Latest research in football - week 27 - 2021

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 Selected, Deselected, and Reselected: A Case Study Analysis of Attributes Associated With Player Reselection Following Closure of a Youth Soccer Academy

Reference: Front Sports Act Living. 2021 Mar 23;3:633124.  doi: 10.3389/fspor.2021.633124. eCollection 2021.

Authors: James H Dugdale, Allistair P McRobert, Viswanath B Unnithan 

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Summary: Considering the perceived benefit of early recruitment and the time and resources spent developing youth players, individuals released from talent development programmes are often re-recruited by rival academies. However, due to the contractual nature of many talent development programmes, limited empirical data exists on players deselected from (or reselected to) youth soccer academies. Adopting a novel case study approach, differences in skill, psychological, and physical attributes associated with reselection following closure of a junior-elite soccer academy were explored. Overall subjective coach ratings for skill, psychological, and physical abilities; subjective coach ratings for skill and psychological attributes; and physical fitness test performance of 79 junior-elite soccer players (U11-U17) were assessed as part of regular scheduled testing and monitoring practices prior to the academy closure. Reselection status was monitored and recorded for all players in the 6 months following the academy closure and was classified as a persistence/progression ("Reselected") or attrition ("Deselected") in playing level. Of the 79 released players, a total of 60 players (76%) were re-signed to a junior-elite academy within 6 months. Differences were observed for overall ratings of skill, psychological, and physical abilities in favor of the "Reselected" player group. "Reselected" players were also rated higher by coaches for all attributes categorized as skill and psychological, as well as performing better at all physical fitness tests. However, "Reselected" players were lesser in stature and body mass and less mature than "Deselected" players. Our findings suggest that reselection is not a product of anthropometric criteria and, therefore, a pathway for selection remains open for later maturing players. We also inform upon desirable qualities associated with player reselection and provide a case study approach of a unique, yet highly relevant, scenario for talent identification and development in youth soccer.



#2 Associations Between Variations in Accumulated Workload and Physiological Variables in Young Male Soccer Players Over the Course of a Season

Reference: Front Physiol. 2021 Mar 18;12:638180.  doi: 10.3389/fphys.2021.638180. eCollection 2021.

Authors: Hadi Nobari, Ana Ruivo Alves, Filipe Manuel Clemente, Jorge Pérez-Gómez, Cain C T Clark, Urs Granacher, Hassane Zouhal

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Summary: This study sought to analyze the relationship between in-season training workload with changes in aerobic power (VO2m ax ), maximum and resting heart rate (HR max and HR rest ), linear sprint medium (LSM), and short test (LSS), in soccer players younger than 16 years (under-16 soccer players). We additionally aimed to explain changes in fitness levels during the in-season through regression models, considering accumulated load, baseline levels, and peak height velocity (PHV) as predictors. Twenty-three male sub-elite soccer players aged 15.5 ± 0.2 years (PHV: 13.6 ± 0.4 years; body height: 172.7 ± 4.2 cm; body mass: 61.3 ± 5.6 kg; body fat: 13.7% ± 3.9%; VO2m ax : 48.4 ± 2.6 mL⋅kg-1⋅min-1), were tested three times across the season (i.e., early-season (EaS), mid-season (MiS), and end-season (EnS) for VO2m ax , HR max , LSM, and LSS. Aerobic and speed variables gradually improved over the season and had a strong association with PHV. Moreover, the HR max demonstrated improvements from EaS to EnS; however, this was more evident in the intermediate period (from EaS to MiS) and had a strong association with VO2m ax . Regression analysis showed significant predictions for VO2m ax [F ( 2, 20) = 8.18, p ≤ 0.001] with an R 2 of 0.45. In conclusion, the meaningful variation of youth players' fitness levels can be observed across the season, and such changes can be partially explained by the load imposed.



#3 Covid-19 and Football: Crisis Creates Opportunity

Reference: Polit Q. Jan-Mar 2021;92(1):132-138.  doi: 10.1111/1467-923X.12961. Epub 2021 Feb 3.

Authors: Kieran Maguire

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Summary: This article looks at the financial performance and position of English professional football before Covid-19 and the impact that the pandemic has had on the industry. It analyses revenue streams in different divisions, the dependency that clubs have on them and how they have changed as a result of the pandemic. The article also reviews key costs for football clubs, the extent to which they can be reduced, different business models that operate, and possible funding sources for the sport from third parties and within the industry.



#4 Comparison of the Morphological Characteristics of South African Sub-Elite Female Football Players According to Playing Position

Reference: Int J Environ Res Public Health. 2021 Mar 31;18(7):3603.  doi: 10.3390/ijerph18073603.

