Latest research in football - week 31 - 2018

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 Validity of the RSA-RANDOM Test for Young Soccer Players
Reference: Int J Sports Med. 2018 Jul 19. doi: 10.1055/a-0637-2094. [Epub ahead of print]
Authors: Martin V, Sanchez-Sanchez J, Ramírez-Campillo R, Nakamura FY, Gonzalo-Skok O
Summary: The present study aimed to examine the reliability, usefulness, responsiveness, age-related differences and construct validity of a novel decision-making RSA test (RSA-RANDOM test) in young soccer players. Twenty-five young male soccer players performed the RSA-RANDOM test on 2 occasions separated by 5-7 days to assess test-retest reliability and determine a priori usefulness. Furthermore, the same players executed the RSA-RANDOM test 4 times throughout the season to analyse responsiveness. Forty-five players (U-13 to U-17) were evaluated in such test to examine age-related differences. Finally, 9 players were used to determine the construct validity of the test. Reliability scores showed a high intraclass correlation coefficient (ICC=0.88 to 0.90) and low coefficient of variation (CV=1.0-1.2%). The responsiveness of the RSA-RANDOM test was good, as the typical short- (1.2-1.9%), mid- (1.4-2.4%) and long-term (2.3-3.2%) changes in RSA-RANDOM performance were higher than the CV. Age-related differences analysis showed better RSA-RANDOM performance as age increased in young soccer players. Low (r=-0.50) to moderate (r=-0.75) relationships were found between the RSA-RANDOM test variables (RSA best and mean times) with high-intensity and total distance covered, respectively. A novel decision-making RSA test (RSA-RANDOM) has shown to be reliable and valid in young soccer players.

#2 Prior Knowledge of the Grading Criteria Increases Functional Movement Screen Scores in Youth Soccer Players
Reference: J Strength Cond Res. 2018 Jul 17. doi: 10.1519/JSC.0000000000002724. [Epub ahead of print]
Authors: Bryson A, Arthur R, Easton C
Summary: We sought to determine whether familiarity with the grading criteria of the Functional Movement Screen (FMS) impacted the outcome score in elite youth soccer players. Thirty-two trained male youth soccer players (aged 17 ± 1 years) participated in a randomized control trial. Participants were randomly assigned to evenly sized control and experimental groups, who each completed the FMS on 2 separate occasions. Participants in the experimental group were provided the FMS grading criteria between their first and second screens. Time-synchronized video footage was used to grade the FMS using standardized criteria. Structured interviews were then conducted with selected participants (n = 4) in the experimental group to establish athletes' perception of the FMS. The experimental group had a large increase in overall FMS score from the first to the second screen in comparison with the control group (Δ2.0 ± 1.0, p < 0.001, d = 1.3). Scores for the deep squat, hurdle step, and rotary stability tests components of the FMS all increased in the experimental group in comparison with the control group (p < 0.05). Thematic analysis of the interview data suggested that the participants in the experimental group improved their understanding between good and poor technique during the FMS. These findings support the notion that FMS scores are influenced by awareness of the grading criteria. As a consequence, the FMS may not be suitable for objectively predicting injury in youth soccer players.

#3 Articular and peri-articular hip lesions in soccer players. The importance of imaging in deciding which lesions will need surgery and which can be treated conservatively?
Reference: Eur J Radiol. 2018 Aug;105:227-238. doi: 10.1016/j.ejrad.2018.06.012. Epub 2018 Jun 20.
Authors: Di Pietto F, Chianca V, Zappia M, Romano S
Summary: Soccer is one of the most popular sports worldwide engaging millions of participants each year. During play, injuries occur rather frequently and most of them involve the hip joint and the surrounding structure. In professional athletes, injuries are often complex scenarios and in the case of misdiagnosis, patients' return to play is delayed or it may progress to a more serious injury with consequent damage for their career and for the soccer team. The most frequent articular pathologies are Femoro-acetabular impingement and labral tears. Stress fracture, avulsion, ischiofemoral impingement, subspine impingement, athletic pubalgia, muscle injuries and Morel-Levallèe lesion are the most frequent hip peri-articular pathologies whereas snapping hip may be both intra- or extra-articular pathology. With an increasing number of football players, the radiologist plays a crucial role in the detection and characterization of the extent of the injuries. This article reviews the current imaging concepts frequently seen in injuries around the hips of professional football players focusing in particular on the most suitable therapeutic approaches, whether surgical or conservative.

