Latest research in football - week 25 - 2020

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 Football Fans' Emotions: Uncertainty Against Brand Perception
Reference: Front Psychol. 2020 May 15;11:659. doi: 10.3389/fpsyg.2020.00659. eCollection 2020.
Authors: Elena Shakina, Thadeu Gasparetto, Angel Barajas
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Summary: Football is an industry driven by emotions. Fans experience many different emotions related to their teams. This paper aims to inspect how emotions impact attendance at football matches, examining whether football fans prefer to watch highly competitive matches or matches between good teams with star-players. The paper also considers behavioral and emotional differences of match spectators when brand-teams play away or at home. Importantly, we are also looking for the effects that the expectations of these emotions have on the tickets' price mechanism. We use data from three seasons of the Brazilian State championship with information on more than 1,100 matches. The OLS estimator with the moderation marginal effects allows for analysis of a brand-team playing with different levels of uncertainty over the outcomes measured by the relative level of the divisions of rivals. We look for the difference between the marginal contribution of the brand-team and the uncertainty of outcomes that might change under some conditions. The analysis is performed later using two subsamples and, finally, we address the problem of endogeneity in price using an instrumental variable. From our results, the main findings are: first, that the price of tickets does not much affect the demand when a brand-team is playing. In case of competitive matches between non-brand-teams, price behavior correlates to the rationality of the demand curve having a negative impact. The fact that price is not relevant for matches with the brand-team comes to corroborate the idea that fans are driven more by emotions than by economic reasoning; second, the phenomena of highly competitive matches does not work when a brand-team is playing against a small one; and third, the effect of a brand-team playing is relatively more important than the uncertainty of outcome. The last two findings mean that the satisfaction of watching star-players or big-teams is stronger than the emotion brought by a competitive match.

#2 Acute Kinematics and Kinetics Changes to Wearable Resistance During Change of Direction Among Soccer Players
Reference: Res Sports Med. 2020 Jun 3;1-15. doi: 10.1080/15438627.2020.1770761. Online ahead of print.
Authors: Xueliang Li, Chunman Li  1 , Yixiong Cui  2 , Del P Wong  3
Summary: This study determined the acute changes in kinematics and kinetics when an additional load equivalent to 5% body mass was attached to the torso during change of direction (COD). In this within-subject repeated measures study, 14 male soccer players (age: 18.29 ± 0.32 years) volunteered to participate. Subjects performed COD under two conditions in randomized order: (1) no WR, and (2) with WR. No significant differences between the loaded and unloaded conditions in actual COD angle, approach speed, braking time, propulsive time, contact time, COD completion time (all p > 0.05, ES = 0.05-0.11), and all measured kinematic parameters (all p > 0.05, ES = 0-0.18). Nonetheless, ankle plantar/dorsi flexion ROM had possibly small increase in the loaded condition (ES = 0.24). Kinetics analysis has shown that the loaded condition was likely to have small increase in relative peak vertical propulsive ground reaction force (GRF, p = 0.11, ES = 0.41), and possible small increases in relative peak braking GRF (vertical: p = 0.21, ES = 0.42; total: p = 0.22, ES = 0.38), relative peak total propulsive GRF (p = 0.24, ES = 0.26), and relative braking impulse (horizontal, vertical, and total; p = 0.27-0.41, ES = 0.26-0.28). WR did not significantly change the acute movement techniques, meanwhile induced small increases in important kinetic stimuli for potential adaptation in COD.

