Latest research in football - week 9 - 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 Vertical and Horizontal Asymmetries are Related to Slower Sprinting and Jump Performance in Elite Youth Female Soccer Players
Reference: J Strength Cond Res. 2018 Feb 27. doi: 10.1519/JSC.0000000000002544. [Epub ahead of print]
Authors: Bishop C, Read P, McCubbine J, Turner A
Summary: Inter-limb asymmetries have been shown to be greater during vertical jumping compared to horizontal jumping. Notable inter-limb differences have also been established at an early age in male youth soccer players. Furthermore, given the multi-planar nature of soccer, establishing between-limb differences from multiple jump tests is warranted. At present, a paucity of data exists regarding asymmetries in youth female soccer players and their effects on physical performance. The aims of this study were to quantify inter-limb asymmetries from unilateral jump tests and examine their effects on speed and jump performance. Nineteen elite youth female soccer players performed a single leg countermovement jump (SLCMJ), single, triple, and crossover hops for distance and a 20 m sprint test. Test reliability was good to excellent (ICC = 0.81-0.99) and variability acceptable (CV = 1.74-5.42%). A one-way ANOVA highlighted larger asymmetries from the SLCMJ compared to all other jump tests (p < 0.05). Pearson's correlations portrayed significant relationships between vertical asymmetries from the SLCMJ and slower sprint times (r = 0.49-0.59). Significant negative relationships were also found between horizontal asymmetries during the triple hop test and horizontal jump performance (r = -0.47 to -0.58) and vertical asymmetries during the SLCMJ and vertical jump performance (r = -0.47 to -0.53). The results from this study highlight that the SLCMJ appears to be the most appropriate jump test for identifying between-limb differences with values ∼12% showing negative associations with sprint times. Furthermore, larger asymmetries are associated with reduced jump performance and would appear to be direction-specific. Practitioners can use this information as normative data to be mindful of when quantifying inter-limb asymmetries and assessing their potential impact on physical performance in youth female soccer players.

#2 Oxidative stress biomarkers after a single maximal test in blind and non-blind soccer players
Reference: J Sports Med Phys Fitness. 2018 Mar 1. doi: 10.23736/S0022-4707.18.08030-1. [Epub ahead of print]
Authors: Viana Gomes D, Santos Vigario P, Lima Piazera BK, Pereira Costa F, Vaisman M, Salerno Pinto V
Summary: Compare oxidative stress biomarkers, antioxidant capacity, muscle damage and hormone response between vision impaired and non-vision impaired athletes after a single maximal exercise test. Eight vision impaired and fifteen non-vision impaired athletes performed a maximal aerobic test with blood collected before and after. Non-vision impaired athletes displayed greater aerobic capacity than blind individuals (p<0.05). Lactate increased by four-fold, while CK and GGT as well as the oxidative stress biomarkers and antioxidants were unchanged. Cortisol increased, but testosterone and their ratio were not altered. Differences were observed for ALT and AST, which were increased only in non-blind athletes. Our data suggest that blind soccer players, in comparison to those with vision, experienced less cellular damage.

#3 The effect of acute match play loading on hip adductor strength & flexibility in soccer players
Reference: J Sports Med Phys Fitness. 2018 Mar 1. doi: 10.23736/S0022-4707.18.08194-X. [Epub ahead of print]
Author: Light N
Summary: Deficits in adductor strength and flexibility are known risk factors for soccer hip/groin injury, yet little is known about the acute effects of soccer match play on these physical features. The aim of this study therefore was to examine the changes in adductor strength and flexibility before; during and immediately after soccer match play. Design: Twenty, male university soccer players (age = 22.35 ± 1.98 years) participated in this field-based, within subject, repeated measures study. Each participant performed three adductor squeeze tests at both 0° and 45° hip flexed test positions alongside a bent knee fall out test. Adductor squeeze scores were quantified using pressure sphygmomanometer and BKFO values recorded in centimetres. Each test was performed before (0 mins) half time (45 mins) and at full time (90 mins) of a competitive match. Adductor strength decreased by 17.7% in 0° test position and 19.1% in 45° test position at 90 minutes of soccer play, whilst BKFO scores increased by 15% indicating a reduction in adductor flexibility. Statistical analysis showed significant effects of time Vs adductor strength and squeeze test position (P=<0.005), Positive correlations between time played and BKFO scores, and BKFO scores vs adductor squeeze scores at 0 and 45 minutes (P=<0.005) were also observed. University soccer players exhibit decreased adductor squeeze test and BKFO values as soccer match duration increases. These findings may have implications hip/groin injury management and recovery strategies, post or during soccer matches.