#4 Relative Age Effect, Biological Maturation, and Coaches' Efficacy Expectations in Young Male Soccer Players
Reference: Res Q Exerc Sport. 2018 Jul 17:1-7. doi: 10.1080/02701367.2018.1486003. [Epub ahead of print]
Authors: Peña-González I, Fernández-Fernández J, Moya-Ramón M, Cervelló E
Summary: The talent identification and selection process in young male soccer players is mainly focused on anthropometrics and physical performance, but social factors are also considered in this process. The purpose of this study was to test the existence of the relative age effect and its possible influence on anthropometrics and physical performance and to analyze coaches' efficacy expectations. Data for 564 young male soccer players (Mage = 13.7 ± 1.5 years; Mweight = 53.7 ± 11.6 kg; Mheight = 160.2 ± 11.6 cm) included their birth quartile, maturity status, anthropometrics, a physical test battery, and coaches' efficacy expectations. Early-born players were overrepresented (p < .05). Early-born players were not statistically taller, heavier, or better at physical performance (p > .05) when maturation and chronological age were controlled as confounding factors. However, coaches expected more from early-born players (p < .05), and the inferential analysis showed likely to very likely worthwhile differences between the coaches' expectations for players born in the first quartile of the year and those born in the fourth quartile of the year. Anthropometrical and physical performance variables were not affected by birth quartile, and coaches' efficacy expectations were related to the relative age effect.

#5 Effect of Dehydration on Passing Decision Making in Soccer Athletes
Reference: Res Q Exerc Sport. 2018 Jul 17:1-8. doi: 10.1080/02701367.2018.1488026. [Epub ahead of print]
Authors: Fortes LS, Nascimento-Júnior JRA, Mortatti AL, Lima-Júnior DRAA, Ferreira MEC
Summary: It seems that dehydration may impair decision-making performance in athletes. This study aimed to investigate the influence of dehydration on passing decision-making performance in soccer players. Participants were 40 male soccer players (Mage = 22.3 ± 2.3 years) who agreed to participate in the study and were randomly assigned to the following conditions: control (CON), dehydration (DEH), and euhydration (EUH). The players played in 2 games of 90 min in duration (2 45-min halves) followed by 2 15-min halves (overtime) with and without proper hydration. The Game Performance Assessment Instrument (GPAI) was considered for the analysis of passing decision making. The GPAI analysis indicated effective reduction in the decision-making index in the DEH condition compared with the EUH and CON conditions, F(2, 38) = 31.4, p < .05, ES = 0.8. In conclusion, dehydration may be considered a mediating factor in the passing decision-making performance of male soccer athletes.

#6 Altered landing mechanics are shown by male youth soccer players at different stages of maturation
Reference: Phys Ther Sport. 2018 Jul 7;33:48-53. doi: 10.1016/j.ptsp.2018.07.001. [Epub ahead of print]
Authors: Read PJ, Oliver JL, Myer GD, De Ste Croix MBA, Belshaw A, Lloyd RS
Summary: Examine the effects of maturation on single leg jumping performance in elite male youth soccer players. 347 male youth players classified as either pre, circa or post-peak height velocity (PHV) participated in this study. Single leg countermovement jump (SLCMJ) height, peak vertical landing forces (pVGRF), knee valgus and trunk side flexion were used as outcome measures. Vertical jump height and absolute pVGRF increased with each stage of maturation (p < 0.001; d = 0.85-2.35). Relative to body weight, significantly higher landing forces were recorded on the left leg in circa versus post-PHV players (p < 0.05; d = -0.40). Knee valgus reduced with maturation but the only notable between-group differences were shown in post-PHV players (p < 0.05; d = 0.67); however, greater ipsilateral lateral trunk flexion angles was also present and these differences were significantly increased relative to circa-PHV players (p < 0.05; d = 0.85). Periods of rapid growth are associated with landing kinetics which may heighten injury risk. While reductions in knee valgus were displayed with maturation; a compensatory strategy of greater trunk lateral flexion was evident in post-PHV players and this may increase the risk of injury.