#3 Reduced Telomere Shortening in Lifelong Trained Male Football Players Compared to Age-Matched Inactive Controls
Reference: Review Prog Cardiovasc Dis. 2020 Jun 1;S0033-0620(20)30117-1. doi: 10.1016/j.pcad.2020.05.009. Online ahead of print.
Authors: Marie Hagman, Christian Werner, Katharina Kamp, Bjørn Fristrup, Therese Hornstrup, Tim Meyer, Michael Böhm, Ulrich Laufs, Peter Krustrup
Summary: Current evidence points to cellular anti-ageing effects of regular endurance training which may differ from other sport modalities. Effects of football training on markers of cell senescence have not been tested. One hundred and forty healthy, non-smoking men participated in the study, including young elite football players aged 18-30 years (YF, n = 35, 21.6 ± 0.5 yrs), elderly football players aged 65-80 years (EF, n = 35, 71.9 ± 0.5 yrs), untrained young controls (YC, n = 35, 24.3 ± 0.6 yrs) and elderly controls (EC, n = 35, 70.1 ± 0.7 yrs). Besides body composition (DXA scan), resting heart rate (RHR), blood pressure (BP) and selected fasting blood variables, mononuclear cells (MNC) were isolated. MNC telomere length was determined by flow-fluorescence in-situ hybridization (FISH) and polymerase chain reaction (PCR). Telomerase activity was quantified using telomerase repeat amplification protocol (TRAP) assay. mRNA expression of anti- and pro-senescent factors was measured with real-time PCR. EF showed 2.5% higher (p = 0.047) granulocyte telomere length and 1.3% higher (p = 0.009) lymphocyte telomere length compared to EC. EF had 37% lower (p = 0.025) mRNA expression of the pro-senescent factor p16 compared to EC. No significant between-group differences (p > 0.050) were observed in telomerase activity or anti-senescent factors (TRF2, Ku70 and POT1a) for EF vs EC. YF had higher telomerase activity (4.2-fold, p = 0.001), telomere repeat binding factor (TRF) 2 mRNA expression (3.2-fold, p = 0.003), Ku70 mRNA expression (2.3-fold, p < 0.001) and POT1a mRNA expression (2.2-fold, p = 0.002) compared to YC, but there was no significant between-group difference in telomere length. This study is the first cross-sectional, controlled trial showing effects of lifelong football participation on telomere shortening and senescence markers in circulating cells, suggesting that football induces cellular anti-senescence mechanisms implying positive long-term cardiovascular health effects.

#4 Curve Sprinting in Soccer: Kinematic and Neuromuscular Analysis
Reference: Int J Sports Med. 2020 Jun 3. doi: 10.1055/a-1144-3175. Online ahead of print.
Authors: Alberto Filter, Jesús Olivares-Jabalera, Alfredo Santalla, Jaime Morente-Sánchez, Jose Robles-Rodríguez, Bernardo Requena, Irineu Loturco
Summary: Sprinting in curvilinear trajectories is an important soccer ability, corresponding to ~85% of the actions performed at maximum velocity in a soccer league. We compared the neuromuscular behavior and foot contact-time between outside leg and inside leg during curve sprinting to both sides in soccer players. Nine soccer players (age=23±4.12 years) performed: 3×Sprint linear, 3×Sprint right curve, and 3×Sprint left curve. An ANOVA with repeated measures was used to compare the differences between inside and outside leg, and Cohen's d was used to calculate the effect-size. Considering the average data, the performance classification (from best to worst) was as follows: 1. Curve "good" side (2.45±0.11 s), 2. Linear (2.47±0.13 s), and 3. Curve "weak" side (2.56±0.17 s). Comparing linear with curve sprinting, inside leg recorded significant differences ("good" and "weak"; effect size=1.20 and 2, respectively); in contrast, for outside leg, there were no significant differences ("good" and "weak"; effect size=0.30 and 0.49, respectively). Electromyography activity showed significant differences (p≤0.05) during curve sprinting between outside (higher in biceps femoris and gluteus medius) and inside leg (higher activity in semitendinosus and adductor). In summary, inside and outside leg play different roles during curved sprints, but inside leg is more affected by the change from straight to curve sprint.

