Latest research in football - week 26 - 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 Backheel Pass During Forward Running as a Mechanism of Severe Acute Hamstring Injury in Football: A Case Report

Reference: Clin J Sport Med. 2023 Jun 23. doi: 10.1097/JSM.0000000000001168. Online ahead of print.

Authors: Goran Markovic, Ivan Karuc

Summary: Proximal hamstring tendon avulsions represent the most severe hamstring injury in sports and are typically sustained during stretch-related movements in closed kinetic chain: forced hip hyperflexion combined with knee extension. Here, we present the case study of the right-foot dominant professional football player with a severe proximal hamstring tendon avulsion injury and concomitant lower-grade injuries of hamstring muscle-tendon complex caused by a potentially new football-specific injury mechanism: right-foot backheel pass during forward running (ie, a kick directly backward). This mechanism involves a specific stretch-shortening cycle action of hamstring muscles in open-kinetic chain movement that has not yet been described in the scientific literature. Although further studies related to this football-specific hamstring injury mechanism are needed, clinicians and coaches working in football should be aware of it and potentially introduce additional injury mechanism-specific exercises and strategies for prevention of severe hamstring injuries which often require surgical intervention.



#2 The correlation of centre of mass evaluation utilising accelerometry-based measurement and the clinical dynamic balance test in professional football athletes with chronic ankle instability

Reference: Heliyon. 2023 Jun 15;9(6):e17318. doi: 10.1016/j.heliyon.2023.e17318. eCollection 2023 Jun.

Authors: Chairat Phuaklikhit, Thanwarat Junsri, Usa Maikaew

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Summary: Similar to a modified star excursion balance test, the Y-balance test is recommended for use in clinical settings to evaluate dynamic balance, particularly in athletes with chronic ankle instability. However, due to the testing errors, there are certain restrictions. As a result, the modification of the centre of mass tracking system was developed in order to aid in the detection of the ability to control the dynamic balance. Therefore, the purpose of this study was to correlate the usage of an accelerometer for the shifting of the centre of mass during a dynamic balance test with a Y-balance test reach distance score. Forty professional football athletes with CAI participated in this study by performing the Y-balance test three times while wearing an accelerometer. The jerk, RMS sway amplitude, mean velocity from the time domain, and the normalised reach distance scores of the Y-balance test in the anterior, posteromedial, and posterolateral directions were all collected. There was a strong positive correlation of jerk and RMS sway amplitude with the normalised reach distance scores in the posteromedial direction (r = 0.706 and 0.777, respectively), a moderate positive correlation of jerk and RMS sway amplitude with the normalised reach distance scores in the posterolateral direction (r = 0.609 and 0.606, respectively), a moderate positive correlation of jerk and RMS sway amplitude with the composite reach distance scores (r = 0.531 and 0.573, respectively) and significant differences in the posteromedial, posterolateral and overall directions (p-value < 0.001). These findings indicate that the area of the centre of mass shifting as represented by the accelerometer can disclose the body's ability to control the centre of mass over the base of support when the body is moving. Furthermore, in this study, the RMS sway variable in the posteromedial direction appears to be the most prominent.



#3 An injury burden heat map of all men's and women's teams of a professional football club over a decade

Reference: Res Sports Med. 2023 Jun 26;1-11. doi: 10.1080/15438627.2023.2228959. Online ahead of print.

Authors: Jon Larruskain, Jose A Lekue, Paco Angulo, Juan M Santisteban, Gontzal Diaz-Beitia, Imanol Martin-Garetxana, Susana M Gil, Iraia Bidaurrazaga-Letona, Xabier Monasterio

Summary: The aim was to present a descriptive 10-season summary of injury data from all teams of a professional football club using a heat map approach. Injuries and exposure time were registered according to the FIFA consensus in all men's and women's teams from Athletic Club over 10 seasons. A team-by-injury table was created, showing the incidence, median severity, and burden in each cell. Cells were coloured based on the injury burden value using a green - yellow-red gradient (lowest to highest). The highest overall injury burden was found in the women's 2nd and 1st teams and the men's U(under)17 team (>200 days lost/1000 h). Muscle injury burden demonstrated an increasing pattern with age. Knee joint/ligament injuries, particularly anterior cruciate ligament ruptures, had the highest impact on women's teams, followed by the men's 2nd team. In comparison, ankle joint/ligament injuries had a relatively low injury burden in most teams. Growth-related injuries were the most impactful injuries in the men's U15 and younger teams, and the women's U14 team. In conclusion, epidemiological data on injuries can inform and guide injury management processes. New and improved visualization methods might be important assets when presenting injury data to key decision-makers.