Authors: Anita Strauss 1 2, Martinique Sparks 2, Cindy Pienaar 2 3

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Summary: Limited information is available on the morphological characteristics of adult female footballers, therefore the aim of this article was to examine if there are position-specific differences in the morphological characteristics of sub-elite female football players and to establish normative standards for this level of female football players. The morphological features of 101 sub-elite female football players (age: 21.8 ± 2.7 years) were assessed. Twenty anthropometric sites were measured for body composition and somatotype. The average value of body fat percentage was 20.8 ± 5.7%. The somatotype of the overall group was 4.0-2.4-2.1. Significant (p ≤ 0.05) differences were found between goalkeepers and outfield players in morphological characteristics. Goalkeepers were taller (166.2 ± 8.4 cm), heavier (66.5 ± 5.1 kg), possessed the highest body fat percentage (17.2 ± 6.2%) and showed higher values for all skinfold (sum of 6 skinfolds = 125.6 ± 45.9 cm), breadth, girth and length measurements. However, there were very few practically worthwhile differences between the outfield positions. Positional groups did not differ (p ≤ 0.05) in somatotype characteristics either. The study suggests that at sub-elite level there are mainly differences between goalkeepers and outfield players, but outfield players are homogeneous when comparing morphological characteristics. These results may serve as normative values for future comparisons regarding the morphological characteristics of female football players.



#5 A Mixed-Methods Evaluation of CARE (Cancer and Rehabilitation Exercise): A Physical Activity and Health Intervention, Delivered in a Community Football Trust

Reference: Int J Environ Res Public Health. 2021 Mar 23;18(6):3327.  doi: 10.3390/ijerph18063327.

Authors: Zoe Rutherford 1 2, Stephen Zwolinsky 3, Nicky Kime 4, Andy Pringle 5

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Summary: With increasing cancer survivorship has come an increased necessity to support people living with cancer (PLWC) to have a good quality of life including being physically active. Using mixed methods, the current study aimed to use the RE-AIM evaluation framework (Reach, Effectiveness, Adoption, Implementation and Maintenance) to determine how the football community trust delivered CARE (Cancer and Rehabilitation Exercise) intervention was able to increase participants' physical activity in order to improve their quality of life and regain physiological and psychological function. Quantitative outcome data were collected at baseline, 3 and 6 months using the Cancer Physical Activity Standard Evaluation Framework questionnaire. Semi-structured focus groups (n = 5) captured participants' (n = 40) lived experience of the reach, effectiveness, adoption, implementation, and maintenance of CARE. Questionnaire data were analysed using repeated measures ANOVAs and qualitative data were thematically analysed. Following diagnosis, CARE was successful in providing participants with a unique and accessible opportunity to become or restart physically activity, by providing a local, socially supportive, and inclusive environment. This resulted in significant increases in physical activity (F(1.58, 23) = 5.98, p = 0.009), quality of life (QoL) (F(2,36) = 13.12, p = 0.000) and significant reductions in fatigue (F(1.57,31) = 11.19, p = 0.000) over 6 months. Participants also reported becoming more active, recovering physical function, regaining independence, and enhanced psychological well-being as a result of attending CARE. Key design features of CARE were also identified across RE-AIM. CARE, a football community trust delivered physical activity intervention was successful in significantly improving participants' QoL and in regaining the physical and psychological functioning of people living with cancer. Results suggest that maintaining engagement in CARE for 6 months and beyond can support people to maintain these changes. Engaging in robust evaluations such as this can help organizations to successfully secure future funding for their programs.



#6 How did three consecutive matches with extra time affect physical performance? A case study of the 2018 football Men's World Cup

Reference: Biol Sport. 2021 Mar;38(1):65-70.  doi: 0.5114/biolsport.2020.97668. Epub 2020 Aug 21.

Authors: Michał Kołodziejczyk, Paweł Chmura, Luka Milanovic, Marek Konefał, Jan Chmura, Andrzej Rokita, Marcin Andrzejewski

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Summary: The purpose of this study was to ascertain the effect of playing three consecutive matches with extra time (ET) on the physical performance of selected Croatian players in their subsequent match, the final of the 2018 Men's World Cup in Russia. The case study consisted of 4 players on the Croatian national team (16 observations) who had played in all three matches up to 120 min. The consecutive full time matches (90 minutes) and extra time (30 minutes) were compared. The analysis was conducted using data collected by an advanced motion analysis system known as STATS and from interviews with the strength and conditioning coach of the Croatian national team. The recorded variables used were: total distance covered [m], distances covered [m] at intensity ranges of 20-25 km/h and above 25 km/h, and number of sprints performed. All the studied parameters systematically increased in each match up to 90 minutes of play, reached their maximum values in the semi-final and then decreased in the final match. Compared to the first extra time period, in the third extra time period the players covered twice as much distance with an intensity of 20-25 km/h and above 25 km/h, and recorded twice as many sprints. This investigation shows that players in central positions on the pitch are able to maintain or even increase high and very high intensity activity in three consecutive matches with extra time. These data complement the developing body of literature relating to the influence of accumulation of match play with extra time periods on high level players.