#5 Recurrent Fifth Metatarsal Stress Fractures in a Professional Soccer Player With Hypoparathyroidism: A Case Report
Reference: BMC Musculoskelet Disord. 2020 Jun 3;21(1):347. doi: 10.1186/s12891-020-03383-2.
Authors: Itaru Kawashima, Atsushi Yamaga, Ryosuke Kawai, Yushi Hoshino, Shinya Ishizuka
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Summary: Hypoparathyroidism is characterized by low or inappropriately normal levels of parathyroid hormone leading to hypocalcemia. In this report, a case of recurrent fifth metatarsal stress fractures in a professional soccer player with hypoparathyroidism is presented. A 23-year-old male professional soccer player developed left foot pain. He had no specific medical or family history. He was diagnosed with a fifth metatarsal stress fracture and underwent osteosynthesis with a cannulated cancellous screw 3 days after the injury. After three and a half months, the X-ray showed bone union, and he returned to full sports activity. However, he felt pain in his left foot again, and a re-fracture was found on X-ray a week later. Osteosynthesis was performed again. Two months after re-operation, the cause of re-fracture was investigated. Laboratory results showed abnormally low levels of serum calcium (8.4 mg/dL) and intact parathyroid hormone (i-PTH: 19.0 pg/mL). However, other laboratory examinations were normal. Therefore, he was diagnosed with primary hypoparathyroidism according to the diagnostic criteria. Medical treatment was started with alfacalcidol 1.0 μg/day. One month after starting medication, the serum calcium improved to 9.4 mg/dL. Four months after the re-operation, the X-ray showed bone union, and he was therefore allowed to play soccer. While he played professional soccer, there were no new subjective complaints. Hypoparathyroidism may be one of the risk factors for stress fractures. We believe that serum calcium levels should be checked in patients with stress fractures, and if the serum calcium is low, hypoparathyroidism should be considered.

#6 Epidemiological Data on LCL and PCL Injuries Over 17 Seasons in Men's Professional Soccer: The UEFA Elite Club Injury Study
Reference: Open Access J Sports Med. 2020 May 13;11:105-112. doi: 10.2147/OAJSM.S237997. eCollection 2020.
Authors: Matilda Lundblad, Martin Hägglund, Christoffer Thomeé, Eric Hamrin Senorski, Jan Ekstrand, Jón Karlsson , Markus Waldén
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Summary: There is limited epidemiological information on injury rates and injury mechanisms for lateral collateral ligament (LCL) and posterior cruciate ligament (PCL) injuries in male professional soccer. In addition, time trends and lay-off times for these injuries have not yet been determined. The purpose was to determine injury rates and circumstances of LCL and PCL injuries over 17 seasons in men's professional soccer. A prospective cohort study, in which 68 professional European soccer teams were followed over 17 consecutive seasons (2001/2002 to 2017/2018). The teams' medical staff recorded player exposure and time-loss injuries. Lay-off time was reported as the median and the first and third quartile. Injury rate was defined as the number of injuries per 1000 player-hours. One hundred and twenty-eight LCL and 28 PCL injuries occurred during 2,554,686 h of exposure (rate 0.05 and 0.01/1000 h, respectively). The median lay-off time for LCL injuries was 15 (Q1=7, Q3=32) days, while it was 31 days for PCL injuries (Q1=15, Q3=74). The match injury rate for LCL injuries was 11 times higher than the training injury rate (0.21 vs 0.02/1000 h, rate ratio [RR] 10.5, 95% CI 7.3 to 15.1 p<0.001) and the match injury rate for PCL injuries was 20 times higher than the training injury rate (0.056 vs 0.003/1000 h, RR 20.1, 95% CI 8.2 to 49.6, p<0.001). LCL injuries saw a significant annual decrease of approximately 3.5% (p=0.006). In total, 58% (63/108) of all LCL injuries and 54% (14/26) of all PCL injuries were related to contact mechanism. This study with prospectively registered data on LCL and PCL injuries in men's professional soccer shows that the median lay-off from soccer for LCL and PCL injuries is approximately 2 and 4 weeks respectively. These rare knee ligament injuries typically occur during matches and are associated with a contact injury mechanism.