#4 The type and extent of travel for professional footballers undertaking national team duties for a national football federation

Reference: Biol Sport. 2023 Jul;40(3):707-713. doi: 10.5114/biolsport.2023.119288. Epub 2022 Oct 6.

Authors: Ewan Clements, Fabian Ehrmann, Andrew Clark, Mark Jones, Donna Lu, Rob Duffield

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Summary: Elite football (soccer) involves club, continental and international fixtures, requiring players to undertake extensive travel [1]. For a national football federation, this includes the transport of players between club and camp/tournament commitments, which is often a point of contention between respective organisations [2]. Partly this contention results from the effects of travel, whereby jet lag and travel fatigue can negatively affect physical performance [3-5] and athlete wellbeing [6, 7]. Given the scarcity of data on elite players following travel, an initial step for any national football federation is to understand the volume and nature of travel undertaken by national team players. Such insight may better identify the schedule, timelines and needs of athletes' post travel. Better awareness of these travel needs can help maximise availability for training and minimise the impact of travel related stresses on performance or wellbeing. However, the regularity and volume of travel to national football team commitments has not previously been described. Further, travel demands are likely to vary significantly based on the location of the athlete and the national team camp. For countries outside of Europe, such as Australia, the travel demands and ensuing effects on player preparation can be substantial for both arrival into national team and on return to clubs [7]. Hence, detailed information regarding the type, frequency, and extent of travel for national team duties is important to aid in planning optimal travel schedules and interventions to assist players for international or club duty.



#5 Position specific physical demands in different phases of competitive matches in national level women's football

Reference: Biol Sport. 2023 Jul;40(3):629-637. doi: 10.5114/biolsport.2023.118337. Epub 2022 Sep 15.

Authors: Juho K Mäkiniemi, Eero Hj Savolainen, Taija Finni, Johanna K Ihalainen

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Summary: The purpose of the present study was twofold: to investigate position-specific physical match demands of national level women's football; and to examine if demands change during a match (comparison between first and second half and in 15-minute intervals). Seven teams from the Finnish National League participated in the study. Eighty-five players met the inclusion criteria, and a total of 340 individual match observations from 68 individual matches were included for analysis. The Polar Team Pro -player tracking system (with 10 Hz GPS units, including 200 Hz tri-axial accelerometer, gyroscope, magnetometer and HR monitor) was used to assess positional data and HR response of the players. This study demonstrated that women's national level football matches place a range of physical demands on players, which in general were highest for wide midfielders, and lowest for central defenders. Wide midfielders and forwards performed significantly more 'very high-speed' running, sprinting, accelerations, and decelerations than other outfield positions (p < 0.05). HRmean varied from 84-87% of HRmax and was significantly lower for central defenders than central midfielders (p < 0.001). External load variables varied during a match and generally decreased especially after 60 minutes of play compared to first 15-min period of the match. Present study showed that national level women football players' positional differences in match demands are similar to those reported with elite players in previous studies. On national level, players' physical performance tended to decrease towards the end of the match, especially in terms of total distance (~10%), high-speed running (~20%), and decelerations (~20%).



#6 Development of an algorithm-based approach using neuromuscular test results to indicate an increased risk for non-contact lower limb injuries in elite football players

Reference: BMJ Open Sport Exerc Med. 2023 Jun 21;9(2):e001614. doi: 10.1136/bmjsem-2023-001614. eCollection 2023.