#7 Incidence of cardiovascular events when watching intense football matches - sex differences

Reference: Acta Cardiol. 2021 Apr 8;1-7.  doi: 10.1080/00015385.2021.1908703. Online ahead of print.

Authors: Luka Matej Mahečić, Florijan Iljazović, Marjeta Mišigoj-Duraković, Zdravko Babić

Summary: FIFA World Cup represent one of the world's greatest phenomena. The spectators watch the matches of national teams with great emotional involvement. It is well documented fact that emotional stress can be a trigger of unwanted cardiovascular (CV) event. The aim of this retrospective study was to determine whether there had been an increase in the number of the emergency admissions for CVD in the Emergency Room and Clinic for Cardiovascular Diseases of the Sestre milosrdnice University Hospital Centre during and after the matches that the Croatian national team played in the FIFA World Cup 2018. The hospital's database was examined for the dates when Croatia played its matches, plus two more days after each match. An unexposed period that included the same dates in 2017 and 2019 was formed. 1093 cases were assessed. The incidence of CV admissions during the exposed period was 1.15 (95% confidence interval [CI]; 1.02 to 1.31) times higher than during the unexposed period. There was a 1.30 (95% CI; 1.1 to 1.54) times higher incidence in women compared to the unexposed period. Arrhythmias and angina pectoris were the CVDs that occurred more frequently in the exposed period. This study showed that watching Croatian national team's matches and cheering represented an additional risk for a CV incident, especially in women.



#8 Is Increased Kicking Leg Iliopsoas Muscle Tightness a Predictive Factor for Developing Spondylolysis in Adolescent Male Soccer Players?

Reference: Clin J Sport Med. 2021 Mar 12. doi: 10.1097/JSM.0000000000000920. 

Authors: Seira Takei, Suguru Torii, Shuji Taketomi, Soichiro Iwanuma, Michio Tojima, Mana Otomo, Satoshi Iizuka, Sakae Tanaka

Summary: The aim was to identify predictive risk factors of lumbar stress (LS) fracture developing from an asymptomatic stress reaction of the pedicle among adolescent male soccer players. Japanese adolescent male soccer players (n = 195) aged 12 to 13 years participated in this study. Height, body weight, body mass index, muscle tightness of both lower extremities (iliopsoas, hamstrings, and quadriceps), lumbar bone mineral content, developmental age, and lumbar lordosis angle were measured as baseline measurements. Players who were diagnosed with an asymptomatic stress reaction of the lumbar spine pedicle at baseline were followed; extension-based lumbar pain was defined 1 year after the baseline. The players were assigned to the LS fracture or control (CON) group at follow-up. At baseline, 40 boys were diagnosed with an asymptomatic stress reaction of the lumbar spine pedicle. The difference in muscle tightness between the kicking leg and supporting leg was significantly different (P = 0.012) between the LS (n = 16) and CON (n = 22) groups. Increase in iliopsoas muscle tightness in the kicking leg was a predictive risk factor of developing extension-based lumbar pain after adjusting for developmental age and body mass index (odds ratio, 1.54; 95% confidence interval, 1.05-2.27). Development of extension-based lumbar pain from an asymptomatic stress reaction of the pedicle among adolescent male soccer players was associated with increased iliopsoas muscle tightness of the kicking leg relative to that of the supporting leg.



#9 Clinical Risk Profile for a Second Anterior Cruciate Ligament Injury in Female Soccer Players After Anterior Cruciate Ligament Reconstruction

Reference: Am J Sports Med. 2021 Apr 15;363546521999109. doi: 10.1177/0363546521999109. 

