Latest research in football - week 27 - 2019

#1 The complex and bidirectional interaction between sex hormones and exercise performance in team sports with emphasis on soccer
Reference: Hormones (Athens). 2019 Jun 29. doi: 10.1007/s42000-019-00115-7. [Epub ahead of print]
Authors: Koundourakis NE, Margioris AN
Summary: A constant topic reported in the lay press is the effect of sex hormones on athletic performance and their abuse by athletes in their effort to enhance their performance or to either boost or sidestep their hard, protracted, and demanding training regimens. However, an issue that it is almost never mentioned is that the athletic training itself affects the endogenous production of androgens and estrogens, while also being affected by them. Among sports, soccer is a particularly demanding activity, soccer players needing to possess high levels of endurance, strength, and both aerobic and anaerobic capacity, with the very great physiological, metabolic, physical, and psychological exertion required of the players being both influenced by sex steroids and, reciprocally, affecting sex steroid levels. This review focuses on the currently available knowledge regarding the complex relationship between athletic training and competition and sex steroid hormone adaptation to the demands of the exercise effort. In the first part of the review, we will examine the effects of endogenous testosterone, estrogen, and adrenal androgens on athletic performance both during training and in competition. In the second part, we will explore the reciprocal effects of exercise on the endogenous sex hormones while briefly discussing the recent data on anabolic androgenic steroid abuse


#2 Isokinetic strength differences between elite senior and youth female soccer players identifies training requirements
Reference: Phys Ther Sport. 2019 Jun 21;39:45-51. doi: 10.1016/j.ptsp.2019.06.008. [Epub ahead of print]
Authors: Eustace SJ, Page RM, Greig M
Summary: The aim was to compare traditional and angle-specific isokinetic strength of eccentric knee flexors and concentric knee extensors in female senior professional and youth soccer players. A total of 34 players (17 seniors [age 25.31 ± 4.51 years; height 167.89 ± 7.04 cm; mass 63.12 ± 7.79 kg] and 17 youths [16.91 ± 1.16 years; height 165.92 ± 4.42 cm; mass 60.07 ± 4.48 kg]) from the Women's Super League 1 completed strength assessments at 180, 270 and 60°∙s-1 participated in this study.  Peak torque (PT), dynamic control ratio (DCR), angle of peak torque (APT), functional range (FR), angle-specific torque (AST) and angle-specific DCR (DCRAST) were compared between age groups. The PT (P = 0.016) AST (P = 0.041) were significantly higher in seniors compared to youths; however APT (P = 0.141), DCR (P = 0.524) FR (P = 0.821) and DCRAST (P = 0.053) were not significant between playing age. The use of absolute and angle-specific strength measures were able to distinguish between female playing ages, whereas DCR and DCRAST was unable to identify differences. The PT and AST metrics may be the most useful metrics to help identify and inform training needs, particularly in youths.


#3 Offensive Transitions in High-Performance Football: Differences Between UEFA Euro 2008 and UEFA Euro 2016
Reference: Front Psychol. 2019 Jun 18;10:1230. doi: 10.3389/fpsyg.2019.01230. eCollection 2019.
Authors: Maneiro R, Casal CA, Álvarez I, Moral JE, López S, Ardá A, Losada JL
Summary: Coaches, footballers and researchers agree that offensive transitions are one of the most important moments in football today. In a sport where defense over attack dominates, with low scores on the scoreboard, the importance of these actions from the offensive point of view becomes very important. Despite this, scientific literature is still very limited on this topic. Therefore, the objectives set out in the present investigation have been two: first, by means of a proportion analysis and the application of a chi-square test, it was intended to describe the possible differences between the offensive transitions made in the UEFA Euro 2008 and UEFA Euro 2016; then, through different multivariate analyzes based on logistic regression models, it was intended to know the possible differences among the proposed models. Using observational methodology as a methodological filter, 1,533 offensive transitions corresponding to the observation of the quarter final, semifinal, and final quarter of UEFA Euro 2008 and UEFA Euro 2016 have been analyzed. The results obtained have shown that offensive transitions between both championships have changed throughout both UEFA Euro, as well as some of the variables or behaviors associated with them (p < 0.05). The predictive models considered, although they have been developed from the same predictor variables, have also yielded different results for both championships, evidencing predictive differences among themselves. These results allow to corroborate that the offensive phase in high level football, specifically in what refers to moments of transition defense-attack, have evolved over these 8 years. At the applied level, the results of this research allow coaches to have current and contemporary information on these actions, potentially allowing them to improve their offensive performance during competition.