#4 Subungual Exostosis in a Young Soccer Player
Reference: Open Access Maced J Med Sci. 2017 Dec 30;6(1):52-54. doi: 10.3889/oamjms.2018.002. eCollection 2018 Jan 25.
Authors: Tchernev G, Grigorov Y, Philipov S, Chokoeva A, Wollina U, Lotti T, Cardoso J, Yungareva I, Lozev I, Maximov GK
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Summary: Subungual exostosis is a relatively uncommon, benign osteocartilaginous tumor of the distal phalanx of the toes or fingers in young adults, considered as a rare variant of osteochondroma. Differential diagnoses include subungual verruca (viral wart), pyogenic granuloma, osteochondroma, amelanotic subungual melanoma and glomus tumour. Misdiagnosis and total onychodystrophy frequently occur as a result of late treatment or inadequate treatment strategy. Dermoscopy could be a useful technique, involved in the diagnostic process, although X-ray examination and histopathology are mandatory for the diagnosis. We report a rare case of subungual exostosis of the great toe associated with repeated trauma of the nail bed. The lack of radiographic and histopathological examination could lead to misdiagnosis and inadequate treatment. Although completely benign, subungual exostosis should be considered in differential diagnosis of nail bed tumors in young adults, in order to avoid associated complications and unneeded aggressive surgical interventions. Complete excision of the lesion and delicate separation from the underlying nail bed structures results in total resolve of the problem, by providing the lowest risk of recurrences.

#5 Acute lateral ankle sprain prediction in collegiate women’s soccer players
Reference: Int J Sports Phys Ther. 2018 Feb;13(1):12-18.
Authors: McCann RS, Kosik KB, Terada M, Beard MQ, Buskirk GE, Gribble PA
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Summary: Women's soccer has among the highest injury rates in collegiate sports, and lateral ankle sprains (LAS) are among the most commonly occurring injuries in that athletic population. However, no established LAS prediction model exists for collegiate women's soccer players.The purpose of this study was to develop a prediction model for acute LAS injuries in collegiate women's soccer players utilizing previous ankle sprain history, height, mass, and BMI as potential predictors.The authors' hypothesized that collegiate women's soccer players with greater height, mass, and body mass index (BMI), as well as a previous history of ankle sprain would have greater odds of sustaining a LAS.  Forty-three NCAA Division I women's soccer players' (19.7 ± 1.1yrs, 166.8 ± 3.7cm, 60.8 ± 4.4kg) height, mass, and BMI were measured one week before beginning preseason practices. Additionally, participants reported whether or not they had sustained a previous ankle sprain. The team athletic trainer tracked LASs over the competitive season. Independent t-tests, binary logistic regression analyses, receiver operating characteristic (ROC) curves, and diagnostic statistics assessed the ability of the variables to differentiate between those that did and did not sustain a LAS. Participants that sustained a LAS (n = 8) were significantly taller than those that did not sustain a LAS (n = 35) (t41 = -2.87, p = 0.01, d = 0.83[0.03,1.60]). A logistic regression analysis (odds ratio=1.30[1.00,1.70]) and area under the ROC curve analysis (AUROC=0.73[0.58,0.89], p=0.04) further exhibited predictive value of height. A height cutoff score of 167.6cm demonstrated excellent sensitivity (0.88), moderate specificity (0.51), and a favorable diagnostic odds ratio (7.5). A logistic regression analysis (odds ratio=1.87[1.22,1.98]) exhibited predictive value of previous ankle sprain history. That variable was also associated with good sensitivity (0.75) and specificity (0.71) within the model, as well as a favorable DOR (7.37). Mass and BMI demonstrated no predictive value for LAS. Taller collegiate women's soccer players and those with previous ankle sprain history may have a greater predisposition to LAS.

