Latest research in football - week 27 - 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 Female Soccer Players' Psychological Profile: Differences Between Professional and Amateur Players
Reference: Int J Environ Res Public Health 2020 Jun 18;17(12):E4357. doi: 10.3390/ijerph17124357.
Authors: Cecilia Ruiz-Esteban , Aurelio Olmedilla, Inmaculada Méndez, Juan Jesús Tobal
Download link:
Summary: The psychological variables that affect competitive performance are called the psychological profile of athletes. In recent years, the interest in female soccer players and the psychological characteristics that affect their performance has increased. The aim of the present study is to analyze the psychological characteristics of female professional soccer players and female amateur soccer players, as well as to determine the differences in the psychological profile of both groups. The participants were 134 federated female soccer players, with an average age of 18.28 years (SD = 4.05). To assess the psychological profile, the questionnaire on Psychological Characteristics related to Sports Performance (CPRD) by Gimeno, Buceta, and Pérez-Llantada (2001) was used. The results showed that female professional players presented higher values for motivation, while the female amateur players presented higher values for stress control and the influence of performance evaluation. These results can have a great impact on coaches' work, since they can help them to establish tasks and training methods consistent with the characteristics of their players.

#2 Directions of Single-Leg Landing Affect Multi-Segment Foot Kinematics and Dynamic Postural Stability in Male Collegiate Soccer Athletes
Reference: Gait Posture. 2020 Jun 13;80:285-291. doi: 10.1016/j.gaitpost.2020.06.007. Online ahead of print.
Authors: Shun Kunugi, Takashi Koumura, Ryota Myotsuzono, Akihiko Masunari, Naruto Yoshida, Shumpei Miyakawa, Naoki Mukai
Summary: Understanding lower limb kinematics and postural control in different directions of single-leg landings is critical to evaluate postural control and prevent lower limb injuries. However, foot and ankle kinematics and postural control during single-leg landings in different directions are less known. Therefore we questioned wheter the difference in the direction of single-leg landing affect the foot kinematics on the frontal plane and dynamic postural stability? A cross-sectional study was conducted. Forty-nine male collegiate soccer players performed single-leg forward (FL), 45° lateral (LL), and medial (ML) direction landings. The lower limb, foot (rearfoot, midfoot, forefoot), and ankle kinematics during an impact phase were evaluated, and a curve analysis was performed using a statistical parametric mapping method to compare the three landings. The three landings were compared in terms of postural control parameters, including time to stabilization (TTS), peak of ground reaction forces (GRFs), root-mean-square of the mediolateral GRFs for 0-0.4 s (GRFML0.4), loading rate, and magnitude of horizontal GRFs from 0-0.4 s (HGRF-0.4), 0.4-2.4 s (HGRF-2.4), and 3.0-5.0 s. Ankle and rearfoot kinematics in LL exhibited smaller eversion and pronation positions than FL and ML (p < 0.01). The TTS-mediolateral (TTS-ML) was longer in the LL than in FL and ML (p < 0.001). The GRFML0.4, HGRF-0.4, and -2.4 in the LL and ML were greater than those in the FL (p < 0.001). Directions of single-leg landing affect foot and ankle kinematics and postural stability. Specifically, the LL exhibits more inverted ankle and supinated rearfoot positions, and longer TTS-ML. Thus, the LL may induce stretching of the lateral ankle ligament. These findings can help understand foot kinematics and assess dynamic postural control.

#3 The Genetic Profile of Elite Youth Soccer Players and Its Association With Power and Speed Depends on Maturity Status