#4 Association Between Match Activity, Endurance Levels and Maturity in Youth Football Players
Reference: Int J Sports Med. 2019 Jul 4. doi: 10.1055/a-0938-5431. [Epub ahead of print]
Authors: Francini L, Rampinini E, Bosio A, Connolly D, Carlomagno D, Castagna C
Summary: The aim of the study was to examine the associations between maximal and submaximal field tests with match physical activity and biological maturation in youth football players. Sixty-eight youth football players (U14, U15, U16, U17) performed maximal and submaximal field endurance tests. Biological maturity was estimated calculating the distance from peak height velocity (Y-PHV). Physical match activities were tracked using GPS units and players' post-match rate of perceived exertion (RPE) was recorded. Mainly moderate associations were found between field tests and match activities. Large correlations were found between Yo-Yo Intermittent Recovery test level 1, distance covered at high and very high-speed running, the quantity of very high and maximal metabolic power running. Small to moderate associations between match activities and Y-PHV were observed. The magnitude of correlation between match activities and field tests increased from moderate to large when matches with an RPE>5 were considered. The results provide further evidence of the association between young football players' aerobic performance and match work rate. Submaximal field tests demonstrate ecological validity and may constitute a practical alternative to performing maximal tests. Maturation was found to have a moderate effect on youth players' match work rate.


#5 Postprandial lipaemia 10 and 34 hours after playing football: Does playing frequency affect the response?
Reference: PLoS One. 2019 Jul 2;14(7):e0218043. doi: 10.1371/journal.pone.0218043. eCollection 2019.
Authors: Paul DJ, Nassis GP, Kerouani AC, Bangsbo J
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0218043&type=printable
Summary: Elevated postprandial triglyceride (TG) is associated with increased risk of cardiovascular disease. The time window for the last bout beneficial effect on postprandial lipaemia after football play is unknown. The aim of the present study was to examine whether playing affects postprandial TG during 1.5 day of reduced activity. Eighteen males were randomly allocated to perform either 1 (1FOOT; n = 9; age = 33.0 ± 5.0 yrs; body mass index = 24.2 ± 3.6 kg/m2) or 3 (3FOOT) consecutive days of 60-min 5 vs 5 football (n = 9; age = 32.8 ± 5.2 yrs; body mass index = 26.2 ± 4.1 kg/m2) matches across a 5-day study period. They arrived to the laboratory 10 hrs and 34 hrs after the final football session and blood samples were collected at fasted (0 min) and 45, 90, 240 and 360 min post a high fat load meal. There were non significant increase for postprandial TG AUC (9.1%; p = 0.17; 95%CI = -0.43 to 2.0; ES = -0.23) and iAUC (14.2%; p = 0.43; 95%CI = -0.92 to 1.9; ES = -0.24) between 10 and 34 hrs after the 1FOOT. For the 3FOOT, there was a non significant decrease in postprandial TG AUC (-2.7%; p = 0.73; 95%CI = -2.0 to 1.5; ES = 0.05) and iAUC (-17.5%; p = 0.41; 95%ci = -2.5 to 1.1; ES = 0.31) from 10 to 34 hrs, respectively. Performing three consecutive days of football exercise may offer no greater protective effect for postprandial TG before a period of reduced activity, compared to a single session.


#6 The role of a trauma-sensitive football group in the recovery of survivors of torture
Reference: Torture. 2019;29(1):97-109. doi: 10.7146/torture.v29i1.106613.
Authors: Horn R, Ewart-Biggs R, Hudson F, Berilgen S, Ironside J, Prodromou A
Summary: Whilst there is some preliminary evidence for the benefits of sports-related interventions for survivors of torture, how sport and exercise can contribute to the rehabilitation of torture survivors needs to be better understood. Specifically, this paper aims to: 1) explore the ways in which a football group contributed to the wellbeing of participants and; 2) suggest characteristics of the football group which could potentially contribute to its effectiveness. An exploratory mixed methods study was undertaken with participants and trainers of a joint programme delivered by Arsenal Football Club and Freedom from Torture in London. Individual discussions, group discussions and participatory ranking activities were used which led to the development of an initial programme model. This model was, subsequently, further developed through a variety of data collection methods. Six potential outcomes of involvement in the football group were identified: relationships, a sense of belonging, hope for the future, emotion management, enjoyment, and improved physical health. In addition, the process highlighted factors contributing to the effectiveness of the football group: a sense of safety, therapeutic aims, similar participants, a partnership approach, staff characteristics, other opportunities, and consistency in terms of approach, session content and staff. This exploratory study outlines the potential benefits of the football programme that would require further validation through a case-control study and participant follow-up. A model is put forward as well as a number of recommendations that serve as a starting point for similar programmes and guides academic research in the area.