Authors: Anne Fältström, Joanna Kvist, Natalia F N Bittencourt, Luciana D Mendonça, Martin Hägglund

Summary: The risk of a second anterior cruciate ligament (ACL) injury when participating in pivoting sports after ACL reconstruction is high. Risk factors associated with a second ACL injury are complex. The purpose was to investigate the combinations of various clinical risk factors associated with second ACL injury in female soccer players with a primary unilateral ACL reconstruction, using Classification and Regression Tree (CART) analysis. A total of 117 active female soccer players (mean ± SD age, 20 ± 2 years) were included. Athletes were enrolled 19 ± 9 months after ACL reconstruction and were prospectively followed for 2 years. At baseline, all players underwent assessment of knee and ankle joint range of motion (ROM), participated in functional tests (postural control, hop performance, and movement asymmetries in the lower limbs and trunk), and answered questionnaires (patient-reported knee function, knee-related quality of life, psychological and personality factors). A clinical prediction model using CART was developed. A total of 28 players (24%) sustained a second ACL injury (21 ipsilateral and 7 contralateral ruptures) while playing soccer. CART analysis selected 9 of 19 independent variables associated with second ACL injury: the 5-jump test, knee collapse on the non-ACL reconstructed leg in a drop vertical jump, tuck jump, limb symmetry index on side hop and the single hop for distance, side difference in ankle dorsiflexion ROM, and scores for the questionnaires ACL-Return to Sport After Injury and the Swedish Universities Scales of Personality subscales of Stress Susceptibility and Adventure Seeking. The accuracy of the model was 89%, with 100% sensitivity and 76% specificity. CART analysis indicated that the interaction of longer jumps in the 5-jump test (>916 cm) with more side difference in ankle dorsiflexion ROM (>-2.5°) and more knee valgus collapse in the nonreconstructed knee (>-1.4 cm) (relative risk, 4.03; 95% CI, 2.21-7.36) best predicted an increased likelihood of a second ACL injury. The risk profiles selected by CART could accurately identify female soccer players at high risk for a second ACL injury. There was an interaction between functional performance, clinical assessment, and psychological factors, and it is reasonable to include these factors in return-to-sport decisions and in athlete screening after ACL injury.



#10 Poor Validity of Functional Performance Tests to Predict Knee Injury in Female Soccer Players With or Without Anterior Cruciate Ligament Reconstruction

Reference: Am J Sports Med. 2021 Apr 12;3635465211002541.  doi: 10.1177/03635465211002541. 

Authors: Anne Fältström, Martin Hägglund, Henrik Hedevik, Joanna Kvist 

Summary: Various tests have been developed to evaluate athletes' functional performance and for use as screening tools for injury prediction. Further validation of their accuracy to predict injury is needed. The purpose was to investigate the validity of predetermined cutoffs used to differentiate between high- and low-risk players in different functional performance tests to predict (1) anterior cruciate ligament (ACL) injury or (2) severe traumatic knee injury in a cohort of female soccer players with a primary unilateral ACL reconstruction and a cohort of knee-healthy players. A total of 117 active female soccer players (mean age ± SD, 20 ± 2 years) an average of 19 ± 9 months after ACL reconstruction and 119 knee-healthy players (age, 19 ± 3 years) were prospectively followed up for 2 years for new knee injuries. At baseline, all players underwent tests to assess postural control (Star Excursion Balance Test), hop performance (single-leg hop for distance, side hop), and movement asymmetries in the lower limbs and trunk (drop vertical jump [DVJ], tuck jump). The predictive validity of the test cutoffs to identify players who would sustain an ACL injury or a severe traumatic knee injury (absence from soccer play, >28 days) was assessed. The risk ratio (RR), area under the receiver operating characteristic curve (AUC), sensitivity, and specificity were calculated. A total of 46 players (39%) with ACL reconstruction sustained 48 severe knee injuries, including 28 ACL ruptures. Of the knee-healthy players, 13 (11%) sustained 14 severe knee injuries, including 8 ACL ruptures. No association was found between the predetermined functional performance test cutoffs and the risk of a new ACL injury or severe knee injury in players with ACL reconstruction. In knee-healthy players, the only variable associated with future ACL injury was ≥6.5 cm knee valgus in the frontal plane (any knee) in the DVJ (RR, 4.93; 95% CI, 1.04-23.40; P = .045), but with only fair predictive validity (AUC, 0.7; sensitivity, 0.75; specificity, 0.65). In our cohorts of female soccer players, the validity of commonly used functional performance tests to predict new knee injuries was poor. Only knee valgus during the DVJ was associated with new ACL injuries in knee-healthy players, but with only fair predictive validity.



#11 Physiological Characteristics of Female Soccer Players and Health and Performance Considerations: A Narrative Review

Reference: Sports Med Review. 2021 Apr 12.  doi: 10.1007/s40279-021-01458-1. Online ahead of print.