#7 Alternative assessment of knee joint muscle balance of soccer players through total work-based hamstring: quadriceps ratios
Reference: Eur J Sport Sci. 2018 Jul 14:1-7. doi: 10.1080/17461391.2018.1495271. [Epub ahead of print]
Authors: Minozzo F, Lopez P, Machado CLF, Wilhelm EN, Grazioli R, Pinto RS
Summary: Isokinetic hamstring-to-quadriceps (H:Q) ratios are frequently used to assess knee muscle strength imbalances and risk of injuries/re-injuries. The use of peak torque (PT) or total work (TW) to estimate joint stability may lead to different results because of the differences between these two neuromuscular variables. Thus, the current study aimed to compare the conventional and functional H:Q ratios calculated by PT and TW. Ninety-three male professional soccer players from Brazilian first division teams performed isokinetic concentric and eccentric contractions of the quadriceps and the hamstrings at 60°/s. Muscle strength balance was calculated using the conventional torque ratio (CTR) and conventional work ratio (CWR), functional torque ratio (FTR) and functional work ratio (FWR) were highly and moderately correlated between them (r = 0.83 and r = 0.73, respectively). The Wilcoxon statistical test revealed significant differences between CTR and CWR, as well as FTR and FWR (p < 0.05). T-test demonstrated significant differences in mean CTR-CWR and FTR-FWR, whereas Bland-Altman plots showed non-consistent bias. In addition, the chi-square test demonstrated significant differences between players below the conventional reference values and functional reference values (p < 0.001). In conclusion, TW ratios seem to provide distinct and additional information regarding the H:Q strength balance in professional soccer players. Moreover, taking into account that TW captures torque information throughout the entire range of motion, it is possible that TW ratios represent a more comprehensive assessment of muscle strength imbalance.

#8 Injuries in girls' soccer and basketball: a comparison of high schools with and without athletic trainers
Reference: Inj Epidemiol. 2018 Jul 16;5(1):29. doi: 10.1186/s40621-018-0159-6.
Authors: Pierpoint LA, LaBella CR, Collins CL, Fields SK, Dawn Comstock R
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Summary: Sports injuries impose physical and economic burdens on high school athletes, yet only 37% of high schools have access to a fulltime certified athletic trainer (AT). Although intuitively there are multiple benefits of AT coverage, research demonstrating the measurable effect of AT coverage on rates and patterns of injury is limited. Our objective was to investigate the epidemiology of girls' basketball and soccer injuries in high schools with and without an AT. We compared data captured by two similar sports injury surveillance systems during the 2006/07-2008/09 academic years. High School Reporting Information Online (RIO) included a national sample of schools with ATs, and the Sports Injury Surveillance System (SISS) included a sample of Chicago public high schools without ATs. Overall injury rates were higher in schools without ATs than schools with ATs in girls' soccer (RR: 1.73, 95% CI: 1.51-2.00) and basketball (RR: 1.22, 95% CI: 1.03-1.45). Recurrent injury rates were even higher in schools without ATs compared to schools with ATs in soccer (RR: 6.00 95% CI: 4.54-7.91) and basketball (RR: 2.99, 95% CI: 2.12-4.14). Conversely, concussion rates were higher in schools with ATs than schools without ATs in soccer (RR: 8.05, 95% CI: 2.00-32.51) and basketball (RR: 4.50, 95% CI: 1.43-14.16). Other injury patterns were similar between the two samples. This study demonstrated the effectiveness of AT coverage of high school girls' soccer and basketball, both in reducing overall and recurrent injury rates and in identifying athletes with concussions. Future studies should evaluate the effect of ATs on other high school sports and on youth sports to determine if these findings are generalizable across sports and age groups.