#7 On-field Rehabilitation Part 2: A 5-Stage Program for the Soccer Player Focused on Linear Movements, Multidirectional Movements, Soccer-Specific Skills, Soccer-Specific Movements, and Modified Practice
Reference: J Orthop Sports Phys Ther. 2019 Jul 10:1-6. doi: 10.2519/jospt.2019.8952. [Epub ahead of print]
Authors: Buckthorpe M, Della Villa F, Della Villa S, Roi GS
Summary: This paper is part 2 of a 2-part series aimed at discussing the key elements of on-field rehabilitation training. In part 1, we described 4 pillars underpinning high-quality on-field rehabilitation: (1) restoring movement quality, (2) physical conditioning, (3) restoring sport-specific skills, and (4) progressively developing chronic training load. In part 2, we describe how the pillars contribute to a 5-stage on-field rehabilitation program to help injured players transition to team practice and match play. We use the example of a soccer player with ambitions to return to sport after anterior cruciate ligament reconstruction. The program moves through 5 field-based training stages: (1) linear movement, (2) multidirectional movement, (3) soccer-specific technical skills, (4) soccer-specific movement, and (5) practice simulation. The staged program is research based and facilitates communication, planning, control, and safety in return to sport following long-term injury.


#8 Anthropometric Profile of Soccer Players as a Determinant of Position Specificity and Methodological Issues of Body Composition Estimation
Reference: Int J Environ Res Public Health. 2019 Jul 5;16(13). pii: E2386. doi: 10.3390/ijerph16132386.
Authors: Leão C, Camões M, Clemente FM, Nikolaidis PT, Lima R, Bezerra P, Rosemann T, Knechtle B
Download link: https://www.mdpi.com/1660-4601/16/13/2386/pdf
Summary: The aim of the present study was (a) to describe the anthropometric profile of a large group of soccer players based on different age groups and their playing positions on the field, and (b) to examine the variations of body composition among adult soccer players using diverse equations based on skinfold thickness. A total of 618 Greek soccer players who were grouped by age (i.e., 12-14, 14-16, 16-18, and 18-37 years) and playing position (i.e., goalkeeper, defender, midfielder, and forward) were evaluated for weight, height, and skinfolds. The Pařízková formula was used to estimate the percentage of body fat. Furthermore, for players who were 18 years or older the Reilly and Evans formulas was used to estimate the percentage of body fat. Independent of the age, in this large sample, goalkeepers presented higher values for weight, height and the percentage of body fat estimation as compared with other field positions. An anthropometric pattern was observed in each tactical position, namely, across a specific age of increasing maturation process (14-16 years). With the Pařízková formula, we found a mean (SD) range of variation in the percentage of body fat estimation between 4.87 ± 1.46 and 5.51 ± 1.46 as compared with the Evans formula. The same pattern of differences was found when the Reilly equation was considered. In conclusion, we observed a position specificity of anthropometric characteristics across different age categories. Additionally, the same data supported different validated equations which resulted in large differences in the final outcome estimations.


#9 Effect of a mindfulness programme training to prevent the sport injury and improve the performance of semi-professional soccer players
Reference: Australas Psychiatry. 2019 Jul 8:1039856219859288. doi: 10.1177/1039856219859288. [Epub ahead of print]
Authors: Zadeh MM, Ajilchi B, Salman Z, Kisely S
Summary: Mindfulness improves psychological outcomes. We examined whether greater mindfulness scores were associated with reduced injury rates in soccer players, as well as improved performance at both the individual and team level. This was a parallel-group, pre- and post-test, randomised controlled pilot trial. Forty-five male amateur soccer players from Tehran, Iran, were randomly assigned into experimental (n=23) and control groups (n=22). Outcomes were scores on the mindfulness sport inventory, as well as injury rates and recovery as assessed by a physiotherapist using standardised criteria. Expert observers assessed the effect on individual and team performance. Data were analysed using mixed analysis of variance and, where indicated, its non-parametric alternative, the Friedman test. Significantly greater mindfulness scores in the intervention group were associated with both reduced injury and improved performance. Mindfulness training shows promise in preventing injury and improving performance. The intervention could be applied to other sports and be helpful in clinical settings given the importance of exercise in promoting psychological well-being.