#7 ACTN3's R577x Single Nucleotide Polymorphism Allele Distribution Differs Significantly in Professional Football Players According to Their Field Position
Reference: Med Princ Pract. 2020 Jun 3. doi: 10.1159/000509089. Online ahead of print.
Authors: Enric Clos, Ricard Pruna, Matilda Lundblad, Rosa Artells, Nicola Maffulli
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Summary: Football is characterised by intermittent high-intensity efforts varying according to the field position of a player. We wished to ascertain whether polymorphisms in the ACTN3 gene are associated to different playing positions in elite professional football players. Genotyping of the ACTN3 gene was conducted in 43 elite professional football players of a single team. Playing position was recorded based on the player's most frequent position. The genotype distribution was not significant between positions (p=0.057), while the allele distribution differed significantly (p=0.035). Goalkeepers (p=0.04, p=0.03), central defenders (p=0.03, p=0.01) and central midfielders (p=0.01, p=0.00) had a significantly different allele distribution compared with wide midfielders and forward players. Genetic biomarkers may be important when analysing performance capability in elite professional football. Identifying the genetic characteristics of a player to adapt his playing position may lead to a position orientation based on physical capabilities and tissue quality in young football players and to performance enhancement in those who are already playing in professional teams.

#8 Using Machine Learning to Improve Our Understanding of Injury Risk and Prediction in Elite Male Youth Football Players
Reference: J Sci Med Sport. 2020 May 18;S1440-2440(19)31676-7. doi: 10.1016/j.jsams.2020.04.021. Online ahead of print.
Authors: Jon L Oliver, Francisco Ayala, Mark B A De Ste Croix, Rhodri S Lloyd, Greg D Myer , Paul J Read
Summary: The purpose of this study was to examine whether the use of machine learning improved the ability of a neuromuscular screen to identify injury risk factors in elite male youth football players.  355 elite youth football players aged 10-18 years old completed a prospective pre-season neuromuscular screen that included anthropometric measures of size, as well as single leg countermovement jump (SLCMJ), single leg hop for distance (SLHD), 75% hop distance and stick (75%Hop), Y-balance anterior reach and tuck jump assessment. Injury incidence was monitored over one competitive season. Risk profiling was assessed using traditional regression analyses and compared to supervised machine learning algorithms constructed using decision trees. Using continuous data, multivariate logistic analysis identified SLCMJ asymmetry as the sole significant predictor of injury (OR 0.94, 0.92-0.97, p<0.001), with a specificity of 97.7% and sensitivity of 15.2% giving an AUC of 0.661. The best performing decision tree model provided a specificity of 74.2% and sensitivity of 55.6% with an AUC of 0.663. All variables contributed to the final machine model, with asymmetry in the SLCMJ, 75%Hop and Y-balance, plus tuck jump knee valgus and anthropometrics being the most frequent contributors. Although both statistical methods reported similar accuracy, logistic regression provided very low sensitivity and only identified a single neuromuscular injury risk factor. The machine learning model provided much improved sensitivity to predict injury and identified interactions of asymmetry, knee valgus angle and body size as contributing factors to an injurious profile in youth football players.