Authors: Jente Wagemans, Arie-Willem De Leeuw, Peter Catteeuw, Dirk Vissers

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Summary: This retrospective cohort study explored an algorithm-based approach using neuromuscular test results to indicate an increased risk for non-contact lower limb injuries in elite football players. Neuromuscular data (eccentric hamstring strength, isometric adduction and abduction strength and countermovement jump) of 77 professional male football players were assessed at the start of the season (baseline) and, respectively, at 4, 3, 2 and 1 weeks before the injury. We included 278 cases (92 injuries; 186 healthy) and applied a subgroup discovery algorithm. More injuries occurred when between-limb abduction imbalance 3 weeks before injury neared or exceeded baseline values (threshold≥0.97), or adduction muscle strength of the right leg 1 week before injury remained the same or decreased compared with baseline values (threshold≤1.01). Moreover, in 50% of the cases, an injury occurred if abduction strength imbalance before the injury is over 97% of the baseline values and peak landing force in the left leg 4 weeks before the injury is lower than 124% compared with baseline. This exploratory analysis provides a proof of concept demonstrating that a subgroup discovery algorithm using neuromuscular tests has potential use for injury prevention in football.



#7 Football and dementia: looking at other factors - Authors' reply

Reference: Lancet Public Health. 2023 Jul;8(7):e483. doi: 10.1016/S2468-2667(23)00104-4.

Authors: Peter Ueda, Björn Pasternak, Carl-Emil Lim, Martin Neovius, Jonas F Ludvigsson, Henrik Svanström

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#8 Multiple regression analysis for competitive performance assessment of professional soccer players

Reference: Technol Health Care. 2023 Jun 29. doi: 10.3233/THC-230275. Online ahead of print.

Authors: Radakovic Radivoje, Dasic Lazar, Dopsaj Milivoj, Filipovic Nenad

Summary: Being in peak physical condition and having specific motor abilities are necessity for every top-level soccer player in order to achieve success in competition. In order to correctly assess soccer players' performance, this research uses laboratory and field measurements, as well as results of competitive performance obtained by direct software measurements of players' movement during the actual soccer game. The main goal of this research is to give insight into the key abilities that soccer players need to have in order to perform in competitive tournaments. Besides training adjustments, this research also gives insight into what variables need to be tracked in order to accurately assess the efficiency and functionality of the players. The collected data need to be analyzed using descriptive statistics. Collected data is also used as input for multiple regression models that can predict certain key measurements: total distance covered, percent of effective movements and high index of effective performance movements. Most of the calculated regression models have high predictability level with statistically significant variables. Based on the results of regression analysis it can be deduced that motor abilities are important factor in measuring soccer player's competitive performance and team's success in the match.



#9 Effect of body composition on the athletic performance of soccer referees

Reference: J Nutr Sci. 2023 Jun 27;12:e66. doi: 10.1017/jns.2023.47. eCollection 2023.

Authors: Azad Ilhan, Surhat Muniroglu, Neslişah Rakıcıoğlu

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Summary: Nutrition plays an important role in improving sports performance. The present study aimed at nutritional assessment and examined the relationship between athletic performance and body composition in soccer referees at different levels. The study participants were 120 male soccer referees. 5, 10 and 30 metres (m) sprint tests to measure speed and cooper test for physical fitness were applied in the referees. Participants were divided into two groups as city and class soccer referee. The anthropometric measurements, excluding fat mass (FM) (%), were higher in class referees. Fat mass (%) differences (14⋅1 ± 4⋅28 v. 12⋅3 ± 4⋅41) were statistically significant (P < 0⋅05). Daily energy and nutrient intakes were similar. The inadequacy percentages of energy, vitamin A and calcium were the highest (29⋅2, 30⋅0 and 34⋅2 %, respectively). It was found that a negative significant correlation between FM% and cooper test score (P < 0⋅01; r = -0⋅35), a positive significant correlation between FM% and 5, 10 and 30 m sprint test scores (P < 0⋅01, r = 0⋅38; P < 0⋅01, r = 0⋅38 and P < 0⋅01, r = 0⋅48, respectively). Similarly, there was a negative significant correlation between waist circumference (WC) and cooper test score (P < 0⋅01; r = -0⋅31), a positive significant correlation between WC and 5, 10 and 30 m sprint test scores (P < 0⋅01, r = 0⋅33; P < 0⋅01, r = 0⋅40; P < 0⋅01, r = 0⋅33, respectively). Nutritional recommendations for soccer referees should be made specific to the individual, considering body composition, training intensity and match frequency by a dietician.



