Ramirez-Campillo

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806743/pdf/JBS-40-114286.pdf

Summary: The aim of this study was to compare the effects of small-sided soccer games (SSSGs) and traditional warm-up (TWU) routines on physical fitness qualities in soccer players. Following a between-subject, randomized design, amateur-level soccer players were assigned to a SSSG warm-up (n = 10; age: 19.3 ± 2.8 years) or TWU group (n = 10; age: 19.3 ± 2.4 years). Players completed multiple trials of 10-m and 30-m linear sprints, change-of-direction speed (CODS) tests, and countermovement jumps (CMJ) prior to and following the warm-up routine. Separate mixed ANOVAs were performed to assess group effects (SSSG vs. TWU), time effects within each group (pre- vs. post-warm-up), and their interaction for each physical fitness quality. No significant interaction effects were observed for any dependent variable. Significant improvements were evident between baseline and follow-up measurements for 10-m sprint time (p = 0.002, Hedges' g effect size [g] = 0.59) and CMJ variables (height: p = 0.016, g = 0.20; power: p = 0.003, g = 0.19; force: p = 0.002, g = 0.14) in the TWU group and for CODS performance time (p = 0.012, g = 0.51) and CMJ variables (height: p < 0.001, g = 0.46; power: p = 0.002, g = 0.35; force: p = 0.001, g = 0.27) in the SSSG warm-up group. Both SSSG and TWU protocols improved selected physical fitness qualities with SSSG more effective at improving CODS and CMJ performance, and TWU more effective at improving linear speed. Soccer coaches may choose between SSSG or traditional warm-up activities according to player needs and preferences; however, the superior effects of SSSG suggest it might offer greater benefits than TWU in preparing players for optimal physical output.

#7 Elite young soccer players have smaller inter-limb asymmetry and better body composition than non-elite players

Reference: Biol Sport. 2023 Jan;40(1):265-272. doi: 10.5114/biolsport.2023.114840. Epub 2022 Apr 21.

Authors: Lucia Mala, Mikulas Hank, Petr Stastny, Frantisek Zahalka, Kevin R Ford, Piotr Zmijewski, David Bujnovsky, Miroslav Petr, Tomas Maly

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806739/pdf/JBS-40-114840.pdf

Summary: Body composition (BC) and inter-limb anthropometric asymmetries (LA) may influence the physical performance of soccer players. This study aimed to determine differences in BC and LA among soccer across four performance levels. The study involved 110 male soccer players participating in Czech senior teams who were grouped into four different performance levels (i.e. G1: national team, G2: 1st division, G3: 2nd division, G4: 3rd division). The following BC and LA parameters were compared among groups: body height, body mass, absolute fat-free mass, relative fat-free mass (FFMrel), percentage of fat mass (FM), total body water (TBW), intracellular water (ICW), extracellular water (ECW), phase angle, and bilateral muscle mass differences in the upper and lower extremities. Significant differences were observed in BC parameters among all groups (λ = 0.06, F75,246 = 5.38, p = 0.01, ηp 2 = 0.62). High-performance players (i.e. G1, G2) had significantly (p < 0.01) lower FM than lower performance players (i.e. G3, G4). The lowest values of FFMrel, relative TBW, relative ICW and ECW were detected in the lowest-performance players (i.e. G4). Significantly lower bilateral muscle mass differences were detected in G1 players (2.71 ± 1.26%; p < 0.01) compared with G4 players (3.95 ± 1.17%). G1 and G2 players had a higher proportion of muscle mass in the torso (p < 0.01) and upper limbs than G3 and G4 (p < 0.01). Elite and high-performance players have better BC and lower inter-limb anthropometric asymmetries compared with low-performance level players.

#8 Machine learning application in soccer: a systematic review

Reference: Biol Sport. 2023 Jan;40(1):249-263. doi: 10.5114/biolsport.2023.112970. Epub 2022 Mar 16.