#9 Functional Neural Substrates of Football Fanaticism: Different Pattern of Brain Responses and Connectivity in Fanatics
Reference: Psychiatry Clin Neurosci. 2020 May 31. doi: 10.1111/pcn.13076. Online ahead of print.
Authors: Başar Bilgiç, Elif Kurt, Çağrı Can Makar, Cigdem Ulasoglu-Yildiz, Bedia Samancı, Hakan Gürvit, Tamer Demiralp, Murat Emre
Summary: Sports activities provide social interaction for humans. Commitment to a given team is a salient feature of being a sports fan and becomes a prominent part of self-identification for fanatics. Emotion, subjective hedonic experience, and non-romantic love are related to fan behaviors. Few studies have evaluated the neural basis of sports fanaticism. Thirty men, including 16 football fanatics and 14 non-fanatics, with a mean age of 27.4 ± 6.4 years (range, 20-48) were enrolled. Subjects underwent fMRI while watching a set of goals scored by favorite, rival, and neutral teams. The analysis of variance in GLM revealed a significant Group-by-Condition interaction effect in the bilateral dorsal anterior cingulate cortex (dACC), more prominent in the left hemisphere. In the post-hoc comparisons, fanatics showed increased activation in bilateral dACC, supplementary motor cortex (SMA), superior frontal cortex, right dorsolateral prefrontal cortex and right insula for favorite>neutral contrast and an increased activation in bilateral dACC and SMA for rival>neutral contrast. Seed-based connectivity analyses using the areas with significant activation differences revealed increased connectivity between dACC and several regions, including left posterior lateral temporal area, insula, and bilateral medial temporal, medial superior frontal areas as well as basal ganglia in fanatics compared to non-fanatics. Our results suggest that football fanatics exhibit different brain activation and connectivity pattern, both under favorable and unfavorable conditions. This brain activity and connectivity pattern under emotionally-laden conditions may represent higher responses to rewards, higher emotional valence attribution, and stronger motivational state of the football fanatics that might underlie their unusual behavioral responses.

#10 Sex-Based Differences in Anterior Cruciate Ligament Injuries Among United States High School Soccer Players: An Epidemiological Study
Reference: Orthop J Sports Med. 2020 May 28;8(5):2325967120919178. doi: 10.1177/2325967120919178. eCollection 2020 May.
Authors: Andrew S Gupta, Lauren A Pierpoint, R Dawn Comstock, Michael G Saper
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Summary: Anterior cruciate ligament (ACL) tears are common among high school athletes, with sex-based differences accounting for higher injury rates in girls. Previous epidemiological studies on ACL injuries focusing on adolescent athletes have looked at injuries across multiple sports, but few have analyzed ACL tears in solely high school soccer athletes.  The purpose was to examine sex-based differences in the epidemiology of ACL injuries among high school soccer players in the United States (US). ACL injury data for US high school soccer players were obtained from the internet-based National High School Sports-Related Injury Surveillance Study's High School RIO (Reporting Information Online) system. Athletic trainers from a random sample of 100 high schools from 8 strata based on US Census geographic region reported data for athlete-exposures (AEs) (practice or competition) and ACL injuries from 2007 through 2017. Injury rates were calculated as the number of ACL injuries per 100,000 AEs. Subgroup differences were evaluated with rate ratios (RRs) or injury proportion ratios (IPRs) and 95% CIs. Statistical differences in demographics between groups were examined using independent t tests. Comparisons of categorical data (ie, level of play) were performed using the Wald chi-square test. The reported number of ACL injuries corresponded to weighted national estimates of 41,025 (95% CI, 33,321-48,730) ACL injuries in boys' soccer and 110,028 (95% CI, 95,349-124,709) in girls' soccer during the study period. The rate of injuries was higher in girls' soccer (13.23/100,000 AEs) than boys' soccer (4.35/100,000 AEs) (RR, 3.04 [95% CI, 2.35-3.98]). The rate of ACL injuries was higher in competition compared with practice for girls (RR, 14.77 [95% CI, 9.85-22.15]) and boys (RR, 8.69 [95% CI, 5.01-15.08]). Overall, a smaller proportion of ACL injuries were caused by player-player contact for girls (30.1%) compared with boys (48.6%) (IPR, 0.62 [95% CI, 0.41-0.93]). ACL injury rates and patterns in high school soccer players differed between sex, type of exposure (practice vs competition), and mechanism of injury.


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