Latest research in football - week 28 - 2013

#1 Kinetic factors of vertical jumping for heading a ball in flexible flatfooted amateur soccer players with and without insole adoption
Authors: Arastoo AA, Aghdam EM, Habibi AH, Zahednejad S.
Reference: Prosthet Orthot Int. 2013 Jul 4. [Epub ahead of print]
Summary: To compare the kinetic and temporal events of two-legged vertical jumping take-off from a force plate for heading a ball in normal and flexible flatfoot subjects with and without insole. Random sampling method was employed to draw a control group of 15 normal foot subjects to a group of 15 flatfoot subjects. A force platform was used to record kinetics of two-legged vertical jump shots. Results indicate that insole did not lead to a significant effect on kinetics regarding anterior-posterior and mediolateral directions (p > 0.05). Results of kinetics related to vertical direction for maximum force due to take-off and stance duration revealed significant differences between the normal and flexible flatfoot subjects without insole (p < 0.05) and no significant differences between the normal foot and flexible flatfoot subjects with insole adoption (p > 0.05). These results suggest that the use of an insole in the flexible flatfoot subjects led to improved stance time and decrease of magnitude of kinetics regarding vertical direction at take-off as the main feature of two-legged vertical jumping function. Adoption of the insole improved the design of the shoe-foot interface support for the flexible flatfoot athletes, enabling them to develop more effective take-off kinetics for vertical jumping in terms of ground reaction force and stance duration similar to that of normal foot subjects without insole.


#2 Evaluation of functional limitations in female soccer players and their relationship with sports level - a cross sectional study
Authors: Grygorowicz M, Piontek T, Dudzinski W.
Reference: PLoS One. 2013 Jun 25;8(6):e66871. doi: 10.1371/journal.pone.0066871. Print 2013.
Summary: The aim of this study was to analyze: a) abnormalities in the length of lower limb muscles, b) the correctness of movement patterns, and c) the impact of functional limitations of muscles on the correctness of fundamental movement patterns in a group of female soccer players, in relation to their skill level. 21 female soccer players from Polish Ekstraklasa and 22 players from the 1(st) Division were tested for lower limb muscle length restrictions and level of fundamental movement skills (with the Fundamental Movement Screen™ test concept by Gray Cook). Chi-square test was used for categorical unrelated variables. Differences between groups in absolute point values were analyzed using the non-parametric Mann-Whitney U test. Statistical significance was set at p<0.05.  Statistically significant higher number of measurements indicating an abnormal length of rectus femoris was observed in the 1st Division group (p = 0.0433). In the group of Ekstraklasa the authors obtained a significantly higher number of abnormal hamstring test results (p = 0.0006). Ekstraklasa players scored higher in the rotational stability test of the trunk (p = 0.0008), whereas the 1st Division players scored higher in the following tests: deep squat (p = 0.0220), in-line lunge (p = 0.0042) and active straight leg raise (p = 0.0125). The results suggest that there are different functional reasons affecting point values obtained in the FMS™ tests in both analyzed groups. CONCLUSIONS:  The differences in the flexibility of rectus femoris and hamstring muscle observed between female soccer players with different levels of training, may result from a long-term impact of soccer training on the muscle-tendon system and articular structures. Different causes of abnormalities in fundamental movement patterns in both analyzed groups suggest the need for tailoring prevention programs to the level of sport skills represented by the players


#3 Nutritional study of a third division soccer team
Authors: Martínez Reñón C, Sánchez Collado P.
Reference: Nutr Hosp. 2013 Marzo-Abril;28(2):319-324.
Summary: To analyze the nutritional habits and attitudes of a semiprofessional soccer team. Nutritional study of 21 semiprofessional soccer players (18-35 years) by analyzing the daily energy intake and expenditure also the distribution of macro and micro-nutrients, differentiated type of day (normal, training or competition). The energy balance is negative in the three days studied (- 31%, - 38% and -31% respectively). There were significant differences in caloric intake between the day of competition, a normal day and a day of training. These differences are observed both in absolute values (2,438 kcal vs 2,127 y 2,221 kcal respectively) as referring to body weight (30.5 kcal/kg vs 27 y 28 kcal/kg respectively). Regarding macronutrient intake, the samples eat a diet with an insufficient amount of carbohydrates (328 g vs 371 and 540 g recommended in function of physical activity). There were no significant differences in the composition of micronutrients. The football players studied show a negative energy balance with a diet low in carbohydrates. This poor nutritional status may interfere with the development of their sporting performance and, ultimately, increase the risk of lesions. This implies the need for design and implementation of a diet and introducing nutritional education programs for these athletes.


