Latest research in football - week 40 - 2015

#1 Technique determinants of knee abduction moments during pivoting in female soccer players
Reference: Clin Biomech (Bristol, Avon). 2015 Sep 25. pii: S0268-0033(15)00253-3. doi: 10.1016/j.clinbiomech.2015.09.012. [Epub ahead of print]
Authors: Jones PA, Herrington LC, Graham-Smith P
Summary: No previous studies have investigated the optimal technique for pivoting with regard to reducing peak knee abduction moments and potential knee injury risk. The aim of this study was to investigate the relationships between technique characteristics and peak knee abduction moments during pivoting. Twenty-seven female soccer players [mean (SD); age: 21 (3.8) years, height: 1.67 (0.07) m, and mass: 60.0 (7.2) kg] participated in the study. Three dimensional motion analyses of pivots on the right leg were performed using 10 Qualysis 'Pro reflex' infrared cameras (240Hz). Ground reaction forces were collected from two AMTI force platforms (1200Hz) embedded into the running track to examine penultimate and final contact. Pearson's correlation coefficients, co-efficients of determination and stepwise multiple regression were used to explore relationships between a range of technique parameters and peak knee abduction moments. Significance was set at P<0.05. Stepwise multiple regression found that initial foot progression and initial knee abduction angles together could explain 35% (30% adjusted) of the variation in peak knee abduction moments (F(2,26)=6.499, P=0.006). The results of the present study suggest that initial-foot progression and knee abduction angles are potential technique factors to lower knee abduction moments during pivoting.


#2 Muscle variables of importance for physiological performance in competitive football
Reference: Eur J Appl Physiol. 2015 Oct 8. [Epub ahead of print]
Authors: Mohr M, Thomassen M, Girard O, Racinais S, Nybo L
Summary: The purpose was to examine how match performance parameters in trained footballers relate to skeletal muscle parameters, sprint ability and intermittent exercise performance. 19 male elite football players completed an experimental game with physical performance determined by video analysis and exercise capacity assessed by intermittent Yo-Yo IR1 and IR2 tests, and a repeated sprint test (RST). Muscle tissue was obtained for analysis of metabolic enzyme maximal activity and key muscle protein expression. Total game distance, distance deficit from first to second half and high-intensity running in the final 15 min of the game were all correlated to the players' Yo-Yo IR1 performance (r = 0.55-0.87) and beta-hydroxyacyl-CoA-dehydrogenase (HAD) maximal activity (r = 0.55-0.65). Furthermore, platelet/endothelial cell adhesion molecule-1 (PECAM1) protein expression was weakly (r = 0.46) correlated to total game distance. Peak 5-min game distance faster than 21 km h-1 was related to the Na+-K+ ATPase subunit (α1, α2, β1 and FXYD1) protein levels (r = 0.54-0.70), while Yo-Yo IR2 performance explained 40 % of the variance in high-intensity game distance. Total and 1-min peak sprint distance correlated to myosin heavy chain II/I ratio (MHCII/I ratio) and sarcoendoplasmic reticulum Ca2+ ATPase isoform-1 (SERCA1) protein (r = 0.56-0.86), while phosphofructokinase (PFK) maximal activity also correlated to total sprint distance (r = 0.46). The findings emphasize the complexity of parameters predicting physical football performance with Yo-Yo IR1 and HAD as the best predictors of total distance, while high expression of Na+-K+ ATPase proteins and the Yo-Yo IR2 test are better predictors of high-intensity performance. Finally, sprint performance relates to skeletal muscle fiber-type composition.


#3 Regular Football Practice Improves Autonomic Cardiac Function in Male Children
Reference: Asian J Sports Med. 2015 Sep;6(3):e24037. doi: 10.5812/asjsm.24037. Epub 2015 Sep 28.
Authors: Fernandes L, Oliveira J, Soares-Miranda L, Rebelo A, Brito J
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4594136/pdf/asjsm-06-24037.pdf
Summary: The role of the autonomic nervous system (ANS) in the cardiovascular regulation is of primal importance. Since it has been associated with adverse conditions such as cardiac arrhythmias, sudden death, sleep disorders, hypertension and obesity. The present study aimed to investigate the impact of recreational football practice on the autonomic cardiac function of male children, as measured by heart rate variability. Forty-seven male children aged 9 - 12 years were selected according to their engagement with football oriented practice outside school context. The children were divided into a football group (FG; n = 22) and a control group (CG; n = 25). The FG had regular football practices, with 2 weekly training sessions and occasional weekend matches. The CG was not engaged with any physical activity other than complementary school-based physical education classes. Data from physical activity, physical fitness, and heart rate variability measured in time and frequency domains were obtained. The anthropometric and body composition characteristics were similar in both groups (P > 0.05). The groups were also similar in time spent daily on moderate-to-vigorous physical activities (FG vs. CG: 114 ± 64 vs. 87 ± 55 minutes; P > 0.05). However, the FG performed better (P < 0.05) in Yo-Yo intermittent endurance test (1394 ± 558 vs. 778 ± 408 m) and 15-m sprint test (3.06 ± 0.17 vs. 3.20 ± 0.23 s). Also, the FG presented enhanced autonomic function. Significant differences were detected (P < 0.05) between groups for low frequency normalized units (38.0 ± 15.2 vs. 47.3 ± 14.2 n.u (normalized units)), high frequency normalized units (62.1 ± 15.2 vs. 52.8 ± 14.2 n.u.), and LF:HF ratio (0.7 ± 0.4 vs. 1.1 ± 0.6 ms(2)). Children engaged with regular football practice presented enhanced physical fitness and autonomic function, by increasing vagal tone at rest.