#6 Characteristics of goalkeepers' injuries: retrospective, self-reported study among adolescence football players
Reference: J Sports Med Phys Fitness. 2018 Feb 26. doi: 10.23736/S0022-4707.18.07849-0. [Epub ahead of print]
Authors: Blazkiewicz A, Grygorowicz M, Bialostocki A, Czaprowski D
Summary: Characteristic types of actions and training/matches loads of football goalkeepers show that goalkeeper's performance differs from other football's formations. Such situation may predispose to the occurrence of other kinds of injuries in this position. The aim of this study was to analyse epidemiology of injuries in young football goalkeepers. 48 football goalkeepers (aged:15.2±1.9 years) were filled the questionnaire aimed at collecting information about all injuries sustained within 12 months before the data collection. The anthropometric data, football experience and information regarding the injury types and occurrence were analysed. The injury rate proportion for acute and overuse injuries and values of injuries including the burden of the match game and training were evaluated. The level of significance was set at p<0.05. 33(68.8%) questionnaires were given back. 24(72.7%) goalkeepers reported the history of football related injury within a year before the survey. 52 injuries were reported. Significantly higher number of acute (76.9%) vs. overuse (23.1%) injuries was described (p=0.0012). Acute injuries involved fractures/subluxations of the fingers and thigh muscle strain/tears. The group of overuse injuries was dominated by trauma of the knee and pelvic girdle muscles. Majority of injuries occurred during training (88,5% of all injuries), and there was significant higher number of injuries sustained on artificial vs. natural grass for all, acute and overuse types of injuries (p<0,0001). Young football goalkeepers suffer mostly acute injuries (within the fingers of hands and muscles of thighs). It might be associated with specific characteristic of performance related to goalkeeper`s position.

#7 The elite player performance plan: the impact of a new national youth development strategy on injury characteristics in a premier league football academy
Reference: J Sports Sci. 2018 Feb 24:1-8. doi: 10.1080/02640414.2018.1443746. [Epub ahead of print]
Authors: Tears C, Chesterton P, Wijnbergen M
Summary: The objective of this study was to investigate the injury incidence and patterns in elite youth football at a category 1 Premier League Academy before and after the introduction of a new development strategy, the Elite Player Performance Plan (EPPP). A prospective study was performed over six consecutive seasons encompassing three years before and after the introduction of the EPPP. The findings revealed a most likely moderate increase in total exposure per player per season when the post-EPPP football exposure (640.86 ± 83.25 hours per player per year) was compared with the pre-EPPP football exposure (539.08 ± 71.59). The total injury incidence pre-EPPP was 3.0/1000 hours compared to 2.1/1000 hours post-EPPP (rate ratio 1.43). 6% of all injuries were re-injuries (20.24 ± 33.43 days) but did not result in a substantially longer absence (16.56 ± 15.77 days). The injury burden decreased for the U12-U15 from pre- to post-EPPP, whereas the injury burden increased for the U16-U18 (respectively 125 and 47% higher). These findings suggest that following the introduction of the EPPP there has been a reduction in injuries in the younger age groups U12-U15 but in the older age groups U16-U18 there has been an increase in the severity of the injuries sustained at this club.