Authors: Markel Rico-González, José Pino-Ortega, Amaia Méndez, Filipe Manuel Clemente, Arnold Baca

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806754/pdf/JBS-40-112970.pdf

Summary: Due to the chaotic nature of soccer, the predictive statistical models have become in a current challenge to decision-making based on scientific evidence. The aim of the present study was to systematically identify original studies that applied machine learning (ML) to soccer data, highlighting current possibilities in ML and future applications. A systematic review of PubMed, SPORTDiscus, and FECYT (Web of Sciences, CCC, DIIDW, KJD, MEDLINE, RSCI, and SCIELO) was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. From the 145 studies initially identified, 32 were fully reviewed, and their outcome measures were extracted and analyzed. In summary, all articles were clustered into three groups: injury (n = 7); performance (n = 21), which was classified in match/league outcomes forecasting, physical/physiological forecasting, and technical/tactical forecasting; and the last group was about talent forecasting (n = 5). The development of technology, and subsequently the large amount of data available, has become ML in an important strategy to help team staff members in decision-making predicting dose-response relationship reducing the chaotic nature of this team sport. However, since ML models depend upon the amount of dataset, further studies should analyze the amount of data input needed make to a relevant predictive attempt which makes accurate predicting available.

#9 A review of machine learning applications in soccer with an emphasis on injury risk

Reference: Biol Sport. 2023 Jan;40(1):233-239. doi: 10.5114/biolsport.2023.114283. Epub 2022 Mar 16.

Authors: George P Nassis, Evert Verhagen, João Brito, Pedro Figueiredo, Peter Krustrup

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806760/pdf/JBS-40-114283.pdf

Summary: This narrative review paper aimed to discuss the literature on machine learning applications in soccer with an emphasis on injury risk assessment. A secondary aim was to provide practical tips for the health and performance staff in soccer clubs on how machine learning can provide a competitive advantage. Performance analysis is the area with the majority of research so far. Other domains of soccer science and medicine with machine learning use are injury risk assessment, players' workload and wellness monitoring, movement analysis, players' career trajectory, club performance, and match attendance. Regarding injuries, which is a hot topic, machine learning does not seem to have a high predictive ability at the moment (models specificity ranged from 74.2%-97.7%. sensitivity from 15.2%-55.6% with area under the curve of 0.66-0.83). It seems, though, that machine learning can help to identify the early signs of elevated risk for a musculoskeletal injury. Future research should account for musculoskeletal injuries' dynamic nature for machine learning to provide more meaningful results for practitioners in soccer.

#10 Injury incidence and risk factors in youth soccer players: a systematic literature review. Part I: epidemiological analysis

Reference: Biol Sport. 2023 Jan;40(1):3-25. doi: 10.5114/biolsport.2023.109961. Epub 2022 Jan 3.

Authors: Mauro Mandorino, António J Figueiredo, Masar Gjaka, Antonio Tessitore

Summary: The analysis of the epidemiological data and the risk factors underlying injuries is crucial to promote prevention strategies in young soccer players. The objective of the present study was to perform a systematic literature review on the epidemiological data, described in the first part, and injury risk factors, presented in the second part. After electronic database searching, articles in line with the inclusion criteria were selected for the systematic review. Epidemiological data were extracted and discussed in this first part of the review. Data were grouped as follows: injury incidence, injury severity, and re-injury, injury types, injury mechanisms, and anatomical location. The principal findings of this first part of the review are as follows: (1) injury incidence is higher in older players and during matches than during training; (2) sex and maturity status may increase risk of injury; (3) male soccer players are more prone to muscle strains and ligament sprains while female players suffer more ligament sprains; (4) most injuries are located in the ankle and thigh in young male soccer players, and in the ankle and knee in female players; (5) severe injuries are less frequent but the incidence increases in older players. Re-injuries represent only a small percentage. Although soccer is considered a safe sport, many injuries are recorded in young soccer players every year. Injury predisposition changes in relation to age, sex, and biological age. Coaches and physical trainers should be aware of individual differences in order to promote prevention strategies and personalised training.