Reference: PLoS One. 2020 Jun 22;15(6):e0234458. doi: 10.1371/journal.pone.0234458. eCollection 2020.
Authors: Conall F Murtagh, Thomas E Brownlee, Edgardo Rienzi, Sebastian Roquero, Sacha Moreno, Gustavo Huertas, Giovani Lugioratto, Philipp Baumert, Daniel C Turner, Dongsun Lee, Peter Dickinson, K Amber Lyon, Bahare Sheikhsaraf, Betül Biyik, Andrew O'Boyle, Ryland Morgans, Andrew Massey, Barry Drust, Robert M Erskine
Download link:
Summary: We investigated the association of multiple single nucleotide polymorphisms (SNPs) with athlete status and power/speed performance in elite male youth soccer players (ESP) and control participants (CON) at different stages of maturity. ESP (n = 535; aged 8-23 years) and CON (n = 151; aged 9-26 years) were genotyped for 10 SNPs and grouped according to years from predicted peak-height-velocity (PHV), i.e. pre- or post-PHV, to determine maturity status. Participants performed bilateral vertical countermovement jumps, bilateral horizontal-forward countermovement jumps, 20m sprints and modified 505-agility tests. Compared to CON, pre-PHV ESP demonstrated a higher ACTN3 (rs1815739) XX ('endurance') genotype frequency distribution, while post-PHV ESP revealed a higher frequency distribution of the PPARA (rs4253778) C-allele, AGT (rs699) GG genotype and NOS3 (rs2070744) T-allele ('power' genotypes/alleles). BDNF (rs6265) CC, COL5A1 (rs12722) CC and NOS3 TT homozygotes sprinted quicker than A-allele carriers, CT heterozygotes and CC homozygotes, respectively. COL2A1 (rs2070739) CC and AMPD1 (rs17602729) GG homozygotes sprinted faster than their respective minor allele carrier counterparts in CON and pre-PHV ESP, respectively. BDNF CC homozygotes jumped further than T-allele carriers, while ESP COL5A1 CC homozygotes jumped higher than TT homozygotes. To conclude, we have shown for the first time that pre- and post-PHV ESP have distinct genetic profiles, with pre-PHV ESP more suited for endurance, and post-PHV ESP for power and speed (the latter phenotypes being crucial attributes for post-PHV ESP). We have also demonstrated that power, acceleration and sprint performance were associated with five SNPs, both individually and in combination, possibly by influencing muscle size and neuromuscular activation.

#4 Talent Identification and Development in Soccer Since the Millennium
Reference: J Sports Sci. 2020 Jun 22;1-12. doi: 10.1080/02640414.2020.1766647. Online ahead of print.
Authors: A Mark Williams, Paul R Ford, Barry Drust
Summary: At the turn of the millennium, a review paper was published in this journal on talent identification and development in soccer (Williams & Reilly, 2000). In the current paper, we assess progress made in this field over the last twenty years relative to the areas for future research highlighted in the original review. We evaluate developments in light of the calls made by Williams and Reilly to: a) undertake more multidisciplinary rather than mono-disciplinary research; b) embrace longitudinal rather than cross-sectional research designs; c) expand the research base on female football; and, d) better identify the subjective criteria used by scouts when selecting one player over another for entry into a formalised training environment. The body of mono-disciplinary research on this topic continues to expand, and progress has been made in publishing multidisciplinary, prospective, longitudinal data sets, along with advanced statistical modelling procedures, as well as in identifying the experiential criteria used by scouts. We found some variables in these studies have predictive value from adolescence to adult performance level in soccer. We present suggestions for future research to enhance knowledge and understanding of the best practices underpinning the identification and development of future generations of professional players.

#5 Brief Cycles of Lower Limb Occlusion Accelerates Recovery Kinetics In Soccer Players
Reference: Phys Sportsmed. 2020 Jun 22. doi: 10.1080/00913847.2020.1785260. Online ahead of print.
Authors: Wael Daab, Mohamed Amine Bouzid, Mehdi Lajri, Mustapha Bouchiba, Haithem Rebai
Summary: The aim of this study was to assess the effect of intermittent vascular occlusion (IVO) on recovery following simulated soccer physical demand test in soccer players. Twelve soccer players completed the Loughborough Intermittent Shuttle Test (LIST) in two conditions placebo (PLA) and IVO followed by intermittent lower limb occlusion. Physical performance (Squat jump: SJ, countermovement jump: CMJ, maximal voluntary contraction: MVC, and 20 meters sprint: SP), muscle damage parameters (creatine kinase: CK, Lactate dehydrogenase: LDH), inflammatory parameter (C-reactive protein: CRP) and perceived muscle soreness (DOMS) were assessed before, immediately after (0h), and 24h, 48h and 72h following the exercise. Following the LIST, a decrease was observed in all Physical performance within 48h in PLA condition (p<0.05),compared to PLA treatment, IVO treatment attenuated the decrease of SJ and CMJ at 24h and at 48hand for MVC and SP within 48h after the LIST (p<0.05). CK and LDH levels increased within 24h post exercise in both conditions (p<0.05), but with a lower level in IVO compared to PLA condition (p<0.05). Likewise, DOMS values were significantly lower with IVO condition compared to PLA condition immediately and at 24hafter exercise. The results of the present study suggest that the application of IVO after simulated soccer physical demand test accelerated recovery kinetics in soccer players.