#10 Technical and locomotor demands in elite soccer: manipulating area per player during small-sided games to replicate official match demands

Reference: Biol Sport. 2023 Jul;40(3):639-647. doi: 10.5114/biolsport.2023.118338. Epub 2022 Sep 15.

Authors: Andrea Riboli, Fabio Esposito, Giuseppe Coratella

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Summary: The present study aimed to investigate the area per player (ApP) to replicate the technical and locomotor match demands using small-sided games (SSGs) in male soccer players (n = 20) competing in major European and UEFA competitions. The relative number of each individual technical activity per minute (number · min-1; technical demands) was counted and the relative (m · min-1) total (TD), high-speed running (HSRD), very high-speed running (VHSRD), sprint and acceleration+deceleration (Acc+Dec) distances were collected during different SSG formats (n = 24; 4 vs 4 to 10 vs 10 with an ApP from 60 to 341 m2 · player-1) and official matches (n = 28). Data were collected during two full seasons. A linear mixed model analysis was used to calculate the individual relationship between technical/locomotor demands and the ApP during SSGs; the correlation coefficient was also calculated. With the exception of an inverse moderate (r = -0.457) correlation for Acc+Dec, each locomotor metric (TD, HSRD, VHSRD and sprint) showed a positive large to very large (r = 0.560 to 0.710) correlation with ApP (P < 0.001). The technical demands showed an inverse moderate correlation (r = -0.529) with ApP. Additionally, inverse moderate to large correlations (r = -0.397 to -0.600; P < 0.05) between the technical demands and the locomotor demands (TD, HSR, VHSR and sprint) were found. Lastly, an ApP of ~243 m2 · player was found to replicate the official match technical demand and it was quite similar to the ApP required to replicate HSRD, VHSRD and sprint. These findings may help practitioners to replicate, overload and underload both technical and locomotor demands using a specific ApP during SSGs in elite soccer.



#11 Association between internal training load and muscle injuries in Brazilian professional soccer players

Reference: Biol Sport. 2023 Jul;40(3):675-679. doi: 10.5114/biolsport.2023.119285. Epub 2022 Sep 15.

Authors: Pedro A Mohr, Thiago S Matias, Ricardo D de Lucas

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Summary: The training load is associated with injury risk in a variety of sports. This study aimed to evaluate the association between the internal training load and injury risk in Brazilian professional soccer players. The data were collected from 32 soccer players across two full seasons (2017 and 2018). The rating of perceived exertion (RPE) for every training/match session was used as an internal load variable. The cumulative training load from 3 and 4 weeks (C3 and C4) and the acute:chronic workload ratio (ACWR) were calculated. A generalized estimating equation analysis was applied to examine associations of non-contact muscle injuries with C3, C4 and ACWR. A total of 33 injuries were recorded across the two full seasons. A significant association was found between cumulative training load for three (C3, p = 0.003) and four weeks (C4, p = 0.023) and the occurrence of injuries. Players in the "high load" group presented greater injury risk in relation to the "moderate load" group (C4: OR = 4.5; IC 95% 1.5-13.3; C3: OR = 3.7; IC 95% 1.7-8.1). There was no association between ACWR and injury occurrence. The athletes exposed to a high cumulative load in a period of 3 to 4 weeks presented higher injury risk in comparison to those who had moderate cumulative training loads. Besides that, there was no association between ACWR and injury occurrence.



#12 The selection advantages associated with advanced biological maturation vary according to playing position in national-level youth soccer

Reference: Biol Sport. 2023 Jul;40(3):715-722. doi: 10.5114/biolsport.2023.119983. Epub 2022 Oct 6.