#11 Injury incidence and risk factors in youth soccer players: a systematic literature review. Part I: epidemiological analysis

Reference: Biol Sport. 2023 Jan;40(1):3-25. doi: 10.5114/biolsport.2023.109961. Epub 2022 Jan 3.

Authors: Mauro Mandorino, António J Figueiredo, Masar Gjaka, Antonio Tessitore

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806741/pdf/JBS-40-109961.pdf

#12 Anterior cruciate ligament ruptures in Spanish soccer first division: An epidemiological retrospective study

Reference: Knee. 2023 Jan 9;41:48-57. doi: 10.1016/j.knee.2022.11.014. Online ahead of print.

Authors: Paula Requejo-Herrero, Consolacion Pineda-Galan, Ivan Medina-Porqueres

Summary: Anterior cruciate ligament (ACL) injury is a severe and complex sport-related injury that can threaten an individual's sporting career. The purpose of this study is to investigate the epidemiological patterns of ACL ruptures in Spanish male first-division soccer players. The Transfermarkt and Besoccer online electronic databases were screened for ACL injuries between 2010-2011 and 2019-2020 seasons. Injury incidence, injury mechanism, side of the injury, recurrence of the injury, days of recovery and severity, player's position, dominance, season, and moment in which the injury occurs were collected. A total of 110 ACL ruptures were registered, with 15.45% of them being re-ruptures either ipsilateral (6.36%) or contralateral ruptures (9.09 %). The ACL incidence rate was 0.0364 per 1000 h of total play with a 68-fold risk in matches compared with training. Predominant injury mechanism was non-contact (56.36%) and the mean lay-off time was 218.8 days, with higher incidence in September-October and March-April. Goalkeeper was found to be the less affected position. This investigation identified an average of 11 ACL tears per season in the Spanish first-division soccer league, most of them occurring in matches with approximately one ACL injury per team every two seasons. Our results from media-based platforms are in accordance with reports based on data from healthcare databases. Further research is needed to corroborate these findings in equivalent contexts. Descriptive studies are classified as Level III evidence according to Daly et al., 2007.

#13 Relationship Between Sensory Organization Testing Scores With Lower Extremity Injuries and Prior Concussion in Professional Soccer Players

Reference: Clin J Sport Med. 2023 Jan 9. doi: 10.1097/JSM.0000000000001104. Online ahead of print.

Authors: James Mooney, Graham D Cochrane, Sara Gould

Summary: The aim was to evaluate for associations between concussion history or lower extremity (LE) injury and computerized sensory organization testing (SOT) performance in professional soccer players. Thirty-three, professional, male soccer players on an American club, between the years 2019 and 2021 participated in this study. Player age, history of reported LE injury (gluteal, hamstring, ankle, knee, hip, groin, and sports hernia), history of diagnosed concussion, and the number of prior concussions were documented for each player. Baseline SOT of postural sway was conducted in 6 sensory conditions for all players. Eleven athletes (33%) reported a previous concussion, and 15 (45%) reported a previous LE injury. There were no significant differences in SOT scores between those with and without a previous diagnosis of concussion (P > 0.05). Those reporting a previous LE injury performed better on condition 3 (eyes open, unstable visual surround) than those who did not (P = 0.03). Athletes aged 25 years or younger performed worse on condition 3 (P = 0.01) and had worse, although not statistically significant, median performance on all other balance measures than those older than 25 years. Intraclass correlation coefficient for repeat SOT assessment was 0.58, indicating moderate reliability, without an evident practice effect. Professional soccer players with a previous concussion or history of LE injury did not demonstrate long-term deficits in postural control, as assessed by multiyear computerized SOT baseline testing. The SOT was reliable over time with younger athletes exhibiting greater postural sway than older athletes.

#14 Is There a Relationship Between Foot Reaction Time and Ankle Frontal Plane Torque in Female Soccer Athletes? A Pilot Study

Reference: Int J Exerc Sci. 2022 Nov 1;15(1):1506-1513. eCollection 2022.