#8 The influence of joint rigidity on impact efficiency and ball velocity in football kicking
Reference: J Biomech. 2018 Feb 20. pii: S0021-9290(18)30112-X. doi: 10.1016/j.jbiomech.2018.02.015. [Epub ahead of print]
Authors: Peacock JCA, Ball K
Summary: Executing any skill with efficiency is important for performance. In football kicking, conflicting and non-significant results have existed between reducing ankle plantarflexion during foot-ball contact with impact efficiency, making it unclear as to its importance as a coaching instruction. The aims of this study were to first validate a mechanical kicking machine with a non-rigid ankle, and secondly compare a rigid to a non-rigid ankle during the impact phase of football kicking. Measures of foot-ball contact for ten trials per ankle configuration were calculated from data recorded at 4000 Hz and compared. The non-rigid ankle was characterised by initial dorsiflexion followed by plantarflexion for the remainder of impact, and based on similarities to punt and instep kicking, was considered valid. Impact efficiency (foot-to-ball speed ratio) was greater for the rigid ankle (rigid = 1.16 ± 0.02; non-rigid = 1.10 ± 0.01; p < 0.001). The rigid ankle was characterised by significantly greater effective mass and significantly less energy losses. Increasing rigidity allowed a greater portion of mass from the shank to be used during the collision. As the ankle remained in plantarflexion at impact end, stored elastic energy was not converted to ball velocity and was considered lost. Increasing rigidity is beneficial for increasing impact efficiency, and therefore ball velocity.

#9 Cardiac Magnetic Resonance Assessment of the Structural and Functional Cardiac Adaptations to Soccer Training in School-Aged Male Children
Reference: Pediatr Cardiol. 2018 Mar 8. doi: 10.1007/s00246-018-1844-5. [Epub ahead of print]
Authors: Barczuk-Falęcka M, Malek LA, Krysztofiak H, Roik D, Brzewski M
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Summary: Physical training is associated with changes in cardiac morphology called the "athlete's heart", which has not been sufficiently studied in children. The aim of the study was to analyze cardiac adaptation to exercise in pre-adolescent soccer players. Thirty-six soccer players (mean age 10.1 ± 1.4 years) and 24 non-athlete male controls (10.4 ± 1.7 years) underwent cardiac magnetic resonance. Measurements of myocardial mass, end-diastolic and end-systolic volume, stroke volume and ejection fraction for left and right ventricle (LV, RV) were performed. Additionally, left and right atrial (LA, RA) areas and volumes were analysed. Relative wall thickness (RWT) was calculated to describe the pattern of cardiac remodeling. Interventricular wall thickness and LV mass were significantly higher in athletes, but remained within the reference (6.9 ± 0.8 vs. 6.2 ± 0.9 mm/√m2, p = 0.003 and 57.1 ± 7.4 vs. 50.0 ± 7.1 g/m2, p = 0.0006, respectively) with no changes in LV size and function between groups. The RWT tended to be higher among athletes (p = 0.09) indicating LV concentric remodeling geometry. Soccer players had significantly larger RV size (p < 0.04) with similar function and mass. Also, the LA volume (p = 0.01), LA area (p = 0.03) and LA diameter (p = 0.009) were significantly greater in players than in controls. Cardiac adaptations in pre-adolescent soccer players are characterized by an increased LV mass without any changes in LV size and systolic function, which is typical of resistance training with tendency to concentric remodeling. This is accompanied by increase of LA and RV size. It should be taken into account during annual pre-participation evaluation.

#11 No better moment to score a goal than just before half time? A soccer myth statistically tested
Reference: PLoS One. 2018 Mar 8;13(3):e0194255. doi: 10.1371/journal.pone.0194255. eCollection 2018.
Authors: Baert S, Amez S
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Summary: We test the soccer myth suggesting that a particularly good moment to score a goal is just before half time. To this end, rich data on 1,179 games played in the UEFA Champions League and UEFA Europa League are analysed. In contrast to the myth, we find that, conditional on the goal difference and other game characteristics at half time, the final goal difference at the advantage of the home team is 0.520 goals lower in case of a goal just before half time by this team. We show that this finding relates to this team's lower probability of scoring a goal during the second half.

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