Latest research in football - week 45 - 2015

As previous literature updates, we have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Influence of the Type of Marking and the Number of Players on Physiological and Physical Demands During Sided Games in Soccer
Reference: J Hum Kinet. 2015 Oct 14;47:259-68. doi: 10.1515/hukin-2015-0081. eCollection 2015
Authors: Casamichana D, Román-Quintana JS, Castellano J, Calleja-González J
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Summary: The aim of this research was to examine the influence of two variables, the type of marking (with or without man-marking) and the number of players per team (3, 6, or 9) on the physical and physiological demands of sided games in soccer. Eighteen amateur players were monitored with GPS and heart rate devices. The following variables were analyzed: a maximum heart rate, a mean heart rate, time spent in each intensity range, total distance covered and distance covered in different speed ranges, a player load, maximum speed reached, and a work:rest ratio. The results showed that the type of marking influenced the physical demands of players, with greater total distance, a player load and a work:rest ratio when man-marking was used in the 3 vs. 3 (737 m, 95 Arbitrary Units (AU) and 3.4 AU, respectively) and 6 vs. 6 (783 m, 95 AU and 5.3 AU, respectively) games (p<0.05). The number of players also had an effect on physiological intensity, with more time being spent at the <80%HRmax during the 9 vs. 9 and 6 vs. 6 games (more than 30%) compared with the 3 vs. 3 format (less than 15%) (p<0.05). These findings could help coaches to understand how the modification of different variables in sided games influences the physical and physiological demands of players.

#2 Relative Age Effect in UEFA Championship Soccer Players
Reference: J Hum Kinet. 2015 Oct 14;47:237-48. doi: 10.1515/hukin-2015-0079. eCollection 2015
Authors: González-Víllora S, Pastor-Vicedo JC, Cordente D
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Summary: Relative Age Effect (RAE) is the breakdown by both age grouping and dates of birth of athletes. In the past 20 years the existence of this effect has been shown with higher or smaller impact in multiple sports, including soccer. The purpose of this study was to identify the existence of RAE in European soccer players. The sample included 841 elite soccer players who were participants in the UEFA European Soccer Championship in different categories. The professional category (n = 368), U-19 (n = 144) and U-17 (n = 145) were in 2012, and U-21 was in 2011 (n = 184). The Kolmogorov-Smirnov test and the Levene test recommended the use of nonparametric statistics. The results obtained by the square test ( the Kruskal-Wallis test and Cohen's effect sizes revealed the existence of RAE (χ(2) = 17.829, p < 0.001; d = 0.30), with the size of their different effects depending on their category or qualifying round achieved by the national team and the existence of significance in the observed differences by category. Therefore, we could continue examining RAE which is present in elite soccer, and could be considered a factor that influences performance of the national teams tested. RAE was not evident in the professional teams analysed, however it was present in the three lower categories analysed (youth categories), with its influence being greater on younger age categories (U-17).

#3 Analysis of Soccer Players' Positional Variability During the 2012 UEFA European Championship: A Case Study
Reference: J Hum Kinet. 2015 Oct 14;47:225-36. doi: 10.1515/hukin-2015-0078. eCollection 2015
Authors: Moura FA, Santana JE, Vieira NA, Santiago PR, Cunha SA
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Summary: The purpose of this study was to analyse players' positional variability during the 2012 UEFA European Championship by applying principal component analysis (PCA) to data gathered from heat maps posted on the UEFA website. We analysed the teams that reached the finals and semi-finals of the competition. The players' 2D coordinates from each match were obtained by applying an image-processing algorithm to the heat maps. With all the players' 2D coordinates for each match, we applied PCA to identify the directions of greatest variability. Then, two orthogonal segments were centred on each player's mean position for all matches. The segments' directions were driven by the eigenvectors of the PCA, and the length of each segment was defined as one standard deviation around the mean. Finally, an ellipse was circumscribed around both segments. To represent player variability, segment lengths and elliptical areas were analysed. The results demonstrate that Portugal exhibited the lowest variability, followed by Germany, Spain and Italy. Additionally, a graphical representation of every player's ellipse provided insight into the teams' organisational features throughout the competition. The presented study provides important information regarding soccer teams' tactical strategy in high-level championships that allows coaches to better control team organisation on the pitch.