Authors: Maggie X Feehan, Andrew L Shim, Guilherme M Cesar, Amy M Burggraff

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9797005/pdf/ijes-15-1-1506.pdf

Summary: The purpose of this study was to determine if a relationship existed between foot reaction time and ankle frontal plane peak torque in female soccer athletes. A one-shot case study design was selected for this investigation. Seventeen female college athletes volunteered to participate. Right and left foot reaction time measurements were assessed using 3×4 switch mats interfaced with a precise timing counter. Participants stood in front of the mat with eyes closed and responded to the auditory stimulus by touching the mat as fast as possible with their foot. Two trials were conducted per foot, and the best time was used to determine the reaction time score per foot. An isokinetic dynamometer assessed inversion and eversion peak torque for both right and left ankle joint at 120°/sec. Left peak torque eversion and right foot reaction time demonstrated a significant negative moderate relationship (r = -0.530; p value = 0.03). Left ankle peak torque eversion does have a significant moderate negative relationship to reaction time of the right foot; therefore, evasive dribbling movements which requires inversion and eversion torque could directly affect foot reaction time, resulting in improved dribbling performance for soccer athletes.

#15 Evaluating Physical and Tactical Performance and Their Connection during Female Soccer Matches Using Global Positioning Systems

Reference: Sensors (Basel). 2022 Dec 21;23(1):69. doi: 10.3390/s23010069.

Authors: Ibai Errekagorri, Ibon Echeazarra, Aratz Olaizola, Julen Castellano

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9823530/pdf/sensors-23-00069.pdf

Summary: The objective of the present study was to evaluate the tactical and physical performance during official matches of a women's soccer league and to correlate both dimensions in periods of 15 min. To do this, eight official matches of a semi-professional soccer team belonging to the Women's Second Division of Spain (Reto Iberdrola) were analysed during the 2020-2021 season. The variables recorded were classified into two dimensions: tactical variables (i.e., Width, Length, Height and Surface Area) and physical variables (i.e., Total Distance Covered (TD), Total Distance Covered in High-Speed Running (HSR) and Total Distance Covered in Sprint). The main results were: (1) there were no differences between the periods in any of the tactical dimension variables; (2) in the physical dimension, a significant decrease in TD and HSR was described at the end of the match (period 60-75); and (3) some positive correlations were found among some variables of the tactical and physical dimension at the beginning and at the end of the match (periods 0-15, 60-75 and 75-90). The findings of the study suggest that connecting the tactical and physical dimension in the interpretation of team performance would allow for a better understanding of player and team performance and during competition.

#16 Changes in the Mechanical Properties of the Horizontal Force-Velocity Profile during a Repeated Sprint Test in Professional Soccer Players

Reference: Int J Environ Res Public Health. 2022 Dec 30;20(1):704. doi: 10.3390/ijerph20010704.

Authors: Felipe Hermosilla-Palma, Juan Francisco Loro-Ferrer, Pablo Merino-Muñoz, Nicolás Gómez-Álvarez, Alejandro Bustamante-Garrido, Hugo Cerda-Kohler, Moacyr Portes-Junior, Esteban Aedo-Muñoz

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9819841/pdf/ijerph-20-00704.pdf

Summary: The objective was to analyze the changes in the horizontal force-velocity profile (HFVP) during the execution of repeated sprinting. Seventeen first-division Chilean soccer players completed a repeated sprint protocol consisting of eight sprints of 30 m with 25-s pauses between repetitions. The behavior of HFVP variables in each attempt was recorded from video recordings and analysis in the MySprint® application. Differences (p < 0.05) were found between sprints in the following: time (T), starting from sprint 5 (F = 35.6; η2p = 0.69); theoretical maximum speed (V0), starting from sprint 4 (F = 29.3; η2p = 0.51); maximum power (PM), starting from sprint 5 (F = 17; η2p = 0.52); rate of decrease in force index produced at each step (DRF), starting from sprint 1 (F = 3.20; η2p = 0.17); and RF10, starting from sprint 1 (F = 15.5; η2p = 0.49). In comparison, F0 and RFpeak did not present any differences (p > 0.05). The HFVP variables more sensitive to the effects of fatigue induced by an RSA protocol are those associated with the production of force at high speeds, being V0, DRF, and Pmax, while those that contribute to the generation of force at the beginning of the sprint, F0 and RFpeak, do not present essential variations.