#4 Comparison of Two Kinds of Endurance Training Programs on the Effects of the Ability to Recover in Amateur Soccer Players
Reference: Asian J Sports Med. 2015 Jun;6(2):e22585. doi: 10.5812/asjsm.6(2)2015.22585. Epub 2015 Jun 20.
Authors: Rogan S
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4592755/pdf/asjsm-06-22585.pdf
Summary: High intensity intermittent aerobic exercise is an elementary endurance training exercise to build soccer endurance. Many studies exist with professional soccer players. But limited research has been conducted with amateur soccer players. The aim of this study was to compare and assess the effects of the shuttle-run method and the Hoff-track method on the ability to recover in amateur soccer players within three weeks. Two amateur soccer teams were randomly assigned to shuttle-run group (n = 24; SRG) (SRG: shuttle-run group) or Hoff-track group (n = 18; HTG) (HTG: hoff-track group). They performed 2 times/week over three weeks their program. SRG performed a 20 m high speed shuttle-run until exhaustion and HTG covered at their highest speed level an obstacle track. Before and after training the yo-yo intermittent recovery test level 2 (YYIRTL2) was conducted. Significant differences were observed within (P < 0.05) and between the groups (P = 0.06; ES = 0.50) in distance covering during YYIRTL2. Both training methods seem to improve the ability to recover in amateur soccer players within a short time period during the competition season.


#5 Distribution of Angiotensin-1 Converting Enzyme Insertion/Deletion and α-Actinin-3 Codon 577 Polymorphisms in Turkish Male Soccer Players
Reference: Genet Epigenet. 2015 Sep 20;7:1-4. doi: 10.4137/GEG.S31479. eCollection 2015.
Authors: Ulucan K, Sercan C, Biyikli T
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4578552/pdf/geg-7-2015-001.pdf
Summary: Angiotensin-1 converting enzyme (ACE) gene and α-actinin-3 (ACTN3) gene polymorphisms are considered to be the most important candidate genes for genetic predisposition to human athletic performance. In the present study, we aimed to analyze the distribution of ACE and ACTN3 polymorphisms for the first time in male Turkish soccer players. In this prospective study, our cohort consisted of 25 professional players, all with Turkish ancestry. Polymerase chain reaction (PCR)-restriction length polymorphism was used for the characterization of the genotype of ACTN3 and single PCR for ACE. For ACE genotype, 16%, 44%, and 40% of the players had insertion/insertion (II), insertion/deletion (ID), and deletion/deletion (DD) genotypes, respectively, whereas 20% had XX, 36% had RX, and 44% had RR genotypes for ACTN3. When we examined the allelic percentages, for ACE, D allele was recorded as 62 and I as 38, and for ACTN3, R allele was 62 and X was 38. Our results were in agreement with the previous reports, indicating the presence of ACTN3 D and ACE X allele in soccer players. We suggest that ACE and ACTN3 genotypes are important biomarkers for genetic counseling for the individuals who are prone to be successful soccer players.


#6 Forearm Skin Blood Flow After Kinesiology Taping in Healthy Soccer Players: An Exploratory Investigation
Reference: J Athl Train. 2015 Oct 7. [Epub ahead of print]
Authors: Woodward KA, Unnithan V, Hopkins ND
Summary: Kinesiology tape (KT) has become popular among athletes for both injury prevention and rehabilitation due to its reported therapeutic effects, including facilitation of lymphatic flow and enhanced peripheral blood flow. However, evidence to support such claims is insufficient. The purpose of the study was to determine whether KT improves skin blood flow (SkBF) responses in young, elite soccer players. Thirteen healthy, elite, adolescent male soccer players (age = 14.7 ± 0.6 years) participated in this study. Participants completed 2 experimental trials; during trial 1, the volar aspect of the dominant forearm was taped. Forearm SkBF was measured within the taped area and 3 cm lateral to the taped area. During trial 2, no tape was applied to either site. Both trials were performed within 7 days. Baseline and maximal thermally (42°C) stimulated SkBF responses were assessed using laser Doppler flowmetry. Continuously measured SkBF and derived mean arterial pressure obtained at 5-minute intervals were used to calculate cutaneous vascular conductance (CVC), the primary outcome measure. No differences were observed for baseline SkBF or CVC between trials or measurement sites. After local heating, no differences were evident for SkBF or CVC between trials or measurement sites. Our findings suggest that, in healthy, trained adolescent males, KT was not associated with increased forearm SkBF.


#7 How the Iranian Football Coaches and Players Know About Doping?
Reference: Asian J Sports Med. 2015 Jun;6(2):e24392. doi: 10.5812/asjsm.6(2)2015.24392. Epub 2015 Jun 20.
Authors: Seif Barghi T, Halabchi F, Dvorak J, Hosseinnejad H
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4592765/pdf/asjsm-06-24392.pdf
Summary: Nowadays, doping is an intricate dilemma. Football is the nationally popular sport in Iran. On the other hand, doping is a serious health hazard sport faces today. Studies dealing with athletes' knowledge, attitudes and behavior concerning doping in football are scarce. Therefore, we aimed to investigate the knowledge and attitudes toward doping among the football coaches and players. In a cross sectional study, 375 participants (239 football players and 136 coaches) were studied. A specially made questionnaire was applied. In this study, football teams of different provinces of the country were selected by randomized clustered sampling and questionnaires were distributed among coaches and players. Knowledge of football coaches and players in three categories of doping definitions, recognition of prohibited drugs and side effects of anabolic steroids was poor or moderate in 45.3%, 88.5% and 96.5%, respectively. Football players and coaches have poor knowledge about doping in Iran. Moreover, they believe in some inappropriate myths without any scientific or rational basis.It seems necessary to design a comprehensive educational program for all of the athletes and coaches in Iran.