Authors: Liam Sweeney, Sean P Cumming, Áine MacNamara, Dan Horan

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Summary: This study investigated the extent to which biological maturation selection biases existed according to playing position in national-level youth soccer. A total of 159 players from the U13 to U16 age groups in the Football Association of Ireland's national talent pathway and international representative squads had their relative biological maturity status assessed using the Khamis-Roche method for the percentage of predicted adult height at the time of observation. Players were categorised as goalkeeper (GK), central defender (CD), full-back (FB), centre defensive midfielder (CDM), centre midfielder (CM), centre attacking midfielder (CAM), wide midfielder (WM) or centre forward (CF). A series of one-sampled means t-tests were used to examine the degree to which biological maturation selection biases existed across playing positions. A non-parametric Kruskal-Wallis test was used to evaluate inter-positional differences. A small to very large selection bias in favour of early maturing players existed for GK (D = 0.7), CD (D = 1.65), FB (D = 0.49), CM (D = 0.62), WM (D = 0.78), and CF (D = 0.76) (p < 0.05). Maturational selection biases did not exist for CDM or CAM. Moreover, CD were significantly more advanced in maturation compared to FB, CDM and CAM (p < 0.05). This study supports the contention that maturation selection biases exist in youth soccer, but the magnitude of this bias is highly dependent upon playing position. The very strong maturity selection biases at the national level evidenced in this investigation highlight the need for Football Associations to explore strategies, such as futures programmes, to help to retain talented, yet late maturing athletes.



#13 The effect of two sessions of combined jump and sprint training per week on fitness parameters in soccer players. A randomized controlled trial

Reference: Biol Sport. 2023 Jul;40(3):699-706. doi: 10.5114/biolsport.2023.119287. Epub 2022 Sep 22.

Authors: Mattia Bianchi, Liam Anderson, Thomas E Brownlee, Lorenzo Bossi, Marco Beato

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Summary: This study aimed to investigate the effect of a combined jump and sprint training program, two sessions a week for 6 weeks, on sprinting, change of directions (COD) and jumping performance in semi-professional soccer players. Twenty soccer players were enrolled in this randomized controlled trial (age 20 ± 2 years, body mass 74.3 ± 5.9 kg). Players were randomized into two groups such as training group (TG, n = 10 players) or control group (CG, n = 10 players). Physical tests were performed before and after 6 weeks of training such as sprint 10 m, sprint 30 m, 505-COD test and standing long jump (LJ). The two groups performed the same training except for the combined jump and sprint training performed twice a week by TG. After 6 weeks of training, between-group analysis reported statistical difference in favor of the TG in sprint 10 m (p = 0.015, η2 = 0.295, large), sprint 30 m (p < 0.001, η2 = 0.599, large), in 505-COD (p = 0.026, η2 = 0.154, large), and LJ (p = 0.025, η2 = 0.027, small). These data indicate that combined sprint and jump training, when performed twice a week, for the duration of 6 weeks, in addition to the regular team training, can improve specific physical performance in male soccer players. This study has shown that a volume increment of 10% after 3 weeks of training can be a suitable training dose progression and that a combination of 64-70 jumps and 675-738 m of sprinting training per session can yield benefits in sprint, COD and jump performance.



#14 Typical weekly physical periodization in French academy soccer teams: a survey

Reference: Biol Sport. 2023 Jul;40(3):731-740. doi: 10.5114/biolsport.2023.119988. Epub 2022 Oct 14.

Authors: Tom Douchet, Christos Paizis, Christopher Carling, Carole Cometti, Nicolas Babault