#4 Prevalence of Abnormal Electrocardiographic Patterns in Icelandic Soccer Players and Relationship with Echocardiographic Findings
Authors: Sigurdsson A, Bjornsdottir H, Gudnason T, Sigurdsson AF.
Reference: Laeknabladid. 2013 Juni;99(6):283-287.
Summary: An abnormal electrocardiogram (ECG) is common among young athletes but the underlying cause is unclear. Therefore it is hard to predict how accurate ECG is when screening for sudden cardiac death (SCD) in elite athletes. The objectives of this study were 1) to determine the prevalence of abnormal ECG patterns, among soccer players, especially in relation to age and 2) to link ECG patterns with echocardiographic findings in order to find out whether the ECG can predict disease and/or physiological changes. A total of 159 male soccer players (16-45 years, mean age 25.5 years) that participated in the UEFA cup competition 2008-2010 were studied. They underwent both an ECG and echocardiography along with routine history and cardiologic examination, according to UEFA protocol. Results were classified and grouped according to standards set by The European Society of Cardiology and The American Society of Echocardiography. 84 (53%) had abnormal ECG patterns. The prevalence of abnormal ECG patterns decreased with age. Echocardiographic findings showed that left ventricular wall thickness, mass and diameter increased with age, along with left atrial diameter. Left ventricular wall thickness, diameter and mass were similar among those with an abnormal ECG and those with a normal ECG. The prevalence of abnormal ECG´s is high in Icelandic soccer players, a finding that usually does not indicate underlying heart disease. There was no relationship between ECG changes and echocardiographic findings. High prevalence of abnormal ECG patterns in young athletes reduces the usefulness of ECG in screening for SCD.


#5 Match running performance fluctuations in elite soccer: Indicative of fatigue, pacing or situational influences?
Authors: Bradley PS, Noakes TD.
Reference: J Sports Sci. 2013 Jul 1. [Epub ahead of print]
Summary: The aims of this study were to: (1) quantify match running performance in 5-min periods to determine if players fatigue or modulate high-intensity running according to a pacing strategy, and (2) examine factors impacting high-intensity running such as score line, match importance and the introduction of substitutes. All players were analysed using a computerised tracking system. Maintaining 'high' levels of activity in the first half resulted in a 12% reduction (P < 0.01) in the second half for high-intensity running (effect size [ES]: 0.8), while no changes were observed in 'moderate' and 'low' groups (ES: 0.0-0.2). The 'high' group covered less (P < 0.01) high-intensity running in the initial 10-min of the second versus first half (ES: 0.6-0.7), but this was not observed in 'moderate' and 'low' groups (ES: 0.2-0.4). After the most intense periods, players demonstrated an 8% drop in high-intensity running (P < 0.05) compared to the match average (ES: 0.2) and this persisted for 5-min before recovering. Players covered similar high-intensity running distances in matches with differing score lines but position-specific trends indicated central defenders covered 17% less (P < 0.01) and attackers 15% more high-intensity running during matches that were heavily won versus lost (ES: 0.9). High-intensity running distances were comparable in matches of differing importance, but between-half trends indicated that only declines (P < 0.01) occurred in the second half of critical matches (ES: 0.2). Substitutes covered 15% more (P < 0.01) high-intensity running versus the same time period when completing a full match (ES: 0.5). The data demonstrate that high-intensity running in the second half is impacted by the activity of the first half and is reduced for 5-min after intense periods. High-intensity running is also influenced by score line and substitutions but not match importance. More research is warranted to establish if fluctuations in match running performance are primarily a consequence of fatigue, pacing or tactical and situational influences.