#6 Femur, Tibia, and Fibula Fractures Secondary to Youth Soccer: A Descriptive Study and Review of the Literature
Reference: Cureus. 2020 May 18;12(5):e8185. doi: 10.7759/cureus.8185.
Authors: Peter Zaki, Sayyar Khakimov, Joseph Hess, William Hennrikus 
Download link:
Summary: Objectives Soccer is the most popular sport in the world and is one of the top sports with increased participation. Despite the vast and increasing numbers of soccer players, limited data are available on pediatric lower extremity injuries. In particular, the purpose of the study is to describe the epidemiology of femur, tibia, and fibula fractures secondary to youth soccer. Methods A retrospective review concerning soccer-related femur, tibia, and fibula fractures was conducted in children under the age of 18 years from January 1, 2000 to December 31, 2015 with statewide data from the Pennsylvania Trauma Systems Foundation (PTSF), Mechanicsburg, PA. Results A total of 258 youth soccer players were admitted for femur, tibia, and fibula fractures from 2000 to 2015. These fractures constituted 33% of soccer-related injuries in youth admitted at trauma centers. Sixty-five percent of the fractures involved the tibia and 34% involved the femur. Body contact injury resulted in 54% of the fractures and non-body contact injury resulted in 46% of the fractures. Athletes the age of 13 and older sustained 67% of the fractures and were more likely to incur contact injuries (p-value=0.000041) than those less than 13. Males sustained 67% of the fractures, and gender was not associated with the mechanism of injury (p-value=0.43). Open fractures included 10% of tibia fractures and did not occur in femur fractures. The growth plate was involved in 24% of the femur fractures and 17% of the tibia fractures. Conclusion Youth soccer has the potential for serious femur, tibia, and fibula fractures. Intervention programs should aim at reducing non-body contact mechanism in children < 13 years of age and body contact mechanism in children ≥ 13 years of age. Further research should investigate injury prevention methods such as potentially reducing body contact mechanism by improving the effectiveness of shin guards.

#7 Tuck jump score is not related to hopping performance or patient-reported outcome measures in female soccer players
Reference: Int J Sports Phys Ther. 2020 May;15(3):395-406.
Authors: Amelia J H Arundale, Joanna Kvist, Martin Hägglund, Anne Fältström
Download link:
Summary: The tuck jump assessment was developed to identify players at risk for anterior cruciate ligament (ACL) injuries or gauge a player's progress through rehabilitation after ACL reconstruction. A tuck jump score of ≥ 6 out of 10 has been labeled poor and thought to identify players with high risk landing patterns. The purpose of this exploratory study was to examine if there was a relationship between tuck jump score, particularly tuck jump scores ≥ 6, hopping performance, and patient-reported outcome measures in female soccer players with ACL reconstruction (ACLR) and knee-healthy controls. Female soccer players (117 after ACLR, 117 knee-healthy) performed the single hop for distance, tuck jump assessment, and drop vertical jump (DVJ). All players were categorized based on as having a total tuck jump score ≥ 6 or < 6. Analyzing all players together, Spearman's rank correlations assessed if there were relationships between total tuck jump score or tuck jump scores ≥ 6 and single-legged hop limb symmetry or DVJ measures. Players with an ACLR also filled out the International Knee Documentation Committee 2000 Subjective Knee Form and the Knee injury Osteoarthritis Outcome Score. Spearman's rank correlations assessed if there were relationships between total tuck jump score or tuck jump scores ≥ 6 and patient-reported outcome measures. The mean tuck jump scores was 4.8 ± 1.8 (tuck jump score ≥ 6, 6.7 ± 0.9, tuck jump score < 6, 3.7 ± 1.1) with 87 (37%) athletes having tuck jump score ≥ 6. There were no significant relationships between tuck jump score or tuck jump score ≥ 6 and hopping performance or patient-reported outcome measures. The results of this current study indicate that tuck jump scores, including tuck jump scores ≥ 6, may not be related to functional or patient-reported outcome measures. Further work is needed to examine the clinical utility of the tuck jump assessment.

#8 Plantar Loading in the Youth Soccer Player During Common Soccer Movements and Risk for Foot Injury
Reference: Injury. 2020 Jun 12;S0020-1383(20)30515-5. doi: 10.1016/j.injury.2020.06.009. Online ahead of print.
Authors: Renato R Azevedo, Suellen B Nery, Darren J Stefanyshyn, Felipe P Carpes
Summary: Soccer players are at high risk of stress injuries in the foot. While most research addresses this issue in professional athletes, there is little information concerning young athletes. As soccer is practiced around the world since early infancy, we set out to determine whether young soccer athletes are susceptible to increased foot loading that increase risk factors for foot injuries in a similar manner as reported by the literature to the adult athlete. Twenty-six male adolescents (mean age 16 years old) were organized into two groups: soccer players (n = 13) and controls (n = 13). Groups were compared regarding foot sensitivity, ankle range of motion, Q-angle, and plantar pressure determined during running and cutting movements performed at maximal speed and using different shoes.  Foot sensitivity, ankle range of motion and Q-angle did not differ between the groups. During performance of soccer actions, young players showed higher peak pressure in the lateral region of the foot including the fifth metatarsal region. These higher peaks were minimized by manipulation of the footwear. In summary, young soccer athletes show dynamic plantar pressure patterns that are related to foot injury in the adult athlete, and this condition can be minimized by the manipulation of the footwear. Additional attention should be paid to the young athlete in soccer aiming to minimize long-term risk for stress injuries in the foot.