#10 Accuracy of the 2017 international recommendations for clinicians who interpret adolescent athletes' ECGs: a cohort study of 11 168 British white and black soccer players
Reference: Br J Sports Med. 2019 Jul 5. pii: bjsports-2017-098528. doi: 10.1136/bjsports-2017-098528. [Epub ahead of print]
Authors: Malhotra A, Dhutia H, Yeo TJ, Finocchiaro G, Gati S, Bulleros P, Fanton Z, Papatheodorou E, Miles C, Keteepe-Arachi T, Basu J, Parry-Williams G, Prakash K, Gray B, D'Silva A, Ensam B, Behr E, Tome M, Papadakis M, Sharma S.
Summary: The aim was to investigate the accuracy of the recently published international recommendations for ECG interpretation in young athletes in a large cohort of white and black adolescent soccer players. 11 168 soccer players (mean age 16.4±1.2 years) were evaluated with a health questionnaire, ECG and echocardiogram; 10 581 (95%) of the players were male and 10 163 (91%) were white. ECGs were retrospectively analysed according to (1) the 2010 European Society of Cardiology (ESC) recommendations, (2) Seattle criteria, (3) refined criteria and (4) the international recommendations for ECG interpretation in young athletes. The ESC recommendations resulted in a higher number of abnormal ECGs compared with the Seattle, refined and international criteria (13.2%, 4.3%, 2.9% and 1.8%, respectively). All four criteria were associated with a higher prevalence of abnormal ECGs in black athletes compared with white athletes (ESC: 16.2% vs 12.9%; Seattle: 5.9% vs 4.2%; refined: 3.8% vs 2.8%; international 3.6% vs 1.6%; p<0.001 each). Compared with ESC recommendations, the Seattle, refined and international criteria identified a lower number of abnormal ECGs-by 67%, 78% and 86%, respectively. All four criteria identified 36 (86%) of 42 athletes with serious cardiac pathology. Compared with ESC recommendations, the Seattle criteria improved specificity from 87% to 96% in white athletes and 84% to 94% in black athletes. The international recommendations demonstrated the highest specificity for white (99%) and black (97%) athletes and a sensitivity of 86%. The 2017 international recommendations for ECG interpretation in young athletes can be applied to adolescent athletes to detect serious cardiac disease. These recommendations perform more effectively than previous ECG criteria in both white and black adolescent soccer players.


#11 Classification of Soccer and Basketball Players' Jumping Performance Characteristics: A Logistic Regression Approach
Reference: Sports (Basel). 2019 Jul 4;7(7). pii: E163. doi: 10.3390/sports7070163.
Authors: Chalitsios C, Nikodelis T, Panoutsakopoulos V, Chassanidis C, Kollias I
Summary: This study aimed to examine countermovement jump (CMJ) kinetic data using logistic regression, in order to distinguish sports-related mechanical profiles. Eighty-one professional basketball and soccer athletes participated, each performing three CMJs on a force platform. Inferential parametric and nonparametric statistics were performed to explore group differences. Binary logistic regression was used to model the response variable (soccer or not soccer). Statistical significance (p < 0.05) was reached for differences between groups in maximum braking rate of force development (RFDDmax, U79 = 1035), mean braking rate of force development (RFDDavg, U79 = 1038), propulsive impulse (IMPU, t79 = 2.375), minimum value of vertical displacement for center of mass (SBCMmin, t79 = 3.135), and time difference (% of impulse time; ΔΤ) between the peak value of maximum force value (FUmax) and SBCMmin (U79 = 1188). Logistic regression showed that RFDDavg, impulse during the downward phase (IMPD), IMPU, and ΔΤ were all significant predictors. The model showed that soccer group membership could be strongly related to IMPU, with the odds ratio being 6.48 times higher from the basketball group, whereas RFDDavg, IMPD, and ΔΤ were related to basketball group. The results imply that soccer players execute CMJ differently compared to basketball players, exhibiting increased countermovement depth and impulse generation during the propulsive phase.