#17 The effects of football practice on children's fundamental movement skills: A systematic review and meta-analysis

Reference: Front Pediatr. 2022 Dec 20;10:1019150. doi: 10.3389/fped.2022.1019150. eCollection 2022.

Authors: Xiaojin Mao, Jingyue Zhang, Yulian Li, Yuang Cao, Meng Ding, Weidong Li, Lixia Fan

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9808820/pdf/fped-10-1019150.pdf

Summary: The purpose of this systematic review and meta-analysis was to explore the effects of different soccer practices on fundamental movement skills (FMS) of children of different ages and genders, in order to help children to improve their fundamental movement skills through soccer practice more effectively. The databases of CNKI, Wanfang database, Pubmed, Web of science and Cochrane library were searched to collect relevant studies on the effects of soccer practices on FMS, and the quality of the included studies was evaluated by using the Cochrane Risk of Bias Tool, and Meta-analysis was conducted by Review Manager 5.4 software. 16 studies were finally included, with a total of 3,121 subjects were included. The results showed that soccer had a positive effect on linear sprint ability [SMD 95% CI = -0.37 (-0.61, -0.14), P = 0.002], horizontal jump [SMD 95% CI = 0.22 (-0.34, 0.77), P = 0.003], object control [SMD 95% CI = 1.32 (0.8, 1.85), P = 0.0003], Closed-eye single-leg test [SMD 95% CI = 0.87(0.48,1.25), P < 0.0001],while countermovement jump [SMD 95% CI = 0.50(-0.35,1.35), P = 0.25] and flamingo balance [SMD 95% CI = -0.16(-0.31,-0.02), P = 0.03] had a less significant effect. Meanwhile, the effect of the practice was mainly influenced by the total duration of the intervention, age and gender of the intervention subjects, in which the total intervention time longer than 1,800 min promoted linear sprint ability, horizontal jump and flamingo balance test better than those below 1,800 min; the promotion effect of linear sprint ability and horizontal jump was better in children aged 7-9 years than 10-13 years, while Children aged 10-13 years showed better improvement in Closed-eye single-leg test after the intervention than 7-9 years; Girls were better promoted in linear sprint ability and Closed-eye single-leg test, but the horizontal jump is better for boys to improve the effect. It is recommended that the effects of different soccer practice contents on fundamental movement skills can be further explored in the future to improve the relevance and efficiency of fundamental movement skill development for children.

#18 Planning the Microcycle in Elite Football: To Rest or Not to Rest?

Reference: Int J Sports Physiol Perform. 2023 Jan 3;1-7. doi: 10.1123/ijspp.2022-0146. Online ahead of print.

Authors: Martin Buchheit, Maxime Settembre, Karim Hader, Derek McHugh

Summary: The aim was to examine the association between the programming of days off (ie, no pitch training, days off feet) within turnarounds of varying length and injury rate in elite soccer. Retrospective data from 56 team seasons of players belonging to 18 elite teams performing in top leagues including the English Premier League, Italian Serie A, Bundesliga, Scottish Premiership, Major League Soccer, and the Dutch Eredivisie from January 2018 to December 2021 were analyzed (total of 1578 players, 2865 injuries, 2859 noninternational matches, and 12,939 training-session days). The turnarounds examined lasted from 3 to 8 days. Only injuries with ≥3-day time loss were retained for analysis. The authors then looked at the injury rate within each microcycle in relation to the presence of a day off or not and its programming sequences in relation to the previous match (ie, day off at D + 1 vs D + 2 for the day after the match or the following, respectively). During 3- and 7-day turnarounds, the sequences including the day off feet at D + 2 were associated with 2 to 3 times lower overall noncontact injury rates than the other programming sequences (Cohen d: 0.9-2.7). For the other turnarounds, the differences between the sequences were unclear. The programming of a day off (or at least "off feet") at D + 2 may be associated with moderately to largely lower incidence of noncontact injuries, especially during 3- and 7-day turnarounds.