#9 Increased Myocardial Mass and Attenuation of Myocardial Strain in Professional Male Soccer Players and Competitive Male Triathletes
Reference: Int J Cardiovasc Imaging. 2020 Jun 20. doi: 10.1007/s10554-020-01918-1. Online ahead of print.
Authors: Jitka Starekova, Tilo Thottakara, Gunnar K Lund, Götz H Welsch, Fabian J Brunner, Kai Muellerleile, Gerhard Adam, Marc Regier, Enver Tahir
Download link:
Summary: The purpose of this prospective study was to analyze the relationship between ventricular morphology and parameters of cardiac function in two different athletic groups and controls, using feature tracking cardiac magnetic resonance (FT-CMR). Twenty-three professional soccer players (22 ± 4 years), 19 competitive triathletes (28 ± 6 years) and 16 controls (26 ± 3 years) were included in the study. CMR was performed using a 1.5 T scanner. Cardiac chamber volumes, mass and biventricular global myocardial strain were obtained and compared. In comparison to the control subjects, athletes were characterized by a higher cardiac volume (p < 0.0001), higher cardiac mass (p < 0.001), reduced longitudinal strain of the left and right ventricle (p < 0.05 and p < 0.01 respectively) and reduced left ventricular radial strain (p < 0.05). Soccer players revealed higher amounts of left ventricular mass (87 ± 15 vs. 75 ± 13 g/m2, p < 0.05) than triathletes. Moreover, they showed a greater decrease in left and right ventricular longitudinal strain (p < 0.05 and p < 0.05) as well as in radial left ventricular strain (p < 0.05) in comparison to triathletes. An increase in left ventricular mass correlated significantly with a decrease in longitudinal (r = 0.47, p < 0.001) and radial (r = - 0.28, p < 0.05) strain. In athletes, attenuation of strain values is associated with cardiac hypertrophy and differ between soccer players and triathletes. Further studies are needed to investigate whether it is an adaptive or maladaptive change of the heart induced by intense athletic training.

#10 Systematic Video Analysis of ACL Injuries in Professional Male Football (Soccer): Injury Mechanisms, Situational Patterns and Biomechanics Study on 134 Consecutive Cases
Reference:  Br J Sports Med. 2020 Jun 19;bjsports-2019-101247. doi: 10.1136/bjsports-2019-101247. Online ahead of print.
Authors: Francesco Della Villa, Matthew Buckthorpe, Alberto Grassi, Alberto Nabiuzzi, Filippo Tosarelli, Stefano Zaffagnini, Stefano Della Villa
Download link:
Summary: A few small studies have reported on the mechanisms of ACL injury in professional male football. The purpose was to describe the mechanisms, situational patterns and biomechanics (kinematics) of ACL injuries in professional male football matches. We identified 148 consecutive ACL injuries across 10 seasons of professional Italian football. 134 (90%) injury videos were analysed for mechanism and situational pattern, while biomechanical analysis was possible in 107 cases. Three independent reviewers evaluated each video. ACL injury epidemiology (month), timing within the match and pitch location at the time of injury were also reported. 59 (44%) injuries were non-contact, 59 (44%) were indirect contact and 16 (12%) were direct contact. Players were frequently perturbed immediately prior to injury. We identified four main situational patterns for players who suffered a non-contact or an indirect contact injury: (1) pressing and tackling (n=55); (2) tackled (n=24); (3) regaining balance after kicking (n=19); and (4) landing from a jump (n=8). Knee valgus loading (n=83, 81%) was the dominant injury pattern across all four of these situational patterns (86%, 86%, 67% and 50%, respectively). 62% of the injuries occurred in the first half of the matches (p<0.01). Injuries peaked at the beginning of the season (September-October) and were also higher at the end of the season (March-May). 88% of ACL injuries occurred without direct knee contact, but indirect contact injuries were as frequent as non-contact injuries, underlying the importance of mechanical perturbation. The most common situational patterns were pressing, being tackled and kicking.

The Training Manager -