#6 Supramaximal intermittent running performance in relation to age and locomotor profile in highly-trained young soccer players
Authors: Buchheit M, Mendez-Villanueva A.
Reference: J Sports Sci. 2013 Jun 28. [Epub ahead of print]
Summary:  The aim of the study was to examine supramaximal intermittent running performance in highly-trained young soccer players, with regard to age and locomotor profile. Twenty-seven Under 14, 19 U16 and 16 U18 highly-trained soccer players performed an incremental intermittent running test (30-15 Intermittent Fitness Test) to assess supramaximal intermittent running performance (VIFT), an incremental running test to estimate maximal aerobic speed (VVam-Eval) and a 40-m sprint to estimate maximal sprinting speed (MSS). U16 and U18 presented very likely greater VIFT (19.2 ± 0.9, 19.7 ± 1.0 vs. 17.4 ± 0.9 km · h-1) and VVam-Eval (16.2 ± 0.9, 16.7 ± 1.0 vs. 14.6 ± 0.9 km · h-1) than U14, while there was no clear difference between U16 and U18. MSS (25.1 ± 1.6, 29.3 ± 1.6 and 31.0 ± 1.1 km · h-1 for U14, U16 and U18) was very likely different between all groups. When data were pooled together, VIFT was very largely correlated with VVam-Eval and MSS (overall r =0.89, partial r = 0.74 and 0.29, respectively). Within-age group correlations showed that the older the players, the greater the magnitude of the correlations between VIFT and VVam-Eval (r = 0.67, 0.73 and 0.87). In conclusion, the major predictors of VIFT were, in order of importance, VVam-Eval and MSS; however, the older the players, the greater the correlations with VVam-Eval.


#7 Time-trends and circumstances surrounding ankle injuries in men's professional football: an 11-year follow-up of the UEFA Champions League injury study
Authors: Waldén M, Hägglund M, Ekstrand J.
Reference: Br J Sports Med. 2013 Jun 27. [Epub ahead of print]
Summary: To investigate the rates, especially time-trends, and circumstances of ankle injuries in male professional football.  27 European clubs with 1743 players were followed prospectively between 2001/2002 and 2011/2012. Time loss injuries and individual-player exposure during training sessions and matches were recorded. Injury rate was defined as the number of injuries/1000 h.  A total of 1080 ankle injuries were recorded (13% of all injuries) with lateral ligament ankle sprain being the most common injury subtype (51% of all ankle injuries). The rates of ankle injury and ankle sprain were 1/1000 h and 0.7/1000 h, respectively. The ankle sprain rate declined slightly over time during the 11-year study period (on average 3.1%/season) with a statistically significant seasonal trend (p=0.041). Foul play according to the referee was involved in 40% of the match-related ankle sprains. Syndesmotic sprains and ankle impingement were uncommon causes of time loss (3% each of all ankle injuries). Lateral ligament ankle sprain constituted half of all ankle injuries in male professional football, whereas ankle impingement syndromes were uncommon. The ankle sprain rate decreased slightly over time, but many ankle sprains were associated with foul play. Our data extend the body of literature that provides football policy makers with a foundation to review existing rules and their enforcement.


#8 Implementation of the FIFA 11+ football warm up program: How to approach and convince the Football associations to invest in prevention
Authors: Bizzini M, Junge A, Dvorak J.
Reference: Br J Sports Med. 2013 Jun 27. [Epub ahead of print]
Summary: In the last decade, injury prevention has received a lot of attention in sports medicine, and recently international sports-governing bodies, such as the International Olympic Committee, declared the protection of the athletes' health as one of their major objectives. In 1994, the Fédération Internationale de Football Association (FIFA) established its Medical Assessment and Research Centre (F-MARC) with the aim 'to prevent football injuries and to promote football as a health-enhancing leisure activity, improving social behaviour'. Since then, FIFA has developed and evaluated its injury-prevention programmes 'The 11' and 'FIFA 11+' have demonstrated in several scientific studies how simple exercise-based programmes can decrease the incidence of injuries in amateur football players. This paper summarises 18 years of scientific and on-field work in injury prevention by an international sports federation (FIFA), from formulating the aim to make its sport safer to the worldwide dissemination of its injury-prevention programme in amateur football.