#19 The Effects of Stress Mindset, Manipulated Through Serious Game Intervention, on Performance and Situation Awareness of Elite Female Football Players in the Context of a Match: An Experimental Study

Reference: Games Health J. 2022 Dec 30. doi: 10.1089/g4h.2022.0209. Online ahead of print.

Authors: Anne-Rixt M Cnossen, Bernard M Maarsingh, Petar Jerčić, Iris Rosier

Summary: Performance levels in football are ever more important and no longer are just physical, technical, and tactical skills, the ones that make an athlete stand out. Cognitive variables, such as stress-coping, become more important and seem to be explaining differences in performance, for example, through reaching an optimal level of arousal. In addition, it is suggested that stress-coping skills also affect situation awareness (SA), important for decision-making in the complex and dynamic situations in football. This study was conducted to examine how stress-coping skills, such as stress mindset, affect performance and SA in the context of a football match. Twenty elite female football players participated in the study. The final sample size consisted of 15 players for the Stress Mindset Measure (SMM) analysis and 8 players for the multilevel model analyses. Two types of intervention were used to manipulate stress mindset and control over heart rate variability (HRV); a serious game called "Stressjam," and a reflection tool called "Brainjam." Questionnaires for stress mindset and SA and video analysis for performance were used. A total of three matches were assessed. The "Stressjam" intervention resulted in significant differences in stress mindset throughout the intervention [F(1,5) = 7.357, P = 0.008]. Subsequently, multilevel analysis showed a positive, strong, and significant correlation between stress mindset, manipulated through "Stressjam" and SA [r(14) = 0.69, P = 0.014]. A correlation of practical interest, given the confidence intervals, was found between stress mindset, manipulated through "Stressjam," and performance. Cognitive variables, such as stress-coping, correlate significantly with SA in football. A correlation of practical interest was found between stress-coping and performance. Further research is needed to study the relationship between stress-coping and performance in football.

#20 Hamstring injury rates have increased during recent seasons and now constitute 24% of all injuries in men's professional football: the UEFA Elite Club Injury Study from 2001/02 to 2021/22

Reference: Br J Sports Med. 2022 Dec 6;bjsports-2021-105407. doi: 10.1136/bjsports-2021-105407.

Authors: Jan Ekstrand, Håkan Bengtsson, Markus Waldén, Michael Davison, Karim M Khan, Martin Hägglund

Summary: The aim was to: (1) describe hamstring injury incidence and burden in male professional football players over 21 seasons (2001/02 to 2021/22); (2) analyse the time-trends of hamstring muscle injuries over the most recent eight seasons (2014/15 to 2021/22); and (3) describe hamstring injury location, mechanism and recurrence rate. 3909 players from 54 teams (in 20 European countries) from 2001/02 to 2021/22 (21 consecutive seasons) were included. Team medical staff recorded individual player exposure and time-loss injuries. Time-trend analyses were performed with Poisson regression using generalised linear models. 2636 hamstring injuries represented 19% of all reported injuries, with the proportion of all injuries increasing from 12% during the first season to 24% in the most recent season. During that same period, the percentage of all injury absence days caused by hamstring injuries increased from 10% to 20%. Between 2014/15 and 2021/22, training hamstring injury incidence increased (6.7% annually, 95% CI 1.7% to 12.5%) as did burden (9.0% annually, 95% CI 1.2% to 18.3%). During those years, the match hamstring injury incidence also increased (3.9% annually, 95% CI 0.1% to 7.9%) and with the same trend (not statistically significant) for match hamstring injury burden (6.2% annually, 95% CI -0.5% to 15.0%). Hamstring injury proportions-in number of injuries and total absence days-doubled during the 21-year period of study. During the last eight seasons, hamstring injury rates have increased both in training and match play.

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