#4 Physical Demands of Top-Class Soccer Friendly Matches in Relation to a Playing Position Using Global Positioning System Technology
Reference: J Hum Kinet. 2015 Oct 14;47:179-88. doi: 10.1515/hukin-2015-0073. eCollection 2015
Authors: Mallo J, Mena E, Nevado F, Paredes V
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Summary: The aim of this study was to examine the physical demands imposed on professional soccer players during 11-a-side friendly matches in relation to their playing position, using global positioning system (GPS) technology. One hundred and eleven match performances of a Spanish "La Liga" team during the 2010-11 and 2011-12 pre-seasons were selected for analysis. The activities of the players were monitored using GPS technology with a sampling frequency of 1 Hz. Total distance covered, distance in different speed categories, accelerations, and heart rate responses were analyzed in relation to five different playing positions: central defenders (n=23), full-backs (n=20), central midfielders (n=22), wide midfielders (n=26), and forwards (n=20). Distance covered during a match averaged 10.8 km, with wide and central midfielders covering the greatest total distance. Specifically, wide midfielders covered the greatest distances by very high-intensity running (>19.8 km·h-1) and central midfielders by jogging and running (7.2-19.7 km·h-1). On the other hand, central defenders covered the least total distance and at high intensity, although carried out more (p<0.05-0.01) accelerations than forwards, wide midfielders, and fullbacks. The work rate profile of the players obtained with the GPS was very similar to that obtained with semi-automatic image technologies. However, when comparing results from this study with data available in the literature, important differences were detected in the amount of distance covered by sprinting, which suggests that caution should be taken when comparing data obtained with the GPS with other motion analysis systems, especially regarding high-intensity activities.

#5 Moderate Altitude Affects High Intensity Running Performance in a Collegiate Women's Soccer Game
Reference: J Hum Kinet. 2015 Oct 14;47:147-54. doi: 10.1515/hukin-2015-0070. eCollection 2015
Authors: Bohner JD, Hoffman JR, McCormack WP, Scanlon TC, Townsend JR, Stout JR, Fragala MS, Fukuda DH
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Summary: The effect of altitude on soccer game activity profiles was retrospectively examined in six NCAA Division I female soccer players. Comparisons were made between two matches played at sea level (SL) and one match played at a moderate altitude (1839 m). A 10-Hz global positioning system device was used to measure distance and velocity. The rate of total distance capacity (TDC) and high intensity running (HIR) as well as percent of time at HIR were evaluated. Significant differences were seen in the distance rate (120.55 ± 8.26 m·min-1 versus 105.77 ± 10.19 m·min-1) and the HIR rate (27.65 ± 9.25 m·min-1 versus 25.07 ± 7.66 m·min-1) between SL and altitude, respectively. The percent of time at HIR was not significantly different (p = 0.064), yet tended to be greater at SL (10.4 ± 3.3%) than at altitude (9.1 ± 2.2%). Results indicate that teams residing at SL and competing at a moderate altitude may have a reduced ability in distance covered and a high intensity run rate.

#6 Developing an Academic-Community Partnership to Promote Soccer-Based Physical Activity Among Latino Youth
Reference: Prog Community Health Partnersh. 2015 Autumn;9(3):397-404. doi: 10.1353/cpr.2015.0052
Authors: Schober DJ, Zarate J, Fawcett SB.
Summary: The Latino Health for All (LHFA) Coalition used a community-based participatory approach to develop an action plan for addressing chronic disease among Latinos in Kansas City. This study examines the development and implementation of community-based soccer sessions for youth (ages 6-15) by an academic partner from the coalition and a community partner from a nonprofit youth soccer organization. The academic and community partners spoke four times over 3 months to plan for these soccer sessions. These conversations ranged from sharing goals to planning logistics. The coalition helped to promote these opportunities through a variety of channels. Eight weekly soccer sessions were implemented, attracting Latino youth who were overweight or obese. These soccer sessions were perceived as enjoyable by youth and were appreciated by their parents. Successful health promotion efforts require strong relationships between academic and community partners that involve shared goals and complementary skills/ expertise.