#12 Bio-banding in Academy Football: Player's Perceptions of a Maturity Matched Tournament
Reference: Ann Hum Biol. 2019 Jul 10:1-28. doi: 10.1080/03014460.2019.1640284. [Epub ahead of print]
Authors: Bradley B, Johnson D, Hill M, McGee D, Kana-Ah A, Sharpin C, Sharp P, Kelly A, Cumming SP, Malina RM
Summary: Individual differences in biological maturation impact player selection and development in youth football. The aim was to evaluate players perceptions of competing in a football tournament where they were matched by maturity rather than chronological age. Participants included male junior footballers from three professional academies (N = 115). The study employed multiple methods of analysis, including one sample means t-tests, equivalence tests, ANOVAs, and thematic analysis of qualitative data derived from open-ended questions. Player's perceived the bio-banding format as providing two main benefits. Early maturing players perceived greater physical and technical challenge, and in turn new opportunities and challenges. Late maturing players perceived less physical and technical challenge, yet greater opportunity to demonstrate technical and tactical abilities. The players reported that they enjoyed and understood the purpose of the bio-banded format, and perceived less risk for injury. Players in all three maturity groups reported more opportunity to engage in leadership behaviours, influence game-play, and express themselves on the ball in the bio-banded format. Bio-banding may facilitate development for both early and late maturing academy players by presenting new learning environments and challenges.


#13 The association between the isokinetic muscle strength and lower extremity injuries in young male football players
Reference: Phys Ther Sport. 2019 Jun 29;39:76-81. doi: 10.1016/j.ptsp.2019.06.013. [Epub ahead of print]
Authors: Namazi P, Zarei M, Hovanloo F, Abbasi H
Summary: Validating any screening test to predict and prevent football injuries is in need of identifying related risk factors through prospective designs. In spite of the extensive use of strength testing in football players, there are limited studies investigating the relationship between isokinetic muscle strength and injury risk in young football players. The present study aimed to evaluate the relationship between isokinetic strength and the risk of lower extremity injury among Iranian young football players. Seventy three U-21 football players participated in this study. Isokinetic strength of hip, knee and ankle muscles were measured using the Isokinetic system pro 4. Injuries and exposure in training and matches were registered prospectively by club medical staff for one season. Significant relationships were revealed between the isokinetic strength of hip abductor and adductor muscles, and isokinetic strength ratio of hip abductor/adductor muscles at an angular speed of 30°/sec, the isokinetic strength of hip abductor muscles at 90°/sec, and isokinetic strength of knee flexor and extensor muscles at 60°/sec and knee flexor/extensor strength ratio at angular velocities of 60°/sec with the injury occurrence among football players. Lower extremity isokinetic strength indices are associated with injuries in young male football players.


#14 A Lethal Blow to the Chest as an Underdiagnosed Cause of Sudden Death in United Kingdom Sports (Football, Cricket, Rugby)
Reference: Am J Cardiol. 2019 Jun 7. pii: S0002-9149(19)30629-0. doi: 10.1016/j.amjcard.2019.05.050. [Epub ahead of print]
Authors: Cooper S, Woodford NW, Maron BJ, Harris KM, Sheppard MN
Summary: Nonpenetrating blunt force trauma to the front of the chest can lead to commotio cordis, a cardiac rhythm disturbance, which can result in cardiac arrest and death. The condition is particularly noted during sport. No series of such cases has been published in the UK. This study is a retrospective analysis of a database of 6000 cases of sudden cardiac death examining commotio cordis in the setting of collapse and death shortly following a blow to the precordium where no structural heart disease was identified at autopsy. Of the 17 cases, 16 were male, and 11 were 18 years old or younger. Eleven occurred whilst playing sport while 6 involved physical interaction including assault. The most common circumstance of death involved a youth being struck in the chest by a ball during sporting activity. In conclusion, this study demonstrates that cases of commotio cordis in the UK follow a similar circumstantial and age profile to those reported in the United States, and indicates that ball sports such as football, cricket, and rugby expose young participants to a similar risk. There is currently no nation-wide registry of deaths occurring during sporting activity in the UK, and although the true incidence of this condition is not currently known, it is most probably under-recognised and underdiagnosed.