#9 Laterality Influences Agility Performance in Elite Soccer Players
Reference: Front Physiol. 2018 Jun 29;9:807. doi: 10.3389/fphys.2018.00807. eCollection 2018.
Authors: Zouhal H, Abderrahman AB, Dupont G, Truptin P, Le Bris R, Le Postec E, Coppalle S, Ravé G, Brughelli M, Bideau B
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Summary: Laterality (i.e., handedness, footedness, and eyedness) could have an impact on highly repeated soccer movements and thus, could influence performance. The purpose of this study was to examine the laterality of high-level football players and its effects on 180° left and right U-turn movements. Handedness, footedness, and eyedness were determined in 72 elite football players (EFP, 18.2 ± 2.2 years) from the Stade Rennais Football Club (French League 1) and 9 amateur football players (AFP, 19.6 ± 2.1 years). Players performed a visual-motor task on a synthetic pitch consisting of 180° left and right rotations as fast as possible in response to a visual light on a computer screen. Movement times and reactive times for each left and right rotation were recorded with an accelerometer and video display. Laterality profiles showed a majority (χ2 = 9.42, df = 2, p = 0.031) of crossed formulas (i.e., dominant leg or hand is controlateral to the dominant eye) for EFP (53 ± 7%) and a majority of non-crossed formulas for AFP (63 ± 9%). Reaction times were significantly faster (p = 0.028, effect size = 0.148, trivial) in EFP right-eyed (568.2 ± 55.5 ms) than in AFP (610.0 ± 43.9 ms). For the left rotation and for right-footed players, movement times were significantly different (p = 0.043, effect size = 0.413, small) between EFP (1.15 ± 0.07 s) and AFP (1.17 ± 0.07 s). A significant difference (p < 0.033) was observed between footedness and rotation movement times in the EFP. Our results showed that laterality profiles differed between EFP and AFP. Hence, in EFP, reaction times depended on the side of the visual stimulus. Moreover, leg laterality of EFP influenced 180° left or right rotation speed. Our results indicate the importance of determining laterality in soccer players and identifying deficits in performance when turning.

#10 Mediating Effects of Parents' Coping Strategies on the Relationship Between Parents' Emotional Intelligence and Sideline Verbal Behaviors in Youth Soccer
Reference: J Sport Exerc Psychol. 2018 Jun 1;40(3):153-162. doi: 10.1123/jsep.2017-0318. Epub 2018 Jul 14.
Authors: Teques P, Calmeiro L, Martins H, Duarte D, Holt NL
Summary: The overall purpose of this study was to examine the mediating effects of parents' coping strategies on the relationship between parents' emotional intelligence and sideline verbal behaviors during their children's soccer games. Participants were 232 parents (120 mothers and 110 fathers) of youth soccer players age 9-13 years. Observations in situ were carried out at 30 soccer games during a soccer tournament. At the end of the game, parents were approached and asked to complete the Emotional Intelligence Scale and the Brief COPE scale. Structural-equation-modeling analyses revealed that adaptive and maladaptive coping mediated the relationship between regulation of emotion and parents' praise/encouragement, and negative and derogatory comments during the game. In addition, game result moderated the relationships between emotional intelligence, coping strategies, and parent behaviors. Emotional regulation and adaptive coping may promote desirable parent sideline behaviors and reduce undesirable behaviors.