Authors: Rebecca K Randell, Thomas Clifford, Barry Drust, Samantha L Moss, Viswanath B Unnithan, Mark B A De Ste Croix, Naomi Datson, Daniel Martin, Hannah Mayho, James M Carter, Ian Rollo 

Summary: Female soccer has seen a substantial rise in participation, as well as increased financial support from governing bodies over the last decade. Thus, there is an onus on researchers and medical departments to develop a better understanding of the physical characteristics and demands, and the health and performance needs of female soccer players. In this review, we discuss the current research, as well as the knowledge gaps, of six major topics: physical demands, talent identification, body composition, injury risk and prevention, health and nutrition. Data on female talent identification are scarce, and future studies need to elucidate the influence of relative age and maturation selection across age groups. Regarding the physical demands, more research is needed on the pattern of high-intensity sprinting during matches and the contribution of soccer-specific movements. Injuries are not uncommon in female soccer players, but targeting intrinsically modifiable factors with injury prevention programmes can reduce injury rates. The anthropometric and physical characteristics of female players are heterogeneous and setting specific targets should be discouraged in youth and sub-elite players. Menstrual cycle phase may influence performance and injury risk; however, there are few studies in soccer players. Nutrition plays a critical role in health and performance and ensuring adequate energy intake remains a priority. Despite recent progress, there is considerably less research in female than male soccer players. Many gaps in our understanding of how best to develop and manage the health and performance of female soccer players remain.



#12 Validity of a Rehab and Reconditioning Program Following an Adductor Longus Injury in Professional Soccer

Reference: J Sport Rehabil. 2021 Apr 9;1-6.  doi: 10.1123/jsr.2020-0360. Online ahead of print.

Authors: Sergio Jiménez-Rubio, José Luis Estévez Rodríguez, Archit Navandar

Summary: The high rates of adductor injuries and reinjuries in soccer have suggested that the current rehabilitation programs may be insufficient; therefore, there is a need to create prevention and reconditioning programs to prepare athletes for the specific demands of the sport. The aim of this study is to validate a rehab and reconditioning program (RRP) for adductor injuries through a panel of experts and determine the effectiveness of this program through its application in professional soccer. A 20-item RRP was developed, which was validated by a panel of experts anonymously and then applied to 12 injured male professional soccer players. Eight rehabilitation fitness coaches (age = 33.25 [2.49] y) and 8 academic researchers (age = 38.50 [3.74] y) with PhDs in sports science and/or physiotherapy. The RRP was applied to 12 male professional players (age = 23.75 [4.97] y; height = 180.56 [8.41] cm; mass = 76.89 [3.43] kg) of the Spanish First and Second Division (La Liga). The experts validated an indoor and on-field reconditioning program, which was based on strengthening the injured muscle and retraining conditional capacities with the aim of reducing the risk of reinjury. Aiken V for each item of the program and number of days taken by the players to return to full team training was taken as outcome measures. The experts evaluated all items of the program very highly as seen from Aiken V values between 0.77 and 0.94 (range: 0.61-0.98) for all drills, and the return to training was in 13.08 (±1.42) days. This RRP following an injury to the adductor longus was validated by injury experts, and initial results suggested that it could permit a faster return to team training.



#13 Assessing Post-Game Emotions in Soccer Teams: The Role of Distinct Emotional Dynamics

Reference: Eur J Sport Sci. 2021 Apr 9;1-22.  doi: 10.1080/17461391.2021.1916079. Online ahead of print.

Authors: James L Rumbold, James A Newman, David Foster, Daniel J A Rhind, Jack Phoenix, Lorcan Hickey

Summary: This study examined the relationships between team (n = 10) and player post-game emotions following two consecutive games. In addition, the relationship between emotional contagion susceptibility and player post-game emotions was assessed. Applying an experience sampling methodology, male amateur and semi-professional soccer players (N = 114, Mage = 25.46 years, SD = 9.24) completed a sport emotion questionnaire shortly after the conclusion of two competitive games. Participants also completed a dispositional emotional contagion questionnaire prior to post-game data collection. Multilevel regressions revealed that teams' collective post-game emotions were strongly associated with players' post-game emotions, after accounting for within- (e.g., time, game outcome) and between-person (e.g., formal leaders, emotional contagion susceptibility) differences. In addition, partial support was found to indicate that emotional contagion susceptibility was associated with players' post-game emotions. In this context of soccer, the findings suggest that collective emotions following a game are more indicative of individual players' emotions than an individual's general tendency to mimic the emotions of others. From an applied perspective, the findings demonstrate the importance of coaches and players being mindful of the team's emotional climate after a game and the impact it may have on players, especially when that climate is negative.

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