#7 Nutritional intake and nutritional status un elite Mexican teenagers soccer players of different ages
Reference: Nutr Hosp. 2015 Oct 1;32(n04):1735-1743.
Authors: Hidalgo Y Teran Elizondo R, Martín Bermudo FM, Peñaloza Mendez R, Berná Amorós G, Lara Padilla E, Berral de la Rosa FJ
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Summary: Nutritional intake and status of soccer players has attracted not much research attention. Many soccer players follow an inadequate nutritional intake and have a poor nutritional status. This is relevant in youngsters soccer players, in order to improve performance and promote healthy dietary practices. The aim of the study was to analyze anthropometric characterizes, evaluate nutritional intake and status, dietary habits and pre- and post-exercise meals in elite teenagers soccer players. Seventy-two young male soccer players (15-20 years) from four junior teams of a soccer Club from the Mexican National Soccer League were measured for height, seat height, weight, 6 skinfolds, 6 diameters and 7 circumferences, height-for-age and BMI-for-age values. Skin, adipose, muscle, bone and residual tissue masses were calculated with the Ross and Kerr equation. Resting energy expenditure and intake was also measured. Daily dietary intake was self-recorded for 4 consecutive days (excluding the match day) using a digital food-weighing scale and a food record questionnaire. Dietary analysis was performed using the NutriBase 7 Clinical software. Several biochemical values were determined. One-way analysis of variance (ANOVA) and post hoc testing was performed using t-tests with a Bonferroni correction. All soccer players were within the normal range values for anthropometric parameters studies, when compared with other adolescent elite soccer teams. Values of plasma glucose, urea, creatinine, uric acid, lipid profile and total proteins were within normal range for young adult population, although albumin levels were high. Moreover, 14% and 20% of soccer players presented hyperuricemia and elevated total cholesterol levels respectively. Energy expenditure and intake were within normal range for all teenager elite soccer players. However, two teams shower significant lower intakes than demands. All macronutrient intakes were within recommendations, except protein that was higher. Micronu trient intake exceeded the recommendations for general population. Soccer players had pre- and post-exercise meals with an appropriate range of carbohydrates. Food intake was mainly based on cereals, derivatives and potatoes; meat, poultry, fish, shellfish and eggs and biscuits and confectionery and poor in fruit, vegetables and milk and dairy products. The population of soccer players did not have optimal nutritional habits. However, their nutritional intake and status was better than in other published studies. The main problems of these teams were that they had a high protein diet and that in some teams the nutritional intake was not enough to cover the demands. Finally, nutritional intake was found to be of poor quality. Thus, we recommend nutritional education for soccer players of these teams.

#8 Review of the tactical evaluation tools for youth players, assessing the tactics in team sports: football
Reference: Springerplus. 2015 Nov 2;4:663. doi: 10.1186/s40064-015-1462-0. eCollection 2015
Authors: González-Víllora S, Serra-Olivares J, Pastor-Vicedo JC, da Costa IT
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Summary: For sports assessment to be comprehensive, it must address all variables of sports development, such as psychological, social-emotional, physical and physiological, technical and tactical. Tactical assessment has been a neglected variable until the 1980s or 1990s. In the last two decades (1995-2015), the evolution of tactical assessment has grown considerably, given its importance in game performance. The aim of this paper is to compile and analyze different tactical measuring tools in team sports, particularly in soccer, through a bibliographical review. Six tools have been selected on five different criteria: (1) Instruments which assess tactics, (2) The studies have an evolution approach related to the tactical principles, (3) With a valid and reliable method, (4) The existence of publications mentioning the tool in the method, v. Applicable in different sports contexts. All six tools are structured around seven headings: introduction, objective(s), tactical principles, materials, procedures, instructions/rules of the game and published studies. In conclusion, the teaching-learning processes more tactical oriented have useful tactical assessment instrument in the literature. The selection of one or another depends some context information, like age and level of expertise of the players.

#9 The acute effects of graded physiological strain on soccer kicking performance: a randomized, controlled cross-over study
Reference: Eur J Appl Physiol. 2015 Nov 14. [Epub ahead of print]
Authors: Radman I, Wessner B, Bachl N, Ruzic L, Hackl M, Prpic T, Markovic G
Summary: The aim of the present study was to examine the acute effects of graded physiological strain on soccer kicking performance. Twenty-eight semi-professional soccer players completed both experimental and control procedure. The experimental protocol incorporated repeated shooting trials combined with a progressive discontinuous maximal shuttle-run intervention. The initial running velocity was 8 km/h and increasing for 1 km/h every 3 min until exhaustion. The control protocol comprised only eight subsequent shooting trials. The soccer-specific kicking accuracy (KA; average distance from the ball-entry point to the goal center), kicking velocity (KV), and kicking quality (KQ; kicking accuracy divided by the time elapsed from hitting the ball to the point of entry) were evaluated via reproducible and valid test over five individually determined exercise intensity zones. Compared with baseline or exercise at intensities below the second lactate threshold (LT2), physiological exertion above the LT2 (blood lactate > 4 mmol/L) resulted in meaningful decrease in KA (11-13 %; p < 0.05), KV (3-4 %; p < 0.05), and overall KQ (13-15 %; p < 0.01). The light and moderate-intensity exercise below the LT2 had no significant effect on soccer kicking performance. The results suggest that high-intensity physiological exertion above the player's LT2 impairs soccer kicking performance. In contrast, light to moderate physiological stress appears to be neither harmful nor beneficial for kicking performance.

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