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Summary: In elite-level youth soccer players, weekly training periodization is of paramount importance to plan for short- and long-term physical development. The present study investigated current practices for physical periodization strategies in elite male French academies. An online survey was completed by elite French academies strength and conditioning coaches to determine the typical weekly periodization with particular reference to daily training in relation to match day (MD) in youth soccer players. The survey attempted to characterize the importance of physical development compared to match result, and practices used (expected difficulty and content) for each training session according to duration, exercises, and objective. The frequency rates of the responses were compared using two-tailed Chi-square tests with the significance level set at p < 0.05. Fortyfive questionnaires were analyzed. Respondents indicated that their training sessions focused mainly on physical development (95.6%) rather than match result. Active recovery (34.2%) and aerobic conditioning exercises (40.8%) were primarily conducted on MD+1 and MD+2 using passing circuits and aerobic technical drills. Physical development was mostly pursued during sessions on MD-4 (38.8%) and MD-3 (37.3%). The number of large-sided games was highest on MD-3 (58.1%). On MD-2 and MD-1, a decrease in the training load was highlighted, with speed (40.4%) and tapering sessions (52.4%) mostly implemented. Intensive use of small-sided games (92.3%) and reactivity exercises was observed at MD-1 (100.0%). Our results revealed discrepancies between the physical objectives set for each day and the content implemented, which could potentially be more physically demanding than expected.



#15 Chronic Traumatic Encephalopathy in Soccer Players: Review of 14 Cases

Reference: Clin J Sport Med. 2023 Jul 4. doi: 10.1097/JSM.0000000000001174. Online ahead of print.

Authors: Gerard Hageman, Ivar Hageman, Jik Nihom

Summary: Exposure to repetitive sports-related concussions or (sub)concussive head trauma may lead to chronic traumatic encephalopathy (CTE). Which impact (heading or concussion) poses the greatest risk of CTE development in soccer players? A literature search (PubMed) was conducted for neuropathologic studies in the period 2005-December 2022, investigating soccer players with dementia and a CTE diagnosis, limited to English language publications. 210 papers were selected for final inclusion, of which 7 papers described 14 soccer players. Magnetic resonance imaging studies in soccer players show that lifetime estimates of heading numbers are inversely correlated with cortical thickness, grey matter volume, and density of the anterior temporal cortex. Using diffusion tensor imaging-magnetic resonance imaging, higher frequency of headings-particularly with rotational accelerations-are associated with impaired white matter integrity. Serum neurofilament light protein is elevated after heading. Chronic traumatic encephalopathy pathology, history of concussion, heading frequency was used as outcome measures. In 10 of 14 soccer players, CTE was the primary diagnosis. In 4 cases, other dementia types formed the primary diagnosis and CTE pathology was a concomitant finding. Remarkably, 6 of the 14 cases had no history of concussion, suggesting that frequent heading may be a risk for CTE in patients without symptomatic concussion. Rule changes in heading duels, management of concussion during the game, and limiting the number of high force headers during training are discussed. Data suggest that heading frequency and concussions are associated with higher risk of developing CTE in (retired) soccer players. However based on this review of only 14 players, questions persist as to whether or not heading is a risk factor for CTE or long-term cognitive decline.



#16 Prediction of ball direction in soccer penalty through kinematic analysis of the kicker

Reference: J Sports Sci. 2023 Jul 6;1-9. doi: 10.1080/02640414.2023.2232679. Online ahead of print.

Authors: Bruno Secco Faquin, Luis Augusto Teixeira, Cristiane Regina Coelho Candido, Daniel Boari Coelho, Juliana Bayeux Dascal, Victor Hugo Alves Okazaki

Summary: The penalty kick is a crucial opportunity to score and determine the outcome of a soccer match or championship. Anticipating the direction of the ball is key for goalkeepers to enhance their defensive capabilities, considering the ball's swift travel time. However, it remains unclear which kinematic cues from the kicker can predict the ball's direction. This study aimed to identify the variables that predict the ball's direction during a soccer penalty kick. Twenty U19 soccer players executed penalty kicks towards four targets positioned in the goal, while kinematic analysis was conducted using a 3D motion analysis system. Logistic regression analysis revealed that trunk rotation in the transverse plane (towards the goal - left; or slightly to the right - right) served as the primary predictor of the ball's horizontal direction at 250 and 150 ms before the kicking foot made contact. Additionally, the height of the kicking foot in the sagittal plane solely predicted the vertical direction at the moment of contact. This information, encompassing trunk rotation and kicking foot height, can be employed in perceptual training to enhance decision-making and the implementation of feints during penalty kicks.



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