#11 Goalkeepers' Reputations Bias Shot Placement in Soccer Penalties
Reference: J Sport Exerc Psychol. 2018 Jun 1;40(3):128-134. doi: 10.1123/jsep.2017-0358. Epub 2018 Jul 14.
Authors: Müller F, Best JF, Cañal-Bruland R
Summary: Research has demonstrated that in addition to minor changes in goalkeepers' position or height, goalkeeper reputation seems to influence penalty takers' shot placement. However, this evidence is based on correlative designs. Here, the authors experimentally manipulated both height and reputation to examine their causal impact on actual shot placement. Penalty takers performed kicks facing goalkeepers of different height (tall vs. short) and reputation (high vs. low) projected on a life-size screen. Results showed that tall goalkeepers were judged as taller than short goalkeepers. Likewise, high-reputation goalkeepers were judged as taller than low-reputation goalkeepers. An important finding was that reputation also influenced shot placement. When facing high-reputation goalkeepers, penalty takers aimed farther away from the goalkeeper and missed the goal more often. It follows that reputation affects both height estimates of goalkeepers and, most important, shot placement. Consequently, manipulating perceived reputation of goalkeepers provides an avenue for sport professionals to subtly influence shot placement of penalty takers.

#12 Physical growth in young Chilean football players: Proposal of percentiles based on chronological and biological age
Reference: Arch Argent Pediatr. 2018 Aug 1;116(4):e508-e514. doi: 10.5546/aap.2018.eng.e508. [Article in English, Spanish; Abstract available in Spanish from the publisher]
Authors: Carrasco López S, Gómez-Campos R, Méndez Cornejo J, Morales L, Urra-Albornoz C, Cossio-Bolañosb M
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Summary: The aim were to a) To compare physical growth to the 2012 American standard from the Centers for Disease Control and Prevention (CDC); b) to analyze physical growth by chronological and biological age; c) to propose physical growth charts based on chronological and biological age. Methodology. A descriptive (cross-sectional) study was conducted in young Chilean football players based on weight, standing height, and sitting height. These were compared to the CDC- 2012 standard. Percentiles were developed using the LMS method. A total of 642 young Chilean football players aged 13.0-18.9 years were studied. Their body weight was lower than that of the CDC standard from 13.0 to 18.9 years old (p < 0.05), whereas their height showed no significant differences in the initial age categories (13.0- 13.9 and 14.0-14.9 years). Differences started to be observed as of 15.0 years old up to 18.9 years old (p < 0.05). In relation to chronological age, weight explained 31%; standing height, 16%; and sitting height, 0.09%, whereas in relation to biological age, weight explained 51%; standing height, 40%; and sitting height, 54%. Percentiles were developed based on chronological and biological age. These youth showed different physical growth patterns compared to the CDC-2012 standard. Their assessment reflects better explanatory percentages for biological age than for chronological age. The proposed percentiles may be an alternative to keep track of the physical growth patterns of young football players in sports settings in the short, medium, and long term.

#13 Mechanisms of acute adductor longus injuries in male football players: a systematic visual video analysis
Reference: Br J Sports Med. 2018 Jul 13. pii: bjsports-2018-099246. doi: 10.1136/bjsports-2018-099246. [Epub ahead of print]
Authors: Serner A, Mosler AB, Tol JL, Bahr R, Weir A
Summary: Change of direction and kicking have been described as the main actions resulting in adductor longus injury. Video descriptions of inciting events are lacking. The purpose was to perform a standardised visual video analysis of a series of acute adductor longus injuries in football. Video footage was reviewed by players, and assessed independently by five sports medicine professionals. Inciting events were described and categorised using standardised scoring, including playing situation, player/opponent behaviour, movement and body positions. Videos of acute adductor longus injuries in 17 professional male football players were analysed. Most injuries occurred in non-contact situations (71%), following a quick reaction to a change in play (53%). Injury actions were: change of direction (35%), kicking (29%), reaching (24%) and jumping (12%). Change of direction and reaching injuries were categorised as closed chain movements (59%), characterised by hip extension and abduction with external rotation. Kicking and jumping injuries were categorised as open chain (41%), characterised by a change from hip extension to hip flexion, and hip abduction to adduction, with external rotation. Acute adductor longus injuries in football occur in a variety of situations. Player actions can be categorised into closed (change of direction and reaching) and open (kicking and jumping) chain movements involving triplanar hip motion. A rapid muscle activation during a rapid muscle lengthening appears to be the fundamental injury mechanism for acute adductor longus injuries.

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